[PATCH v4 00/20] powerpc: Syscall wrapper and register clearing

[PATCH v4 00/20] powerpc: Syscall wrapper and register clearing

[Rohan McLure]

V3 available here:

Link: https://lore.kernel.org/all/4C3A8815-67FF-41EB-A703-981920CA1201@linux.ibm.com/T/

Implement a syscall wrapper, causing arguments to handlers to be passed
via a struct pt_regs on the stack. The syscall wrapper is implemented
for all platforms other than the Cell processor, from which SPUs expect
the ability to directly call syscall handler symbols with the regular
in-register calling convention.

Adopting syscall wrappers requires redefinition of architecture-specific
syscalls and compatibility syscalls to use the SYSCALL_DEFINE and
COMPAT_SYSCALL_DEFINE macros, as well as removal of direct-references to
the emitted syscall-handler symbols from within the kernel. This work
lead to the following modernisations of powerpc's syscall handlers:

 - Replace syscall 82 semantics with sys_old_select and remove
   ppc_select handler, which features direct call to both sys_old_select
   and sys_select.
 - Use a generic fallocate compatibility syscall

Replace asm implementation of syscall table with C implementation for
more compile-time checks.

Many compatibility syscalls are candidates to be removed in favour of
generically defined handlers, but exhibit different parameter orderings
and numberings due to 32-bit ABI support for 64-bit parameters. The
parameter reorderings are however consistent with arm. A future patch
series will serve to modernise syscalls by providing generic
implementations featuring these reorderings.

The design of this syscall is very similar to the s390, x86 and arm64
implementations. See also Commit 4378a7d4be30 (arm64: implement syscall wrappers).
The motivation for this change is that it allows for the clearing of
register state when entering the kernel via through interrupt handlers
on 64-bit servers. This serves to reduce the influence of values in
registers carried over from the interrupted process, e.g. syscall
parameters from user space, or user state at the site of a pagefault.
All values in registers are saved and zeroized at the entry to an
interrupt handler and restored afterward. While this may sound like a
heavy-weight mitigation, many gprs are already saved and restored on
handling of an interrupt, and the mmap_bench benchmark on Power 9 guest,
repeatedly invoking the pagefault handler suggests at most ~0.8%
regression in performance. Realistic workloads are not constantly
producing interrupts, and so this does not indicate realistic slowdown.

Using wrapped syscalls yields to a performance improvement of ~5.6% on
the null_syscall benchmark on pseries guests, by removing the need for
system_call_exception to allocate its own stack frame. This amortises
the additional costs of saving and restoring non-volatile registers
(register clearing is cheap on super scalar platforms), and so the
final mitigation actually yields a net performance improvement of ~0.6%
on the null_syscall benchmark.

Patch Changelog:

 - Fix instances where NULLIFY_GPRS were still present
 - Minimise unrecoverable windows in entry_32.S between SRR0/1 restores
   and RFI
 - Remove all references to syscall symbols prior to introducing syscall
   wrapper.
 - Remove unnecessary duplication of syscall handlers with sys_... and
   powerpc_sys_... symbols.
 - Clear non-volatile registers on Book3E systems, as some of these
   systems feature hardware speculation, and we already unconditionally
   restore NVGPRS.

Rohan McLure (20):
  powerpc: Remove asmlinkage from syscall handler definitions
  powerpc: Use generic fallocate compatibility syscall
  powerpc/32: Remove powerpc select specialisation
  powerpc: Provide do_ppc64_personality helper
  powerpc: Remove direct call to personality syscall handler
  powerpc: Remove direct call to mmap2 syscall handlers
  powerpc: Adopt SYSCALL_DEFINE for arch-specific syscall handlers
  powerpc: Include all arch-specific syscall prototypes
  powerpc: Enable compile-time check for syscall handlers
  powerpc: Use common syscall handler type
  powerpc: Add ZEROIZE_GPRS macros for register clears
  Revert "powerpc/syscall: Save r3 in regs->orig_r3"
  powerpc: Provide syscall wrapper
  powerpc/64s: Clear/restore caller gprs in syscall interrupt/return
  powerpc/64s: Use {ZEROIZE,SAVE,REST}_GPRS macros in sc, scv 0 handlers
  powerpc/32: Clarify interrupt restores with REST_GPR macro in
    entry_32.S
  powerpc/64e: Clarify register saves and clears with
    {SAVE,ZEROIZE}_GPRS
  powerpc/64s: Fix comment on interrupt handler prologue
  powerpc/64s: Clear gprs on interrupt routine entry in Book3S
  powerpc/64e: Clear gprs on interrupt routine entry

 arch/powerpc/Kconfig                         |   1 +
 arch/powerpc/include/asm/compat.h            |   5 +
 arch/powerpc/include/asm/interrupt.h         |   3 +-
 arch/powerpc/include/asm/ppc_asm.h           |  22 +++
 arch/powerpc/include/asm/syscall.h           |  11 +-
 arch/powerpc/include/asm/syscall_wrapper.h   |  84 +++++++++++
 arch/powerpc/include/asm/syscalls.h          | 128 +++++++++++++----
 .../ppc32.h => include/asm/syscalls_32.h}    |   0
 arch/powerpc/include/asm/unistd.h            |   1 +
 arch/powerpc/kernel/entry_32.S               |  40 +++---
 arch/powerpc/kernel/exceptions-64e.S         |  31 ++--
 arch/powerpc/kernel/exceptions-64s.S         |  25 ++--
 arch/powerpc/kernel/interrupt_64.S           |  92 +++++-------
 arch/powerpc/kernel/signal_32.c              |   2 +-
 arch/powerpc/kernel/sys_ppc32.c              |  54 ++++---
 arch/powerpc/kernel/syscall.c                |  32 ++---
 arch/powerpc/kernel/syscalls.c               |  51 ++++---
 arch/powerpc/kernel/syscalls/syscall.tbl     |  24 ++--
 arch/powerpc/kernel/{systbl.S => systbl.c}   |  29 ++--
 arch/powerpc/kernel/vdso.c                   |   6 +-
 arch/powerpc/perf/callchain_32.c             |   2 +-
 arch/powerpc/platforms/cell/spu_callbacks.c  |   6 +-
 .../arch/powerpc/entry/syscalls/syscall.tbl  |  24 ++--
 23 files changed, 415 insertions(+), 258 deletions(-)
 create mode 100644 arch/powerpc/include/asm/syscall_wrapper.h
 rename arch/powerpc/{kernel/ppc32.h => include/asm/syscalls_32.h} (100%)
 rename arch/powerpc/kernel/{systbl.S => systbl.c} (55%)

-- 
2.34.1

[PATCH v4 01/20] powerpc: Remove asmlinkage from syscall handler definitions

[Rohan McLure]

The asmlinkage macro has no special meaning in powerpc, and prior to
this patch is used sporadically on some syscall handler definitions. On
architectures that do not define asmlinkage, it resolves to extern "C"
for C++ compilers and a nop otherwise. The current invocations of
asmlinkage provide far from complete support for C++ toolchains, and so
the macro serves no purpose in powerpc.

Remove all invocations of asmlinkage in arch/powerpc. These incidentally
only occur in syscall definitions and prototypes.

Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
---
V2 -> V3: new patch
---
 arch/powerpc/include/asm/syscalls.h | 16 ++++++++--------
 arch/powerpc/kernel/sys_ppc32.c     |  8 ++++----
 2 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/arch/powerpc/include/asm/syscalls.h b/arch/powerpc/include/asm/syscalls.h
index a2b13e55254f..21c2faaa2957 100644
--- a/arch/powerpc/include/asm/syscalls.h
+++ b/arch/powerpc/include/asm/syscalls.h
@@ -10,14 +10,14 @@
 
 struct rtas_args;
 
-asmlinkage long sys_mmap(unsigned long addr, size_t len,
-		unsigned long prot, unsigned long flags,
-		unsigned long fd, off_t offset);
-asmlinkage long sys_mmap2(unsigned long addr, size_t len,
-		unsigned long prot, unsigned long flags,
-		unsigned long fd, unsigned long pgoff);
-asmlinkage long ppc64_personality(unsigned long personality);
-asmlinkage long sys_rtas(struct rtas_args __user *uargs);
+long sys_mmap(unsigned long addr, size_t len,
+	      unsigned long prot, unsigned long flags,
+	      unsigned long fd, off_t offset);
+long sys_mmap2(unsigned long addr, size_t len,
+	       unsigned long prot, unsigned long flags,
+	       unsigned long fd, unsigned long pgoff);
+long ppc64_personality(unsigned long personality);
+long sys_rtas(struct rtas_args __user *uargs);
 int ppc_select(int n, fd_set __user *inp, fd_set __user *outp,
 	       fd_set __user *exp, struct __kernel_old_timeval __user *tvp);
 long ppc_fadvise64_64(int fd, int advice, u32 offset_high, u32 offset_low,
diff --git a/arch/powerpc/kernel/sys_ppc32.c b/arch/powerpc/kernel/sys_ppc32.c
index 16ff0399a257..f4edcc9489fb 100644
--- a/arch/powerpc/kernel/sys_ppc32.c
+++ b/arch/powerpc/kernel/sys_ppc32.c
@@ -85,20 +85,20 @@ compat_ssize_t compat_sys_readahead(int fd, u32 r4, u32 offset1, u32 offset2, u3
 	return ksys_readahead(fd, merge_64(offset1, offset2), count);
 }
 
-asmlinkage int compat_sys_truncate64(const char __user * path, u32 reg4,
+int compat_sys_truncate64(const char __user * path, u32 reg4,
 				unsigned long len1, unsigned long len2)
 {
 	return ksys_truncate(path, merge_64(len1, len2));
 }
 
-asmlinkage long compat_sys_fallocate(int fd, int mode, u32 offset1, u32 offset2,
+long compat_sys_fallocate(int fd, int mode, u32 offset1, u32 offset2,
 				     u32 len1, u32 len2)
 {
 	return ksys_fallocate(fd, mode, ((loff_t)offset1 << 32) | offset2,
 			     merge_64(len1, len2));
 }
 
-asmlinkage int compat_sys_ftruncate64(unsigned int fd, u32 reg4, unsigned long len1,
+int compat_sys_ftruncate64(unsigned int fd, u32 reg4, unsigned long len1,
 				 unsigned long len2)
 {
 	return ksys_ftruncate(fd, merge_64(len1, len2));
@@ -111,7 +111,7 @@ long ppc32_fadvise64(int fd, u32 unused, u32 offset1, u32 offset2,
 				 advice);
 }
 
-asmlinkage long compat_sys_sync_file_range2(int fd, unsigned int flags,
+long compat_sys_sync_file_range2(int fd, unsigned int flags,
 				   unsigned offset1, unsigned offset2,
 				   unsigned nbytes1, unsigned nbytes2)
 {
-- 
2.34.1

[PATCH v4 02/20] powerpc: Use generic fallocate compatibility syscall

[Rohan McLure]

The powerpc fallocate compat syscall handler is identical to the
generic implementation provided by commit 59c10c52f573f ("riscv:
compat: syscall: Add compat_sys_call_table implementation"), and as
such can be removed in favour of the generic implementation.

A future patch series will replace more architecture-defined syscall
handlers with generic implementations, dependent on introducing generic
implementations that are compatible with powerpc and arm's parameter
reorderings.

Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
---
V1 -> V2: Remove arch-specific fallocate handler.
V2 -> V3: Remove generic fallocate prototype. Move to beginning of
series.
---
 arch/powerpc/include/asm/compat.h   | 5 +++++
 arch/powerpc/include/asm/syscalls.h | 2 --
 arch/powerpc/include/asm/unistd.h   | 1 +
 3 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/include/asm/compat.h b/arch/powerpc/include/asm/compat.h
index dda4091fd012..f20caae3f019 100644
--- a/arch/powerpc/include/asm/compat.h
+++ b/arch/powerpc/include/asm/compat.h
@@ -16,6 +16,11 @@ typedef u16		compat_ipc_pid_t;
 #include <asm-generic/compat.h>
 
 #ifdef __BIG_ENDIAN__
+#define compat_arg_u64(name)		u32  name##_hi, u32  name##_lo
+#define compat_arg_u64_dual(name)	u32, name##_hi, u32, name##_lo
+#define compat_arg_u64_glue(name)	(((u64)name##_lo & 0xffffffffUL) | \
+					 ((u64)name##_hi << 32))
+
 #define COMPAT_UTS_MACHINE	"ppc\0\0"
 #else
 #define COMPAT_UTS_MACHINE	"ppcle\0\0"
diff --git a/arch/powerpc/include/asm/syscalls.h b/arch/powerpc/include/asm/syscalls.h
index 21c2faaa2957..675a8f5ec3ca 100644
--- a/arch/powerpc/include/asm/syscalls.h
+++ b/arch/powerpc/include/asm/syscalls.h
@@ -39,8 +39,6 @@ compat_ssize_t compat_sys_readahead(int fd, u32 r4, u32 offset1, u32 offset2, u3
 int compat_sys_truncate64(const char __user *path, u32 reg4,
 			  unsigned long len1, unsigned long len2);
 
-long compat_sys_fallocate(int fd, int mode, u32 offset1, u32 offset2, u32 len1, u32 len2);
-
 int compat_sys_ftruncate64(unsigned int fd, u32 reg4, unsigned long len1,
 			   unsigned long len2);
 
diff --git a/arch/powerpc/include/asm/unistd.h b/arch/powerpc/include/asm/unistd.h
index b1129b4ef57d..659a996c75aa 100644
--- a/arch/powerpc/include/asm/unistd.h
+++ b/arch/powerpc/include/asm/unistd.h
@@ -45,6 +45,7 @@
 #define __ARCH_WANT_SYS_UTIME
 #define __ARCH_WANT_SYS_NEWFSTATAT
 #define __ARCH_WANT_COMPAT_STAT
+#define __ARCH_WANT_COMPAT_FALLOCATE
 #define __ARCH_WANT_COMPAT_SYS_SENDFILE
 #endif
 #define __ARCH_WANT_SYS_FORK
-- 
2.34.1

[PATCH v4 03/20] powerpc/32: Remove powerpc select specialisation

[Rohan McLure]

Syscall #82 has been implemented for 32-bit platforms in a unique way on
powerpc systems. This hack will in effect guess whether the caller is
expecting new select semantics or old select semantics. It does so via a
guess, based off the first parameter. In new select, this parameter
represents the length of a user-memory array of file descriptors, and in
old select this is a pointer to an arguments structure.

The heuristic simply interprets sufficiently large values of its first
parameter as being a call to old select. The following is a discussion
on how this syscall should be handled.

Link: https://lore.kernel.org/lkml/13737de5-0eb7-e881-9af0-163b0d29a1a0@csgroup.eu/

As discussed in this thread, the existence of such a hack suggests that for
whatever powerpc binaries may predate glibc, it is most likely that they
would have taken use of the old select semantics. x86 and arm64 both
implement this syscall with oldselect semantics.

Remove the powerpc implementation, and update syscall.tbl to refer to emit
a reference to sys_old_select for 32-bit binaries, in keeping with how
other architectures support syscall #82.

Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
---
V1 -> V2: Remove arch-specific select handler
V2 -> V3: Remove ppc_old_select prototype in <asm/syscalls.h>. Move to
earlier in patch series
---
 arch/powerpc/include/asm/syscalls.h           |  2 --
 arch/powerpc/kernel/syscalls.c                | 17 -----------------
 arch/powerpc/kernel/syscalls/syscall.tbl      |  2 +-
 .../arch/powerpc/entry/syscalls/syscall.tbl   |  2 +-
 4 files changed, 2 insertions(+), 21 deletions(-)

diff --git a/arch/powerpc/include/asm/syscalls.h b/arch/powerpc/include/asm/syscalls.h
index 675a8f5ec3ca..739498c358a1 100644
--- a/arch/powerpc/include/asm/syscalls.h
+++ b/arch/powerpc/include/asm/syscalls.h
@@ -18,8 +18,6 @@ long sys_mmap2(unsigned long addr, size_t len,
 	       unsigned long fd, unsigned long pgoff);
 long ppc64_personality(unsigned long personality);
 long sys_rtas(struct rtas_args __user *uargs);
-int ppc_select(int n, fd_set __user *inp, fd_set __user *outp,
-	       fd_set __user *exp, struct __kernel_old_timeval __user *tvp);
 long ppc_fadvise64_64(int fd, int advice, u32 offset_high, u32 offset_low,
 		      u32 len_high, u32 len_low);
 
diff --git a/arch/powerpc/kernel/syscalls.c b/arch/powerpc/kernel/syscalls.c
index fc999140bc27..ef5896bee818 100644
--- a/arch/powerpc/kernel/syscalls.c
+++ b/arch/powerpc/kernel/syscalls.c
@@ -63,23 +63,6 @@ SYSCALL_DEFINE6(mmap, unsigned long, addr, size_t, len,
 	return do_mmap2(addr, len, prot, flags, fd, offset, PAGE_SHIFT);
 }
 
-#ifdef CONFIG_PPC32
-/*
- * Due to some executables calling the wrong select we sometimes
- * get wrong args.  This determines how the args are being passed
- * (a single ptr to them all args passed) then calls
- * sys_select() with the appropriate args. -- Cort
- */
-int
-ppc_select(int n, fd_set __user *inp, fd_set __user *outp, fd_set __user *exp, struct __kernel_old_timeval __user *tvp)
-{
-	if ((unsigned long)n >= 4096)
-		return sys_old_select((void __user *)n);
-
-	return sys_select(n, inp, outp, exp, tvp);
-}
-#endif
-
 #ifdef CONFIG_PPC64
 long ppc64_personality(unsigned long personality)
 {
diff --git a/arch/powerpc/kernel/syscalls/syscall.tbl b/arch/powerpc/kernel/syscalls/syscall.tbl
index 2600b4237292..4cbbb810ae10 100644
--- a/arch/powerpc/kernel/syscalls/syscall.tbl
+++ b/arch/powerpc/kernel/syscalls/syscall.tbl
@@ -110,7 +110,7 @@
 79	common	settimeofday			sys_settimeofday		compat_sys_settimeofday
 80	common	getgroups			sys_getgroups
 81	common	setgroups			sys_setgroups
-82	32	select				ppc_select			sys_ni_syscall
+82	32	select				sys_old_select			sys_ni_syscall
 82	64	select				sys_ni_syscall
 82	spu	select				sys_ni_syscall
 83	common	symlink				sys_symlink
diff --git a/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl b/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl
index 2600b4237292..4cbbb810ae10 100644
--- a/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl
+++ b/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl
@@ -110,7 +110,7 @@
 79	common	settimeofday			sys_settimeofday		compat_sys_settimeofday
 80	common	getgroups			sys_getgroups
 81	common	setgroups			sys_setgroups
-82	32	select				ppc_select			sys_ni_syscall
+82	32	select				sys_old_select			sys_ni_syscall
 82	64	select				sys_ni_syscall
 82	spu	select				sys_ni_syscall
 83	common	symlink				sys_symlink
-- 
2.34.1

[PATCH v4 04/20] powerpc: Provide do_ppc64_personality helper

[Rohan McLure]

Avoid duplication in future patch that will define the ppc64_personality
syscall handler in terms of the SYSCALL_DEFINE and COMPAT_SYSCALL_DEFINE
macros, by extracting the common body of ppc64_personality into a helper
function.

Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
---
V2  -> V3: New commit.
---
 arch/powerpc/kernel/syscalls.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/syscalls.c b/arch/powerpc/kernel/syscalls.c
index ef5896bee818..9f29e451e2de 100644
--- a/arch/powerpc/kernel/syscalls.c
+++ b/arch/powerpc/kernel/syscalls.c
@@ -64,7 +64,7 @@ SYSCALL_DEFINE6(mmap, unsigned long, addr, size_t, len,
 }
 
 #ifdef CONFIG_PPC64
-long ppc64_personality(unsigned long personality)
+static inline long do_ppc64_personality(unsigned long personality)
 {
 	long ret;
 
@@ -76,6 +76,10 @@ long ppc64_personality(unsigned long personality)
 		ret = (ret & ~PER_MASK) | PER_LINUX;
 	return ret;
 }
+long ppc64_personality(unsigned long personality)
+{
+	return do_ppc64_personality(personality);
+}
 #endif
 
 long ppc_fadvise64_64(int fd, int advice, u32 offset_high, u32 offset_low,
-- 
2.34.1

[PATCH v4 05/20] powerpc: Remove direct call to personality syscall handler

[Rohan McLure]

Syscall handlers should not be invoked internally by their symbol names,
as these symbols defined by the architecture-defined SYSCALL_DEFINE
macro. Fortunately, in the case of ppc64_personality, its call to
sys_personality can be replaced with an invocation to the
equivalent ksys_personality inline helper in <linux/syscalls.h>.

Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
---
V1 -> V2: Use inline helper to deduplicate bodies in compat/regular
implementations.
V3 -> V4: Move to be applied before syscall wrapper.
---
 arch/powerpc/kernel/syscalls.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/syscalls.c b/arch/powerpc/kernel/syscalls.c
index 9f29e451e2de..b8461128c8f7 100644
--- a/arch/powerpc/kernel/syscalls.c
+++ b/arch/powerpc/kernel/syscalls.c
@@ -71,7 +71,7 @@ static inline long do_ppc64_personality(unsigned long personality)
 	if (personality(current->personality) == PER_LINUX32
 	    && personality(personality) == PER_LINUX)
 		personality = (personality & ~PER_MASK) | PER_LINUX32;
-	ret = sys_personality(personality);
+	ret = ksys_personality(personality);
 	if (personality(ret) == PER_LINUX32)
 		ret = (ret & ~PER_MASK) | PER_LINUX;
 	return ret;
-- 
2.34.1

[PATCH v4 06/20] powerpc: Remove direct call to mmap2 syscall handlers

[Rohan McLure]

Syscall handlers should not be invoked internally by their symbol names,
as these symbols defined by the architecture-defined SYSCALL_DEFINE
macro. Move the compatibility syscall definition for mmap2 to
syscalls.c, so that all mmap implementations can share an inline helper
function, as is done with the personality handlers.

Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
---
V1 -> V2: Move mmap2 compat implementation to asm/kernel/syscalls.c.
V3 -> V4: Move to be applied before syscall wrapper introduced.
---
 arch/powerpc/kernel/sys_ppc32.c |  9 ---------
 arch/powerpc/kernel/syscalls.c  | 11 +++++++++++
 2 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/arch/powerpc/kernel/sys_ppc32.c b/arch/powerpc/kernel/sys_ppc32.c
index f4edcc9489fb..bc6491ed6454 100644
--- a/arch/powerpc/kernel/sys_ppc32.c
+++ b/arch/powerpc/kernel/sys_ppc32.c
@@ -25,7 +25,6 @@
 #include <linux/poll.h>
 #include <linux/personality.h>
 #include <linux/stat.h>
-#include <linux/mman.h>
 #include <linux/in.h>
 #include <linux/syscalls.h>
 #include <linux/unistd.h>
@@ -48,14 +47,6 @@
 #include <asm/syscalls.h>
 #include <asm/switch_to.h>
 
-unsigned long compat_sys_mmap2(unsigned long addr, size_t len,
-			  unsigned long prot, unsigned long flags,
-			  unsigned long fd, unsigned long pgoff)
-{
-	/* This should remain 12 even if PAGE_SIZE changes */
-	return sys_mmap(addr, len, prot, flags, fd, pgoff << 12);
-}
-
 /* 
  * long long munging:
  * The 32 bit ABI passes long longs in an odd even register pair.
diff --git a/arch/powerpc/kernel/syscalls.c b/arch/powerpc/kernel/syscalls.c
index b8461128c8f7..32fadf3c2cd3 100644
--- a/arch/powerpc/kernel/syscalls.c
+++ b/arch/powerpc/kernel/syscalls.c
@@ -56,6 +56,17 @@ SYSCALL_DEFINE6(mmap2, unsigned long, addr, size_t, len,
 	return do_mmap2(addr, len, prot, flags, fd, pgoff, PAGE_SHIFT-12);
 }
 
+#ifdef CONFIG_COMPAT
+COMPAT_SYSCALL_DEFINE6(mmap2,
+		       unsigned long, addr, size_t, len,
+		       unsigned long, prot, unsigned long, flags,
+		       unsigned long, fd, unsigned long, pgoff)
+{
+	/* This should remain 12 even if PAGE_SIZE changes */
+	return do_mmap2(addr, len, prot, flags, fd, pgoff << 12, PAGE_SHIFT-12);
+}
+#endif
+
 SYSCALL_DEFINE6(mmap, unsigned long, addr, size_t, len,
 		unsigned long, prot, unsigned long, flags,
 		unsigned long, fd, off_t, offset)
-- 
2.34.1

[PATCH v4 07/20] powerpc: Adopt SYSCALL_DEFINE for arch-specific syscall handlers

[Rohan McLure]

Arch-specific implementations of syscall handlers are currently used
over generic implementations for the following reasons:

1. Semantics unique to powerpc
2. Compatibility syscalls require 'argument padding' to comply with
   64-bit argument convention in ELF32 abi.
3. Parameter types or order is different in other architectures.

These syscall handlers have been defined prior to this patch series
without invoking the SYSCALL_DEFINE or COMPAT_SYSCALL_DEFINE macros with
custom input and output types. We remove every such direct definition in
favour of the aforementioned macros.

Also update syscalls.tbl in order to refer to the symbol names generated
by each of these macros. Since ppc64_personality can be called by both
64 bit and 32 bit binaries through compatibility, we must generate both
both compat_sys_ and sys_ symbols for this handler.

A number of architectures including arm and powerpc agree on an
alternative argument order and numbering for most of these arch-specific
handlers. A future patch series may allow for asm/unistd.h to signal
through its defines that a generic implementation of these syscall
handlers with the correct calling convention be omitted, through the
__ARCH_WANT_COMPAT_SYS_... convention.

Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
---
V1 -> V2: All syscall handlers wrapped by this macro.
V2 -> V3: Move creation of do_ppc64_personality helper to prior patch.
V3 -> V4: Fix parenthesis alignment. Don't emit sys_*** symbols.
---
 arch/powerpc/include/asm/syscalls.h          | 10 ++--
 arch/powerpc/kernel/sys_ppc32.c              | 45 ++++++++++--------
 arch/powerpc/kernel/syscalls.c               | 17 +++++--
 arch/powerpc/kernel/syscalls/syscall.tbl     | 22 ++++-----
 .../arch/powerpc/entry/syscalls/syscall.tbl  | 22 ++++-----
 5 files changed, 64 insertions(+), 52 deletions(-)

diff --git a/arch/powerpc/include/asm/syscalls.h b/arch/powerpc/include/asm/syscalls.h
index 739498c358a1..3e3aff0835a6 100644
--- a/arch/powerpc/include/asm/syscalls.h
+++ b/arch/powerpc/include/asm/syscalls.h
@@ -16,10 +16,10 @@ long sys_mmap(unsigned long addr, size_t len,
 long sys_mmap2(unsigned long addr, size_t len,
 	       unsigned long prot, unsigned long flags,
 	       unsigned long fd, unsigned long pgoff);
-long ppc64_personality(unsigned long personality);
+long sys_ppc64_personality(unsigned long personality);
 long sys_rtas(struct rtas_args __user *uargs);
-long ppc_fadvise64_64(int fd, int advice, u32 offset_high, u32 offset_low,
-		      u32 len_high, u32 len_low);
+long sys_ppc_fadvise64_64(int fd, int advice, u32 offset_high, u32 offset_low,
+			  u32 len_high, u32 len_low);
 
 #ifdef CONFIG_COMPAT
 unsigned long compat_sys_mmap2(unsigned long addr, size_t len,
@@ -40,8 +40,8 @@ int compat_sys_truncate64(const char __user *path, u32 reg4,
 int compat_sys_ftruncate64(unsigned int fd, u32 reg4, unsigned long len1,
 			   unsigned long len2);
 
-long ppc32_fadvise64(int fd, u32 unused, u32 offset1, u32 offset2,
-		     size_t len, int advice);
+long compat_sys_ppc32_fadvise64(int fd, u32 unused, u32 offset1, u32 offset2,
+				size_t len, int advice);
 
 long compat_sys_sync_file_range2(int fd, unsigned int flags,
 				 unsigned int offset1, unsigned int offset2,
diff --git a/arch/powerpc/kernel/sys_ppc32.c b/arch/powerpc/kernel/sys_ppc32.c
index bc6491ed6454..dd9039671227 100644
--- a/arch/powerpc/kernel/sys_ppc32.c
+++ b/arch/powerpc/kernel/sys_ppc32.c
@@ -59,52 +59,55 @@
 #define merge_64(high, low) ((u64)high << 32) | low
 #endif
 
-compat_ssize_t compat_sys_pread64(unsigned int fd, char __user *ubuf, compat_size_t count,
-			     u32 reg6, u32 pos1, u32 pos2)
+COMPAT_SYSCALL_DEFINE6(ppc_pread64,
+		       unsigned int, fd,
+		       char __user *, ubuf, compat_size_t, count,
+		       u32, reg6, u32, pos1, u32, pos2)
 {
 	return ksys_pread64(fd, ubuf, count, merge_64(pos1, pos2));
 }
 
-compat_ssize_t compat_sys_pwrite64(unsigned int fd, const char __user *ubuf, compat_size_t count,
-			      u32 reg6, u32 pos1, u32 pos2)
+COMPAT_SYSCALL_DEFINE6(ppc_pwrite64,
+		       unsigned int, fd,
+		       const char __user *, ubuf, compat_size_t, count,
+		       u32, reg6, u32, pos1, u32, pos2)
 {
 	return ksys_pwrite64(fd, ubuf, count, merge_64(pos1, pos2));
 }
 
-compat_ssize_t compat_sys_readahead(int fd, u32 r4, u32 offset1, u32 offset2, u32 count)
+COMPAT_SYSCALL_DEFINE5(ppc_readahead,
+		       int, fd, u32, r4,
+		       u32, offset1, u32, offset2, u32, count)
 {
 	return ksys_readahead(fd, merge_64(offset1, offset2), count);
 }
 
-int compat_sys_truncate64(const char __user * path, u32 reg4,
-				unsigned long len1, unsigned long len2)
+COMPAT_SYSCALL_DEFINE4(ppc_truncate64,
+		       const char __user *, path, u32, reg4,
+		       unsigned long, len1, unsigned long, len2)
 {
 	return ksys_truncate(path, merge_64(len1, len2));
 }
 
-long compat_sys_fallocate(int fd, int mode, u32 offset1, u32 offset2,
-				     u32 len1, u32 len2)
-{
-	return ksys_fallocate(fd, mode, ((loff_t)offset1 << 32) | offset2,
-			     merge_64(len1, len2));
-}
-
-int compat_sys_ftruncate64(unsigned int fd, u32 reg4, unsigned long len1,
-				 unsigned long len2)
+COMPAT_SYSCALL_DEFINE4(ppc_ftruncate64,
+		       unsigned int, fd, u32, reg4,
+		       unsigned long, len1, unsigned long, len2)
 {
 	return ksys_ftruncate(fd, merge_64(len1, len2));
 }
 
-long ppc32_fadvise64(int fd, u32 unused, u32 offset1, u32 offset2,
-		     size_t len, int advice)
+COMPAT_SYSCALL_DEFINE6(ppc32_fadvise64,
+		       int, fd, u32, unused, u32, offset1, u32, offset2,
+		       size_t, len, int, advice)
 {
 	return ksys_fadvise64_64(fd, merge_64(offset1, offset2), len,
 				 advice);
 }
 
-long compat_sys_sync_file_range2(int fd, unsigned int flags,
-				   unsigned offset1, unsigned offset2,
-				   unsigned nbytes1, unsigned nbytes2)
+COMPAT_SYSCALL_DEFINE6(ppc_sync_file_range2,
+		       int, fd, unsigned int, flags,
+		       unsigned int, offset1, unsigned int, offset2,
+		       unsigned int, nbytes1, unsigned int, nbytes2)
 {
 	loff_t offset = merge_64(offset1, offset2);
 	loff_t nbytes = merge_64(nbytes1, nbytes2);
diff --git a/arch/powerpc/kernel/syscalls.c b/arch/powerpc/kernel/syscalls.c
index 32fadf3c2cd3..2d4c62e5bac7 100644
--- a/arch/powerpc/kernel/syscalls.c
+++ b/arch/powerpc/kernel/syscalls.c
@@ -87,14 +87,23 @@ static inline long do_ppc64_personality(unsigned long personality)
 		ret = (ret & ~PER_MASK) | PER_LINUX;
 	return ret;
 }
-long ppc64_personality(unsigned long personality)
+
+SYSCALL_DEFINE1(ppc64_personality, unsigned long, personality)
 {
 	return do_ppc64_personality(personality);
 }
-#endif
 
-long ppc_fadvise64_64(int fd, int advice, u32 offset_high, u32 offset_low,
-		      u32 len_high, u32 len_low)
+#ifdef CONFIG_COMPAT
+COMPAT_SYSCALL_DEFINE1(ppc64_personality, unsigned long, personality)
+{
+	return do_ppc64_personality(personality);
+}
+#endif /* CONFIG_COMPAT */
+#endif /* CONFIG_PPC64 */
+
+SYSCALL_DEFINE6(ppc_fadvise64_64,
+		int, fd, int, advice, u32, offset_high, u32, offset_low,
+		u32, len_high, u32, len_low)
 {
 	return ksys_fadvise64_64(fd, (u64)offset_high << 32 | offset_low,
 				 (u64)len_high << 32 | len_low, advice);
diff --git a/arch/powerpc/kernel/syscalls/syscall.tbl b/arch/powerpc/kernel/syscalls/syscall.tbl
index 4cbbb810ae10..b4c970c9c6b1 100644
--- a/arch/powerpc/kernel/syscalls/syscall.tbl
+++ b/arch/powerpc/kernel/syscalls/syscall.tbl
@@ -178,9 +178,9 @@
 133	common	fchdir				sys_fchdir
 134	common	bdflush				sys_ni_syscall
 135	common	sysfs				sys_sysfs
-136	32	personality			sys_personality			ppc64_personality
-136	64	personality			ppc64_personality
-136	spu	personality			ppc64_personality
+136	32	personality			sys_personality			compat_sys_ppc64_personality
+136	64	personality			sys_ppc64_personality
+136	spu	personality			sys_ppc64_personality
 137	common	afs_syscall			sys_ni_syscall
 138	common	setfsuid			sys_setfsuid
 139	common	setfsgid			sys_setfsgid
@@ -228,8 +228,8 @@
 176	64	rt_sigtimedwait			sys_rt_sigtimedwait
 177	nospu 	rt_sigqueueinfo			sys_rt_sigqueueinfo		compat_sys_rt_sigqueueinfo
 178	nospu 	rt_sigsuspend			sys_rt_sigsuspend		compat_sys_rt_sigsuspend
-179	common	pread64				sys_pread64			compat_sys_pread64
-180	common	pwrite64			sys_pwrite64			compat_sys_pwrite64
+179	common	pread64				sys_pread64			compat_sys_ppc_pread64
+180	common	pwrite64			sys_pwrite64			compat_sys_ppc_pwrite64
 181	common	chown				sys_chown
 182	common	getcwd				sys_getcwd
 183	common	capget				sys_capget
@@ -242,10 +242,10 @@
 188	common 	putpmsg				sys_ni_syscall
 189	nospu	vfork				sys_vfork
 190	common	ugetrlimit			sys_getrlimit			compat_sys_getrlimit
-191	common	readahead			sys_readahead			compat_sys_readahead
+191	common	readahead			sys_readahead			compat_sys_ppc_readahead
 192	32	mmap2				sys_mmap2			compat_sys_mmap2
-193	32	truncate64			sys_truncate64			compat_sys_truncate64
-194	32	ftruncate64			sys_ftruncate64			compat_sys_ftruncate64
+193	32	truncate64			sys_truncate64			compat_sys_ppc_truncate64
+194	32	ftruncate64			sys_ftruncate64			compat_sys_ppc_ftruncate64
 195	32	stat64				sys_stat64
 196	32	lstat64				sys_lstat64
 197	32	fstat64				sys_fstat64
@@ -288,7 +288,7 @@
 230	common	io_submit			sys_io_submit			compat_sys_io_submit
 231	common	io_cancel			sys_io_cancel
 232	nospu	set_tid_address			sys_set_tid_address
-233	common	fadvise64			sys_fadvise64			ppc32_fadvise64
+233	common	fadvise64			sys_fadvise64			compat_sys_ppc32_fadvise64
 234	nospu	exit_group			sys_exit_group
 235	nospu	lookup_dcookie			sys_lookup_dcookie		compat_sys_lookup_dcookie
 236	common	epoll_create			sys_epoll_create
@@ -323,7 +323,7 @@
 251	spu	utimes				sys_utimes
 252	common	statfs64			sys_statfs64			compat_sys_statfs64
 253	common	fstatfs64			sys_fstatfs64			compat_sys_fstatfs64
-254	32	fadvise64_64			ppc_fadvise64_64
+254	32	fadvise64_64			sys_ppc_fadvise64_64
 254	spu	fadvise64_64			sys_ni_syscall
 255	common	rtas				sys_rtas
 256	32	sys_debug_setcontext		sys_debug_setcontext		sys_ni_syscall
@@ -390,7 +390,7 @@
 305	common	signalfd			sys_signalfd			compat_sys_signalfd
 306	common	timerfd_create			sys_timerfd_create
 307	common	eventfd				sys_eventfd
-308	common	sync_file_range2		sys_sync_file_range2		compat_sys_sync_file_range2
+308	common	sync_file_range2		sys_sync_file_range2		compat_sys_ppc_sync_file_range2
 309	nospu	fallocate			sys_fallocate			compat_sys_fallocate
 310	nospu	subpage_prot			sys_subpage_prot
 311	32	timerfd_settime			sys_timerfd_settime32
diff --git a/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl b/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl
index 4cbbb810ae10..b4c970c9c6b1 100644
--- a/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl
+++ b/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl
@@ -178,9 +178,9 @@
 133	common	fchdir				sys_fchdir
 134	common	bdflush				sys_ni_syscall
 135	common	sysfs				sys_sysfs
-136	32	personality			sys_personality			ppc64_personality
-136	64	personality			ppc64_personality
-136	spu	personality			ppc64_personality
+136	32	personality			sys_personality			compat_sys_ppc64_personality
+136	64	personality			sys_ppc64_personality
+136	spu	personality			sys_ppc64_personality
 137	common	afs_syscall			sys_ni_syscall
 138	common	setfsuid			sys_setfsuid
 139	common	setfsgid			sys_setfsgid
@@ -228,8 +228,8 @@
 176	64	rt_sigtimedwait			sys_rt_sigtimedwait
 177	nospu 	rt_sigqueueinfo			sys_rt_sigqueueinfo		compat_sys_rt_sigqueueinfo
 178	nospu 	rt_sigsuspend			sys_rt_sigsuspend		compat_sys_rt_sigsuspend
-179	common	pread64				sys_pread64			compat_sys_pread64
-180	common	pwrite64			sys_pwrite64			compat_sys_pwrite64
+179	common	pread64				sys_pread64			compat_sys_ppc_pread64
+180	common	pwrite64			sys_pwrite64			compat_sys_ppc_pwrite64
 181	common	chown				sys_chown
 182	common	getcwd				sys_getcwd
 183	common	capget				sys_capget
@@ -242,10 +242,10 @@
 188	common 	putpmsg				sys_ni_syscall
 189	nospu	vfork				sys_vfork
 190	common	ugetrlimit			sys_getrlimit			compat_sys_getrlimit
-191	common	readahead			sys_readahead			compat_sys_readahead
+191	common	readahead			sys_readahead			compat_sys_ppc_readahead
 192	32	mmap2				sys_mmap2			compat_sys_mmap2
-193	32	truncate64			sys_truncate64			compat_sys_truncate64
-194	32	ftruncate64			sys_ftruncate64			compat_sys_ftruncate64
+193	32	truncate64			sys_truncate64			compat_sys_ppc_truncate64
+194	32	ftruncate64			sys_ftruncate64			compat_sys_ppc_ftruncate64
 195	32	stat64				sys_stat64
 196	32	lstat64				sys_lstat64
 197	32	fstat64				sys_fstat64
@@ -288,7 +288,7 @@
 230	common	io_submit			sys_io_submit			compat_sys_io_submit
 231	common	io_cancel			sys_io_cancel
 232	nospu	set_tid_address			sys_set_tid_address
-233	common	fadvise64			sys_fadvise64			ppc32_fadvise64
+233	common	fadvise64			sys_fadvise64			compat_sys_ppc32_fadvise64
 234	nospu	exit_group			sys_exit_group
 235	nospu	lookup_dcookie			sys_lookup_dcookie		compat_sys_lookup_dcookie
 236	common	epoll_create			sys_epoll_create
@@ -323,7 +323,7 @@
 251	spu	utimes				sys_utimes
 252	common	statfs64			sys_statfs64			compat_sys_statfs64
 253	common	fstatfs64			sys_fstatfs64			compat_sys_fstatfs64
-254	32	fadvise64_64			ppc_fadvise64_64
+254	32	fadvise64_64			sys_ppc_fadvise64_64
 254	spu	fadvise64_64			sys_ni_syscall
 255	common	rtas				sys_rtas
 256	32	sys_debug_setcontext		sys_debug_setcontext		sys_ni_syscall
@@ -390,7 +390,7 @@
 305	common	signalfd			sys_signalfd			compat_sys_signalfd
 306	common	timerfd_create			sys_timerfd_create
 307	common	eventfd				sys_eventfd
-308	common	sync_file_range2		sys_sync_file_range2		compat_sys_sync_file_range2
+308	common	sync_file_range2		sys_sync_file_range2		compat_sys_ppc_sync_file_range2
 309	nospu	fallocate			sys_fallocate			compat_sys_fallocate
 310	nospu	subpage_prot			sys_subpage_prot
 311	32	timerfd_settime			sys_timerfd_settime32
-- 
2.34.1

[PATCH v4 08/20] powerpc: Include all arch-specific syscall prototypes

[Rohan McLure]

Forward declare all syscall handler prototypes where a generic prototype
is not provided in either linux/syscalls.h or linux/compat.h in
asm/syscalls.h. This is required for compile-time type-checking for
syscall handlers, which is implemented later in this series.

32-bit compatibility syscall handlers are expressed in terms of types in
ppc32.h. Expose this header globally.

Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
---
V1 -> V2: Explicitly include prototypes.
V2 -> V3: Remove extraneous #include <asm/compat.h> and ppc_fallocate
prototype. Rename header.
---
 arch/powerpc/include/asm/syscalls.h          | 90 +++++++++++++-----
 .../ppc32.h => include/asm/syscalls_32.h}    |  0
 arch/powerpc/kernel/signal_32.c              |  2 +-
 arch/powerpc/perf/callchain_32.c             |  2 +-
 4 files changed, 70 insertions(+), 24 deletions(-)

diff --git a/arch/powerpc/include/asm/syscalls.h b/arch/powerpc/include/asm/syscalls.h
index 3e3aff0835a6..91417dee534e 100644
--- a/arch/powerpc/include/asm/syscalls.h
+++ b/arch/powerpc/include/asm/syscalls.h
@@ -8,45 +8,91 @@
 #include <linux/types.h>
 #include <linux/compat.h>
 
+#ifdef CONFIG_PPC64
+#include <asm/syscalls_32.h>
+#endif
+#include <asm/unistd.h>
+#include <asm/ucontext.h>
+
 struct rtas_args;
 
+#ifndef CONFIG_ARCH_HAS_SYSCALL_WRAPPER
+
+/*
+ * PowerPC architecture-specific syscalls
+ */
+
+long sys_rtas(struct rtas_args __user *uargs);
+long sys_ni_syscall(void);
+
+#ifdef CONFIG_PPC64
+long sys_ppc64_personality(unsigned long personality);
+#ifdef CONFIG_COMPAT
+long compat_sys_ppc64_personality(unsigned long personality);
+#endif /* CONFIG_COMPAT */
+#endif /* CONFIG_PPC64 */
+
+/* Parameters are reordered for powerpc to avoid padding */
+long sys_ppc_fadvise64_64(int fd, int advice,
+			  u32 offset_high, u32 offset_low,
+			  u32 len_high, u32 len_low);
+long sys_swapcontext(struct ucontext __user *old_ctx,
+		     struct ucontext __user *new_ctx, long ctx_size);
 long sys_mmap(unsigned long addr, size_t len,
 	      unsigned long prot, unsigned long flags,
 	      unsigned long fd, off_t offset);
 long sys_mmap2(unsigned long addr, size_t len,
 	       unsigned long prot, unsigned long flags,
 	       unsigned long fd, unsigned long pgoff);
-long sys_ppc64_personality(unsigned long personality);
-long sys_rtas(struct rtas_args __user *uargs);
-long sys_ppc_fadvise64_64(int fd, int advice, u32 offset_high, u32 offset_low,
-			  u32 len_high, u32 len_low);
+long sys_switch_endian(void);
 
-#ifdef CONFIG_COMPAT
-unsigned long compat_sys_mmap2(unsigned long addr, size_t len,
-			       unsigned long prot, unsigned long flags,
-			       unsigned long fd, unsigned long pgoff);
-
-compat_ssize_t compat_sys_pread64(unsigned int fd, char __user *ubuf, compat_size_t count,
-				  u32 reg6, u32 pos1, u32 pos2);
+#ifdef CONFIG_PPC32
+long sys_sigreturn(void);
+long sys_debug_setcontext(struct ucontext __user *ctx, int ndbg,
+			  struct sig_dbg_op __user *dbg);
+#endif
 
-compat_ssize_t compat_sys_pwrite64(unsigned int fd, const char __user *ubuf, compat_size_t count,
-				   u32 reg6, u32 pos1, u32 pos2);
+long sys_rt_sigreturn(void);
 
-compat_ssize_t compat_sys_readahead(int fd, u32 r4, u32 offset1, u32 offset2, u32 count);
+long sys_subpage_prot(unsigned long addr,
+		      unsigned long len, u32 __user *map);
 
-int compat_sys_truncate64(const char __user *path, u32 reg4,
-			  unsigned long len1, unsigned long len2);
+#ifdef CONFIG_COMPAT
+long compat_sys_swapcontext(struct ucontext32 __user *old_ctx,
+			    struct ucontext32 __user *new_ctx,
+			    int ctx_size);
+long compat_sys_old_getrlimit(unsigned int resource,
+			      struct compat_rlimit __user *rlim);
+long compat_sys_sigreturn(void);
+long compat_sys_rt_sigreturn(void);
 
-int compat_sys_ftruncate64(unsigned int fd, u32 reg4, unsigned long len1,
-			   unsigned long len2);
+/* Architecture-specific implementations in sys_ppc32.c */
 
+long compat_sys_mmap2(unsigned long addr, size_t len,
+		      unsigned long prot, unsigned long flags,
+		      unsigned long fd, unsigned long pgoff);
+long compat_sys_ppc_pread64(unsigned int fd,
+			    char __user *ubuf, compat_size_t count,
+			    u32 reg6, u32 pos1, u32 pos2);
+long compat_sys_ppc_pwrite64(unsigned int fd,
+			     const char __user *ubuf, compat_size_t count,
+			     u32 reg6, u32 pos1, u32 pos2);
+long compat_sys_ppc_readahead(int fd, u32 r4,
+			      u32 offset1, u32 offset2, u32 count);
+long compat_sys_ppc_truncate64(const char __user *path, u32 reg4,
+			       unsigned long len1, unsigned long len2);
+long compat_sys_ppc_ftruncate64(unsigned int fd, u32 reg4,
+				unsigned long len1, unsigned long len2);
 long compat_sys_ppc32_fadvise64(int fd, u32 unused, u32 offset1, u32 offset2,
 				size_t len, int advice);
+long compat_sys_ppc_sync_file_range2(int fd, unsigned int flags,
+				     unsigned int offset1,
+				     unsigned int offset2,
+				     unsigned int nbytes1,
+				     unsigned int nbytes2);
+#endif /* CONFIG_COMPAT */
 
-long compat_sys_sync_file_range2(int fd, unsigned int flags,
-				 unsigned int offset1, unsigned int offset2,
-				 unsigned int nbytes1, unsigned int nbytes2);
-#endif
+#endif /* CONFIG_ARCH_HAS_SYSCALL_WRAPPER */
 
 #endif /* __KERNEL__ */
 #endif /* __ASM_POWERPC_SYSCALLS_H */
diff --git a/arch/powerpc/kernel/ppc32.h b/arch/powerpc/include/asm/syscalls_32.h
similarity index 100%
rename from arch/powerpc/kernel/ppc32.h
rename to arch/powerpc/include/asm/syscalls_32.h
diff --git a/arch/powerpc/kernel/signal_32.c b/arch/powerpc/kernel/signal_32.c
index 157a7403e3eb..c114c7f25645 100644
--- a/arch/powerpc/kernel/signal_32.c
+++ b/arch/powerpc/kernel/signal_32.c
@@ -43,7 +43,7 @@
 #include <asm/tm.h>
 #include <asm/asm-prototypes.h>
 #ifdef CONFIG_PPC64
-#include "ppc32.h"
+#include <asm/syscalls_32.h>
 #include <asm/unistd.h>
 #else
 #include <asm/ucontext.h>
diff --git a/arch/powerpc/perf/callchain_32.c b/arch/powerpc/perf/callchain_32.c
index b83c47b7947f..ea8cfe3806dc 100644
--- a/arch/powerpc/perf/callchain_32.c
+++ b/arch/powerpc/perf/callchain_32.c
@@ -19,7 +19,7 @@
 #include "callchain.h"
 
 #ifdef CONFIG_PPC64
-#include "../kernel/ppc32.h"
+#include <asm/syscalls_32.h>
 #else  /* CONFIG_PPC64 */
 
 #define __SIGNAL_FRAMESIZE32	__SIGNAL_FRAMESIZE
-- 
2.34.1

[PATCH v4 09/20] powerpc: Enable compile-time check for syscall handlers

[Rohan McLure]

The table of syscall handlers and registered compatibility syscall
handlers has in past been produced using assembly, with function
references resolved at link time. This moves link-time errors to
compile-time, by rewriting systbl.S in C, and including the
linux/syscalls.h, linux/compat.h and asm/syscalls.h headers for
prototypes.

Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
---
V1 -> V2: New patch.
---
 arch/powerpc/kernel/{systbl.S => systbl.c} | 27 ++++++++++----------
 1 file changed, 14 insertions(+), 13 deletions(-)

diff --git a/arch/powerpc/kernel/systbl.S b/arch/powerpc/kernel/systbl.c
similarity index 59%
rename from arch/powerpc/kernel/systbl.S
rename to arch/powerpc/kernel/systbl.c
index cb3358886203..99ffdfef6b9c 100644
--- a/arch/powerpc/kernel/systbl.S
+++ b/arch/powerpc/kernel/systbl.c
@@ -10,31 +10,32 @@
  * PPC64 updates by Dave Engebretsen (engebret@us.ibm.com) 
  */
 
-#include <asm/ppc_asm.h>
+#include <linux/syscalls.h>
+#include <linux/compat.h>
+#include <asm/unistd.h>
+#include <asm/syscalls.h>
 
-.section .rodata,"a"
+#define __SYSCALL_WITH_COMPAT(nr, entry, compat) __SYSCALL(nr, entry)
 
-#ifdef CONFIG_PPC64
-	.p2align	3
-#define __SYSCALL(nr, entry)	.8byte entry
+#ifdef CONFIG_ARCH_HAS_SYSCALL_WRAPPER
+#define __SYSCALL(nr, entry) [nr] = __powerpc_##entry,
+#define __powerpc_sys_ni_syscall	sys_ni_syscall
 #else
-#define __SYSCALL(nr, entry)	.long entry
+#define __SYSCALL(nr, entry) [nr] = entry,
 #endif
 
-#define __SYSCALL_WITH_COMPAT(nr, native, compat)	__SYSCALL(nr, native)
-.globl sys_call_table
-sys_call_table:
+void *sys_call_table[] = {
 #ifdef CONFIG_PPC64
 #include <asm/syscall_table_64.h>
 #else
 #include <asm/syscall_table_32.h>
 #endif
+};
 
 #ifdef CONFIG_COMPAT
 #undef __SYSCALL_WITH_COMPAT
 #define __SYSCALL_WITH_COMPAT(nr, native, compat)	__SYSCALL(nr, compat)
-.globl compat_sys_call_table
-compat_sys_call_table:
-#define compat_sys_sigsuspend	sys_sigsuspend
+void *compat_sys_call_table[] = {
 #include <asm/syscall_table_32.h>
-#endif
+};
+#endif /* CONFIG_COMPAT */
-- 
2.34.1

[PATCH v4 10/20] powerpc: Use common syscall handler type

[Rohan McLure]

Cause syscall handlers to be typed as follows when called indirectly
throughout the kernel.

typedef long (*syscall_fn)(unsigned long, unsigned long, unsigned long,
                           unsigned long, unsigned long, unsigned long);

Since both 32 and 64-bit abis allow for at least the first six
machine-word length parameters to a function to be passed by registers,
even handlers which admit fewer than six parameters may be viewed as
having the above type.

Fixup comparisons in VDSO to avoid pointer-integer comparison. Introduce
explicit cast on systems with SPUs.

Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
---
V1 -> V2: New patch.
V2 -> V3: Remove unnecessary cast from const syscall_fn to syscall_fn
---
 arch/powerpc/include/asm/syscall.h          | 7 +++++--
 arch/powerpc/include/asm/syscalls.h         | 1 +
 arch/powerpc/kernel/systbl.c                | 6 +++---
 arch/powerpc/kernel/vdso.c                  | 4 ++--
 arch/powerpc/platforms/cell/spu_callbacks.c | 6 +++---
 5 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/include/asm/syscall.h b/arch/powerpc/include/asm/syscall.h
index 25fc8ad9a27a..d2a8dfd5de33 100644
--- a/arch/powerpc/include/asm/syscall.h
+++ b/arch/powerpc/include/asm/syscall.h
@@ -14,9 +14,12 @@
 #include <linux/sched.h>
 #include <linux/thread_info.h>
 
+typedef long (*syscall_fn)(unsigned long, unsigned long, unsigned long,
+			   unsigned long, unsigned long, unsigned long);
+
 /* ftrace syscalls requires exporting the sys_call_table */
-extern const unsigned long sys_call_table[];
-extern const unsigned long compat_sys_call_table[];
+extern const syscall_fn sys_call_table[];
+extern const syscall_fn compat_sys_call_table[];
 
 static inline int syscall_get_nr(struct task_struct *task, struct pt_regs *regs)
 {
diff --git a/arch/powerpc/include/asm/syscalls.h b/arch/powerpc/include/asm/syscalls.h
index 91417dee534e..e979b7593d2b 100644
--- a/arch/powerpc/include/asm/syscalls.h
+++ b/arch/powerpc/include/asm/syscalls.h
@@ -8,6 +8,7 @@
 #include <linux/types.h>
 #include <linux/compat.h>
 
+#include <asm/syscall.h>
 #ifdef CONFIG_PPC64
 #include <asm/syscalls_32.h>
 #endif
diff --git a/arch/powerpc/kernel/systbl.c b/arch/powerpc/kernel/systbl.c
index 99ffdfef6b9c..b88a9c2a1f50 100644
--- a/arch/powerpc/kernel/systbl.c
+++ b/arch/powerpc/kernel/systbl.c
@@ -21,10 +21,10 @@
 #define __SYSCALL(nr, entry) [nr] = __powerpc_##entry,
 #define __powerpc_sys_ni_syscall	sys_ni_syscall
 #else
-#define __SYSCALL(nr, entry) [nr] = entry,
+#define __SYSCALL(nr, entry) [nr] = (void *) entry,
 #endif
 
-void *sys_call_table[] = {
+const syscall_fn sys_call_table[] = {
 #ifdef CONFIG_PPC64
 #include <asm/syscall_table_64.h>
 #else
@@ -35,7 +35,7 @@ void *sys_call_table[] = {
 #ifdef CONFIG_COMPAT
 #undef __SYSCALL_WITH_COMPAT
 #define __SYSCALL_WITH_COMPAT(nr, native, compat)	__SYSCALL(nr, compat)
-void *compat_sys_call_table[] = {
+const syscall_fn compat_sys_call_table[] = {
 #include <asm/syscall_table_32.h>
 };
 #endif /* CONFIG_COMPAT */
diff --git a/arch/powerpc/kernel/vdso.c b/arch/powerpc/kernel/vdso.c
index 0da287544054..080c9e7de0c0 100644
--- a/arch/powerpc/kernel/vdso.c
+++ b/arch/powerpc/kernel/vdso.c
@@ -313,10 +313,10 @@ static void __init vdso_setup_syscall_map(void)
 	unsigned int i;
 
 	for (i = 0; i < NR_syscalls; i++) {
-		if (sys_call_table[i] != (unsigned long)&sys_ni_syscall)
+		if (sys_call_table[i] != (void *)&sys_ni_syscall)
 			vdso_data->syscall_map[i >> 5] |= 0x80000000UL >> (i & 0x1f);
 		if (IS_ENABLED(CONFIG_COMPAT) &&
-		    compat_sys_call_table[i] != (unsigned long)&sys_ni_syscall)
+		    compat_sys_call_table[i] != (void *)&sys_ni_syscall)
 			vdso_data->compat_syscall_map[i >> 5] |= 0x80000000UL >> (i & 0x1f);
 	}
 }
diff --git a/arch/powerpc/platforms/cell/spu_callbacks.c b/arch/powerpc/platforms/cell/spu_callbacks.c
index fe0d8797a00a..e780c14c5733 100644
--- a/arch/powerpc/platforms/cell/spu_callbacks.c
+++ b/arch/powerpc/platforms/cell/spu_callbacks.c
@@ -34,15 +34,15 @@
  *	mbind, mq_open, ipc, ...
  */
 
-static void *spu_syscall_table[] = {
+static const syscall_fn spu_syscall_table[] = {
 #define __SYSCALL_WITH_COMPAT(nr, entry, compat) __SYSCALL(nr, entry)
-#define __SYSCALL(nr, entry) [nr] = entry,
+#define __SYSCALL(nr, entry) [nr] = (void *) entry,
 #include <asm/syscall_table_spu.h>
 };
 
 long spu_sys_callback(struct spu_syscall_block *s)
 {
-	long (*syscall)(u64 a1, u64 a2, u64 a3, u64 a4, u64 a5, u64 a6);
+	syscall_fn syscall;
 
 	if (s->nr_ret >= ARRAY_SIZE(spu_syscall_table)) {
 		pr_debug("%s: invalid syscall #%lld", __func__, s->nr_ret);
-- 
2.34.1

[PATCH v4 11/20] powerpc: Add ZEROIZE_GPRS macros for register clears

[Rohan McLure]

Macros for restoring and saving registers to and from the stack exist.
Provide macros with the same interface for clearing a range of gprs by
setting each register's value in that range to zero.

The resulting macros are called ZEROIZE_GPRS and ZEROIZE_NVGPRS, keeping
with the naming of the accompanying restore and save macros, and usage
of zeroize to describe this operation elsewhere in the kernel.

Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
---
V1 -> V2: Change 'ZERO' usage in naming to 'NULLIFY', a more obvious verb
V2 -> V3: Change 'NULLIFY' usage in naming to 'ZEROIZE', which has
precedent in kernel and explicitly specifies that we are zeroing.
V3 -> V4: Update commit message to use zeroize.
---
 arch/powerpc/include/asm/ppc_asm.h | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/arch/powerpc/include/asm/ppc_asm.h b/arch/powerpc/include/asm/ppc_asm.h
index 83c02f5a7f2a..b95689ada59c 100644
--- a/arch/powerpc/include/asm/ppc_asm.h
+++ b/arch/powerpc/include/asm/ppc_asm.h
@@ -33,6 +33,20 @@
 	.endr
 .endm
 
+/*
+ * This expands to a sequence of register clears for regs start to end
+ * inclusive, of the form:
+ *
+ *   li rN, 0
+ */
+.macro ZEROIZE_REGS start, end
+	.Lreg=\start
+	.rept (\end - \start + 1)
+	li	.Lreg, 0
+	.Lreg=.Lreg+1
+	.endr
+.endm
+
 /*
  * Macros for storing registers into and loading registers from
  * exception frames.
@@ -49,6 +63,14 @@
 #define REST_NVGPRS(base)		REST_GPRS(13, 31, base)
 #endif
 
+#define	ZEROIZE_GPRS(start, end)	ZEROIZE_REGS start, end
+#ifdef __powerpc64__
+#define	ZEROIZE_NVGPRS()		ZEROIZE_GPRS(14, 31)
+#else
+#define	ZEROIZE_NVGPRS()		ZEROIZE_GPRS(13, 31)
+#endif
+#define	ZEROIZE_GPR(n)			ZEROIZE_GPRS(n, n)
+
 #define SAVE_GPR(n, base)		SAVE_GPRS(n, n, base)
 #define REST_GPR(n, base)		REST_GPRS(n, n, base)
 
-- 
2.34.1

[PATCH v4 12/20] Revert "powerpc/syscall: Save r3 in regs->orig_r3"

[Rohan McLure]

This reverts commit 8875f47b7681aa4e4484a9b612577b044725f839.

Save caller's original r3 state to the kernel stackframe before entering
system_call_exception. This allows for user registers to be cleared by
the time system_call_exception is entered, reducing the influence of
user registers on speculation within the kernel.

Prior to this commit, orig_r3 was saved at the beginning of
system_call_exception. Instead, save orig_r3 while the user value is
still live in r3.

Also replicate this early save in 32-bit. A similar save was removed in
commit 6f76a01173cc ("powerpc/syscall: implement system call entry/exit logic in C for PPC32")
when 32-bit adopted system_call_exception. Revert its removal of orig_r3
saves.

Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
---
V2 -> V3: New commit.
---
 arch/powerpc/kernel/entry_32.S     | 1 +
 arch/powerpc/kernel/interrupt_64.S | 2 ++
 arch/powerpc/kernel/syscall.c      | 1 -
 3 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index 1d599df6f169..44dfce9a60c5 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -101,6 +101,7 @@ __kuep_unlock:
 
 	.globl	transfer_to_syscall
 transfer_to_syscall:
+	stw	r3, ORIG_GPR3(r1)
 	stw	r11, GPR1(r1)
 	stw	r11, 0(r1)
 	mflr	r12
diff --git a/arch/powerpc/kernel/interrupt_64.S b/arch/powerpc/kernel/interrupt_64.S
index ce25b28cf418..71d2d9497283 100644
--- a/arch/powerpc/kernel/interrupt_64.S
+++ b/arch/powerpc/kernel/interrupt_64.S
@@ -91,6 +91,7 @@ _ASM_NOKPROBE_SYMBOL(system_call_vectored_\name)
 	li	r11,\trapnr
 	std	r11,_TRAP(r1)
 	std	r12,_CCR(r1)
+	std	r3,ORIG_GPR3(r1)
 	addi	r10,r1,STACK_FRAME_OVERHEAD
 	ld	r11,exception_marker@toc(r2)
 	std	r11,-16(r10)		/* "regshere" marker */
@@ -275,6 +276,7 @@ END_BTB_FLUSH_SECTION
 	std	r10,_LINK(r1)
 	std	r11,_TRAP(r1)
 	std	r12,_CCR(r1)
+	std	r3,ORIG_GPR3(r1)
 	addi	r10,r1,STACK_FRAME_OVERHEAD
 	ld	r11,exception_marker@toc(r2)
 	std	r11,-16(r10)		/* "regshere" marker */
diff --git a/arch/powerpc/kernel/syscall.c b/arch/powerpc/kernel/syscall.c
index 81ace9e8b72b..64102a64fd84 100644
--- a/arch/powerpc/kernel/syscall.c
+++ b/arch/powerpc/kernel/syscall.c
@@ -25,7 +25,6 @@ notrace long system_call_exception(long r3, long r4, long r5,
 	kuap_lock();
 
 	add_random_kstack_offset();
-	regs->orig_gpr3 = r3;
 
 	if (IS_ENABLED(CONFIG_PPC_IRQ_SOFT_MASK_DEBUG))
 		BUG_ON(irq_soft_mask_return() != IRQS_ALL_DISABLED);
-- 
2.34.1

[PATCH v4 13/20] powerpc: Provide syscall wrapper

[Rohan McLure]

Implement syscall wrapper as per s390, x86, arm64. When enabled
cause handlers to accept parameters from a stack frame rather than
from user scratch register state. This allows for user registers to be
safely cleared in order to reduce caller influence on speculation
within syscall routine. The wrapper is a macro that emits syscall
handler symbols that call into the target handler, obtaining its
parameters from a struct pt_regs on the stack.

As registers are already saved to the stack prior to calling
system_call_exception, it appears that this function is executed more
efficiently with the new stack-pointer convention than with parameters
passed by registers, avoiding the allocation of a stack frame for this
method. On a 32-bit system, we see >20% performance increases on the
null_syscall microbenchmark, and on a Power 8 the performance gains
amortise the cost of clearing and restoring registers which is
implemented at the end of this series, seeing final result of ~5.6%
performance improvement on null_syscall.

Syscalls are wrapped in this fashion on all platforms except for the
Cell processor as this commit does not provide SPU support. This can be
quickly fixed in a successive patch, but requires spu_sys_callback to
allocate a pt_regs structure to satisfy the wrapped calling convention.

Co-developed-by: Andrew Donnellan <ajd@linux.ibm.com>
Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com>
Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
---
V1 -> V2: Generate prototypes for symbols produced by the wrapper.
V2 -> V3: Rebased to remove conflict with 1547db7d1f44
("powerpc: Move system_call_exception() to syscall.c"). Also remove copy
from gpr3 save slot on stackframe to orig_r3's slot. Fix whitespace with
preprocessor defines in system_call_exception.
---
 arch/powerpc/Kconfig                       |  1 +
 arch/powerpc/include/asm/interrupt.h       |  3 +-
 arch/powerpc/include/asm/syscall.h         |  4 +
 arch/powerpc/include/asm/syscall_wrapper.h | 84 ++++++++++++++++++++
 arch/powerpc/include/asm/syscalls.h        | 25 +++++-
 arch/powerpc/kernel/entry_32.S             |  6 +-
 arch/powerpc/kernel/interrupt_64.S         | 16 ++--
 arch/powerpc/kernel/syscall.c              | 31 +++-----
 arch/powerpc/kernel/systbl.c               |  2 +
 arch/powerpc/kernel/vdso.c                 |  2 +
 10 files changed, 142 insertions(+), 32 deletions(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 4c466acdc70d..ef6c83e79c9b 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -137,6 +137,7 @@ config PPC
 	select ARCH_HAS_STRICT_KERNEL_RWX	if (PPC_BOOK3S || PPC_8xx || 40x) && !HIBERNATION
 	select ARCH_HAS_STRICT_KERNEL_RWX	if FSL_BOOKE && !HIBERNATION && !RANDOMIZE_BASE
 	select ARCH_HAS_STRICT_MODULE_RWX	if ARCH_HAS_STRICT_KERNEL_RWX
+	select ARCH_HAS_SYSCALL_WRAPPER		if !SPU_BASE
 	select ARCH_HAS_TICK_BROADCAST		if GENERIC_CLOCKEVENTS_BROADCAST
 	select ARCH_HAS_UACCESS_FLUSHCACHE
 	select ARCH_HAS_UBSAN_SANITIZE_ALL
diff --git a/arch/powerpc/include/asm/interrupt.h b/arch/powerpc/include/asm/interrupt.h
index 8069dbc4b8d1..3f9cad81585c 100644
--- a/arch/powerpc/include/asm/interrupt.h
+++ b/arch/powerpc/include/asm/interrupt.h
@@ -665,8 +665,7 @@ static inline void interrupt_cond_local_irq_enable(struct pt_regs *regs)
 		local_irq_enable();
 }
 
-long system_call_exception(long r3, long r4, long r5, long r6, long r7, long r8,
-			   unsigned long r0, struct pt_regs *regs);
+long system_call_exception(unsigned long r0, struct pt_regs *regs);
 notrace unsigned long syscall_exit_prepare(unsigned long r3, struct pt_regs *regs, long scv);
 notrace unsigned long interrupt_exit_user_prepare(struct pt_regs *regs);
 notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs);
diff --git a/arch/powerpc/include/asm/syscall.h b/arch/powerpc/include/asm/syscall.h
index d2a8dfd5de33..3dd36c5e334a 100644
--- a/arch/powerpc/include/asm/syscall.h
+++ b/arch/powerpc/include/asm/syscall.h
@@ -14,8 +14,12 @@
 #include <linux/sched.h>
 #include <linux/thread_info.h>
 
+#ifdef CONFIG_ARCH_HAS_SYSCALL_WRAPPER
+typedef long (*syscall_fn)(const struct pt_regs *);
+#else
 typedef long (*syscall_fn)(unsigned long, unsigned long, unsigned long,
 			   unsigned long, unsigned long, unsigned long);
+#endif
 
 /* ftrace syscalls requires exporting the sys_call_table */
 extern const syscall_fn sys_call_table[];
diff --git a/arch/powerpc/include/asm/syscall_wrapper.h b/arch/powerpc/include/asm/syscall_wrapper.h
new file mode 100644
index 000000000000..91bcfa40f740
--- /dev/null
+++ b/arch/powerpc/include/asm/syscall_wrapper.h
@@ -0,0 +1,84 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * syscall_wrapper.h - powerpc specific wrappers to syscall definitions
+ *
+ * Based on arch/{x86,arm64}/include/asm/syscall_wrapper.h
+ */
+
+#ifndef __ASM_SYSCALL_WRAPPER_H
+#define __ASM_SYSCALL_WRAPPER_H
+
+struct pt_regs;
+
+#define SC_POWERPC_REGS_TO_ARGS(x, ...)				\
+	__MAP(x,__SC_ARGS					\
+	      ,,regs->gpr[3],,regs->gpr[4],,regs->gpr[5]	\
+	      ,,regs->gpr[6],,regs->gpr[7],,regs->gpr[8])
+
+#ifdef CONFIG_COMPAT
+
+#define COMPAT_SYSCALL_DEFINEx(x, name, ...)						\
+	long __powerpc_compat_sys##name(const struct pt_regs *regs);			\
+	ALLOW_ERROR_INJECTION(__powerpc_compat_sys##name, ERRNO);			\
+	static long __se_compat_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__));		\
+	static inline long __do_compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));	\
+	long __powerpc_compat_sys##name(const struct pt_regs *regs)			\
+	{										\
+		return __se_compat_sys##name(SC_POWERPC_REGS_TO_ARGS(x,__VA_ARGS__));	\
+	}										\
+	static long __se_compat_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__))		\
+	{										\
+		return __do_compat_sys##name(__MAP(x,__SC_DELOUSE,__VA_ARGS__));	\
+	}										\
+	static inline long __do_compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))
+
+#define COMPAT_SYSCALL_DEFINE0(sname)						\
+	long __powerpc_compat_sys_##sname(const struct pt_regs *__unused);	\
+	ALLOW_ERROR_INJECTION(__powerpc_compat_sys_##sname, ERRNO);		\
+	long __powerpc_compat_sys_##sname(const struct pt_regs *__unused)
+
+#define COND_SYSCALL_COMPAT(name)						\
+	long __powerpc_compat_sys_##name(const struct pt_regs *regs);		\
+	long __weak __powerpc_compat_sys_##name(const struct pt_regs *regs)	\
+	{									\
+		return sys_ni_syscall();					\
+	}
+#define COMPAT_SYS_NI(name) \
+	SYSCALL_ALIAS(__powerpc_compat_sys_##name, sys_ni_posix_timers);
+
+#endif /* CONFIG_COMPAT */
+
+#define __SYSCALL_DEFINEx(x, name, ...)						\
+	long __powerpc_sys##name(const struct pt_regs *regs);			\
+	ALLOW_ERROR_INJECTION(__powerpc_sys##name, ERRNO);			\
+	static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__));		\
+	static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));	\
+	long __powerpc_sys##name(const struct pt_regs *regs)			\
+	{									\
+		return __se_sys##name(SC_POWERPC_REGS_TO_ARGS(x,__VA_ARGS__));	\
+	}									\
+	static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__))		\
+	{									\
+		long ret = __do_sys##name(__MAP(x,__SC_CAST,__VA_ARGS__));	\
+		__MAP(x,__SC_TEST,__VA_ARGS__);					\
+		__PROTECT(x, ret,__MAP(x,__SC_ARGS,__VA_ARGS__));		\
+		return ret;							\
+	}									\
+	static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))
+
+#define SYSCALL_DEFINE0(sname)							\
+	SYSCALL_METADATA(_##sname, 0);						\
+	long __powerpc_sys_##sname(const struct pt_regs *__unused);		\
+	ALLOW_ERROR_INJECTION(__powerpc_sys_##sname, ERRNO);			\
+	long __powerpc_sys_##sname(const struct pt_regs *__unused)
+
+#define COND_SYSCALL(name)							\
+	long __powerpc_sys_##name(const struct pt_regs *regs);			\
+	long __weak __powerpc_sys_##name(const struct pt_regs *regs)		\
+	{									\
+		return sys_ni_syscall();					\
+	}
+
+#define SYS_NI(name) SYSCALL_ALIAS(__powerpc_sys_##name, sys_ni_posix_timers);
+
+#endif /* __ASM_SYSCALL_WRAPPER_H */
diff --git a/arch/powerpc/include/asm/syscalls.h b/arch/powerpc/include/asm/syscalls.h
index e979b7593d2b..14af648ee82c 100644
--- a/arch/powerpc/include/asm/syscalls.h
+++ b/arch/powerpc/include/asm/syscalls.h
@@ -15,6 +15,12 @@
 #include <asm/unistd.h>
 #include <asm/ucontext.h>
 
+#ifndef CONFIG_ARCH_HAS_SYSCALL_WRAPPER
+long sys_ni_syscall(void);
+#else
+long sys_ni_syscall(const struct pt_regs *regs);
+#endif
+
 struct rtas_args;
 
 #ifndef CONFIG_ARCH_HAS_SYSCALL_WRAPPER
@@ -24,7 +30,6 @@ struct rtas_args;
  */
 
 long sys_rtas(struct rtas_args __user *uargs);
-long sys_ni_syscall(void);
 
 #ifdef CONFIG_PPC64
 long sys_ppc64_personality(unsigned long personality);
@@ -93,6 +98,24 @@ long compat_sys_ppc_sync_file_range2(int fd, unsigned int flags,
 				     unsigned int nbytes2);
 #endif /* CONFIG_COMPAT */
 
+#else
+
+#define __SYSCALL_WITH_COMPAT(nr, native, compat)	__SYSCALL(nr, native)
+#define __SYSCALL(nr, entry) \
+	long __powerpc_##entry(const struct pt_regs *regs);
+
+#ifdef CONFIG_PPC64
+#include <asm/syscall_table_64.h>
+#else
+#include <asm/syscall_table_32.h>
+#endif /* CONFIG_PPC64 */
+
+#ifdef CONFIG_COMPAT
+#undef __SYSCALL_WITH_COMPAT
+#define __SYSCALL_WITH_COMPAT(nr, native, compat)	__SYSCALL(nr, compat)
+#include <asm/syscall_table_32.h>
+#endif /* CONFIG_COMPAT */
+
 #endif /* CONFIG_ARCH_HAS_SYSCALL_WRAPPER */
 
 #endif /* __KERNEL__ */
diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index 44dfce9a60c5..8d6e02ef5dc0 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -122,9 +122,9 @@ transfer_to_syscall:
 	SAVE_NVGPRS(r1)
 	kuep_lock
 
-	/* Calling convention has r9 = orig r0, r10 = regs */
-	addi	r10,r1,STACK_FRAME_OVERHEAD
-	mr	r9,r0
+	/* Calling convention has r3 = orig r0, r4 = regs */
+	addi	r4,r1,STACK_FRAME_OVERHEAD
+	mr	r3,r0
 	bl	system_call_exception
 
 ret_from_syscall:
diff --git a/arch/powerpc/kernel/interrupt_64.S b/arch/powerpc/kernel/interrupt_64.S
index 71d2d9497283..0178aeba3820 100644
--- a/arch/powerpc/kernel/interrupt_64.S
+++ b/arch/powerpc/kernel/interrupt_64.S
@@ -92,9 +92,9 @@ _ASM_NOKPROBE_SYMBOL(system_call_vectored_\name)
 	std	r11,_TRAP(r1)
 	std	r12,_CCR(r1)
 	std	r3,ORIG_GPR3(r1)
-	addi	r10,r1,STACK_FRAME_OVERHEAD
+	addi	r4,r1,STACK_FRAME_OVERHEAD
 	ld	r11,exception_marker@toc(r2)
-	std	r11,-16(r10)		/* "regshere" marker */
+	std	r11,-16(r4)		/* "regshere" marker */
 
 BEGIN_FTR_SECTION
 	HMT_MEDIUM
@@ -109,8 +109,8 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
 	 * but this is the best we can do.
 	 */
 
-	/* Calling convention has r9 = orig r0, r10 = regs */
-	mr	r9,r0
+	/* Calling convention has r3 = orig r0, r4 = regs */
+	mr	r3,r0
 	bl	system_call_exception
 
 .Lsyscall_vectored_\name\()_exit:
@@ -277,9 +277,9 @@ END_BTB_FLUSH_SECTION
 	std	r11,_TRAP(r1)
 	std	r12,_CCR(r1)
 	std	r3,ORIG_GPR3(r1)
-	addi	r10,r1,STACK_FRAME_OVERHEAD
+	addi	r4,r1,STACK_FRAME_OVERHEAD
 	ld	r11,exception_marker@toc(r2)
-	std	r11,-16(r10)		/* "regshere" marker */
+	std	r11,-16(r4)		/* "regshere" marker */
 
 #ifdef CONFIG_PPC_BOOK3S
 	li	r11,1
@@ -300,8 +300,8 @@ END_BTB_FLUSH_SECTION
 	wrteei	1
 #endif
 
-	/* Calling convention has r9 = orig r0, r10 = regs */
-	mr	r9,r0
+	/* Calling convention has r3 = orig r0, r4 = regs */
+	mr	r3,r0
 	bl	system_call_exception
 
 .Lsyscall_exit:
diff --git a/arch/powerpc/kernel/syscall.c b/arch/powerpc/kernel/syscall.c
index 64102a64fd84..bda5221b420e 100644
--- a/arch/powerpc/kernel/syscall.c
+++ b/arch/powerpc/kernel/syscall.c
@@ -12,12 +12,8 @@
 #include <asm/unistd.h>
 
 
-typedef long (*syscall_fn)(long, long, long, long, long, long);
-
 /* Has to run notrace because it is entered not completely "reconciled" */
-notrace long system_call_exception(long r3, long r4, long r5,
-				   long r6, long r7, long r8,
-				   unsigned long r0, struct pt_regs *regs)
+notrace long system_call_exception(unsigned long r0, struct pt_regs *regs)
 {
 	long ret;
 	syscall_fn f;
@@ -138,12 +134,6 @@ notrace long system_call_exception(long r3, long r4, long r5,
 		r0 = do_syscall_trace_enter(regs);
 		if (unlikely(r0 >= NR_syscalls))
 			return regs->gpr[3];
-		r3 = regs->gpr[3];
-		r4 = regs->gpr[4];
-		r5 = regs->gpr[5];
-		r6 = regs->gpr[6];
-		r7 = regs->gpr[7];
-		r8 = regs->gpr[8];
 
 	} else if (unlikely(r0 >= NR_syscalls)) {
 		if (unlikely(trap_is_unsupported_scv(regs))) {
@@ -160,18 +150,23 @@ notrace long system_call_exception(long r3, long r4, long r5,
 	if (unlikely(is_compat_task())) {
 		f = (void *)compat_sys_call_table[r0];
 
-		r3 &= 0x00000000ffffffffULL;
-		r4 &= 0x00000000ffffffffULL;
-		r5 &= 0x00000000ffffffffULL;
-		r6 &= 0x00000000ffffffffULL;
-		r7 &= 0x00000000ffffffffULL;
-		r8 &= 0x00000000ffffffffULL;
+		regs->gpr[3] &= 0x00000000ffffffffULL;
+		regs->gpr[4] &= 0x00000000ffffffffULL;
+		regs->gpr[5] &= 0x00000000ffffffffULL;
+		regs->gpr[6] &= 0x00000000ffffffffULL;
+		regs->gpr[7] &= 0x00000000ffffffffULL;
+		regs->gpr[8] &= 0x00000000ffffffffULL;
 
 	} else {
 		f = (void *)sys_call_table[r0];
 	}
 
-	ret = f(r3, r4, r5, r6, r7, r8);
+#ifdef CONFIG_ARCH_HAS_SYSCALL_WRAPPER
+	ret = f(regs);
+#else
+	ret = f(regs->gpr[3], regs->gpr[4], regs->gpr[5],
+		regs->gpr[6], regs->gpr[7], regs->gpr[8]);
+#endif
 
 	/*
 	 * Ultimately, this value will get limited by KSTACK_OFFSET_MAX(),
diff --git a/arch/powerpc/kernel/systbl.c b/arch/powerpc/kernel/systbl.c
index b88a9c2a1f50..cb05e302ea58 100644
--- a/arch/powerpc/kernel/systbl.c
+++ b/arch/powerpc/kernel/systbl.c
@@ -15,8 +15,10 @@
 #include <asm/unistd.h>
 #include <asm/syscalls.h>
 
+#undef __SYSCALL_WITH_COMPAT
 #define __SYSCALL_WITH_COMPAT(nr, entry, compat) __SYSCALL(nr, entry)
 
+#undef __SYSCALL
 #ifdef CONFIG_ARCH_HAS_SYSCALL_WRAPPER
 #define __SYSCALL(nr, entry) [nr] = __powerpc_##entry,
 #define __powerpc_sys_ni_syscall	sys_ni_syscall
diff --git a/arch/powerpc/kernel/vdso.c b/arch/powerpc/kernel/vdso.c
index 080c9e7de0c0..88d83162eaf1 100644
--- a/arch/powerpc/kernel/vdso.c
+++ b/arch/powerpc/kernel/vdso.c
@@ -39,6 +39,8 @@
 extern char vdso32_start, vdso32_end;
 extern char vdso64_start, vdso64_end;
 
+long sys_ni_syscall(void);
+
 /*
  * The vdso data page (aka. systemcfg for old ppc64 fans) is here.
  * Once the early boot kernel code no longer needs to muck around
-- 
2.34.1

[PATCH v4 14/20] powerpc/64s: Clear/restore caller gprs in syscall interrupt/return

[Rohan McLure]

Clear user state in gprs (assign to zero) to reduce the influence of user
registers on speculation within kernel syscall handlers. Clears occur
at the very beginning of the sc and scv 0 interrupt handlers, with
restores occurring following the execution of the syscall handler.

Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
---
V1 -> V2: Update summary
V2 -> V3: Remove erroneous summary paragraph on syscall_exit_prepare
V3 -> V4: Use ZEROIZE instead of NULLIFY
---
 arch/powerpc/kernel/interrupt_64.S | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/kernel/interrupt_64.S b/arch/powerpc/kernel/interrupt_64.S
index 0178aeba3820..a8065209dd8c 100644
--- a/arch/powerpc/kernel/interrupt_64.S
+++ b/arch/powerpc/kernel/interrupt_64.S
@@ -70,7 +70,7 @@ _ASM_NOKPROBE_SYMBOL(system_call_vectored_\name)
 	ld	r2,PACATOC(r13)
 	mfcr	r12
 	li	r11,0
-	/* Can we avoid saving r3-r8 in common case? */
+	/* Save syscall parameters in r3-r8 */
 	std	r3,GPR3(r1)
 	std	r4,GPR4(r1)
 	std	r5,GPR5(r1)
@@ -109,6 +109,13 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
 	 * but this is the best we can do.
 	 */
 
+	/*
+	 * Zero user registers to prevent influencing speculative execution
+	 * state of kernel code.
+	 */
+	ZEROIZE_GPRS(5, 12)
+	ZEROIZE_NVGPRS()
+
 	/* Calling convention has r3 = orig r0, r4 = regs */
 	mr	r3,r0
 	bl	system_call_exception
@@ -139,6 +146,7 @@ BEGIN_FTR_SECTION
 	HMT_MEDIUM_LOW
 END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
 
+	REST_NVGPRS(r1)
 	cmpdi	r3,0
 	bne	.Lsyscall_vectored_\name\()_restore_regs
 
@@ -181,7 +189,6 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
 	ld	r4,_LINK(r1)
 	ld	r5,_XER(r1)
 
-	REST_NVGPRS(r1)
 	ld	r0,GPR0(r1)
 	mtcr	r2
 	mtctr	r3
@@ -249,7 +256,7 @@ END_BTB_FLUSH_SECTION
 	ld	r2,PACATOC(r13)
 	mfcr	r12
 	li	r11,0
-	/* Can we avoid saving r3-r8 in common case? */
+	/* Save syscall parameters in r3-r8 */
 	std	r3,GPR3(r1)
 	std	r4,GPR4(r1)
 	std	r5,GPR5(r1)
@@ -300,6 +307,13 @@ END_BTB_FLUSH_SECTION
 	wrteei	1
 #endif
 
+	/*
+	 * Zero user registers to prevent influencing speculative execution
+	 * state of kernel code.
+	 */
+	ZEROIZE_GPRS(5, 12)
+	ZEROIZE_NVGPRS()
+
 	/* Calling convention has r3 = orig r0, r4 = regs */
 	mr	r3,r0
 	bl	system_call_exception
@@ -342,6 +356,7 @@ BEGIN_FTR_SECTION
 	stdcx.	r0,0,r1			/* to clear the reservation */
 END_FTR_SECTION_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS)
 
+	REST_NVGPRS(r1)
 	cmpdi	r3,0
 	bne	.Lsyscall_restore_regs
 	/* Zero volatile regs that may contain sensitive kernel data */
@@ -377,7 +392,6 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
 .Lsyscall_restore_regs:
 	ld	r3,_CTR(r1)
 	ld	r4,_XER(r1)
-	REST_NVGPRS(r1)
 	mtctr	r3
 	mtspr	SPRN_XER,r4
 	ld	r0,GPR0(r1)
-- 
2.34.1

[PATCH v4 15/20] powerpc/64s: Use {ZEROIZE,SAVE,REST}_GPRS macros in sc, scv 0 handlers

[Rohan McLure]

Use the convenience macros for saving/clearing/restoring gprs in keeping
with syscall calling conventions. The plural variants of these macros
can store a range of registers for concision.

This works well when the user gpr value we are hoping to save is still
live. In the syscall interrupt handlers, user register state is
sometimes juggled between registers. Hold-off from issuing the SAVE_GPR
macro for applicable neighbouring lines to highlight the delicate
register save logic.

Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
---
V1 -> V2: Update summary
V2 -> V3: Update summary regarding exclusions for the SAVE_GPR marco.
Acknowledge new name for ZEROIZE_GPR{,S} macros.
---
 arch/powerpc/kernel/interrupt_64.S | 43 ++++++----------------------
 1 file changed, 9 insertions(+), 34 deletions(-)

diff --git a/arch/powerpc/kernel/interrupt_64.S b/arch/powerpc/kernel/interrupt_64.S
index a8065209dd8c..ad302ad93433 100644
--- a/arch/powerpc/kernel/interrupt_64.S
+++ b/arch/powerpc/kernel/interrupt_64.S
@@ -71,12 +71,7 @@ _ASM_NOKPROBE_SYMBOL(system_call_vectored_\name)
 	mfcr	r12
 	li	r11,0
 	/* Save syscall parameters in r3-r8 */
-	std	r3,GPR3(r1)
-	std	r4,GPR4(r1)
-	std	r5,GPR5(r1)
-	std	r6,GPR6(r1)
-	std	r7,GPR7(r1)
-	std	r8,GPR8(r1)
+	SAVE_GPRS(3, 8, r1)
 	/* Zero r9-r12, this should only be required when restoring all GPRs */
 	std	r11,GPR9(r1)
 	std	r11,GPR10(r1)
@@ -157,17 +152,10 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
 	/* Could zero these as per ABI, but we may consider a stricter ABI
 	 * which preserves these if libc implementations can benefit, so
 	 * restore them for now until further measurement is done. */
-	ld	r0,GPR0(r1)
-	ld	r4,GPR4(r1)
-	ld	r5,GPR5(r1)
-	ld	r6,GPR6(r1)
-	ld	r7,GPR7(r1)
-	ld	r8,GPR8(r1)
+	REST_GPR(0, r1)
+	REST_GPRS(4, 8, r1)
 	/* Zero volatile regs that may contain sensitive kernel data */
-	li	r9,0
-	li	r10,0
-	li	r11,0
-	li	r12,0
+	ZEROIZE_GPRS(9, 12)
 	mtspr	SPRN_XER,r0
 
 	/*
@@ -189,7 +177,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
 	ld	r4,_LINK(r1)
 	ld	r5,_XER(r1)
 
-	ld	r0,GPR0(r1)
+	REST_GPR(0, r1)
 	mtcr	r2
 	mtctr	r3
 	mtlr	r4
@@ -257,12 +245,7 @@ END_BTB_FLUSH_SECTION
 	mfcr	r12
 	li	r11,0
 	/* Save syscall parameters in r3-r8 */
-	std	r3,GPR3(r1)
-	std	r4,GPR4(r1)
-	std	r5,GPR5(r1)
-	std	r6,GPR6(r1)
-	std	r7,GPR7(r1)
-	std	r8,GPR8(r1)
+	SAVE_GPRS(3, 8, r1)
 	/* Zero r9-r12, this should only be required when restoring all GPRs */
 	std	r11,GPR9(r1)
 	std	r11,GPR10(r1)
@@ -360,16 +343,8 @@ END_FTR_SECTION_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS)
 	cmpdi	r3,0
 	bne	.Lsyscall_restore_regs
 	/* Zero volatile regs that may contain sensitive kernel data */
-	li	r0,0
-	li	r4,0
-	li	r5,0
-	li	r6,0
-	li	r7,0
-	li	r8,0
-	li	r9,0
-	li	r10,0
-	li	r11,0
-	li	r12,0
+	ZEROIZE_GPR(0)
+	ZEROIZE_GPRS(4, 12)
 	mtctr	r0
 	mtspr	SPRN_XER,r0
 .Lsyscall_restore_regs_cont:
@@ -394,7 +369,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
 	ld	r4,_XER(r1)
 	mtctr	r3
 	mtspr	SPRN_XER,r4
-	ld	r0,GPR0(r1)
+	REST_GPR(0, r1)
 	REST_GPRS(4, 12, r1)
 	b	.Lsyscall_restore_regs_cont
 .Lsyscall_rst_end:
-- 
2.34.1

[PATCH v4 16/20] powerpc/32: Clarify interrupt restores with REST_GPR macro in entry_32.S

[Rohan McLure]

Restoring the register state of the interrupted thread involves issuing
a large number of predictable loads to the kernel stack frame. Issue the
REST_GPR{,S} macros to clearly signal when this is happening, and bunch
together restores at the end of the interrupt handler where the saved
value is not consumed earlier in the handler code.

Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
Reported-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
V2 -> V3: New patch.
V3 -> V4: Minimise restores in the unrecoverable window between
restoring SRR0/1 and return from interrupt.
---
 arch/powerpc/kernel/entry_32.S | 33 +++++++++++++-------------------
 1 file changed, 13 insertions(+), 20 deletions(-)

diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index 8d6e02ef5dc0..963d646915fe 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -68,7 +68,7 @@ prepare_transfer_to_handler:
 	lwz	r9,_MSR(r11)		/* if sleeping, clear MSR.EE */
 	rlwinm	r9,r9,0,~MSR_EE
 	lwz	r12,_LINK(r11)		/* and return to address in LR */
-	lwz	r2, GPR2(r11)
+	REST_GPR(2, r11)
 	b	fast_exception_return
 _ASM_NOKPROBE_SYMBOL(prepare_transfer_to_handler)
 #endif /* CONFIG_PPC_BOOK3S_32 || CONFIG_E500 */
@@ -144,7 +144,7 @@ ret_from_syscall:
 	lwz	r7,_NIP(r1)
 	lwz	r8,_MSR(r1)
 	cmpwi	r3,0
-	lwz	r3,GPR3(r1)
+	REST_GPR(3, r1)
 syscall_exit_finish:
 	mtspr	SPRN_SRR0,r7
 	mtspr	SPRN_SRR1,r8
@@ -152,8 +152,8 @@ syscall_exit_finish:
 	bne	3f
 	mtcr	r5
 
-1:	lwz	r2,GPR2(r1)
-	lwz	r1,GPR1(r1)
+1:	REST_GPR(2, r1)
+	REST_GPR(1, r1)
 	rfi
 #ifdef CONFIG_40x
 	b .	/* Prevent prefetch past rfi */
@@ -165,10 +165,8 @@ syscall_exit_finish:
 	REST_NVGPRS(r1)
 	mtctr	r4
 	mtxer	r5
-	lwz	r0,GPR0(r1)
-	lwz	r3,GPR3(r1)
-	REST_GPRS(4, 11, r1)
-	lwz	r12,GPR12(r1)
+	REST_GPR(0, r1)
+	REST_GPRS(3, 12, r1)
 	b	1b
 
 #ifdef CONFIG_44x
@@ -260,9 +258,8 @@ fast_exception_return:
 	beq	3f			/* if not, we've got problems */
 #endif
 
-2:	REST_GPRS(3, 6, r11)
-	lwz	r10,_CCR(r11)
-	REST_GPRS(1, 2, r11)
+2:	lwz	r10,_CCR(r11)
+	REST_GPRS(1, 6, r11)
 	mtcr	r10
 	lwz	r10,_LINK(r11)
 	mtlr	r10
@@ -277,7 +274,7 @@ fast_exception_return:
 	mtspr	SPRN_SRR0,r12
 	REST_GPR(9, r11)
 	REST_GPR(12, r11)
-	lwz	r11,GPR11(r11)
+	REST_GPR(11, r11)
 	rfi
 #ifdef CONFIG_40x
 	b .	/* Prevent prefetch past rfi */
@@ -454,9 +451,8 @@ _ASM_NOKPROBE_SYMBOL(interrupt_return)
 	lwz	r3,_MSR(r1);						\
 	andi.	r3,r3,MSR_PR;						\
 	bne	interrupt_return;					\
-	lwz	r0,GPR0(r1);						\
-	lwz	r2,GPR2(r1);						\
-	REST_GPRS(3, 8, r1);						\
+	REST_GPR(0, r1);						\
+	REST_GPRS(2, 8, r1);						\
 	lwz	r10,_XER(r1);						\
 	lwz	r11,_CTR(r1);						\
 	mtspr	SPRN_XER,r10;						\
@@ -475,11 +471,8 @@ _ASM_NOKPROBE_SYMBOL(interrupt_return)
 	lwz	r12,_MSR(r1);						\
 	mtspr	exc_lvl_srr0,r11;					\
 	mtspr	exc_lvl_srr1,r12;					\
-	lwz	r9,GPR9(r1);						\
-	lwz	r12,GPR12(r1);						\
-	lwz	r10,GPR10(r1);						\
-	lwz	r11,GPR11(r1);						\
-	lwz	r1,GPR1(r1);						\
+	REST_GPRS(9, 12, r1);						\
+	REST_GPR(1, r1);						\
 	exc_lvl_rfi;							\
 	b	.;		/* prevent prefetch past exc_lvl_rfi */
 
-- 
2.34.1

[PATCH v4 17/20] powerpc/64e: Clarify register saves and clears with {SAVE,ZEROIZE}_GPRS

[Rohan McLure]

The common interrupt handler prologue macro and the bad_stack
trampolines include consecutive sequences of register saves, and some
register clears. Neaten such instances by expanding use of the SAVE_GPRS
macro and employing the ZEROIZE_GPR macro when appropriate.

Also simplify an invocation of SAVE_GPRS targetting all non-volatile
registers to SAVE_NVGPRS.

Signed-off-by: Rohan Mclure <rmclure@linux.ibm.com>
---
V3 -> V4: New commit.
---
 arch/powerpc/kernel/exceptions-64e.S | 27 +++++++++++---------------
 1 file changed, 11 insertions(+), 16 deletions(-)

diff --git a/arch/powerpc/kernel/exceptions-64e.S b/arch/powerpc/kernel/exceptions-64e.S
index 67dc4e3179a0..48c640ca425d 100644
--- a/arch/powerpc/kernel/exceptions-64e.S
+++ b/arch/powerpc/kernel/exceptions-64e.S
@@ -216,17 +216,14 @@ END_FTR_SECTION_IFSET(CPU_FTR_EMB_HV)
 	mtlr	r10
 	mtcr	r11
 
-	ld	r10,GPR10(r1)
-	ld	r11,GPR11(r1)
-	ld	r12,GPR12(r1)
+	REST_GPRS(10, 12, r1)
 	mtspr	\scratch,r0
 
 	std	r10,\paca_ex+EX_R10(r13);
 	std	r11,\paca_ex+EX_R11(r13);
 	ld	r10,_NIP(r1)
 	ld	r11,_MSR(r1)
-	ld	r0,GPR0(r1)
-	ld	r1,GPR1(r1)
+	REST_GPRS(0, 1, r1)
 	mtspr	\srr0,r10
 	mtspr	\srr1,r11
 	ld	r10,\paca_ex+EX_R10(r13)
@@ -372,16 +369,15 @@ ret_from_mc_except:
 /* Core exception code for all exceptions except TLB misses. */
 #define EXCEPTION_COMMON_LVL(n, scratch, excf)				    \
 exc_##n##_common:							    \
-	std	r0,GPR0(r1);		/* save r0 in stackframe */	    \
-	std	r2,GPR2(r1);		/* save r2 in stackframe */	    \
-	SAVE_GPRS(3, 9, r1);		/* save r3 - r9 in stackframe */    \
+	SAVE_GPR(0, r1);		/* save r0 in stackframe */	    \
+	SAVE_GPRS(2, 9, r1);		/* save r2 - r9 in stackframe */    \
 	std	r10,_NIP(r1);		/* save SRR0 to stackframe */	    \
 	std	r11,_MSR(r1);		/* save SRR1 to stackframe */	    \
 	beq	2f;			/* if from kernel mode */	    \
 2:	ld	r3,excf+EX_R10(r13);	/* get back r10 */		    \
 	ld	r4,excf+EX_R11(r13);	/* get back r11 */		    \
 	mfspr	r5,scratch;		/* get back r13 */		    \
-	std	r12,GPR12(r1);		/* save r12 in stackframe */	    \
+	SAVE_GPR(12, r1);		/* save r12 in stackframe */	    \
 	ld	r2,PACATOC(r13);	/* get kernel TOC into r2 */	    \
 	mflr	r6;			/* save LR in stackframe */	    \
 	mfctr	r7;			/* save CTR in stackframe */	    \
@@ -390,7 +386,7 @@ exc_##n##_common:							    \
 	lwz	r10,excf+EX_CR(r13);	/* load orig CR back from PACA	*/  \
 	lbz	r11,PACAIRQSOFTMASK(r13); /* get current IRQ softe */	    \
 	ld	r12,exception_marker@toc(r2);				    \
-	li	r0,0;							    \
+	ZEROIZE_GPR(0);							    \
 	std	r3,GPR10(r1);		/* save r10 to stackframe */	    \
 	std	r4,GPR11(r1);		/* save r11 to stackframe */	    \
 	std	r5,GPR13(r1);		/* save it to stackframe */	    \
@@ -1056,15 +1052,14 @@ bad_stack_book3e:
 	mfspr	r11,SPRN_ESR
 	std	r10,_DEAR(r1)
 	std	r11,_ESR(r1)
-	std	r0,GPR0(r1);		/* save r0 in stackframe */	    \
-	std	r2,GPR2(r1);		/* save r2 in stackframe */	    \
-	SAVE_GPRS(3, 9, r1);		/* save r3 - r9 in stackframe */    \
+	SAVE_GPR(0, r1);		/* save r0 in stackframe */	    \
+	SAVE_GPRS(2, 9, r1);		/* save r2 - r9 in stackframe */    \
 	ld	r3,PACA_EXGEN+EX_R10(r13);/* get back r10 */		    \
 	ld	r4,PACA_EXGEN+EX_R11(r13);/* get back r11 */		    \
 	mfspr	r5,SPRN_SPRG_GEN_SCRATCH;/* get back r13 XXX can be wrong */ \
 	std	r3,GPR10(r1);		/* save r10 to stackframe */	    \
 	std	r4,GPR11(r1);		/* save r11 to stackframe */	    \
-	std	r12,GPR12(r1);		/* save r12 in stackframe */	    \
+	SAVE_GPR(12, r1);		/* save r12 in stackframe */	    \
 	std	r5,GPR13(r1);		/* save it to stackframe */	    \
 	mflr	r10
 	mfctr	r11
@@ -1072,12 +1067,12 @@ bad_stack_book3e:
 	std	r10,_LINK(r1)
 	std	r11,_CTR(r1)
 	std	r12,_XER(r1)
-	SAVE_GPRS(14, 31, r1)
+	SAVE_NVGPRS(r1)
 	lhz	r12,PACA_TRAP_SAVE(r13)
 	std	r12,_TRAP(r1)
 	addi	r11,r1,INT_FRAME_SIZE
 	std	r11,0(r1)
-	li	r12,0
+	ZEROIZE_GPR(12)
 	std	r12,0(r11)
 	ld	r2,PACATOC(r13)
 1:	addi	r3,r1,STACK_FRAME_OVERHEAD
-- 
2.34.1

[PATCH v4 18/20] powerpc/64s: Fix comment on interrupt handler prologue

[Rohan McLure]

Interrupt handlers on 64s systems will often need to save register state
from the interrupted process to make space for loading special purpose
registers or for internal state.

Fix a comment documenting a common code path macro in the beginning of
interrupt handlers where r10 is saved to the PACA to afford space for
the value of the CFAR. Comment is currently written as if r10-r12 are
saved to PACA, but in fact only r10 is saved, with r11-r12 saved much
later. The distance in code between these saves has grown over the many
revisions of this macro. Fix this by signalling with a comment where
r11-r12 are saved to the PACA.

Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
---
V1 -> V2: Given its own commit
V2 -> V3: Annotate r11-r12 save locations with comment.
---
 arch/powerpc/kernel/exceptions-64s.S | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index 3d0dc133a9ae..a3b51441b039 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -281,7 +281,7 @@ BEGIN_FTR_SECTION
 	mfspr	r9,SPRN_PPR
 END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
 	HMT_MEDIUM
-	std	r10,IAREA+EX_R10(r13)		/* save r10 - r12 */
+	std	r10,IAREA+EX_R10(r13)		/* save r10 */
 	.if ICFAR
 BEGIN_FTR_SECTION
 	mfspr	r10,SPRN_CFAR
@@ -321,7 +321,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_CFAR)
 	mfctr	r10
 	std	r10,IAREA+EX_CTR(r13)
 	mfcr	r9
-	std	r11,IAREA+EX_R11(r13)
+	std	r11,IAREA+EX_R11(r13)		/* save r11 - r12 */
 	std	r12,IAREA+EX_R12(r13)
 
 	/*
-- 
2.34.1

[PATCH v4 19/20] powerpc/64s: Clear gprs on interrupt routine entry in Book3S

[Rohan McLure]

Zero GPRS r0, r2-r11, r14-r31, on entry into the kernel for all
other interrupt sources to limit influence of user-space values
in potential speculation gadgets. The remaining gprs are overwritten by
entry macros to interrupt handlers, irrespective of whether or not a
given handler consumes these register values.

Prior to this commit, r14-r31 are restored on a per-interrupt basis at
exit, but now they are always restored. Remove explicit REST_NVGPRS
invocations as non-volatiles must now always be restored. 32-bit systems
do not clear user registers on interrupt, and continue to depend on the
return value of interrupt_exit_user_prepare to determine whether or not
to restore non-volatiles.

The mmap_bench benchmark in selftests should rapidly invoke pagefaults.
See ~0.8% performance regression with this mitigation, but this
indicates the worst-case performance due to heavier-weight interrupt
handlers.

Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
---
V1 -> V2: Add benchmark data
V2 -> V3: Use ZEROIZE_GPR{,S} macro renames, clarify
interrupt_exit_user_prepare changes in summary.
---
 arch/powerpc/kernel/exceptions-64s.S | 21 ++++++++-------------
 arch/powerpc/kernel/interrupt_64.S   |  9 ++-------
 2 files changed, 10 insertions(+), 20 deletions(-)

diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index a3b51441b039..038e42fb2182 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -502,6 +502,7 @@ DEFINE_FIXED_SYMBOL(\name\()_common_real, text)
 	std	r10,0(r1)		/* make stack chain pointer	*/
 	std	r0,GPR0(r1)		/* save r0 in stackframe	*/
 	std	r10,GPR1(r1)		/* save r1 in stackframe	*/
+	ZEROIZE_GPR(0)
 
 	/* Mark our [H]SRRs valid for return */
 	li	r10,1
@@ -538,14 +539,18 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
 	ld	r10,IAREA+EX_R10(r13)
 	std	r9,GPR9(r1)
 	std	r10,GPR10(r1)
+	ZEROIZE_GPRS(9, 10)
 	ld	r9,IAREA+EX_R11(r13)	/* move r11 - r13 to stackframe	*/
 	ld	r10,IAREA+EX_R12(r13)
 	ld	r11,IAREA+EX_R13(r13)
 	std	r9,GPR11(r1)
 	std	r10,GPR12(r1)
 	std	r11,GPR13(r1)
+	/* keep r12 ([H]SRR1/MSR), r13 (PACA) for interrupt routine */
+	ZEROIZE_GPR(11)
 
 	SAVE_NVGPRS(r1)
+	ZEROIZE_NVGPRS()
 
 	.if IDAR
 	.if IISIDE
@@ -577,8 +582,8 @@ BEGIN_FTR_SECTION
 END_FTR_SECTION_IFSET(CPU_FTR_CFAR)
 	ld	r10,IAREA+EX_CTR(r13)
 	std	r10,_CTR(r1)
-	std	r2,GPR2(r1)		/* save r2 in stackframe	*/
-	SAVE_GPRS(3, 8, r1)		/* save r3 - r8 in stackframe   */
+	SAVE_GPRS(2, 8, r1)		/* save r2 - r8 in stackframe   */
+	ZEROIZE_GPRS(2, 8)
 	mflr	r9			/* Get LR, later save to stack	*/
 	ld	r2,PACATOC(r13)		/* get kernel TOC into r2	*/
 	std	r9,_LINK(r1)
@@ -696,6 +701,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_CFAR)
 	mtlr	r9
 	ld	r9,_CCR(r1)
 	mtcr	r9
+	REST_NVGPRS(r1)
 	REST_GPRS(2, 13, r1)
 	REST_GPR(0, r1)
 	/* restore original r1. */
@@ -1368,11 +1374,6 @@ ALT_MMU_FTR_SECTION_END_IFCLR(MMU_FTR_TYPE_RADIX)
 	b	interrupt_return_srr
 
 1:	bl	do_break
-	/*
-	 * do_break() may have changed the NV GPRS while handling a breakpoint.
-	 * If so, we need to restore them with their updated values.
-	 */
-	REST_NVGPRS(r1)
 	b	interrupt_return_srr
 
 
@@ -1598,7 +1599,6 @@ EXC_COMMON_BEGIN(alignment_common)
 	GEN_COMMON alignment
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	alignment_exception
-	REST_NVGPRS(r1) /* instruction emulation may change GPRs */
 	b	interrupt_return_srr
 
 
@@ -1708,7 +1708,6 @@ EXC_COMMON_BEGIN(program_check_common)
 .Ldo_program_check:
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	program_check_exception
-	REST_NVGPRS(r1) /* instruction emulation may change GPRs */
 	b	interrupt_return_srr
 
 
@@ -2139,7 +2138,6 @@ EXC_COMMON_BEGIN(emulation_assist_common)
 	GEN_COMMON emulation_assist
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	emulation_assist_interrupt
-	REST_NVGPRS(r1) /* instruction emulation may change GPRs */
 	b	interrupt_return_hsrr
 
 
@@ -2457,7 +2455,6 @@ EXC_COMMON_BEGIN(facility_unavailable_common)
 	GEN_COMMON facility_unavailable
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	facility_unavailable_exception
-	REST_NVGPRS(r1) /* instruction emulation may change GPRs */
 	b	interrupt_return_srr
 
 
@@ -2485,7 +2482,6 @@ EXC_COMMON_BEGIN(h_facility_unavailable_common)
 	GEN_COMMON h_facility_unavailable
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	facility_unavailable_exception
-	REST_NVGPRS(r1) /* XXX Shouldn't be necessary in practice */
 	b	interrupt_return_hsrr
 
 
@@ -2711,7 +2707,6 @@ EXC_COMMON_BEGIN(altivec_assist_common)
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 #ifdef CONFIG_ALTIVEC
 	bl	altivec_assist_exception
-	REST_NVGPRS(r1) /* instruction emulation may change GPRs */
 #else
 	bl	unknown_exception
 #endif
diff --git a/arch/powerpc/kernel/interrupt_64.S b/arch/powerpc/kernel/interrupt_64.S
index ad302ad93433..f9ee93e3a0d3 100644
--- a/arch/powerpc/kernel/interrupt_64.S
+++ b/arch/powerpc/kernel/interrupt_64.S
@@ -432,9 +432,6 @@ interrupt_return_\srr\()_user: /* make backtraces match the _kernel variant */
 _ASM_NOKPROBE_SYMBOL(interrupt_return_\srr\()_user)
 	addi	r3,r1,STACK_FRAME_OVERHEAD
 	bl	interrupt_exit_user_prepare
-	cmpdi	r3,0
-	bne-	.Lrestore_nvgprs_\srr
-.Lrestore_nvgprs_\srr\()_cont:
 	std	r1,PACA_EXIT_SAVE_R1(r13) /* save r1 for restart */
 #ifdef CONFIG_PPC_BOOK3S
 .Linterrupt_return_\srr\()_user_rst_start:
@@ -448,6 +445,7 @@ _ASM_NOKPROBE_SYMBOL(interrupt_return_\srr\()_user)
 	stb	r11,PACAIRQHAPPENED(r13) # clear out possible HARD_DIS
 
 .Lfast_user_interrupt_return_\srr\():
+	REST_NVGPRS(r1)
 #ifdef CONFIG_PPC_BOOK3S
 	.ifc \srr,srr
 	lbz	r4,PACASRR_VALID(r13)
@@ -517,10 +515,6 @@ ALT_FTR_SECTION_END_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS)
 	b	.	/* prevent speculative execution */
 .Linterrupt_return_\srr\()_user_rst_end:
 
-.Lrestore_nvgprs_\srr\():
-	REST_NVGPRS(r1)
-	b	.Lrestore_nvgprs_\srr\()_cont
-
 #ifdef CONFIG_PPC_BOOK3S
 interrupt_return_\srr\()_user_restart:
 _ASM_NOKPROBE_SYMBOL(interrupt_return_\srr\()_user_restart)
@@ -561,6 +555,7 @@ _ASM_NOKPROBE_SYMBOL(interrupt_return_\srr\()_kernel)
 1:
 
 .Lfast_kernel_interrupt_return_\srr\():
+	REST_NVGPRS(r1)
 	cmpdi	cr1,r3,0
 #ifdef CONFIG_PPC_BOOK3S
 	.ifc \srr,srr
-- 
2.34.1

[PATCH v4 20/20] powerpc/64e: Clear gprs on interrupt routine entry

[Rohan McLure]

Zero GPRS r14-r31 on entry into the kernel for interrupt sources to
limit influence of user-space values in potential speculation gadgets.
Prior to this commit, all other GPRS are reassigned during the common
prologue to interrupt handlers and so need not be zeroised explicitly.

This may be done safely, without loss of register state prior to the
interrupt, as the common prologue saves the initial values of
non-volatiles, which are unconditionally restored in interrupt_64.S.

Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
---
V3 -> V4: New patch.
---
 arch/powerpc/kernel/exceptions-64e.S | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/exceptions-64e.S b/arch/powerpc/kernel/exceptions-64e.S
index 48c640ca425d..296b3bf6b2a6 100644
--- a/arch/powerpc/kernel/exceptions-64e.S
+++ b/arch/powerpc/kernel/exceptions-64e.S
@@ -401,7 +401,8 @@ exc_##n##_common:							    \
 	std	r12,STACK_FRAME_OVERHEAD-16(r1); /* mark the frame */	    \
 	std	r3,_TRAP(r1);		/* set trap number		*/  \
 	std	r0,RESULT(r1);		/* clear regs->result */	    \
-	SAVE_NVGPRS(r1);
+	SAVE_NVGPRS(r1);						    \
+	ZEROIZE_NVGPRS();		/* minimise speculation influence */
 
 #define EXCEPTION_COMMON(n) \
 	EXCEPTION_COMMON_LVL(n, SPRN_SPRG_GEN_SCRATCH, PACA_EXGEN)
@@ -1068,6 +1069,7 @@ bad_stack_book3e:
 	std	r11,_CTR(r1)
 	std	r12,_XER(r1)
 	SAVE_NVGPRS(r1)
+	ZEROIZE_NVGPRS()
 	lhz	r12,PACA_TRAP_SAVE(r13)
 	std	r12,_TRAP(r1)
 	addi	r11,r1,INT_FRAME_SIZE
-- 
2.34.1

Re: [PATCH v4 01/20] powerpc: Remove asmlinkage from syscall handler definitions

[Andrew Donnellan]

On Wed, 2022-08-24 at 12:05 +1000, Rohan McLure wrote:
> The asmlinkage macro has no special meaning in powerpc, and prior to
> this patch is used sporadically on some syscall handler definitions.
> On
> architectures that do not define asmlinkage, it resolves to extern
> "C"
> for C++ compilers and a nop otherwise. The current invocations of
> asmlinkage provide far from complete support for C++ toolchains, and
> so
> the macro serves no purpose in powerpc.
> 
> Remove all invocations of asmlinkage in arch/powerpc. These
> incidentally
> only occur in syscall definitions and prototypes.
> 
> Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>

This does indeed get rid of every reference to asmlinkage in
arch/powerpc.

Reviewed-by: Andrew Donnellan <ajd@linux.ibm.com>

> ---
> V2 -> V3: new patch
> ---
>  arch/powerpc/include/asm/syscalls.h | 16 ++++++++--------
>  arch/powerpc/kernel/sys_ppc32.c     |  8 ++++----
>  2 files changed, 12 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/syscalls.h
> b/arch/powerpc/include/asm/syscalls.h
> index a2b13e55254f..21c2faaa2957 100644
> --- a/arch/powerpc/include/asm/syscalls.h
> +++ b/arch/powerpc/include/asm/syscalls.h
> @@ -10,14 +10,14 @@
>  
>  struct rtas_args;
>  
> -asmlinkage long sys_mmap(unsigned long addr, size_t len,
> -               unsigned long prot, unsigned long flags,
> -               unsigned long fd, off_t offset);
> -asmlinkage long sys_mmap2(unsigned long addr, size_t len,
> -               unsigned long prot, unsigned long flags,
> -               unsigned long fd, unsigned long pgoff);
> -asmlinkage long ppc64_personality(unsigned long personality);
> -asmlinkage long sys_rtas(struct rtas_args __user *uargs);
> +long sys_mmap(unsigned long addr, size_t len,
> +             unsigned long prot, unsigned long flags,
> +             unsigned long fd, off_t offset);
> +long sys_mmap2(unsigned long addr, size_t len,
> +              unsigned long prot, unsigned long flags,
> +              unsigned long fd, unsigned long pgoff);
> +long ppc64_personality(unsigned long personality);
> +long sys_rtas(struct rtas_args __user *uargs);
>  int ppc_select(int n, fd_set __user *inp, fd_set __user *outp,
>                fd_set __user *exp, struct __kernel_old_timeval __user
> *tvp);
>  long ppc_fadvise64_64(int fd, int advice, u32 offset_high, u32
> offset_low,
> diff --git a/arch/powerpc/kernel/sys_ppc32.c
> b/arch/powerpc/kernel/sys_ppc32.c
> index 16ff0399a257..f4edcc9489fb 100644
> --- a/arch/powerpc/kernel/sys_ppc32.c
> +++ b/arch/powerpc/kernel/sys_ppc32.c
> @@ -85,20 +85,20 @@ compat_ssize_t compat_sys_readahead(int fd, u32
> r4, u32 offset1, u32 offset2, u3
>         return ksys_readahead(fd, merge_64(offset1, offset2), count);
>  }
>  
> -asmlinkage int compat_sys_truncate64(const char __user * path, u32
> reg4,
> +int compat_sys_truncate64(const char __user * path, u32 reg4,
>                                 unsigned long len1, unsigned long
> len2)
>  {
>         return ksys_truncate(path, merge_64(len1, len2));
>  }
>  
> -asmlinkage long compat_sys_fallocate(int fd, int mode, u32 offset1,
> u32 offset2,
> +long compat_sys_fallocate(int fd, int mode, u32 offset1, u32
> offset2,
>                                      u32 len1, u32 len2)
>  {
>         return ksys_fallocate(fd, mode, ((loff_t)offset1 << 32) |
> offset2,
>                              merge_64(len1, len2));
>  }
>  
> -asmlinkage int compat_sys_ftruncate64(unsigned int fd, u32 reg4,
> unsigned long len1,
> +int compat_sys_ftruncate64(unsigned int fd, u32 reg4, unsigned long
> len1,
>                                  unsigned long len2)
>  {
>         return ksys_ftruncate(fd, merge_64(len1, len2));
> @@ -111,7 +111,7 @@ long ppc32_fadvise64(int fd, u32 unused, u32
> offset1, u32 offset2,
>                                  advice);
>  }
>  
> -asmlinkage long compat_sys_sync_file_range2(int fd, unsigned int
> flags,
> +long compat_sys_sync_file_range2(int fd, unsigned int flags,
>                                    unsigned offset1, unsigned
> offset2,
>                                    unsigned nbytes1, unsigned
> nbytes2)
>  {

-- 
Andrew Donnellan    OzLabs, ADL Canberra
ajd@linux.ibm.com   IBM Australia Limited

Re: [PATCH v4 00/20] powerpc: Syscall wrapper and register clearing

[Rohan McLure]

Any comments for this revision? Hopefully these revisions address 32-bit and embedded systems appropriately.

Thanks,
Rohan

> On 24 Aug 2022, at 12:05 pm, Rohan McLure <rmclure@linux.ibm.com> wrote:
> 
> V3 available here:
> 
> Link: https://lore.kernel.org/all/4C3A8815-67FF-41EB-A703-981920CA1201@linux.ibm.com/T/
> 
> Implement a syscall wrapper, causing arguments to handlers to be passed
> via a struct pt_regs on the stack. The syscall wrapper is implemented
> for all platforms other than the Cell processor, from which SPUs expect
> the ability to directly call syscall handler symbols with the regular
> in-register calling convention.
> 
> Adopting syscall wrappers requires redefinition of architecture-specific
> syscalls and compatibility syscalls to use the SYSCALL_DEFINE and
> COMPAT_SYSCALL_DEFINE macros, as well as removal of direct-references to
> the emitted syscall-handler symbols from within the kernel. This work
> lead to the following modernisations of powerpc's syscall handlers:
> 
> - Replace syscall 82 semantics with sys_old_select and remove
>   ppc_select handler, which features direct call to both sys_old_select
>   and sys_select.
> - Use a generic fallocate compatibility syscall
> 
> Replace asm implementation of syscall table with C implementation for
> more compile-time checks.
> 
> Many compatibility syscalls are candidates to be removed in favour of
> generically defined handlers, but exhibit different parameter orderings
> and numberings due to 32-bit ABI support for 64-bit parameters. The
> parameter reorderings are however consistent with arm. A future patch
> series will serve to modernise syscalls by providing generic
> implementations featuring these reorderings.
> 
> The design of this syscall is very similar to the s390, x86 and arm64
> implementations. See also Commit 4378a7d4be30 (arm64: implement syscall wrappers).
> The motivation for this change is that it allows for the clearing of
> register state when entering the kernel via through interrupt handlers
> on 64-bit servers. This serves to reduce the influence of values in
> registers carried over from the interrupted process, e.g. syscall
> parameters from user space, or user state at the site of a pagefault.
> All values in registers are saved and zeroized at the entry to an
> interrupt handler and restored afterward. While this may sound like a
> heavy-weight mitigation, many gprs are already saved and restored on
> handling of an interrupt, and the mmap_bench benchmark on Power 9 guest,
> repeatedly invoking the pagefault handler suggests at most ~0.8%
> regression in performance. Realistic workloads are not constantly
> producing interrupts, and so this does not indicate realistic slowdown.
> 
> Using wrapped syscalls yields to a performance improvement of ~5.6% on
> the null_syscall benchmark on pseries guests, by removing the need for
> system_call_exception to allocate its own stack frame. This amortises
> the additional costs of saving and restoring non-volatile registers
> (register clearing is cheap on super scalar platforms), and so the
> final mitigation actually yields a net performance improvement of ~0.6%
> on the null_syscall benchmark.
> 
> Patch Changelog:
> 
> - Fix instances where NULLIFY_GPRS were still present
> - Minimise unrecoverable windows in entry_32.S between SRR0/1 restores
>   and RFI
> - Remove all references to syscall symbols prior to introducing syscall
>   wrapper.
> - Remove unnecessary duplication of syscall handlers with sys_... and
>   powerpc_sys_... symbols.
> - Clear non-volatile registers on Book3E systems, as some of these
>   systems feature hardware speculation, and we already unconditionally
>   restore NVGPRS.
> 
> Rohan McLure (20):
>  powerpc: Remove asmlinkage from syscall handler definitions
>  powerpc: Use generic fallocate compatibility syscall
>  powerpc/32: Remove powerpc select specialisation
>  powerpc: Provide do_ppc64_personality helper
>  powerpc: Remove direct call to personality syscall handler
>  powerpc: Remove direct call to mmap2 syscall handlers
>  powerpc: Adopt SYSCALL_DEFINE for arch-specific syscall handlers
>  powerpc: Include all arch-specific syscall prototypes
>  powerpc: Enable compile-time check for syscall handlers
>  powerpc: Use common syscall handler type
>  powerpc: Add ZEROIZE_GPRS macros for register clears
>  Revert "powerpc/syscall: Save r3 in regs->orig_r3"
>  powerpc: Provide syscall wrapper
>  powerpc/64s: Clear/restore caller gprs in syscall interrupt/return
>  powerpc/64s: Use {ZEROIZE,SAVE,REST}_GPRS macros in sc, scv 0 handlers
>  powerpc/32: Clarify interrupt restores with REST_GPR macro in
>    entry_32.S
>  powerpc/64e: Clarify register saves and clears with
>    {SAVE,ZEROIZE}_GPRS
>  powerpc/64s: Fix comment on interrupt handler prologue
>  powerpc/64s: Clear gprs on interrupt routine entry in Book3S
>  powerpc/64e: Clear gprs on interrupt routine entry
> 
> arch/powerpc/Kconfig                         |   1 +
> arch/powerpc/include/asm/compat.h            |   5 +
> arch/powerpc/include/asm/interrupt.h         |   3 +-
> arch/powerpc/include/asm/ppc_asm.h           |  22 +++
> arch/powerpc/include/asm/syscall.h           |  11 +-
> arch/powerpc/include/asm/syscall_wrapper.h   |  84 +++++++++++
> arch/powerpc/include/asm/syscalls.h          | 128 +++++++++++++----
> .../ppc32.h => include/asm/syscalls_32.h}    |   0
> arch/powerpc/include/asm/unistd.h            |   1 +
> arch/powerpc/kernel/entry_32.S               |  40 +++---
> arch/powerpc/kernel/exceptions-64e.S         |  31 ++--
> arch/powerpc/kernel/exceptions-64s.S         |  25 ++--
> arch/powerpc/kernel/interrupt_64.S           |  92 +++++-------
> arch/powerpc/kernel/signal_32.c              |   2 +-
> arch/powerpc/kernel/sys_ppc32.c              |  54 ++++---
> arch/powerpc/kernel/syscall.c                |  32 ++---
> arch/powerpc/kernel/syscalls.c               |  51 ++++---
> arch/powerpc/kernel/syscalls/syscall.tbl     |  24 ++--
> arch/powerpc/kernel/{systbl.S => systbl.c}   |  29 ++--
> arch/powerpc/kernel/vdso.c                   |   6 +-
> arch/powerpc/perf/callchain_32.c             |   2 +-
> arch/powerpc/platforms/cell/spu_callbacks.c  |   6 +-
> .../arch/powerpc/entry/syscalls/syscall.tbl  |  24 ++--
> 23 files changed, 415 insertions(+), 258 deletions(-)
> create mode 100644 arch/powerpc/include/asm/syscall_wrapper.h
> rename arch/powerpc/{kernel/ppc32.h => include/asm/syscalls_32.h} (100%)
> rename arch/powerpc/kernel/{systbl.S => systbl.c} (55%)
> 
> -- 
> 2.34.1
> 

Re: [PATCH v4 01/20] powerpc: Remove asmlinkage from syscall handler definitions

[Nicholas Piggin]

On Wed Aug 24, 2022 at 12:05 PM AEST, Rohan McLure wrote:
> The asmlinkage macro has no special meaning in powerpc, and prior to
> this patch is used sporadically on some syscall handler definitions. On
> architectures that do not define asmlinkage, it resolves to extern "C"
> for C++ compilers and a nop otherwise. The current invocations of
> asmlinkage provide far from complete support for C++ toolchains, and so
> the macro serves no purpose in powerpc.
>
> Remove all invocations of asmlinkage in arch/powerpc. These incidentally
> only occur in syscall definitions and prototypes.
>
> Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>

Re: [PATCH v4 02/20] powerpc: Use generic fallocate compatibility syscall

[Nicholas Piggin]

On Wed Aug 24, 2022 at 12:05 PM AEST, Rohan McLure wrote:
> The powerpc fallocate compat syscall handler is identical to the
> generic implementation provided by commit 59c10c52f573f ("riscv:
> compat: syscall: Add compat_sys_call_table implementation"), and as
> such can be removed in favour of the generic implementation.
>
> A future patch series will replace more architecture-defined syscall
> handlers with generic implementations, dependent on introducing generic
> implementations that are compatible with powerpc and arm's parameter
> reorderings.
>
> Reported-by: Arnd Bergmann <arnd@arndb.de>
> Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
> ---
> V1 -> V2: Remove arch-specific fallocate handler.
> V2 -> V3: Remove generic fallocate prototype. Move to beginning of
> series.
> ---
>  arch/powerpc/include/asm/compat.h   | 5 +++++
>  arch/powerpc/include/asm/syscalls.h | 2 --
>  arch/powerpc/include/asm/unistd.h   | 1 +
>  3 files changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/compat.h b/arch/powerpc/include/asm/compat.h
> index dda4091fd012..f20caae3f019 100644
> --- a/arch/powerpc/include/asm/compat.h
> +++ b/arch/powerpc/include/asm/compat.h
> @@ -16,6 +16,11 @@ typedef u16		compat_ipc_pid_t;
>  #include <asm-generic/compat.h>
>  
>  #ifdef __BIG_ENDIAN__
> +#define compat_arg_u64(name)		u32  name##_hi, u32  name##_lo
> +#define compat_arg_u64_dual(name)	u32, name##_hi, u32, name##_lo
> +#define compat_arg_u64_glue(name)	(((u64)name##_lo & 0xffffffffUL) | \
> +					 ((u64)name##_hi << 32))

Is there a reason not to put this in asm-generic/compat.h?

Possibly you want to put this with the other compat definitions and
above the asm-generic include. The generic header expects the arch to
include it after defining what it wants to override.

Not sure why x_lo gets cast from u32 to u64 and masked before the |
there, but generic code does the same so this isn't the place to
change it.

Thanks,
Nick


> +
>  #define COMPAT_UTS_MACHINE	"ppc\0\0"
>  #else
>  #define COMPAT_UTS_MACHINE	"ppcle\0\0"
> diff --git a/arch/powerpc/include/asm/syscalls.h b/arch/powerpc/include/asm/syscalls.h
> index 21c2faaa2957..675a8f5ec3ca 100644
> --- a/arch/powerpc/include/asm/syscalls.h
> +++ b/arch/powerpc/include/asm/syscalls.h
> @@ -39,8 +39,6 @@ compat_ssize_t compat_sys_readahead(int fd, u32 r4, u32 offset1, u32 offset2, u3
>  int compat_sys_truncate64(const char __user *path, u32 reg4,
>  			  unsigned long len1, unsigned long len2);
>  
> -long compat_sys_fallocate(int fd, int mode, u32 offset1, u32 offset2, u32 len1, u32 len2);
> -
>  int compat_sys_ftruncate64(unsigned int fd, u32 reg4, unsigned long len1,
>  			   unsigned long len2);
>  
> diff --git a/arch/powerpc/include/asm/unistd.h b/arch/powerpc/include/asm/unistd.h
> index b1129b4ef57d..659a996c75aa 100644
> --- a/arch/powerpc/include/asm/unistd.h
> +++ b/arch/powerpc/include/asm/unistd.h
> @@ -45,6 +45,7 @@
>  #define __ARCH_WANT_SYS_UTIME
>  #define __ARCH_WANT_SYS_NEWFSTATAT
>  #define __ARCH_WANT_COMPAT_STAT
> +#define __ARCH_WANT_COMPAT_FALLOCATE
>  #define __ARCH_WANT_COMPAT_SYS_SENDFILE
>  #endif
>  #define __ARCH_WANT_SYS_FORK
> -- 
> 2.34.1

Re: [PATCH v4 03/20] powerpc/32: Remove powerpc select specialisation

[Nicholas Piggin]

On Wed Aug 24, 2022 at 12:05 PM AEST, Rohan McLure wrote:
> Syscall #82 has been implemented for 32-bit platforms in a unique way on
> powerpc systems. This hack will in effect guess whether the caller is
> expecting new select semantics or old select semantics. It does so via a
> guess, based off the first parameter. In new select, this parameter
> represents the length of a user-memory array of file descriptors, and in
> old select this is a pointer to an arguments structure.
>
> The heuristic simply interprets sufficiently large values of its first
> parameter as being a call to old select. The following is a discussion
> on how this syscall should be handled.
>
> Link: https://lore.kernel.org/lkml/13737de5-0eb7-e881-9af0-163b0d29a1a0@csgroup.eu/

Seems okay to me, probably Christophe needs to ack it.
Should some of that history be included directly in this changelog?

Should ppc64 compat be added back too, if this is being updated instead
of removed? I don't know much about compat but it seems odd not provide
it (considering it's just using compat_sys_old_select, isn't it?

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>

>
> As discussed in this thread, the existence of such a hack suggests that for
> whatever powerpc binaries may predate glibc, it is most likely that they
> would have taken use of the old select semantics. x86 and arm64 both
> implement this syscall with oldselect semantics.
>
> Remove the powerpc implementation, and update syscall.tbl to refer to emit
> a reference to sys_old_select for 32-bit binaries, in keeping with how
> other architectures support syscall #82.
>
> Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
> ---
> V1 -> V2: Remove arch-specific select handler
> V2 -> V3: Remove ppc_old_select prototype in <asm/syscalls.h>. Move to
> earlier in patch series
> ---
>  arch/powerpc/include/asm/syscalls.h           |  2 --
>  arch/powerpc/kernel/syscalls.c                | 17 -----------------
>  arch/powerpc/kernel/syscalls/syscall.tbl      |  2 +-
>  .../arch/powerpc/entry/syscalls/syscall.tbl   |  2 +-
>  4 files changed, 2 insertions(+), 21 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/syscalls.h b/arch/powerpc/include/asm/syscalls.h
> index 675a8f5ec3ca..739498c358a1 100644
> --- a/arch/powerpc/include/asm/syscalls.h
> +++ b/arch/powerpc/include/asm/syscalls.h
> @@ -18,8 +18,6 @@ long sys_mmap2(unsigned long addr, size_t len,
>  	       unsigned long fd, unsigned long pgoff);
>  long ppc64_personality(unsigned long personality);
>  long sys_rtas(struct rtas_args __user *uargs);
> -int ppc_select(int n, fd_set __user *inp, fd_set __user *outp,
> -	       fd_set __user *exp, struct __kernel_old_timeval __user *tvp);
>  long ppc_fadvise64_64(int fd, int advice, u32 offset_high, u32 offset_low,
>  		      u32 len_high, u32 len_low);
>  
> diff --git a/arch/powerpc/kernel/syscalls.c b/arch/powerpc/kernel/syscalls.c
> index fc999140bc27..ef5896bee818 100644
> --- a/arch/powerpc/kernel/syscalls.c
> +++ b/arch/powerpc/kernel/syscalls.c
> @@ -63,23 +63,6 @@ SYSCALL_DEFINE6(mmap, unsigned long, addr, size_t, len,
>  	return do_mmap2(addr, len, prot, flags, fd, offset, PAGE_SHIFT);
>  }
>  
> -#ifdef CONFIG_PPC32
> -/*
> - * Due to some executables calling the wrong select we sometimes
> - * get wrong args.  This determines how the args are being passed
> - * (a single ptr to them all args passed) then calls
> - * sys_select() with the appropriate args. -- Cort
> - */
> -int
> -ppc_select(int n, fd_set __user *inp, fd_set __user *outp, fd_set __user *exp, struct __kernel_old_timeval __user *tvp)
> -{
> -	if ((unsigned long)n >= 4096)
> -		return sys_old_select((void __user *)n);
> -
> -	return sys_select(n, inp, outp, exp, tvp);
> -}
> -#endif
> -
>  #ifdef CONFIG_PPC64
>  long ppc64_personality(unsigned long personality)
>  {
> diff --git a/arch/powerpc/kernel/syscalls/syscall.tbl b/arch/powerpc/kernel/syscalls/syscall.tbl
> index 2600b4237292..4cbbb810ae10 100644
> --- a/arch/powerpc/kernel/syscalls/syscall.tbl
> +++ b/arch/powerpc/kernel/syscalls/syscall.tbl
> @@ -110,7 +110,7 @@
>  79	common	settimeofday			sys_settimeofday		compat_sys_settimeofday
>  80	common	getgroups			sys_getgroups
>  81	common	setgroups			sys_setgroups
> -82	32	select				ppc_select			sys_ni_syscall
> +82	32	select				sys_old_select			sys_ni_syscall
>  82	64	select				sys_ni_syscall
>  82	spu	select				sys_ni_syscall
>  83	common	symlink				sys_symlink
> diff --git a/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl b/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl
> index 2600b4237292..4cbbb810ae10 100644
> --- a/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl
> +++ b/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl
> @@ -110,7 +110,7 @@
>  79	common	settimeofday			sys_settimeofday		compat_sys_settimeofday
>  80	common	getgroups			sys_getgroups
>  81	common	setgroups			sys_setgroups
> -82	32	select				ppc_select			sys_ni_syscall
> +82	32	select				sys_old_select			sys_ni_syscall
>  82	64	select				sys_ni_syscall
>  82	spu	select				sys_ni_syscall
>  83	common	symlink				sys_symlink
> -- 
> 2.34.1

Re: [PATCH v4 04/20] powerpc: Provide do_ppc64_personality helper

[Nicholas Piggin]

On Wed Aug 24, 2022 at 12:05 PM AEST, Rohan McLure wrote:
> Avoid duplication in future patch that will define the ppc64_personality
> syscall handler in terms of the SYSCALL_DEFINE and COMPAT_SYSCALL_DEFINE
> macros, by extracting the common body of ppc64_personality into a helper
> function.
>
> Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
> ---
> V2  -> V3: New commit.
> ---
>  arch/powerpc/kernel/syscalls.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/kernel/syscalls.c b/arch/powerpc/kernel/syscalls.c
> index ef5896bee818..9f29e451e2de 100644
> --- a/arch/powerpc/kernel/syscalls.c
> +++ b/arch/powerpc/kernel/syscalls.c
> @@ -64,7 +64,7 @@ SYSCALL_DEFINE6(mmap, unsigned long, addr, size_t, len,
>  }
>  
>  #ifdef CONFIG_PPC64
> -long ppc64_personality(unsigned long personality)
> +static inline long do_ppc64_personality(unsigned long personality)
>  {
>  	long ret;
>  

If this was merged in patch 7 it would just include the above, right?
I don't really mind if you prefer to split it this way though and make
fewer changes in patch 7.

Could you drop the 'inline'? I don't think it's necessary for modern
compliers. do_mmap2 could drop it too.

I did have a question about the duplication in patch 7, but assuming
you still need this patch

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>

>  
>  long ppc_fadvise64_64(int fd, int advice, u32 offset_high, u32 offset_low,
> -- 
> 2.34.1

Re: [PATCH v4 05/20] powerpc: Remove direct call to personality syscall handler

[Nicholas Piggin]

On Wed Aug 24, 2022 at 12:05 PM AEST, Rohan McLure wrote:
> Syscall handlers should not be invoked internally by their symbol names,
> as these symbols defined by the architecture-defined SYSCALL_DEFINE
> macro. Fortunately, in the case of ppc64_personality, its call to
> sys_personality can be replaced with an invocation to the
> equivalent ksys_personality inline helper in <linux/syscalls.h>.

Huh. I wonder why sys_personality doesn't just call ksys_personality
too. Anyway this looks good.

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>

Several of your steps like this one look like they apply to other archs
as well. You might consider ccing linux-arch for some of these.

>
> Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
> ---
> V1 -> V2: Use inline helper to deduplicate bodies in compat/regular
> implementations.
> V3 -> V4: Move to be applied before syscall wrapper.
> ---
>  arch/powerpc/kernel/syscalls.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/kernel/syscalls.c b/arch/powerpc/kernel/syscalls.c
> index 9f29e451e2de..b8461128c8f7 100644
> --- a/arch/powerpc/kernel/syscalls.c
> +++ b/arch/powerpc/kernel/syscalls.c
> @@ -71,7 +71,7 @@ static inline long do_ppc64_personality(unsigned long personality)
>  	if (personality(current->personality) == PER_LINUX32
>  	    && personality(personality) == PER_LINUX)
>  		personality = (personality & ~PER_MASK) | PER_LINUX32;
> -	ret = sys_personality(personality);
> +	ret = ksys_personality(personality);
>  	if (personality(ret) == PER_LINUX32)
>  		ret = (ret & ~PER_MASK) | PER_LINUX;
>  	return ret;
> -- 
> 2.34.1

Re: [PATCH v4 06/20] powerpc: Remove direct call to mmap2 syscall handlers

[Nicholas Piggin]

On Wed Aug 24, 2022 at 12:05 PM AEST, Rohan McLure wrote:
> Syscall handlers should not be invoked internally by their symbol names,
> as these symbols defined by the architecture-defined SYSCALL_DEFINE
> macro. Move the compatibility syscall definition for mmap2 to
> syscalls.c, so that all mmap implementations can share an inline helper
> function, as is done with the personality handlers.
>
> Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>

Is there any point to keping sys_ppc32.c at all? Might as well move them
all to syscall.c IMO.

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>

> ---
> V1 -> V2: Move mmap2 compat implementation to asm/kernel/syscalls.c.
> V3 -> V4: Move to be applied before syscall wrapper introduced.
> ---
>  arch/powerpc/kernel/sys_ppc32.c |  9 ---------
>  arch/powerpc/kernel/syscalls.c  | 11 +++++++++++
>  2 files changed, 11 insertions(+), 9 deletions(-)
>
> diff --git a/arch/powerpc/kernel/sys_ppc32.c b/arch/powerpc/kernel/sys_ppc32.c
> index f4edcc9489fb..bc6491ed6454 100644
> --- a/arch/powerpc/kernel/sys_ppc32.c
> +++ b/arch/powerpc/kernel/sys_ppc32.c
> @@ -25,7 +25,6 @@
>  #include <linux/poll.h>
>  #include <linux/personality.h>
>  #include <linux/stat.h>
> -#include <linux/mman.h>
>  #include <linux/in.h>
>  #include <linux/syscalls.h>
>  #include <linux/unistd.h>
> @@ -48,14 +47,6 @@
>  #include <asm/syscalls.h>
>  #include <asm/switch_to.h>
>  
> -unsigned long compat_sys_mmap2(unsigned long addr, size_t len,
> -			  unsigned long prot, unsigned long flags,
> -			  unsigned long fd, unsigned long pgoff)
> -{
> -	/* This should remain 12 even if PAGE_SIZE changes */
> -	return sys_mmap(addr, len, prot, flags, fd, pgoff << 12);
> -}
> -
>  /* 
>   * long long munging:
>   * The 32 bit ABI passes long longs in an odd even register pair.
> diff --git a/arch/powerpc/kernel/syscalls.c b/arch/powerpc/kernel/syscalls.c
> index b8461128c8f7..32fadf3c2cd3 100644
> --- a/arch/powerpc/kernel/syscalls.c
> +++ b/arch/powerpc/kernel/syscalls.c
> @@ -56,6 +56,17 @@ SYSCALL_DEFINE6(mmap2, unsigned long, addr, size_t, len,
>  	return do_mmap2(addr, len, prot, flags, fd, pgoff, PAGE_SHIFT-12);
>  }
>  
> +#ifdef CONFIG_COMPAT
> +COMPAT_SYSCALL_DEFINE6(mmap2,
> +		       unsigned long, addr, size_t, len,
> +		       unsigned long, prot, unsigned long, flags,
> +		       unsigned long, fd, unsigned long, pgoff)
> +{
> +	/* This should remain 12 even if PAGE_SIZE changes */
> +	return do_mmap2(addr, len, prot, flags, fd, pgoff << 12, PAGE_SHIFT-12);
> +}
> +#endif
> +
>  SYSCALL_DEFINE6(mmap, unsigned long, addr, size_t, len,
>  		unsigned long, prot, unsigned long, flags,
>  		unsigned long, fd, off_t, offset)
> -- 
> 2.34.1

Re: [PATCH v4 02/20] powerpc: Use generic fallocate compatibility syscall

[Arnd Bergmann]

On Mon, Sep 12, 2022, at 10:38 AM, Nicholas Piggin wrote:
> On Wed Aug 24, 2022 at 12:05 PM AEST, Rohan McLure wrote:
>> The powerpc fallocate compat syscall handler is identical to the
>> generic implementation provided by commit 59c10c52f573f ("riscv:
>> compat: syscall: Add compat_sys_call_table implementation"), and as
>> such can be removed in favour of the generic implementation.
>>
>> A future patch series will replace more architecture-defined syscall
>> handlers with generic implementations, dependent on introducing generic
>> implementations that are compatible with powerpc and arm's parameter
>> reorderings.
>>
>> Reported-by: Arnd Bergmann <arnd@arndb.de>
>> Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
>> ---
>> V1 -> V2: Remove arch-specific fallocate handler.
>> V2 -> V3: Remove generic fallocate prototype. Move to beginning of
>> series.
>> ---

>> @@ -16,6 +16,11 @@ typedef u16		compat_ipc_pid_t;
>>  #include <asm-generic/compat.h>
>>  
>>  #ifdef __BIG_ENDIAN__
>> +#define compat_arg_u64(name)		u32  name##_hi, u32  name##_lo
>> +#define compat_arg_u64_dual(name)	u32, name##_hi, u32, name##_lo
>> +#define compat_arg_u64_glue(name)	(((u64)name##_lo & 0xffffffffUL) | \
>> +					 ((u64)name##_hi << 32))
>
> Is there a reason not to put this in asm-generic/compat.h?
>
> Possibly you want to put this with the other compat definitions and
> above the asm-generic include. The generic header expects the arch to
> include it after defining what it wants to override.

Yes, makes sense. I think the riscv people added this to asm-generic,
they tried to do only the minimal parts.

In theory, any architecture could have its own calling conventions
for each syscall and have them in the opposite order for one
endianess. I checked the seven non-generic implementations of the
sys_fallocate() syscall and all except powerpc have the same
ABI as the generic one.

The powerpc difference is that in little-endian mode, only
the 'len' argument is swapped but the 'offset' argument is
still high/low:

long compat_sys_fallocate(int fd, int mode, u32 offset1, u32 offset2,
                                    u32 len1, u32 len2)
{
       return ksys_fallocate(fd, mode, ((loff_t)offset1 << 32) | offset2,
                            merge_64(len1, len2));
}

It's probably best to first fix this by using merge_64(offset1,
offset2) and allow that patch to be backported to stable kernels,
before changing it over to the generic code in a separate patch
within that series.

A related issue seems to exist in ppc_fadvise64_64(), which
uses the wrong argument order on ppc32le compat tasks, in addition
to having at least three different calling conventions across
architectures.

      Arnd

Re: [PATCH v4 07/20] powerpc: Adopt SYSCALL_DEFINE for arch-specific syscall handlers

[Nicholas Piggin]

On Wed Aug 24, 2022 at 12:05 PM AEST, Rohan McLure wrote:
> Arch-specific implementations of syscall handlers are currently used
> over generic implementations for the following reasons:
>
> 1. Semantics unique to powerpc
> 2. Compatibility syscalls require 'argument padding' to comply with
>    64-bit argument convention in ELF32 abi.
> 3. Parameter types or order is different in other architectures.
>
> These syscall handlers have been defined prior to this patch series
> without invoking the SYSCALL_DEFINE or COMPAT_SYSCALL_DEFINE macros with
> custom input and output types. We remove every such direct definition in
> favour of the aforementioned macros.

And what about sys_fallocate, where did that go?

>
> Also update syscalls.tbl in order to refer to the symbol names generated
> by each of these macros. Since ppc64_personality can be called by both
> 64 bit and 32 bit binaries through compatibility, we must generate both
> both compat_sys_ and sys_ symbols for this handler.

Actually I don't have a concern about this patch, I thoughtthere was
something odd going on with ppc64_personality but I misread, it all
looks pretty good.

>
> A number of architectures including arm and powerpc agree on an
> alternative argument order and numbering for most of these arch-specific
> handlers. A future patch series may allow for asm/unistd.h to signal
> through its defines that a generic implementation of these syscall
> handlers with the correct calling convention be omitted, through the
> __ARCH_WANT_COMPAT_SYS_... convention.

I'm on the fence about including this in changelog. arm developers
might not see it, for example. Putting it in include/linux/compat.h
as a comment  might be better.

If you keep it in the changelog, maybe preface with something like
aside, side note, in future or something so that's clear it's not part
of the current patch.

Thanks,
Nick

>
> Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
> ---
> V1 -> V2: All syscall handlers wrapped by this macro.
> V2 -> V3: Move creation of do_ppc64_personality helper to prior patch.
> V3 -> V4: Fix parenthesis alignment. Don't emit sys_*** symbols.
> ---
>  arch/powerpc/include/asm/syscalls.h          | 10 ++--
>  arch/powerpc/kernel/sys_ppc32.c              | 45 ++++++++++--------
>  arch/powerpc/kernel/syscalls.c               | 17 +++++--
>  arch/powerpc/kernel/syscalls/syscall.tbl     | 22 ++++-----
>  .../arch/powerpc/entry/syscalls/syscall.tbl  | 22 ++++-----
>  5 files changed, 64 insertions(+), 52 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/syscalls.h b/arch/powerpc/include/asm/syscalls.h
> index 739498c358a1..3e3aff0835a6 100644
> --- a/arch/powerpc/include/asm/syscalls.h
> +++ b/arch/powerpc/include/asm/syscalls.h
> @@ -16,10 +16,10 @@ long sys_mmap(unsigned long addr, size_t len,
>  long sys_mmap2(unsigned long addr, size_t len,
>  	       unsigned long prot, unsigned long flags,
>  	       unsigned long fd, unsigned long pgoff);
> -long ppc64_personality(unsigned long personality);
> +long sys_ppc64_personality(unsigned long personality);
>  long sys_rtas(struct rtas_args __user *uargs);
> -long ppc_fadvise64_64(int fd, int advice, u32 offset_high, u32 offset_low,
> -		      u32 len_high, u32 len_low);
> +long sys_ppc_fadvise64_64(int fd, int advice, u32 offset_high, u32 offset_low,
> +			  u32 len_high, u32 len_low);
>  
>  #ifdef CONFIG_COMPAT
>  unsigned long compat_sys_mmap2(unsigned long addr, size_t len,
> @@ -40,8 +40,8 @@ int compat_sys_truncate64(const char __user *path, u32 reg4,
>  int compat_sys_ftruncate64(unsigned int fd, u32 reg4, unsigned long len1,
>  			   unsigned long len2);
>  
> -long ppc32_fadvise64(int fd, u32 unused, u32 offset1, u32 offset2,
> -		     size_t len, int advice);
> +long compat_sys_ppc32_fadvise64(int fd, u32 unused, u32 offset1, u32 offset2,
> +				size_t len, int advice);
>  
>  long compat_sys_sync_file_range2(int fd, unsigned int flags,
>  				 unsigned int offset1, unsigned int offset2,
> diff --git a/arch/powerpc/kernel/sys_ppc32.c b/arch/powerpc/kernel/sys_ppc32.c
> index bc6491ed6454..dd9039671227 100644
> --- a/arch/powerpc/kernel/sys_ppc32.c
> +++ b/arch/powerpc/kernel/sys_ppc32.c
> @@ -59,52 +59,55 @@
>  #define merge_64(high, low) ((u64)high << 32) | low
>  #endif
>  
> -compat_ssize_t compat_sys_pread64(unsigned int fd, char __user *ubuf, compat_size_t count,
> -			     u32 reg6, u32 pos1, u32 pos2)
> +COMPAT_SYSCALL_DEFINE6(ppc_pread64,
> +		       unsigned int, fd,
> +		       char __user *, ubuf, compat_size_t, count,
> +		       u32, reg6, u32, pos1, u32, pos2)
>  {
>  	return ksys_pread64(fd, ubuf, count, merge_64(pos1, pos2));
>  }
>  
> -compat_ssize_t compat_sys_pwrite64(unsigned int fd, const char __user *ubuf, compat_size_t count,
> -			      u32 reg6, u32 pos1, u32 pos2)
> +COMPAT_SYSCALL_DEFINE6(ppc_pwrite64,
> +		       unsigned int, fd,
> +		       const char __user *, ubuf, compat_size_t, count,
> +		       u32, reg6, u32, pos1, u32, pos2)
>  {
>  	return ksys_pwrite64(fd, ubuf, count, merge_64(pos1, pos2));
>  }
>  
> -compat_ssize_t compat_sys_readahead(int fd, u32 r4, u32 offset1, u32 offset2, u32 count)
> +COMPAT_SYSCALL_DEFINE5(ppc_readahead,
> +		       int, fd, u32, r4,
> +		       u32, offset1, u32, offset2, u32, count)
>  {
>  	return ksys_readahead(fd, merge_64(offset1, offset2), count);
>  }
>  
> -int compat_sys_truncate64(const char __user * path, u32 reg4,
> -				unsigned long len1, unsigned long len2)
> +COMPAT_SYSCALL_DEFINE4(ppc_truncate64,
> +		       const char __user *, path, u32, reg4,
> +		       unsigned long, len1, unsigned long, len2)
>  {
>  	return ksys_truncate(path, merge_64(len1, len2));
>  }
>  
> -long compat_sys_fallocate(int fd, int mode, u32 offset1, u32 offset2,
> -				     u32 len1, u32 len2)
> -{
> -	return ksys_fallocate(fd, mode, ((loff_t)offset1 << 32) | offset2,
> -			     merge_64(len1, len2));
> -}
> -
> -int compat_sys_ftruncate64(unsigned int fd, u32 reg4, unsigned long len1,
> -				 unsigned long len2)
> +COMPAT_SYSCALL_DEFINE4(ppc_ftruncate64,
> +		       unsigned int, fd, u32, reg4,
> +		       unsigned long, len1, unsigned long, len2)
>  {
>  	return ksys_ftruncate(fd, merge_64(len1, len2));
>  }
>  
> -long ppc32_fadvise64(int fd, u32 unused, u32 offset1, u32 offset2,
> -		     size_t len, int advice)
> +COMPAT_SYSCALL_DEFINE6(ppc32_fadvise64,
> +		       int, fd, u32, unused, u32, offset1, u32, offset2,
> +		       size_t, len, int, advice)
>  {
>  	return ksys_fadvise64_64(fd, merge_64(offset1, offset2), len,
>  				 advice);
>  }
>  
> -long compat_sys_sync_file_range2(int fd, unsigned int flags,
> -				   unsigned offset1, unsigned offset2,
> -				   unsigned nbytes1, unsigned nbytes2)
> +COMPAT_SYSCALL_DEFINE6(ppc_sync_file_range2,
> +		       int, fd, unsigned int, flags,
> +		       unsigned int, offset1, unsigned int, offset2,
> +		       unsigned int, nbytes1, unsigned int, nbytes2)
>  {
>  	loff_t offset = merge_64(offset1, offset2);
>  	loff_t nbytes = merge_64(nbytes1, nbytes2);
> diff --git a/arch/powerpc/kernel/syscalls.c b/arch/powerpc/kernel/syscalls.c
> index 32fadf3c2cd3..2d4c62e5bac7 100644
> --- a/arch/powerpc/kernel/syscalls.c
> +++ b/arch/powerpc/kernel/syscalls.c
> @@ -87,14 +87,23 @@ static inline long do_ppc64_personality(unsigned long personality)
>  		ret = (ret & ~PER_MASK) | PER_LINUX;
>  	return ret;
>  }
> -long ppc64_personality(unsigned long personality)
> +
> +SYSCALL_DEFINE1(ppc64_personality, unsigned long, personality)
>  {
>  	return do_ppc64_personality(personality);
>  }
> -#endif
>  
> -long ppc_fadvise64_64(int fd, int advice, u32 offset_high, u32 offset_low,
> -		      u32 len_high, u32 len_low)
> +#ifdef CONFIG_COMPAT
> +COMPAT_SYSCALL_DEFINE1(ppc64_personality, unsigned long, personality)
> +{
> +	return do_ppc64_personality(personality);
> +}
> +#endif /* CONFIG_COMPAT */
> +#endif /* CONFIG_PPC64 */
> +
> +SYSCALL_DEFINE6(ppc_fadvise64_64,
> +		int, fd, int, advice, u32, offset_high, u32, offset_low,
> +		u32, len_high, u32, len_low)
>  {
>  	return ksys_fadvise64_64(fd, (u64)offset_high << 32 | offset_low,
>  				 (u64)len_high << 32 | len_low, advice);
> diff --git a/arch/powerpc/kernel/syscalls/syscall.tbl b/arch/powerpc/kernel/syscalls/syscall.tbl
> index 4cbbb810ae10..b4c970c9c6b1 100644
> --- a/arch/powerpc/kernel/syscalls/syscall.tbl
> +++ b/arch/powerpc/kernel/syscalls/syscall.tbl
> @@ -178,9 +178,9 @@
>  133	common	fchdir				sys_fchdir
>  134	common	bdflush				sys_ni_syscall
>  135	common	sysfs				sys_sysfs
> -136	32	personality			sys_personality			ppc64_personality
> -136	64	personality			ppc64_personality
> -136	spu	personality			ppc64_personality
> +136	32	personality			sys_personality			compat_sys_ppc64_personality
> +136	64	personality			sys_ppc64_personality
> +136	spu	personality			sys_ppc64_personality
>  137	common	afs_syscall			sys_ni_syscall
>  138	common	setfsuid			sys_setfsuid
>  139	common	setfsgid			sys_setfsgid
> @@ -228,8 +228,8 @@
>  176	64	rt_sigtimedwait			sys_rt_sigtimedwait
>  177	nospu 	rt_sigqueueinfo			sys_rt_sigqueueinfo		compat_sys_rt_sigqueueinfo
>  178	nospu 	rt_sigsuspend			sys_rt_sigsuspend		compat_sys_rt_sigsuspend
> -179	common	pread64				sys_pread64			compat_sys_pread64
> -180	common	pwrite64			sys_pwrite64			compat_sys_pwrite64
> +179	common	pread64				sys_pread64			compat_sys_ppc_pread64
> +180	common	pwrite64			sys_pwrite64			compat_sys_ppc_pwrite64
>  181	common	chown				sys_chown
>  182	common	getcwd				sys_getcwd
>  183	common	capget				sys_capget
> @@ -242,10 +242,10 @@
>  188	common 	putpmsg				sys_ni_syscall
>  189	nospu	vfork				sys_vfork
>  190	common	ugetrlimit			sys_getrlimit			compat_sys_getrlimit
> -191	common	readahead			sys_readahead			compat_sys_readahead
> +191	common	readahead			sys_readahead			compat_sys_ppc_readahead
>  192	32	mmap2				sys_mmap2			compat_sys_mmap2
> -193	32	truncate64			sys_truncate64			compat_sys_truncate64
> -194	32	ftruncate64			sys_ftruncate64			compat_sys_ftruncate64
> +193	32	truncate64			sys_truncate64			compat_sys_ppc_truncate64
> +194	32	ftruncate64			sys_ftruncate64			compat_sys_ppc_ftruncate64
>  195	32	stat64				sys_stat64
>  196	32	lstat64				sys_lstat64
>  197	32	fstat64				sys_fstat64
> @@ -288,7 +288,7 @@
>  230	common	io_submit			sys_io_submit			compat_sys_io_submit
>  231	common	io_cancel			sys_io_cancel
>  232	nospu	set_tid_address			sys_set_tid_address
> -233	common	fadvise64			sys_fadvise64			ppc32_fadvise64
> +233	common	fadvise64			sys_fadvise64			compat_sys_ppc32_fadvise64
>  234	nospu	exit_group			sys_exit_group
>  235	nospu	lookup_dcookie			sys_lookup_dcookie		compat_sys_lookup_dcookie
>  236	common	epoll_create			sys_epoll_create
> @@ -323,7 +323,7 @@
>  251	spu	utimes				sys_utimes
>  252	common	statfs64			sys_statfs64			compat_sys_statfs64
>  253	common	fstatfs64			sys_fstatfs64			compat_sys_fstatfs64
> -254	32	fadvise64_64			ppc_fadvise64_64
> +254	32	fadvise64_64			sys_ppc_fadvise64_64
>  254	spu	fadvise64_64			sys_ni_syscall
>  255	common	rtas				sys_rtas
>  256	32	sys_debug_setcontext		sys_debug_setcontext		sys_ni_syscall
> @@ -390,7 +390,7 @@
>  305	common	signalfd			sys_signalfd			compat_sys_signalfd
>  306	common	timerfd_create			sys_timerfd_create
>  307	common	eventfd				sys_eventfd
> -308	common	sync_file_range2		sys_sync_file_range2		compat_sys_sync_file_range2
> +308	common	sync_file_range2		sys_sync_file_range2		compat_sys_ppc_sync_file_range2
>  309	nospu	fallocate			sys_fallocate			compat_sys_fallocate
>  310	nospu	subpage_prot			sys_subpage_prot
>  311	32	timerfd_settime			sys_timerfd_settime32
> diff --git a/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl b/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl
> index 4cbbb810ae10..b4c970c9c6b1 100644
> --- a/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl
> +++ b/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl
> @@ -178,9 +178,9 @@
>  133	common	fchdir				sys_fchdir
>  134	common	bdflush				sys_ni_syscall
>  135	common	sysfs				sys_sysfs
> -136	32	personality			sys_personality			ppc64_personality
> -136	64	personality			ppc64_personality
> -136	spu	personality			ppc64_personality
> +136	32	personality			sys_personality			compat_sys_ppc64_personality
> +136	64	personality			sys_ppc64_personality
> +136	spu	personality			sys_ppc64_personality
>  137	common	afs_syscall			sys_ni_syscall
>  138	common	setfsuid			sys_setfsuid
>  139	common	setfsgid			sys_setfsgid
> @@ -228,8 +228,8 @@
>  176	64	rt_sigtimedwait			sys_rt_sigtimedwait
>  177	nospu 	rt_sigqueueinfo			sys_rt_sigqueueinfo		compat_sys_rt_sigqueueinfo
>  178	nospu 	rt_sigsuspend			sys_rt_sigsuspend		compat_sys_rt_sigsuspend
> -179	common	pread64				sys_pread64			compat_sys_pread64
> -180	common	pwrite64			sys_pwrite64			compat_sys_pwrite64
> +179	common	pread64				sys_pread64			compat_sys_ppc_pread64
> +180	common	pwrite64			sys_pwrite64			compat_sys_ppc_pwrite64
>  181	common	chown				sys_chown
>  182	common	getcwd				sys_getcwd
>  183	common	capget				sys_capget
> @@ -242,10 +242,10 @@
>  188	common 	putpmsg				sys_ni_syscall
>  189	nospu	vfork				sys_vfork
>  190	common	ugetrlimit			sys_getrlimit			compat_sys_getrlimit
> -191	common	readahead			sys_readahead			compat_sys_readahead
> +191	common	readahead			sys_readahead			compat_sys_ppc_readahead
>  192	32	mmap2				sys_mmap2			compat_sys_mmap2
> -193	32	truncate64			sys_truncate64			compat_sys_truncate64
> -194	32	ftruncate64			sys_ftruncate64			compat_sys_ftruncate64
> +193	32	truncate64			sys_truncate64			compat_sys_ppc_truncate64
> +194	32	ftruncate64			sys_ftruncate64			compat_sys_ppc_ftruncate64
>  195	32	stat64				sys_stat64
>  196	32	lstat64				sys_lstat64
>  197	32	fstat64				sys_fstat64
> @@ -288,7 +288,7 @@
>  230	common	io_submit			sys_io_submit			compat_sys_io_submit
>  231	common	io_cancel			sys_io_cancel
>  232	nospu	set_tid_address			sys_set_tid_address
> -233	common	fadvise64			sys_fadvise64			ppc32_fadvise64
> +233	common	fadvise64			sys_fadvise64			compat_sys_ppc32_fadvise64
>  234	nospu	exit_group			sys_exit_group
>  235	nospu	lookup_dcookie			sys_lookup_dcookie		compat_sys_lookup_dcookie
>  236	common	epoll_create			sys_epoll_create
> @@ -323,7 +323,7 @@
>  251	spu	utimes				sys_utimes
>  252	common	statfs64			sys_statfs64			compat_sys_statfs64
>  253	common	fstatfs64			sys_fstatfs64			compat_sys_fstatfs64
> -254	32	fadvise64_64			ppc_fadvise64_64
> +254	32	fadvise64_64			sys_ppc_fadvise64_64
>  254	spu	fadvise64_64			sys_ni_syscall
>  255	common	rtas				sys_rtas
>  256	32	sys_debug_setcontext		sys_debug_setcontext		sys_ni_syscall
> @@ -390,7 +390,7 @@
>  305	common	signalfd			sys_signalfd			compat_sys_signalfd
>  306	common	timerfd_create			sys_timerfd_create
>  307	common	eventfd				sys_eventfd
> -308	common	sync_file_range2		sys_sync_file_range2		compat_sys_sync_file_range2
> +308	common	sync_file_range2		sys_sync_file_range2		compat_sys_ppc_sync_file_range2
>  309	nospu	fallocate			sys_fallocate			compat_sys_fallocate
>  310	nospu	subpage_prot			sys_subpage_prot
>  311	32	timerfd_settime			sys_timerfd_settime32
> -- 
> 2.34.1

Re: [PATCH v4 08/20] powerpc: Include all arch-specific syscall prototypes

[Nicholas Piggin]

On Wed Aug 24, 2022 at 12:05 PM AEST, Rohan McLure wrote:
> Forward declare all syscall handler prototypes where a generic prototype
> is not provided in either linux/syscalls.h or linux/compat.h in
> asm/syscalls.h. This is required for compile-time type-checking for
> syscall handlers, which is implemented later in this series.
>
> 32-bit compatibility syscall handlers are expressed in terms of types in
> ppc32.h. Expose this header globally.
>
> Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
> ---
> V1 -> V2: Explicitly include prototypes.
> V2 -> V3: Remove extraneous #include <asm/compat.h> and ppc_fallocate
> prototype. Rename header.
> ---
>  arch/powerpc/include/asm/syscalls.h          | 90 +++++++++++++-----
>  .../ppc32.h => include/asm/syscalls_32.h}    |  0
>  arch/powerpc/kernel/signal_32.c              |  2 +-
>  arch/powerpc/perf/callchain_32.c             |  2 +-
>  4 files changed, 70 insertions(+), 24 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/syscalls.h b/arch/powerpc/include/asm/syscalls.h
> index 3e3aff0835a6..91417dee534e 100644
> --- a/arch/powerpc/include/asm/syscalls.h
> +++ b/arch/powerpc/include/asm/syscalls.h
> @@ -8,45 +8,91 @@
>  #include <linux/types.h>
>  #include <linux/compat.h>
>  
> +#ifdef CONFIG_PPC64
> +#include <asm/syscalls_32.h>
> +#endif
> +#include <asm/unistd.h>
> +#include <asm/ucontext.h>
> +
>  struct rtas_args;
>  
> +#ifndef CONFIG_ARCH_HAS_SYSCALL_WRAPPER

Do you need this ifdef?

> +
> +/*
> + * PowerPC architecture-specific syscalls
> + */
> +
> +long sys_rtas(struct rtas_args __user *uargs);
> +long sys_ni_syscall(void);
> +
> +#ifdef CONFIG_PPC64
> +long sys_ppc64_personality(unsigned long personality);
> +#ifdef CONFIG_COMPAT
> +long compat_sys_ppc64_personality(unsigned long personality);
> +#endif /* CONFIG_COMPAT */
> +#endif /* CONFIG_PPC64 */
> +
> +/* Parameters are reordered for powerpc to avoid padding */
> +long sys_ppc_fadvise64_64(int fd, int advice,
> +			  u32 offset_high, u32 offset_low,
> +			  u32 len_high, u32 len_low);

Should this be under PPC32 since you're adding the ifdefs?

Because you added a new comment here... This is register padding
to do with something, even/odd pair calling convention? I can't
remember the details would you be able to expand the comment a bit
because I'm sure I'll forget it again too.

Thanks,
Nick

Re: [PATCH v4 09/20] powerpc: Enable compile-time check for syscall handlers

[Nicholas Piggin]

On Wed Aug 24, 2022 at 12:05 PM AEST, Rohan McLure wrote:
> The table of syscall handlers and registered compatibility syscall
> handlers has in past been produced using assembly, with function
> references resolved at link time. This moves link-time errors to
> compile-time, by rewriting systbl.S in C, and including the
> linux/syscalls.h, linux/compat.h and asm/syscalls.h headers for
> prototypes.

Well this is pretty cool.

Unrelated, but since commit ab66dcc76d6a, is
arch/powerpc/kernel/systbl_chk.sh unused in the tree?

>
> Reported-by: Arnd Bergmann <arnd@arndb.de>
> Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
> ---
> V1 -> V2: New patch.
> ---
>  arch/powerpc/kernel/{systbl.S => systbl.c} | 27 ++++++++++----------
>  1 file changed, 14 insertions(+), 13 deletions(-)
>
> diff --git a/arch/powerpc/kernel/systbl.S b/arch/powerpc/kernel/systbl.c
> similarity index 59%
> rename from arch/powerpc/kernel/systbl.S
> rename to arch/powerpc/kernel/systbl.c
> index cb3358886203..99ffdfef6b9c 100644
> --- a/arch/powerpc/kernel/systbl.S
> +++ b/arch/powerpc/kernel/systbl.c
> @@ -10,31 +10,32 @@
>   * PPC64 updates by Dave Engebretsen (engebret@us.ibm.com) 
>   */
>  
> -#include <asm/ppc_asm.h>
> +#include <linux/syscalls.h>
> +#include <linux/compat.h>
> +#include <asm/unistd.h>
> +#include <asm/syscalls.h>
>  
> -.section .rodata,"a"
> +#define __SYSCALL_WITH_COMPAT(nr, entry, compat) __SYSCALL(nr, entry)
>  
> -#ifdef CONFIG_PPC64
> -	.p2align	3
> -#define __SYSCALL(nr, entry)	.8byte entry
> +#ifdef CONFIG_ARCH_HAS_SYSCALL_WRAPPER
> +#define __SYSCALL(nr, entry) [nr] = __powerpc_##entry,
> +#define __powerpc_sys_ni_syscall	sys_ni_syscall
>  #else
> -#define __SYSCALL(nr, entry)	.long entry
> +#define __SYSCALL(nr, entry) [nr] = entry,
>  #endif
>  
> -#define __SYSCALL_WITH_COMPAT(nr, native, compat)	__SYSCALL(nr, native)
> -.globl sys_call_table
> -sys_call_table:
> +void *sys_call_table[] = {

Humour me, the asm version had this in rodata, does this change that or
does it somehow get put back in there? Should this be const?

Otherwise, 

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>

>  #ifdef CONFIG_PPC64
>  #include <asm/syscall_table_64.h>
>  #else
>  #include <asm/syscall_table_32.h>
>  #endif
> +};
>  
>  #ifdef CONFIG_COMPAT
>  #undef __SYSCALL_WITH_COMPAT
>  #define __SYSCALL_WITH_COMPAT(nr, native, compat)	__SYSCALL(nr, compat)
> -.globl compat_sys_call_table
> -compat_sys_call_table:
> -#define compat_sys_sigsuspend	sys_sigsuspend
> +void *compat_sys_call_table[] = {
>  #include <asm/syscall_table_32.h>
> -#endif
> +};
> +#endif /* CONFIG_COMPAT */
> -- 
> 2.34.1

Re: [PATCH v4 10/20] powerpc: Use common syscall handler type

[Nicholas Piggin]

On Wed Aug 24, 2022 at 12:05 PM AEST, Rohan McLure wrote:
> Cause syscall handlers to be typed as follows when called indirectly
> throughout the kernel.
>
> typedef long (*syscall_fn)(unsigned long, unsigned long, unsigned long,
>                            unsigned long, unsigned long, unsigned long);

The point is... better type checking?

>
> Since both 32 and 64-bit abis allow for at least the first six
> machine-word length parameters to a function to be passed by registers,
> even handlers which admit fewer than six parameters may be viewed as
> having the above type.
>
> Fixup comparisons in VDSO to avoid pointer-integer comparison. Introduce
> explicit cast on systems with SPUs.
>
> Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
> ---
> V1 -> V2: New patch.
> V2 -> V3: Remove unnecessary cast from const syscall_fn to syscall_fn
> ---
>  arch/powerpc/include/asm/syscall.h          | 7 +++++--
>  arch/powerpc/include/asm/syscalls.h         | 1 +
>  arch/powerpc/kernel/systbl.c                | 6 +++---
>  arch/powerpc/kernel/vdso.c                  | 4 ++--
>  arch/powerpc/platforms/cell/spu_callbacks.c | 6 +++---
>  5 files changed, 14 insertions(+), 10 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/syscall.h b/arch/powerpc/include/asm/syscall.h
> index 25fc8ad9a27a..d2a8dfd5de33 100644
> --- a/arch/powerpc/include/asm/syscall.h
> +++ b/arch/powerpc/include/asm/syscall.h
> @@ -14,9 +14,12 @@
>  #include <linux/sched.h>
>  #include <linux/thread_info.h>
>  
> +typedef long (*syscall_fn)(unsigned long, unsigned long, unsigned long,
> +			   unsigned long, unsigned long, unsigned long);
> +
>  /* ftrace syscalls requires exporting the sys_call_table */
> -extern const unsigned long sys_call_table[];
> -extern const unsigned long compat_sys_call_table[];
> +extern const syscall_fn sys_call_table[];
> +extern const syscall_fn compat_sys_call_table[];

Ah you constify it in this patch. I think the previous patch should have
kept the const, and it should keep the unsigned long type rather than
use void *. Either that or do this patch first.

>  static inline int syscall_get_nr(struct task_struct *task, struct pt_regs *regs)
>  {
> diff --git a/arch/powerpc/include/asm/syscalls.h b/arch/powerpc/include/asm/syscalls.h
> index 91417dee534e..e979b7593d2b 100644
> --- a/arch/powerpc/include/asm/syscalls.h
> +++ b/arch/powerpc/include/asm/syscalls.h
> @@ -8,6 +8,7 @@
>  #include <linux/types.h>
>  #include <linux/compat.h>
>  
> +#include <asm/syscall.h>
>  #ifdef CONFIG_PPC64
>  #include <asm/syscalls_32.h>
>  #endif

Is this necessary or should be in another patch?

> diff --git a/arch/powerpc/kernel/systbl.c b/arch/powerpc/kernel/systbl.c
> index 99ffdfef6b9c..b88a9c2a1f50 100644
> --- a/arch/powerpc/kernel/systbl.c
> +++ b/arch/powerpc/kernel/systbl.c
> @@ -21,10 +21,10 @@
>  #define __SYSCALL(nr, entry) [nr] = __powerpc_##entry,
>  #define __powerpc_sys_ni_syscall	sys_ni_syscall
>  #else
> -#define __SYSCALL(nr, entry) [nr] = entry,
> +#define __SYSCALL(nr, entry) [nr] = (void *) entry,
>  #endif

Also perhaps this should have been in the prior pach and this pach
should change the cast from void to syscall_fn ?

>  
> -void *sys_call_table[] = {
> +const syscall_fn sys_call_table[] = {
>  #ifdef CONFIG_PPC64
>  #include <asm/syscall_table_64.h>
>  #else
> @@ -35,7 +35,7 @@ void *sys_call_table[] = {
>  #ifdef CONFIG_COMPAT
>  #undef __SYSCALL_WITH_COMPAT
>  #define __SYSCALL_WITH_COMPAT(nr, native, compat)	__SYSCALL(nr, compat)
> -void *compat_sys_call_table[] = {
> +const syscall_fn compat_sys_call_table[] = {
>  #include <asm/syscall_table_32.h>
>  };
>  #endif /* CONFIG_COMPAT */
> diff --git a/arch/powerpc/kernel/vdso.c b/arch/powerpc/kernel/vdso.c
> index 0da287544054..080c9e7de0c0 100644
> --- a/arch/powerpc/kernel/vdso.c
> +++ b/arch/powerpc/kernel/vdso.c
> @@ -313,10 +313,10 @@ static void __init vdso_setup_syscall_map(void)
>  	unsigned int i;
>  
>  	for (i = 0; i < NR_syscalls; i++) {
> -		if (sys_call_table[i] != (unsigned long)&sys_ni_syscall)
> +		if (sys_call_table[i] != (void *)&sys_ni_syscall)
>  			vdso_data->syscall_map[i >> 5] |= 0x80000000UL >> (i & 0x1f);
>  		if (IS_ENABLED(CONFIG_COMPAT) &&
> -		    compat_sys_call_table[i] != (unsigned long)&sys_ni_syscall)
> +		    compat_sys_call_table[i] != (void *)&sys_ni_syscall)

Also these.

Thanks,
Nick

>  			vdso_data->compat_syscall_map[i >> 5] |= 0x80000000UL >> (i & 0x1f);
>  	}
>  }
> diff --git a/arch/powerpc/platforms/cell/spu_callbacks.c b/arch/powerpc/platforms/cell/spu_callbacks.c
> index fe0d8797a00a..e780c14c5733 100644
> --- a/arch/powerpc/platforms/cell/spu_callbacks.c
> +++ b/arch/powerpc/platforms/cell/spu_callbacks.c
> @@ -34,15 +34,15 @@
>   *	mbind, mq_open, ipc, ...
>   */
>  
> -static void *spu_syscall_table[] = {
> +static const syscall_fn spu_syscall_table[] = {
>  #define __SYSCALL_WITH_COMPAT(nr, entry, compat) __SYSCALL(nr, entry)
> -#define __SYSCALL(nr, entry) [nr] = entry,
> +#define __SYSCALL(nr, entry) [nr] = (void *) entry,
>  #include <asm/syscall_table_spu.h>
>  };
>  
>  long spu_sys_callback(struct spu_syscall_block *s)
>  {
> -	long (*syscall)(u64 a1, u64 a2, u64 a3, u64 a4, u64 a5, u64 a6);
> +	syscall_fn syscall;
>  
>  	if (s->nr_ret >= ARRAY_SIZE(spu_syscall_table)) {
>  		pr_debug("%s: invalid syscall #%lld", __func__, s->nr_ret);
> -- 
> 2.34.1

Re: [PATCH v4 02/20] powerpc: Use generic fallocate compatibility syscall

[Christophe Leroy]

Le 12/09/2022 à 11:57, Arnd Bergmann a écrit :
> On Mon, Sep 12, 2022, at 10:38 AM, Nicholas Piggin wrote:
>> On Wed Aug 24, 2022 at 12:05 PM AEST, Rohan McLure wrote:
>>> The powerpc fallocate compat syscall handler is identical to the
>>> generic implementation provided by commit 59c10c52f573f ("riscv:
>>> compat: syscall: Add compat_sys_call_table implementation"), and as
>>> such can be removed in favour of the generic implementation.
>>>
>>> A future patch series will replace more architecture-defined syscall
>>> handlers with generic implementations, dependent on introducing generic
>>> implementations that are compatible with powerpc and arm's parameter
>>> reorderings.
>>>
>>> Reported-by: Arnd Bergmann <arnd@arndb.de>
>>> Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
>>> ---
>>> V1 -> V2: Remove arch-specific fallocate handler.
>>> V2 -> V3: Remove generic fallocate prototype. Move to beginning of
>>> series.
>>> ---
> 
>>> @@ -16,6 +16,11 @@ typedef u16		compat_ipc_pid_t;
>>>   #include <asm-generic/compat.h>
>>>   
>>>   #ifdef __BIG_ENDIAN__
>>> +#define compat_arg_u64(name)		u32  name##_hi, u32  name##_lo
>>> +#define compat_arg_u64_dual(name)	u32, name##_hi, u32, name##_lo
>>> +#define compat_arg_u64_glue(name)	(((u64)name##_lo & 0xffffffffUL) | \
>>> +					 ((u64)name##_hi << 32))
>>
>> Is there a reason not to put this in asm-generic/compat.h?
>>
>> Possibly you want to put this with the other compat definitions and
>> above the asm-generic include. The generic header expects the arch to
>> include it after defining what it wants to override.
> 
> Yes, makes sense. I think the riscv people added this to asm-generic,
> they tried to do only the minimal parts.
> 
> In theory, any architecture could have its own calling conventions
> for each syscall and have them in the opposite order for one
> endianess. I checked the seven non-generic implementations of the
> sys_fallocate() syscall and all except powerpc have the same
> ABI as the generic one.
> 
> The powerpc difference is that in little-endian mode, only
> the 'len' argument is swapped but the 'offset' argument is
> still high/low:
> 
> long compat_sys_fallocate(int fd, int mode, u32 offset1, u32 offset2,
>                                      u32 len1, u32 len2)
> {
>         return ksys_fallocate(fd, mode, ((loff_t)offset1 << 32) | offset2,
>                              merge_64(len1, len2));
> }
> 
> It's probably best to first fix this by using merge_64(offset1,
> offset2) and allow that patch to be backported to stable kernels,
> before changing it over to the generic code in a separate patch
> within that series.
> 
> A related issue seems to exist in ppc_fadvise64_64(), which
> uses the wrong argument order on ppc32le compat tasks, in addition
> to having at least three different calling conventions across
> architectures.

Do ppc32le exist at all ?

Native ppc32 is be only, and I'm not aware that ppc64 is able to run 
ppc32le compat tasks.

Christophe

Re: [PATCH v4 02/20] powerpc: Use generic fallocate compatibility syscall

[Arnd Bergmann]

On Mon, Sep 12, 2022, at 1:00 PM, Christophe Leroy wrote:
> Le 12/09/2022 à 11:57, Arnd Bergmann a écrit :
>> On Mon, Sep 12, 2022, at 10:38 AM, Nicholas Piggin wrote:
>> 
>> The powerpc difference is that in little-endian mode, only
>> the 'len' argument is swapped but the 'offset' argument is
>> still high/low:
>> 
>> long compat_sys_fallocate(int fd, int mode, u32 offset1, u32 offset2,
>>                                      u32 len1, u32 len2)
>> {
>>         return ksys_fallocate(fd, mode, ((loff_t)offset1 << 32) | offset2,
>>                              merge_64(len1, len2));
>> }
>> 
>> It's probably best to first fix this by using merge_64(offset1,
>> offset2) and allow that patch to be backported to stable kernels,
>> before changing it over to the generic code in a separate patch
>> within that series.
>> 
>> A related issue seems to exist in ppc_fadvise64_64(), which
>> uses the wrong argument order on ppc32le compat tasks, in addition
>> to having at least three different calling conventions across
>> architectures.
>
> Do ppc32le exist at all ?
>
> Native ppc32 is be only, and I'm not aware that ppc64 is able to run 
> ppc32le compat tasks.

I'm not aware of anyone using it, but commit 6e944aed8859
("powerpc/64: Make COMPAT user-selectable disabled on littleendian
by default.") added support to the kernel, and commit
57f48b4b74e7 ("powerpc/compat_sys: swap hi/lo parts of 64-bit
syscall args in LE mode") changed the compat syscall helpers
to pass 64-bit arguments correctly but apparently got fallocate()
and fadvise64_64() wrong.

With Rohan's series, we use generic implementation, which
is the sensible ABI but the change is technically an ABI
change for ppc32le, and it makes sense to split the change
that fixes the behavior from the cleanup.

       Arnd

Re: [PATCH v4 11/20] powerpc: Add ZEROIZE_GPRS macros for register clears

[Nicholas Piggin]

On Wed Aug 24, 2022 at 12:05 PM AEST, Rohan McLure wrote:
> Macros for restoring and saving registers to and from the stack exist.
> Provide macros with the same interface for clearing a range of gprs by
> setting each register's value in that range to zero.

Can I bikeshed this a bit more and ask if you would change the order?

Saving and restoring macros are incidental, and are neither the change
nor the reson for it. I think the changelog reads better if you state
the change (or the problem) up front.

Provid register zeroing macros ... follow the same convention as
existing register stack save/restore macros ... will be used in later
change to zero registers.

Or not, if you disagree.

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>

> The resulting macros are called ZEROIZE_GPRS and ZEROIZE_NVGPRS, keeping
> with the naming of the accompanying restore and save macros, and usage
> of zeroize to describe this operation elsewhere in the kernel.
>
> Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
> ---
> V1 -> V2: Change 'ZERO' usage in naming to 'NULLIFY', a more obvious verb
> V2 -> V3: Change 'NULLIFY' usage in naming to 'ZEROIZE', which has
> precedent in kernel and explicitly specifies that we are zeroing.
> V3 -> V4: Update commit message to use zeroize.
> ---
>  arch/powerpc/include/asm/ppc_asm.h | 22 ++++++++++++++++++++++
>  1 file changed, 22 insertions(+)
>
> diff --git a/arch/powerpc/include/asm/ppc_asm.h b/arch/powerpc/include/asm/ppc_asm.h
> index 83c02f5a7f2a..b95689ada59c 100644
> --- a/arch/powerpc/include/asm/ppc_asm.h
> +++ b/arch/powerpc/include/asm/ppc_asm.h
> @@ -33,6 +33,20 @@
>  	.endr
>  .endm
>  
> +/*
> + * This expands to a sequence of register clears for regs start to end
> + * inclusive, of the form:
> + *
> + *   li rN, 0
> + */
> +.macro ZEROIZE_REGS start, end
> +	.Lreg=\start
> +	.rept (\end - \start + 1)
> +	li	.Lreg, 0
> +	.Lreg=.Lreg+1
> +	.endr
> +.endm
> +
>  /*
>   * Macros for storing registers into and loading registers from
>   * exception frames.
> @@ -49,6 +63,14 @@
>  #define REST_NVGPRS(base)		REST_GPRS(13, 31, base)
>  #endif
>  
> +#define	ZEROIZE_GPRS(start, end)	ZEROIZE_REGS start, end
> +#ifdef __powerpc64__
> +#define	ZEROIZE_NVGPRS()		ZEROIZE_GPRS(14, 31)
> +#else
> +#define	ZEROIZE_NVGPRS()		ZEROIZE_GPRS(13, 31)
> +#endif
> +#define	ZEROIZE_GPR(n)			ZEROIZE_GPRS(n, n)
> +
>  #define SAVE_GPR(n, base)		SAVE_GPRS(n, n, base)
>  #define REST_GPR(n, base)		REST_GPRS(n, n, base)
>  
> -- 
> 2.34.1

Re: [PATCH v4 12/20] Revert "powerpc/syscall: Save r3 in regs->orig_r3"

[Nicholas Piggin]

On Wed Aug 24, 2022 at 12:05 PM AEST, Rohan McLure wrote:
> This reverts commit 8875f47b7681aa4e4484a9b612577b044725f839.

Can you use short hash and commit title format? Also it's no longer
just reverting that patch, so maybe just come up with a new title
for this patch and reference the two patches here?

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>

Oh, I meant to say for the last patch and this one. Can you move
them to after patch 13? That way all your build and wrapper mucking
are in the first patches, and then all the zeroizing comes next.

Thanks,
Nick

>
> Save caller's original r3 state to the kernel stackframe before entering
> system_call_exception. This allows for user registers to be cleared by
> the time system_call_exception is entered, reducing the influence of
> user registers on speculation within the kernel.
>
> Prior to this commit, orig_r3 was saved at the beginning of
> system_call_exception. Instead, save orig_r3 while the user value is
> still live in r3.
>
> Also replicate this early save in 32-bit. A similar save was removed in
> commit 6f76a01173cc ("powerpc/syscall: implement system call entry/exit logic in C for PPC32")
> when 32-bit adopted system_call_exception. Revert its removal of orig_r3
> saves.
>
> Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
> ---
> V2 -> V3: New commit.
> ---
>  arch/powerpc/kernel/entry_32.S     | 1 +
>  arch/powerpc/kernel/interrupt_64.S | 2 ++
>  arch/powerpc/kernel/syscall.c      | 1 -
>  3 files changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
> index 1d599df6f169..44dfce9a60c5 100644
> --- a/arch/powerpc/kernel/entry_32.S
> +++ b/arch/powerpc/kernel/entry_32.S
> @@ -101,6 +101,7 @@ __kuep_unlock:
>  
>  	.globl	transfer_to_syscall
>  transfer_to_syscall:
> +	stw	r3, ORIG_GPR3(r1)
>  	stw	r11, GPR1(r1)
>  	stw	r11, 0(r1)
>  	mflr	r12
> diff --git a/arch/powerpc/kernel/interrupt_64.S b/arch/powerpc/kernel/interrupt_64.S
> index ce25b28cf418..71d2d9497283 100644
> --- a/arch/powerpc/kernel/interrupt_64.S
> +++ b/arch/powerpc/kernel/interrupt_64.S
> @@ -91,6 +91,7 @@ _ASM_NOKPROBE_SYMBOL(system_call_vectored_\name)
>  	li	r11,\trapnr
>  	std	r11,_TRAP(r1)
>  	std	r12,_CCR(r1)
> +	std	r3,ORIG_GPR3(r1)
>  	addi	r10,r1,STACK_FRAME_OVERHEAD
>  	ld	r11,exception_marker@toc(r2)
>  	std	r11,-16(r10)		/* "regshere" marker */
> @@ -275,6 +276,7 @@ END_BTB_FLUSH_SECTION
>  	std	r10,_LINK(r1)
>  	std	r11,_TRAP(r1)
>  	std	r12,_CCR(r1)
> +	std	r3,ORIG_GPR3(r1)
>  	addi	r10,r1,STACK_FRAME_OVERHEAD
>  	ld	r11,exception_marker@toc(r2)
>  	std	r11,-16(r10)		/* "regshere" marker */
> diff --git a/arch/powerpc/kernel/syscall.c b/arch/powerpc/kernel/syscall.c
> index 81ace9e8b72b..64102a64fd84 100644
> --- a/arch/powerpc/kernel/syscall.c
> +++ b/arch/powerpc/kernel/syscall.c
> @@ -25,7 +25,6 @@ notrace long system_call_exception(long r3, long r4, long r5,
>  	kuap_lock();
>  
>  	add_random_kstack_offset();
> -	regs->orig_gpr3 = r3;
>  
>  	if (IS_ENABLED(CONFIG_PPC_IRQ_SOFT_MASK_DEBUG))
>  		BUG_ON(irq_soft_mask_return() != IRQS_ALL_DISABLED);
> -- 
> 2.34.1

Re: [PATCH v4 13/20] powerpc: Provide syscall wrapper

[Nicholas Piggin]

On Wed Aug 24, 2022 at 12:05 PM AEST, Rohan McLure wrote:
> Implement syscall wrapper as per s390, x86, arm64. When enabled
> cause handlers to accept parameters from a stack frame rather than
> from user scratch register state. This allows for user registers to be
> safely cleared in order to reduce caller influence on speculation
> within syscall routine. The wrapper is a macro that emits syscall
> handler symbols that call into the target handler, obtaining its
> parameters from a struct pt_regs on the stack.
>
> As registers are already saved to the stack prior to calling
> system_call_exception, it appears that this function is executed more
> efficiently with the new stack-pointer convention than with parameters
> passed by registers, avoiding the allocation of a stack frame for this
> method. On a 32-bit system, we see >20% performance increases on the
> null_syscall microbenchmark, and on a Power 8 the performance gains
> amortise the cost of clearing and restoring registers which is
> implemented at the end of this series, seeing final result of ~5.6%
> performance improvement on null_syscall.
>
> Syscalls are wrapped in this fashion on all platforms except for the
> Cell processor as this commit does not provide SPU support. This can be
> quickly fixed in a successive patch, but requires spu_sys_callback to
> allocate a pt_regs structure to satisfy the wrapped calling convention.

I didn't look closely at the syscall wrapper macro gunk but it
generally looks pretty fine, not much change to actual code which
is good...

>
> Co-developed-by: Andrew Donnellan <ajd@linux.ibm.com>
> Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com>
> Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
> ---
> V1 -> V2: Generate prototypes for symbols produced by the wrapper.
> V2 -> V3: Rebased to remove conflict with 1547db7d1f44
> ("powerpc: Move system_call_exception() to syscall.c"). Also remove copy
> from gpr3 save slot on stackframe to orig_r3's slot. Fix whitespace with
> preprocessor defines in system_call_exception.
> ---
>  arch/powerpc/Kconfig                       |  1 +
>  arch/powerpc/include/asm/interrupt.h       |  3 +-
>  arch/powerpc/include/asm/syscall.h         |  4 +
>  arch/powerpc/include/asm/syscall_wrapper.h | 84 ++++++++++++++++++++
>  arch/powerpc/include/asm/syscalls.h        | 25 +++++-
>  arch/powerpc/kernel/entry_32.S             |  6 +-
>  arch/powerpc/kernel/interrupt_64.S         | 16 ++--
>  arch/powerpc/kernel/syscall.c              | 31 +++-----
>  arch/powerpc/kernel/systbl.c               |  2 +
>  arch/powerpc/kernel/vdso.c                 |  2 +
>  10 files changed, 142 insertions(+), 32 deletions(-)
>
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 4c466acdc70d..ef6c83e79c9b 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -137,6 +137,7 @@ config PPC
>  	select ARCH_HAS_STRICT_KERNEL_RWX	if (PPC_BOOK3S || PPC_8xx || 40x) && !HIBERNATION
>  	select ARCH_HAS_STRICT_KERNEL_RWX	if FSL_BOOKE && !HIBERNATION && !RANDOMIZE_BASE
>  	select ARCH_HAS_STRICT_MODULE_RWX	if ARCH_HAS_STRICT_KERNEL_RWX
> +	select ARCH_HAS_SYSCALL_WRAPPER		if !SPU_BASE
>  	select ARCH_HAS_TICK_BROADCAST		if GENERIC_CLOCKEVENTS_BROADCAST
>  	select ARCH_HAS_UACCESS_FLUSHCACHE
>  	select ARCH_HAS_UBSAN_SANITIZE_ALL
> diff --git a/arch/powerpc/include/asm/interrupt.h b/arch/powerpc/include/asm/interrupt.h
> index 8069dbc4b8d1..3f9cad81585c 100644
> --- a/arch/powerpc/include/asm/interrupt.h
> +++ b/arch/powerpc/include/asm/interrupt.h
> @@ -665,8 +665,7 @@ static inline void interrupt_cond_local_irq_enable(struct pt_regs *regs)
>  		local_irq_enable();
>  }
>  
> -long system_call_exception(long r3, long r4, long r5, long r6, long r7, long r8,
> -			   unsigned long r0, struct pt_regs *regs);
> +long system_call_exception(unsigned long r0, struct pt_regs *regs);

Can you change the calling convention to be regs then r0 so regs matches
the argument position in the syscall?

Then we perhaps should look at storing the registers to pt_regs using
the same r3 as base register to save the values in the asm too. That
way it's friendlier to possible static load hit store predictors. Not
for your series but just a possible later idea.

Thanks,
Nick


>  notrace unsigned long syscall_exit_prepare(unsigned long r3, struct pt_regs *regs, long scv);
>  notrace unsigned long interrupt_exit_user_prepare(struct pt_regs *regs);
>  notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs);
> diff --git a/arch/powerpc/include/asm/syscall.h b/arch/powerpc/include/asm/syscall.h
> index d2a8dfd5de33..3dd36c5e334a 100644
> --- a/arch/powerpc/include/asm/syscall.h
> +++ b/arch/powerpc/include/asm/syscall.h
> @@ -14,8 +14,12 @@
>  #include <linux/sched.h>
>  #include <linux/thread_info.h>
>  
> +#ifdef CONFIG_ARCH_HAS_SYSCALL_WRAPPER
> +typedef long (*syscall_fn)(const struct pt_regs *);
> +#else
>  typedef long (*syscall_fn)(unsigned long, unsigned long, unsigned long,
>  			   unsigned long, unsigned long, unsigned long);
> +#endif
>  
>  /* ftrace syscalls requires exporting the sys_call_table */
>  extern const syscall_fn sys_call_table[];
> diff --git a/arch/powerpc/include/asm/syscall_wrapper.h b/arch/powerpc/include/asm/syscall_wrapper.h
> new file mode 100644
> index 000000000000..91bcfa40f740
> --- /dev/null
> +++ b/arch/powerpc/include/asm/syscall_wrapper.h
> @@ -0,0 +1,84 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * syscall_wrapper.h - powerpc specific wrappers to syscall definitions
> + *
> + * Based on arch/{x86,arm64}/include/asm/syscall_wrapper.h
> + */
> +
> +#ifndef __ASM_SYSCALL_WRAPPER_H
> +#define __ASM_SYSCALL_WRAPPER_H
> +
> +struct pt_regs;
> +
> +#define SC_POWERPC_REGS_TO_ARGS(x, ...)				\
> +	__MAP(x,__SC_ARGS					\
> +	      ,,regs->gpr[3],,regs->gpr[4],,regs->gpr[5]	\
> +	      ,,regs->gpr[6],,regs->gpr[7],,regs->gpr[8])
> +
> +#ifdef CONFIG_COMPAT
> +
> +#define COMPAT_SYSCALL_DEFINEx(x, name, ...)						\
> +	long __powerpc_compat_sys##name(const struct pt_regs *regs);			\
> +	ALLOW_ERROR_INJECTION(__powerpc_compat_sys##name, ERRNO);			\
> +	static long __se_compat_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__));		\
> +	static inline long __do_compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));	\
> +	long __powerpc_compat_sys##name(const struct pt_regs *regs)			\
> +	{										\
> +		return __se_compat_sys##name(SC_POWERPC_REGS_TO_ARGS(x,__VA_ARGS__));	\
> +	}										\
> +	static long __se_compat_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__))		\
> +	{										\
> +		return __do_compat_sys##name(__MAP(x,__SC_DELOUSE,__VA_ARGS__));	\
> +	}										\
> +	static inline long __do_compat_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))
> +
> +#define COMPAT_SYSCALL_DEFINE0(sname)						\
> +	long __powerpc_compat_sys_##sname(const struct pt_regs *__unused);	\
> +	ALLOW_ERROR_INJECTION(__powerpc_compat_sys_##sname, ERRNO);		\
> +	long __powerpc_compat_sys_##sname(const struct pt_regs *__unused)
> +
> +#define COND_SYSCALL_COMPAT(name)						\
> +	long __powerpc_compat_sys_##name(const struct pt_regs *regs);		\
> +	long __weak __powerpc_compat_sys_##name(const struct pt_regs *regs)	\
> +	{									\
> +		return sys_ni_syscall();					\
> +	}
> +#define COMPAT_SYS_NI(name) \
> +	SYSCALL_ALIAS(__powerpc_compat_sys_##name, sys_ni_posix_timers);
> +
> +#endif /* CONFIG_COMPAT */
> +
> +#define __SYSCALL_DEFINEx(x, name, ...)						\
> +	long __powerpc_sys##name(const struct pt_regs *regs);			\
> +	ALLOW_ERROR_INJECTION(__powerpc_sys##name, ERRNO);			\
> +	static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__));		\
> +	static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__));	\
> +	long __powerpc_sys##name(const struct pt_regs *regs)			\
> +	{									\
> +		return __se_sys##name(SC_POWERPC_REGS_TO_ARGS(x,__VA_ARGS__));	\
> +	}									\
> +	static long __se_sys##name(__MAP(x,__SC_LONG,__VA_ARGS__))		\
> +	{									\
> +		long ret = __do_sys##name(__MAP(x,__SC_CAST,__VA_ARGS__));	\
> +		__MAP(x,__SC_TEST,__VA_ARGS__);					\
> +		__PROTECT(x, ret,__MAP(x,__SC_ARGS,__VA_ARGS__));		\
> +		return ret;							\
> +	}									\
> +	static inline long __do_sys##name(__MAP(x,__SC_DECL,__VA_ARGS__))
> +
> +#define SYSCALL_DEFINE0(sname)							\
> +	SYSCALL_METADATA(_##sname, 0);						\
> +	long __powerpc_sys_##sname(const struct pt_regs *__unused);		\
> +	ALLOW_ERROR_INJECTION(__powerpc_sys_##sname, ERRNO);			\
> +	long __powerpc_sys_##sname(const struct pt_regs *__unused)
> +
> +#define COND_SYSCALL(name)							\
> +	long __powerpc_sys_##name(const struct pt_regs *regs);			\
> +	long __weak __powerpc_sys_##name(const struct pt_regs *regs)		\
> +	{									\
> +		return sys_ni_syscall();					\
> +	}
> +
> +#define SYS_NI(name) SYSCALL_ALIAS(__powerpc_sys_##name, sys_ni_posix_timers);
> +
> +#endif /* __ASM_SYSCALL_WRAPPER_H */
> diff --git a/arch/powerpc/include/asm/syscalls.h b/arch/powerpc/include/asm/syscalls.h
> index e979b7593d2b..14af648ee82c 100644
> --- a/arch/powerpc/include/asm/syscalls.h
> +++ b/arch/powerpc/include/asm/syscalls.h
> @@ -15,6 +15,12 @@
>  #include <asm/unistd.h>
>  #include <asm/ucontext.h>
>  
> +#ifndef CONFIG_ARCH_HAS_SYSCALL_WRAPPER
> +long sys_ni_syscall(void);
> +#else
> +long sys_ni_syscall(const struct pt_regs *regs);
> +#endif
> +
>  struct rtas_args;
>  
>  #ifndef CONFIG_ARCH_HAS_SYSCALL_WRAPPER
> @@ -24,7 +30,6 @@ struct rtas_args;
>   */
>  
>  long sys_rtas(struct rtas_args __user *uargs);
> -long sys_ni_syscall(void);
>  
>  #ifdef CONFIG_PPC64
>  long sys_ppc64_personality(unsigned long personality);
> @@ -93,6 +98,24 @@ long compat_sys_ppc_sync_file_range2(int fd, unsigned int flags,
>  				     unsigned int nbytes2);
>  #endif /* CONFIG_COMPAT */
>  
> +#else
> +
> +#define __SYSCALL_WITH_COMPAT(nr, native, compat)	__SYSCALL(nr, native)
> +#define __SYSCALL(nr, entry) \
> +	long __powerpc_##entry(const struct pt_regs *regs);
> +
> +#ifdef CONFIG_PPC64
> +#include <asm/syscall_table_64.h>
> +#else
> +#include <asm/syscall_table_32.h>
> +#endif /* CONFIG_PPC64 */
> +
> +#ifdef CONFIG_COMPAT
> +#undef __SYSCALL_WITH_COMPAT
> +#define __SYSCALL_WITH_COMPAT(nr, native, compat)	__SYSCALL(nr, compat)
> +#include <asm/syscall_table_32.h>
> +#endif /* CONFIG_COMPAT */
> +
>  #endif /* CONFIG_ARCH_HAS_SYSCALL_WRAPPER */
>  
>  #endif /* __KERNEL__ */
> diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
> index 44dfce9a60c5..8d6e02ef5dc0 100644
> --- a/arch/powerpc/kernel/entry_32.S
> +++ b/arch/powerpc/kernel/entry_32.S
> @@ -122,9 +122,9 @@ transfer_to_syscall:
>  	SAVE_NVGPRS(r1)
>  	kuep_lock
>  
> -	/* Calling convention has r9 = orig r0, r10 = regs */
> -	addi	r10,r1,STACK_FRAME_OVERHEAD
> -	mr	r9,r0
> +	/* Calling convention has r3 = orig r0, r4 = regs */
> +	addi	r4,r1,STACK_FRAME_OVERHEAD
> +	mr	r3,r0
>  	bl	system_call_exception
>  
>  ret_from_syscall:
> diff --git a/arch/powerpc/kernel/interrupt_64.S b/arch/powerpc/kernel/interrupt_64.S
> index 71d2d9497283..0178aeba3820 100644
> --- a/arch/powerpc/kernel/interrupt_64.S
> +++ b/arch/powerpc/kernel/interrupt_64.S
> @@ -92,9 +92,9 @@ _ASM_NOKPROBE_SYMBOL(system_call_vectored_\name)
>  	std	r11,_TRAP(r1)
>  	std	r12,_CCR(r1)
>  	std	r3,ORIG_GPR3(r1)
> -	addi	r10,r1,STACK_FRAME_OVERHEAD
> +	addi	r4,r1,STACK_FRAME_OVERHEAD
>  	ld	r11,exception_marker@toc(r2)
> -	std	r11,-16(r10)		/* "regshere" marker */
> +	std	r11,-16(r4)		/* "regshere" marker */
>  
>  BEGIN_FTR_SECTION
>  	HMT_MEDIUM
> @@ -109,8 +109,8 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
>  	 * but this is the best we can do.
>  	 */
>  
> -	/* Calling convention has r9 = orig r0, r10 = regs */
> -	mr	r9,r0
> +	/* Calling convention has r3 = orig r0, r4 = regs */
> +	mr	r3,r0
>  	bl	system_call_exception
>  
>  .Lsyscall_vectored_\name\()_exit:
> @@ -277,9 +277,9 @@ END_BTB_FLUSH_SECTION
>  	std	r11,_TRAP(r1)
>  	std	r12,_CCR(r1)
>  	std	r3,ORIG_GPR3(r1)
> -	addi	r10,r1,STACK_FRAME_OVERHEAD
> +	addi	r4,r1,STACK_FRAME_OVERHEAD
>  	ld	r11,exception_marker@toc(r2)
> -	std	r11,-16(r10)		/* "regshere" marker */
> +	std	r11,-16(r4)		/* "regshere" marker */
>  
>  #ifdef CONFIG_PPC_BOOK3S
>  	li	r11,1
> @@ -300,8 +300,8 @@ END_BTB_FLUSH_SECTION
>  	wrteei	1
>  #endif
>  
> -	/* Calling convention has r9 = orig r0, r10 = regs */
> -	mr	r9,r0
> +	/* Calling convention has r3 = orig r0, r4 = regs */
> +	mr	r3,r0
>  	bl	system_call_exception
>  
>  .Lsyscall_exit:
> diff --git a/arch/powerpc/kernel/syscall.c b/arch/powerpc/kernel/syscall.c
> index 64102a64fd84..bda5221b420e 100644
> --- a/arch/powerpc/kernel/syscall.c
> +++ b/arch/powerpc/kernel/syscall.c
> @@ -12,12 +12,8 @@
>  #include <asm/unistd.h>
>  
>  
> -typedef long (*syscall_fn)(long, long, long, long, long, long);
> -
>  /* Has to run notrace because it is entered not completely "reconciled" */
> -notrace long system_call_exception(long r3, long r4, long r5,
> -				   long r6, long r7, long r8,
> -				   unsigned long r0, struct pt_regs *regs)
> +notrace long system_call_exception(unsigned long r0, struct pt_regs *regs)
>  {
>  	long ret;
>  	syscall_fn f;
> @@ -138,12 +134,6 @@ notrace long system_call_exception(long r3, long r4, long r5,
>  		r0 = do_syscall_trace_enter(regs);
>  		if (unlikely(r0 >= NR_syscalls))
>  			return regs->gpr[3];
> -		r3 = regs->gpr[3];
> -		r4 = regs->gpr[4];
> -		r5 = regs->gpr[5];
> -		r6 = regs->gpr[6];
> -		r7 = regs->gpr[7];
> -		r8 = regs->gpr[8];
>  
>  	} else if (unlikely(r0 >= NR_syscalls)) {
>  		if (unlikely(trap_is_unsupported_scv(regs))) {
> @@ -160,18 +150,23 @@ notrace long system_call_exception(long r3, long r4, long r5,
>  	if (unlikely(is_compat_task())) {
>  		f = (void *)compat_sys_call_table[r0];
>  
> -		r3 &= 0x00000000ffffffffULL;
> -		r4 &= 0x00000000ffffffffULL;
> -		r5 &= 0x00000000ffffffffULL;
> -		r6 &= 0x00000000ffffffffULL;
> -		r7 &= 0x00000000ffffffffULL;
> -		r8 &= 0x00000000ffffffffULL;
> +		regs->gpr[3] &= 0x00000000ffffffffULL;
> +		regs->gpr[4] &= 0x00000000ffffffffULL;
> +		regs->gpr[5] &= 0x00000000ffffffffULL;
> +		regs->gpr[6] &= 0x00000000ffffffffULL;
> +		regs->gpr[7] &= 0x00000000ffffffffULL;
> +		regs->gpr[8] &= 0x00000000ffffffffULL;
>  
>  	} else {
>  		f = (void *)sys_call_table[r0];
>  	}
>  
> -	ret = f(r3, r4, r5, r6, r7, r8);
> +#ifdef CONFIG_ARCH_HAS_SYSCALL_WRAPPER
> +	ret = f(regs);
> +#else
> +	ret = f(regs->gpr[3], regs->gpr[4], regs->gpr[5],
> +		regs->gpr[6], regs->gpr[7], regs->gpr[8]);
> +#endif
>  
>  	/*
>  	 * Ultimately, this value will get limited by KSTACK_OFFSET_MAX(),
> diff --git a/arch/powerpc/kernel/systbl.c b/arch/powerpc/kernel/systbl.c
> index b88a9c2a1f50..cb05e302ea58 100644
> --- a/arch/powerpc/kernel/systbl.c
> +++ b/arch/powerpc/kernel/systbl.c
> @@ -15,8 +15,10 @@
>  #include <asm/unistd.h>
>  #include <asm/syscalls.h>
>  
> +#undef __SYSCALL_WITH_COMPAT
>  #define __SYSCALL_WITH_COMPAT(nr, entry, compat) __SYSCALL(nr, entry)
>  
> +#undef __SYSCALL
>  #ifdef CONFIG_ARCH_HAS_SYSCALL_WRAPPER
>  #define __SYSCALL(nr, entry) [nr] = __powerpc_##entry,
>  #define __powerpc_sys_ni_syscall	sys_ni_syscall
> diff --git a/arch/powerpc/kernel/vdso.c b/arch/powerpc/kernel/vdso.c
> index 080c9e7de0c0..88d83162eaf1 100644
> --- a/arch/powerpc/kernel/vdso.c
> +++ b/arch/powerpc/kernel/vdso.c
> @@ -39,6 +39,8 @@
>  extern char vdso32_start, vdso32_end;
>  extern char vdso64_start, vdso64_end;
>  
> +long sys_ni_syscall(void);
> +
>  /*
>   * The vdso data page (aka. systemcfg for old ppc64 fans) is here.
>   * Once the early boot kernel code no longer needs to muck around
> -- 
> 2.34.1

Re: [PATCH v4 14/20] powerpc/64s: Clear/restore caller gprs in syscall interrupt/return

[Nicholas Piggin]

On Wed Aug 24, 2022 at 12:05 PM AEST, Rohan McLure wrote:
> Clear user state in gprs (assign to zero) to reduce the influence of user
> registers on speculation within kernel syscall handlers. Clears occur
> at the very beginning of the sc and scv 0 interrupt handlers, with
> restores occurring following the execution of the syscall handler.
>
> Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
> ---
> V1 -> V2: Update summary
> V2 -> V3: Remove erroneous summary paragraph on syscall_exit_prepare
> V3 -> V4: Use ZEROIZE instead of NULLIFY
> ---
>  arch/powerpc/kernel/interrupt_64.S | 22 ++++++++++++++++++----
>  1 file changed, 18 insertions(+), 4 deletions(-)
>
> diff --git a/arch/powerpc/kernel/interrupt_64.S b/arch/powerpc/kernel/interrupt_64.S
> index 0178aeba3820..a8065209dd8c 100644
> --- a/arch/powerpc/kernel/interrupt_64.S
> +++ b/arch/powerpc/kernel/interrupt_64.S
> @@ -70,7 +70,7 @@ _ASM_NOKPROBE_SYMBOL(system_call_vectored_\name)
>  	ld	r2,PACATOC(r13)
>  	mfcr	r12
>  	li	r11,0
> -	/* Can we avoid saving r3-r8 in common case? */
> +	/* Save syscall parameters in r3-r8 */
>  	std	r3,GPR3(r1)
>  	std	r4,GPR4(r1)
>  	std	r5,GPR5(r1)
> @@ -109,6 +109,13 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
>  	 * but this is the best we can do.
>  	 */
>  
> +	/*
> +	 * Zero user registers to prevent influencing speculative execution
> +	 * state of kernel code.
> +	 */
> +	ZEROIZE_GPRS(5, 12)
> +	ZEROIZE_NVGPRS()
> +
>  	/* Calling convention has r3 = orig r0, r4 = regs */
>  	mr	r3,r0

Ther's not much reason for this to go right against
system_call_exception. You could set it up above where you set r4,
and zero r0 as well with the rest of the volatiles? I guess it'll
be overwritten by mflr r0 right away... although that could be an
implementation detail not everything requires it and mcount call
gets noped out. So probably doesn't hurt to zero it, while we're
being paranoid.

Thanks,
Nick

>  	bl	system_call_exception
> @@ -139,6 +146,7 @@ BEGIN_FTR_SECTION
>  	HMT_MEDIUM_LOW
>  END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
>  
> +	REST_NVGPRS(r1)
>  	cmpdi	r3,0
>  	bne	.Lsyscall_vectored_\name\()_restore_regs
>  
> @@ -181,7 +189,6 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
>  	ld	r4,_LINK(r1)
>  	ld	r5,_XER(r1)
>  
> -	REST_NVGPRS(r1)
>  	ld	r0,GPR0(r1)
>  	mtcr	r2
>  	mtctr	r3
> @@ -249,7 +256,7 @@ END_BTB_FLUSH_SECTION
>  	ld	r2,PACATOC(r13)
>  	mfcr	r12
>  	li	r11,0
> -	/* Can we avoid saving r3-r8 in common case? */
> +	/* Save syscall parameters in r3-r8 */
>  	std	r3,GPR3(r1)
>  	std	r4,GPR4(r1)
>  	std	r5,GPR5(r1)
> @@ -300,6 +307,13 @@ END_BTB_FLUSH_SECTION
>  	wrteei	1
>  #endif
>  
> +	/*
> +	 * Zero user registers to prevent influencing speculative execution
> +	 * state of kernel code.
> +	 */
> +	ZEROIZE_GPRS(5, 12)
> +	ZEROIZE_NVGPRS()
> +
>  	/* Calling convention has r3 = orig r0, r4 = regs */
>  	mr	r3,r0
>  	bl	system_call_exception
> @@ -342,6 +356,7 @@ BEGIN_FTR_SECTION
>  	stdcx.	r0,0,r1			/* to clear the reservation */
>  END_FTR_SECTION_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS)
>  
> +	REST_NVGPRS(r1)
>  	cmpdi	r3,0
>  	bne	.Lsyscall_restore_regs
>  	/* Zero volatile regs that may contain sensitive kernel data */
> @@ -377,7 +392,6 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
>  .Lsyscall_restore_regs:
>  	ld	r3,_CTR(r1)
>  	ld	r4,_XER(r1)
> -	REST_NVGPRS(r1)
>  	mtctr	r3
>  	mtspr	SPRN_XER,r4
>  	ld	r0,GPR0(r1)
> -- 
> 2.34.1

Re: [PATCH v4 15/20] powerpc/64s: Use {ZEROIZE,SAVE,REST}_GPRS macros in sc, scv 0 handlers

[Nicholas Piggin]

On Wed Aug 24, 2022 at 12:05 PM AEST, Rohan McLure wrote:
> Use the convenience macros for saving/clearing/restoring gprs in keeping
> with syscall calling conventions. The plural variants of these macros
> can store a range of registers for concision.
>
> This works well when the user gpr value we are hoping to save is still
> live. In the syscall interrupt handlers, user register state is
> sometimes juggled between registers. Hold-off from issuing the SAVE_GPR
> macro for applicable neighbouring lines to highlight the delicate
> register save logic.
>

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>

> Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
> ---
> V1 -> V2: Update summary
> V2 -> V3: Update summary regarding exclusions for the SAVE_GPR marco.
> Acknowledge new name for ZEROIZE_GPR{,S} macros.
> ---
>  arch/powerpc/kernel/interrupt_64.S | 43 ++++++----------------------
>  1 file changed, 9 insertions(+), 34 deletions(-)
>
> diff --git a/arch/powerpc/kernel/interrupt_64.S b/arch/powerpc/kernel/interrupt_64.S
> index a8065209dd8c..ad302ad93433 100644
> --- a/arch/powerpc/kernel/interrupt_64.S
> +++ b/arch/powerpc/kernel/interrupt_64.S
> @@ -71,12 +71,7 @@ _ASM_NOKPROBE_SYMBOL(system_call_vectored_\name)
>  	mfcr	r12
>  	li	r11,0
>  	/* Save syscall parameters in r3-r8 */
> -	std	r3,GPR3(r1)
> -	std	r4,GPR4(r1)
> -	std	r5,GPR5(r1)
> -	std	r6,GPR6(r1)
> -	std	r7,GPR7(r1)
> -	std	r8,GPR8(r1)
> +	SAVE_GPRS(3, 8, r1)
>  	/* Zero r9-r12, this should only be required when restoring all GPRs */
>  	std	r11,GPR9(r1)
>  	std	r11,GPR10(r1)
> @@ -157,17 +152,10 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
>  	/* Could zero these as per ABI, but we may consider a stricter ABI
>  	 * which preserves these if libc implementations can benefit, so
>  	 * restore them for now until further measurement is done. */
> -	ld	r0,GPR0(r1)
> -	ld	r4,GPR4(r1)
> -	ld	r5,GPR5(r1)
> -	ld	r6,GPR6(r1)
> -	ld	r7,GPR7(r1)
> -	ld	r8,GPR8(r1)
> +	REST_GPR(0, r1)
> +	REST_GPRS(4, 8, r1)
>  	/* Zero volatile regs that may contain sensitive kernel data */
> -	li	r9,0
> -	li	r10,0
> -	li	r11,0
> -	li	r12,0
> +	ZEROIZE_GPRS(9, 12)
>  	mtspr	SPRN_XER,r0
>  
>  	/*
> @@ -189,7 +177,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
>  	ld	r4,_LINK(r1)
>  	ld	r5,_XER(r1)
>  
> -	ld	r0,GPR0(r1)
> +	REST_GPR(0, r1)
>  	mtcr	r2
>  	mtctr	r3
>  	mtlr	r4
> @@ -257,12 +245,7 @@ END_BTB_FLUSH_SECTION
>  	mfcr	r12
>  	li	r11,0
>  	/* Save syscall parameters in r3-r8 */
> -	std	r3,GPR3(r1)
> -	std	r4,GPR4(r1)
> -	std	r5,GPR5(r1)
> -	std	r6,GPR6(r1)
> -	std	r7,GPR7(r1)
> -	std	r8,GPR8(r1)
> +	SAVE_GPRS(3, 8, r1)
>  	/* Zero r9-r12, this should only be required when restoring all GPRs */
>  	std	r11,GPR9(r1)
>  	std	r11,GPR10(r1)
> @@ -360,16 +343,8 @@ END_FTR_SECTION_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS)
>  	cmpdi	r3,0
>  	bne	.Lsyscall_restore_regs
>  	/* Zero volatile regs that may contain sensitive kernel data */
> -	li	r0,0
> -	li	r4,0
> -	li	r5,0
> -	li	r6,0
> -	li	r7,0
> -	li	r8,0
> -	li	r9,0
> -	li	r10,0
> -	li	r11,0
> -	li	r12,0
> +	ZEROIZE_GPR(0)
> +	ZEROIZE_GPRS(4, 12)
>  	mtctr	r0
>  	mtspr	SPRN_XER,r0
>  .Lsyscall_restore_regs_cont:
> @@ -394,7 +369,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
>  	ld	r4,_XER(r1)
>  	mtctr	r3
>  	mtspr	SPRN_XER,r4
> -	ld	r0,GPR0(r1)
> +	REST_GPR(0, r1)
>  	REST_GPRS(4, 12, r1)
>  	b	.Lsyscall_restore_regs_cont
>  .Lsyscall_rst_end:
> -- 
> 2.34.1

Re: [PATCH v4 18/20] powerpc/64s: Fix comment on interrupt handler prologue

[Nicholas Piggin]

On Wed Aug 24, 2022 at 12:05 PM AEST, Rohan McLure wrote:
> Interrupt handlers on 64s systems will often need to save register state
> from the interrupted process to make space for loading special purpose
> registers or for internal state.
>
> Fix a comment documenting a common code path macro in the beginning of
> interrupt handlers where r10 is saved to the PACA to afford space for
> the value of the CFAR. Comment is currently written as if r10-r12 are
> saved to PACA, but in fact only r10 is saved, with r11-r12 saved much
> later. The distance in code between these saves has grown over the many
> revisions of this macro. Fix this by signalling with a comment where
> r11-r12 are saved to the PACA.

Wondering if this kind of comment is useful at all really... But it is
better than broken comment.

Reviewed-by: Nicholas Piggin <npiggin@gmail.com>

>
> Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
> ---
> V1 -> V2: Given its own commit
> V2 -> V3: Annotate r11-r12 save locations with comment.
> ---
>  arch/powerpc/kernel/exceptions-64s.S | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
> index 3d0dc133a9ae..a3b51441b039 100644
> --- a/arch/powerpc/kernel/exceptions-64s.S
> +++ b/arch/powerpc/kernel/exceptions-64s.S
> @@ -281,7 +281,7 @@ BEGIN_FTR_SECTION
>  	mfspr	r9,SPRN_PPR
>  END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
>  	HMT_MEDIUM
> -	std	r10,IAREA+EX_R10(r13)		/* save r10 - r12 */
> +	std	r10,IAREA+EX_R10(r13)		/* save r10 */
>  	.if ICFAR
>  BEGIN_FTR_SECTION
>  	mfspr	r10,SPRN_CFAR
> @@ -321,7 +321,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_CFAR)
>  	mfctr	r10
>  	std	r10,IAREA+EX_CTR(r13)
>  	mfcr	r9
> -	std	r11,IAREA+EX_R11(r13)
> +	std	r11,IAREA+EX_R11(r13)		/* save r11 - r12 */
>  	std	r12,IAREA+EX_R12(r13)
>  
>  	/*
> -- 
> 2.34.1

Re: [PATCH v4 19/20] powerpc/64s: Clear gprs on interrupt routine entry in Book3S

[Nicholas Piggin]

On Wed Aug 24, 2022 at 12:05 PM AEST, Rohan McLure wrote:
> Zero GPRS r0, r2-r11, r14-r31, on entry into the kernel for all
> other interrupt sources to limit influence of user-space values
> in potential speculation gadgets. The remaining gprs are overwritten by
> entry macros to interrupt handlers, irrespective of whether or not a
> given handler consumes these register values.
>
> Prior to this commit, r14-r31 are restored on a per-interrupt basis at
> exit, but now they are always restored. Remove explicit REST_NVGPRS
> invocations as non-volatiles must now always be restored. 32-bit systems
> do not clear user registers on interrupt, and continue to depend on the
> return value of interrupt_exit_user_prepare to determine whether or not
> to restore non-volatiles.
>
> The mmap_bench benchmark in selftests should rapidly invoke pagefaults.
> See ~0.8% performance regression with this mitigation, but this
> indicates the worst-case performance due to heavier-weight interrupt
> handlers.

Ow, my heart :(

Are we not keeping a CONFIG option to rid ourselves of this vile
performance robbing thing? Are we getting rid of the whole
_TIF_RESTOREALL thing too, or does PPC32 want to keep it?

>
> Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
> ---
> V1 -> V2: Add benchmark data
> V2 -> V3: Use ZEROIZE_GPR{,S} macro renames, clarify
> interrupt_exit_user_prepare changes in summary.
> ---
>  arch/powerpc/kernel/exceptions-64s.S | 21 ++++++++-------------
>  arch/powerpc/kernel/interrupt_64.S   |  9 ++-------
>  2 files changed, 10 insertions(+), 20 deletions(-)
>
> diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
> index a3b51441b039..038e42fb2182 100644
> --- a/arch/powerpc/kernel/exceptions-64s.S
> +++ b/arch/powerpc/kernel/exceptions-64s.S
> @@ -502,6 +502,7 @@ DEFINE_FIXED_SYMBOL(\name\()_common_real, text)
>  	std	r10,0(r1)		/* make stack chain pointer	*/
>  	std	r0,GPR0(r1)		/* save r0 in stackframe	*/
>  	std	r10,GPR1(r1)		/* save r1 in stackframe	*/
> +	ZEROIZE_GPR(0)
>  
>  	/* Mark our [H]SRRs valid for return */
>  	li	r10,1
> @@ -538,14 +539,18 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
>  	ld	r10,IAREA+EX_R10(r13)
>  	std	r9,GPR9(r1)
>  	std	r10,GPR10(r1)
> +	ZEROIZE_GPRS(9, 10)

You use 9/10 right afterwards, this'd have to move down to where
you zero r11 at least.

>  	ld	r9,IAREA+EX_R11(r13)	/* move r11 - r13 to stackframe	*/
>  	ld	r10,IAREA+EX_R12(r13)
>  	ld	r11,IAREA+EX_R13(r13)
>  	std	r9,GPR11(r1)
>  	std	r10,GPR12(r1)
>  	std	r11,GPR13(r1)
> +	/* keep r12 ([H]SRR1/MSR), r13 (PACA) for interrupt routine */
> +	ZEROIZE_GPR(11)

Kernel always has to keep r13 so no need to comment that. Keeping r11,
is that for those annoying fp_unavailable etc handlers?

There's probably not much a user can do with this, given they're set
from the MSR. Use can influence some bits of its MSR though. So long
as we're being paranoid, you could add an IOPTION to retain r11 only for
the handlers that need it, or have them load it from MSR and zero it
here.

Thanks,
Nick

>  
>  	SAVE_NVGPRS(r1)
> +	ZEROIZE_NVGPRS()
>  
>  	.if IDAR
>  	.if IISIDE
> @@ -577,8 +582,8 @@ BEGIN_FTR_SECTION
>  END_FTR_SECTION_IFSET(CPU_FTR_CFAR)
>  	ld	r10,IAREA+EX_CTR(r13)
>  	std	r10,_CTR(r1)
> -	std	r2,GPR2(r1)		/* save r2 in stackframe	*/
> -	SAVE_GPRS(3, 8, r1)		/* save r3 - r8 in stackframe   */
> +	SAVE_GPRS(2, 8, r1)		/* save r2 - r8 in stackframe   */
> +	ZEROIZE_GPRS(2, 8)
>  	mflr	r9			/* Get LR, later save to stack	*/
>  	ld	r2,PACATOC(r13)		/* get kernel TOC into r2	*/
>  	std	r9,_LINK(r1)
> @@ -696,6 +701,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_CFAR)
>  	mtlr	r9
>  	ld	r9,_CCR(r1)
>  	mtcr	r9
> +	REST_NVGPRS(r1)
>  	REST_GPRS(2, 13, r1)
>  	REST_GPR(0, r1)
>  	/* restore original r1. */
> @@ -1368,11 +1374,6 @@ ALT_MMU_FTR_SECTION_END_IFCLR(MMU_FTR_TYPE_RADIX)
>  	b	interrupt_return_srr
>  
>  1:	bl	do_break
> -	/*
> -	 * do_break() may have changed the NV GPRS while handling a breakpoint.
> -	 * If so, we need to restore them with their updated values.
> -	 */
> -	REST_NVGPRS(r1)
>  	b	interrupt_return_srr
>  
>  
> @@ -1598,7 +1599,6 @@ EXC_COMMON_BEGIN(alignment_common)
>  	GEN_COMMON alignment
>  	addi	r3,r1,STACK_FRAME_OVERHEAD
>  	bl	alignment_exception
> -	REST_NVGPRS(r1) /* instruction emulation may change GPRs */
>  	b	interrupt_return_srr
>  
>  
> @@ -1708,7 +1708,6 @@ EXC_COMMON_BEGIN(program_check_common)
>  .Ldo_program_check:
>  	addi	r3,r1,STACK_FRAME_OVERHEAD
>  	bl	program_check_exception
> -	REST_NVGPRS(r1) /* instruction emulation may change GPRs */
>  	b	interrupt_return_srr
>  
>  
> @@ -2139,7 +2138,6 @@ EXC_COMMON_BEGIN(emulation_assist_common)
>  	GEN_COMMON emulation_assist
>  	addi	r3,r1,STACK_FRAME_OVERHEAD
>  	bl	emulation_assist_interrupt
> -	REST_NVGPRS(r1) /* instruction emulation may change GPRs */
>  	b	interrupt_return_hsrr
>  
>  
> @@ -2457,7 +2455,6 @@ EXC_COMMON_BEGIN(facility_unavailable_common)
>  	GEN_COMMON facility_unavailable
>  	addi	r3,r1,STACK_FRAME_OVERHEAD
>  	bl	facility_unavailable_exception
> -	REST_NVGPRS(r1) /* instruction emulation may change GPRs */
>  	b	interrupt_return_srr
>  
>  
> @@ -2485,7 +2482,6 @@ EXC_COMMON_BEGIN(h_facility_unavailable_common)
>  	GEN_COMMON h_facility_unavailable
>  	addi	r3,r1,STACK_FRAME_OVERHEAD
>  	bl	facility_unavailable_exception
> -	REST_NVGPRS(r1) /* XXX Shouldn't be necessary in practice */
>  	b	interrupt_return_hsrr
>  
>  
> @@ -2711,7 +2707,6 @@ EXC_COMMON_BEGIN(altivec_assist_common)
>  	addi	r3,r1,STACK_FRAME_OVERHEAD
>  #ifdef CONFIG_ALTIVEC
>  	bl	altivec_assist_exception
> -	REST_NVGPRS(r1) /* instruction emulation may change GPRs */
>  #else
>  	bl	unknown_exception
>  #endif
> diff --git a/arch/powerpc/kernel/interrupt_64.S b/arch/powerpc/kernel/interrupt_64.S
> index ad302ad93433..f9ee93e3a0d3 100644
> --- a/arch/powerpc/kernel/interrupt_64.S
> +++ b/arch/powerpc/kernel/interrupt_64.S
> @@ -432,9 +432,6 @@ interrupt_return_\srr\()_user: /* make backtraces match the _kernel variant */
>  _ASM_NOKPROBE_SYMBOL(interrupt_return_\srr\()_user)
>  	addi	r3,r1,STACK_FRAME_OVERHEAD
>  	bl	interrupt_exit_user_prepare
> -	cmpdi	r3,0
> -	bne-	.Lrestore_nvgprs_\srr
> -.Lrestore_nvgprs_\srr\()_cont:
>  	std	r1,PACA_EXIT_SAVE_R1(r13) /* save r1 for restart */
>  #ifdef CONFIG_PPC_BOOK3S
>  .Linterrupt_return_\srr\()_user_rst_start:
> @@ -448,6 +445,7 @@ _ASM_NOKPROBE_SYMBOL(interrupt_return_\srr\()_user)
>  	stb	r11,PACAIRQHAPPENED(r13) # clear out possible HARD_DIS
>  
>  .Lfast_user_interrupt_return_\srr\():
> +	REST_NVGPRS(r1)
>  #ifdef CONFIG_PPC_BOOK3S
>  	.ifc \srr,srr
>  	lbz	r4,PACASRR_VALID(r13)
> @@ -517,10 +515,6 @@ ALT_FTR_SECTION_END_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS)
>  	b	.	/* prevent speculative execution */
>  .Linterrupt_return_\srr\()_user_rst_end:
>  
> -.Lrestore_nvgprs_\srr\():
> -	REST_NVGPRS(r1)
> -	b	.Lrestore_nvgprs_\srr\()_cont
> -
>  #ifdef CONFIG_PPC_BOOK3S
>  interrupt_return_\srr\()_user_restart:
>  _ASM_NOKPROBE_SYMBOL(interrupt_return_\srr\()_user_restart)
> @@ -561,6 +555,7 @@ _ASM_NOKPROBE_SYMBOL(interrupt_return_\srr\()_kernel)
>  1:
>  
>  .Lfast_kernel_interrupt_return_\srr\():
> +	REST_NVGPRS(r1)
>  	cmpdi	cr1,r3,0
>  #ifdef CONFIG_PPC_BOOK3S
>  	.ifc \srr,srr
> -- 
> 2.34.1

Re: [PATCH v4 17/20] powerpc/64e: Clarify register saves and clears with {SAVE,ZEROIZE}_GPRS

[Nicholas Piggin]

On Wed Aug 24, 2022 at 12:05 PM AEST, Rohan McLure wrote:
> The common interrupt handler prologue macro and the bad_stack
> trampolines include consecutive sequences of register saves, and some
> register clears. Neaten such instances by expanding use of the SAVE_GPRS
> macro and employing the ZEROIZE_GPR macro when appropriate.
>
> Also simplify an invocation of SAVE_GPRS targetting all non-volatile
> registers to SAVE_NVGPRS.
>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>

> Signed-off-by: Rohan Mclure <rmclure@linux.ibm.com>
> ---
> V3 -> V4: New commit.
> ---
>  arch/powerpc/kernel/exceptions-64e.S | 27 +++++++++++---------------
>  1 file changed, 11 insertions(+), 16 deletions(-)
>
> diff --git a/arch/powerpc/kernel/exceptions-64e.S b/arch/powerpc/kernel/exceptions-64e.S
> index 67dc4e3179a0..48c640ca425d 100644
> --- a/arch/powerpc/kernel/exceptions-64e.S
> +++ b/arch/powerpc/kernel/exceptions-64e.S
> @@ -216,17 +216,14 @@ END_FTR_SECTION_IFSET(CPU_FTR_EMB_HV)
>  	mtlr	r10
>  	mtcr	r11
>  
> -	ld	r10,GPR10(r1)
> -	ld	r11,GPR11(r1)
> -	ld	r12,GPR12(r1)
> +	REST_GPRS(10, 12, r1)
>  	mtspr	\scratch,r0
>  
>  	std	r10,\paca_ex+EX_R10(r13);
>  	std	r11,\paca_ex+EX_R11(r13);
>  	ld	r10,_NIP(r1)
>  	ld	r11,_MSR(r1)
> -	ld	r0,GPR0(r1)
> -	ld	r1,GPR1(r1)
> +	REST_GPRS(0, 1, r1)
>  	mtspr	\srr0,r10
>  	mtspr	\srr1,r11
>  	ld	r10,\paca_ex+EX_R10(r13)
> @@ -372,16 +369,15 @@ ret_from_mc_except:
>  /* Core exception code for all exceptions except TLB misses. */
>  #define EXCEPTION_COMMON_LVL(n, scratch, excf)				    \
>  exc_##n##_common:							    \
> -	std	r0,GPR0(r1);		/* save r0 in stackframe */	    \
> -	std	r2,GPR2(r1);		/* save r2 in stackframe */	    \
> -	SAVE_GPRS(3, 9, r1);		/* save r3 - r9 in stackframe */    \
> +	SAVE_GPR(0, r1);		/* save r0 in stackframe */	    \
> +	SAVE_GPRS(2, 9, r1);		/* save r2 - r9 in stackframe */    \
>  	std	r10,_NIP(r1);		/* save SRR0 to stackframe */	    \
>  	std	r11,_MSR(r1);		/* save SRR1 to stackframe */	    \
>  	beq	2f;			/* if from kernel mode */	    \
>  2:	ld	r3,excf+EX_R10(r13);	/* get back r10 */		    \
>  	ld	r4,excf+EX_R11(r13);	/* get back r11 */		    \
>  	mfspr	r5,scratch;		/* get back r13 */		    \
> -	std	r12,GPR12(r1);		/* save r12 in stackframe */	    \
> +	SAVE_GPR(12, r1);		/* save r12 in stackframe */	    \
>  	ld	r2,PACATOC(r13);	/* get kernel TOC into r2 */	    \
>  	mflr	r6;			/* save LR in stackframe */	    \
>  	mfctr	r7;			/* save CTR in stackframe */	    \
> @@ -390,7 +386,7 @@ exc_##n##_common:							    \
>  	lwz	r10,excf+EX_CR(r13);	/* load orig CR back from PACA	*/  \
>  	lbz	r11,PACAIRQSOFTMASK(r13); /* get current IRQ softe */	    \
>  	ld	r12,exception_marker@toc(r2);				    \
> -	li	r0,0;							    \
> +	ZEROIZE_GPR(0);							    \
>  	std	r3,GPR10(r1);		/* save r10 to stackframe */	    \
>  	std	r4,GPR11(r1);		/* save r11 to stackframe */	    \
>  	std	r5,GPR13(r1);		/* save it to stackframe */	    \
> @@ -1056,15 +1052,14 @@ bad_stack_book3e:
>  	mfspr	r11,SPRN_ESR
>  	std	r10,_DEAR(r1)
>  	std	r11,_ESR(r1)
> -	std	r0,GPR0(r1);		/* save r0 in stackframe */	    \
> -	std	r2,GPR2(r1);		/* save r2 in stackframe */	    \
> -	SAVE_GPRS(3, 9, r1);		/* save r3 - r9 in stackframe */    \
> +	SAVE_GPR(0, r1);		/* save r0 in stackframe */	    \
> +	SAVE_GPRS(2, 9, r1);		/* save r2 - r9 in stackframe */    \
>  	ld	r3,PACA_EXGEN+EX_R10(r13);/* get back r10 */		    \
>  	ld	r4,PACA_EXGEN+EX_R11(r13);/* get back r11 */		    \
>  	mfspr	r5,SPRN_SPRG_GEN_SCRATCH;/* get back r13 XXX can be wrong */ \
>  	std	r3,GPR10(r1);		/* save r10 to stackframe */	    \
>  	std	r4,GPR11(r1);		/* save r11 to stackframe */	    \
> -	std	r12,GPR12(r1);		/* save r12 in stackframe */	    \
> +	SAVE_GPR(12, r1);		/* save r12 in stackframe */	    \
>  	std	r5,GPR13(r1);		/* save it to stackframe */	    \
>  	mflr	r10
>  	mfctr	r11
> @@ -1072,12 +1067,12 @@ bad_stack_book3e:
>  	std	r10,_LINK(r1)
>  	std	r11,_CTR(r1)
>  	std	r12,_XER(r1)
> -	SAVE_GPRS(14, 31, r1)
> +	SAVE_NVGPRS(r1)
>  	lhz	r12,PACA_TRAP_SAVE(r13)
>  	std	r12,_TRAP(r1)
>  	addi	r11,r1,INT_FRAME_SIZE
>  	std	r11,0(r1)
> -	li	r12,0
> +	ZEROIZE_GPR(12)
>  	std	r12,0(r11)
>  	ld	r2,PACATOC(r13)
>  1:	addi	r3,r1,STACK_FRAME_OVERHEAD
> -- 
> 2.34.1

Re: [PATCH v4 09/20] powerpc: Enable compile-time check for syscall handlers

[Michael Ellerman]

"Nicholas Piggin" <npiggin@gmail.com> writes:
> On Wed Aug 24, 2022 at 12:05 PM AEST, Rohan McLure wrote:
...
>> diff --git a/arch/powerpc/kernel/systbl.S b/arch/powerpc/kernel/systbl.c
>> similarity index 59%
>> rename from arch/powerpc/kernel/systbl.S
>> rename to arch/powerpc/kernel/systbl.c
>> index cb3358886203..99ffdfef6b9c 100644
>> --- a/arch/powerpc/kernel/systbl.S
>> +++ b/arch/powerpc/kernel/systbl.c
>> @@ -10,31 +10,32 @@
>>   * PPC64 updates by Dave Engebretsen (engebret@us.ibm.com) 
>>   */
>>  
>> -#include <asm/ppc_asm.h>
>> +#include <linux/syscalls.h>
>> +#include <linux/compat.h>
>> +#include <asm/unistd.h>
>> +#include <asm/syscalls.h>
>>  
>> -.section .rodata,"a"
>> +#define __SYSCALL_WITH_COMPAT(nr, entry, compat) __SYSCALL(nr, entry)
>>  
>> -#ifdef CONFIG_PPC64
>> -	.p2align	3
>> -#define __SYSCALL(nr, entry)	.8byte entry
>> +#ifdef CONFIG_ARCH_HAS_SYSCALL_WRAPPER
>> +#define __SYSCALL(nr, entry) [nr] = __powerpc_##entry,
>> +#define __powerpc_sys_ni_syscall	sys_ni_syscall
>>  #else
>> -#define __SYSCALL(nr, entry)	.long entry
>> +#define __SYSCALL(nr, entry) [nr] = entry,
>>  #endif
>>  
>> -#define __SYSCALL_WITH_COMPAT(nr, native, compat)	__SYSCALL(nr, native)
>> -.globl sys_call_table
>> -sys_call_table:
>> +void *sys_call_table[] = {
>
> Humour me, the asm version had this in rodata, does this change that or
> does it somehow get put back in there? Should this be const?

Even with const I still see it not landing in rodata for some reason.

$ grep -e start_rodata -e end_rodata -e sys_call_table .build/System.map
c000000000f90000 D __start_rodata
c0000000012b0000 R __end_rodata
c0000000027d51b0 D sys_call_table

vs before the series:

c000000000f80000 D __start_rodata
c000000000f805f0 D sys_call_table
c0000000012a0000 R __end_rodata


cheers

Re: [PATCH v4 08/20] powerpc: Include all arch-specific syscall prototypes

[Rohan McLure]

> On 12 Sep 2022, at 8:33 pm, Nicholas Piggin <npiggin@gmail.com> wrote:
> 
> On Wed Aug 24, 2022 at 12:05 PM AEST, Rohan McLure wrote:
>> Forward declare all syscall handler prototypes where a generic prototype
>> is not provided in either linux/syscalls.h or linux/compat.h in
>> asm/syscalls.h. This is required for compile-time type-checking for
>> syscall handlers, which is implemented later in this series.
>> 
>> 32-bit compatibility syscall handlers are expressed in terms of types in
>> ppc32.h. Expose this header globally.
>> 
>> Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
>> ---
>> V1 -> V2: Explicitly include prototypes.
>> V2 -> V3: Remove extraneous #include <asm/compat.h> and ppc_fallocate
>> prototype. Rename header.
>> ---
>> arch/powerpc/include/asm/syscalls.h          | 90 +++++++++++++-----
>> .../ppc32.h => include/asm/syscalls_32.h}    |  0
>> arch/powerpc/kernel/signal_32.c              |  2 +-
>> arch/powerpc/perf/callchain_32.c             |  2 +-
>> 4 files changed, 70 insertions(+), 24 deletions(-)
>> 
>> diff --git a/arch/powerpc/include/asm/syscalls.h b/arch/powerpc/include/asm/syscalls.h
>> index 3e3aff0835a6..91417dee534e 100644
>> --- a/arch/powerpc/include/asm/syscalls.h
>> +++ b/arch/powerpc/include/asm/syscalls.h
>> @@ -8,45 +8,91 @@
>> #include <linux/types.h>
>> #include <linux/compat.h>
>> 
>> +#ifdef CONFIG_PPC64
>> +#include <asm/syscalls_32.h>
>> +#endif
>> +#include <asm/unistd.h>
>> +#include <asm/ucontext.h>
>> +
>> struct rtas_args;
>> 
>> +#ifndef CONFIG_ARCH_HAS_SYSCALL_WRAPPER
> 
> Do you need this ifdef?

Good spot. I’ll introduce that with syscall wrappers.

>> +
>> +/*
>> + * PowerPC architecture-specific syscalls
>> + */
>> +
>> +long sys_rtas(struct rtas_args __user *uargs);
>> +long sys_ni_syscall(void);
>> +
>> +#ifdef CONFIG_PPC64
>> +long sys_ppc64_personality(unsigned long personality);
>> +#ifdef CONFIG_COMPAT
>> +long compat_sys_ppc64_personality(unsigned long personality);
>> +#endif /* CONFIG_COMPAT */
>> +#endif /* CONFIG_PPC64 */
>> +
>> +/* Parameters are reordered for powerpc to avoid padding */
>> +long sys_ppc_fadvise64_64(int fd, int advice,
>> +			  u32 offset_high, u32 offset_low,
>> +			  u32 len_high, u32 len_low);
> 
> Should this be under PPC32 since you're adding the ifdefs?
> 
> Because you added a new comment here... This is register padding
> to do with something, even/odd pair calling convention? I can't
> remember the details would you be able to expand the comment a bit
> because I'm sure I'll forget it again too.

Cool. I’ll neaten this up and change that comment.

> 
> Thanks,
> Nick

Re: [PATCH v4 03/20] powerpc/32: Remove powerpc select specialisation

[Rohan McLure]

> On 12 Sep 2022, at 7:03 pm, Nicholas Piggin <npiggin@gmail.com> wrote:
> 
> On Wed Aug 24, 2022 at 12:05 PM AEST, Rohan McLure wrote:
>> Syscall #82 has been implemented for 32-bit platforms in a unique way on
>> powerpc systems. This hack will in effect guess whether the caller is
>> expecting new select semantics or old select semantics. It does so via a
>> guess, based off the first parameter. In new select, this parameter
>> represents the length of a user-memory array of file descriptors, and in
>> old select this is a pointer to an arguments structure.
>> 
>> The heuristic simply interprets sufficiently large values of its first
>> parameter as being a call to old select. The following is a discussion
>> on how this syscall should be handled.
>> 
>> Link: https://lore.kernel.org/lkml/13737de5-0eb7-e881-9af0-163b0d29a1a0@csgroup.eu/
> 
> Seems okay to me, probably Christophe needs to ack it.
> Should some of that history be included directly in this changelog?
> 
> Should ppc64 compat be added back too, if this is being updated instead
> of removed? I don't know much about compat but it seems odd not provide
> it (considering it's just using compat_sys_old_select, isn't it?

That would make sense to me. I’ll put that in syscall.tbl.

> Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
> 
>> 
>> As discussed in this thread, the existence of such a hack suggests that for
>> whatever powerpc binaries may predate glibc, it is most likely that they
>> would have taken use of the old select semantics. x86 and arm64 both
>> implement this syscall with oldselect semantics.
>> 
>> Remove the powerpc implementation, and update syscall.tbl to refer to emit
>> a reference to sys_old_select for 32-bit binaries, in keeping with how
>> other architectures support syscall #82.
>> 
>> Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
>> ---
>> V1 -> V2: Remove arch-specific select handler
>> V2 -> V3: Remove ppc_old_select prototype in <asm/syscalls.h>. Move to
>> earlier in patch series
>> ---
>> arch/powerpc/include/asm/syscalls.h           |  2 --
>> arch/powerpc/kernel/syscalls.c                | 17 -----------------
>> arch/powerpc/kernel/syscalls/syscall.tbl      |  2 +-
>> .../arch/powerpc/entry/syscalls/syscall.tbl   |  2 +-
>> 4 files changed, 2 insertions(+), 21 deletions(-)
>> 
>> diff --git a/arch/powerpc/include/asm/syscalls.h b/arch/powerpc/include/asm/syscalls.h
>> index 675a8f5ec3ca..739498c358a1 100644
>> --- a/arch/powerpc/include/asm/syscalls.h
>> +++ b/arch/powerpc/include/asm/syscalls.h
>> @@ -18,8 +18,6 @@ long sys_mmap2(unsigned long addr, size_t len,
>> 	       unsigned long fd, unsigned long pgoff);
>> long ppc64_personality(unsigned long personality);
>> long sys_rtas(struct rtas_args __user *uargs);
>> -int ppc_select(int n, fd_set __user *inp, fd_set __user *outp,
>> -	       fd_set __user *exp, struct __kernel_old_timeval __user *tvp);
>> long ppc_fadvise64_64(int fd, int advice, u32 offset_high, u32 offset_low,
>> 		      u32 len_high, u32 len_low);
>> 
>> diff --git a/arch/powerpc/kernel/syscalls.c b/arch/powerpc/kernel/syscalls.c
>> index fc999140bc27..ef5896bee818 100644
>> --- a/arch/powerpc/kernel/syscalls.c
>> +++ b/arch/powerpc/kernel/syscalls.c
>> @@ -63,23 +63,6 @@ SYSCALL_DEFINE6(mmap, unsigned long, addr, size_t, len,
>> 	return do_mmap2(addr, len, prot, flags, fd, offset, PAGE_SHIFT);
>> }
>> 
>> -#ifdef CONFIG_PPC32
>> -/*
>> - * Due to some executables calling the wrong select we sometimes
>> - * get wrong args.  This determines how the args are being passed
>> - * (a single ptr to them all args passed) then calls
>> - * sys_select() with the appropriate args. -- Cort
>> - */
>> -int
>> -ppc_select(int n, fd_set __user *inp, fd_set __user *outp, fd_set __user *exp, struct __kernel_old_timeval __user *tvp)
>> -{
>> -	if ((unsigned long)n >= 4096)
>> -		return sys_old_select((void __user *)n);
>> -
>> -	return sys_select(n, inp, outp, exp, tvp);
>> -}
>> -#endif
>> -
>> #ifdef CONFIG_PPC64
>> long ppc64_personality(unsigned long personality)
>> {
>> diff --git a/arch/powerpc/kernel/syscalls/syscall.tbl b/arch/powerpc/kernel/syscalls/syscall.tbl
>> index 2600b4237292..4cbbb810ae10 100644
>> --- a/arch/powerpc/kernel/syscalls/syscall.tbl
>> +++ b/arch/powerpc/kernel/syscalls/syscall.tbl
>> @@ -110,7 +110,7 @@
>> 79	common	settimeofday			sys_settimeofday		compat_sys_settimeofday
>> 80	common	getgroups			sys_getgroups
>> 81	common	setgroups			sys_setgroups
>> -82	32	select				ppc_select			sys_ni_syscall
>> +82	32	select				sys_old_select			sys_ni_syscall
>> 82	64	select				sys_ni_syscall
>> 82	spu	select				sys_ni_syscall
>> 83	common	symlink				sys_symlink
>> diff --git a/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl b/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl
>> index 2600b4237292..4cbbb810ae10 100644
>> --- a/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl
>> +++ b/tools/perf/arch/powerpc/entry/syscalls/syscall.tbl
>> @@ -110,7 +110,7 @@
>> 79	common	settimeofday			sys_settimeofday		compat_sys_settimeofday
>> 80	common	getgroups			sys_getgroups
>> 81	common	setgroups			sys_setgroups
>> -82	32	select				ppc_select			sys_ni_syscall
>> +82	32	select				sys_old_select			sys_ni_syscall
>> 82	64	select				sys_ni_syscall
>> 82	spu	select				sys_ni_syscall
>> 83	common	symlink				sys_symlink
>> -- 
>> 2.34.1

Re: [PATCH v4 06/20] powerpc: Remove direct call to mmap2 syscall handlers

[Rohan McLure]

> On 12 Sep 2022, at 7:47 pm, Nicholas Piggin <npiggin@gmail.com> wrote:
> 
> On Wed Aug 24, 2022 at 12:05 PM AEST, Rohan McLure wrote:
>> Syscall handlers should not be invoked internally by their symbol names,
>> as these symbols defined by the architecture-defined SYSCALL_DEFINE
>> macro. Move the compatibility syscall definition for mmap2 to
>> syscalls.c, so that all mmap implementations can share an inline helper
>> function, as is done with the personality handlers.
>> 
>> Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
> 
> Is there any point to keping sys_ppc32.c at all? Might as well move them
> all to syscall.c IMO.

Currently serves as a fairly arbitrary distinginction between compat calls
and others, noting that a compat variant of personality is in syscalls.c.
May as well get rid of it.

> Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
> 
>> ---
>> V1 -> V2: Move mmap2 compat implementation to asm/kernel/syscalls.c.
>> V3 -> V4: Move to be applied before syscall wrapper introduced.
>> ---
>> arch/powerpc/kernel/sys_ppc32.c |  9 ---------
>> arch/powerpc/kernel/syscalls.c  | 11 +++++++++++
>> 2 files changed, 11 insertions(+), 9 deletions(-)
>> 
>> diff --git a/arch/powerpc/kernel/sys_ppc32.c b/arch/powerpc/kernel/sys_ppc32.c
>> index f4edcc9489fb..bc6491ed6454 100644
>> --- a/arch/powerpc/kernel/sys_ppc32.c
>> +++ b/arch/powerpc/kernel/sys_ppc32.c
>> @@ -25,7 +25,6 @@
>> #include <linux/poll.h>
>> #include <linux/personality.h>
>> #include <linux/stat.h>
>> -#include <linux/mman.h>
>> #include <linux/in.h>
>> #include <linux/syscalls.h>
>> #include <linux/unistd.h>
>> @@ -48,14 +47,6 @@
>> #include <asm/syscalls.h>
>> #include <asm/switch_to.h>
>> 
>> -unsigned long compat_sys_mmap2(unsigned long addr, size_t len,
>> -			  unsigned long prot, unsigned long flags,
>> -			  unsigned long fd, unsigned long pgoff)
>> -{
>> -	/* This should remain 12 even if PAGE_SIZE changes */
>> -	return sys_mmap(addr, len, prot, flags, fd, pgoff << 12);
>> -}
>> -
>> /* 
>>  * long long munging:
>>  * The 32 bit ABI passes long longs in an odd even register pair.
>> diff --git a/arch/powerpc/kernel/syscalls.c b/arch/powerpc/kernel/syscalls.c
>> index b8461128c8f7..32fadf3c2cd3 100644
>> --- a/arch/powerpc/kernel/syscalls.c
>> +++ b/arch/powerpc/kernel/syscalls.c
>> @@ -56,6 +56,17 @@ SYSCALL_DEFINE6(mmap2, unsigned long, addr, size_t, len,
>> 	return do_mmap2(addr, len, prot, flags, fd, pgoff, PAGE_SHIFT-12);
>> }
>> 
>> +#ifdef CONFIG_COMPAT
>> +COMPAT_SYSCALL_DEFINE6(mmap2,
>> +		       unsigned long, addr, size_t, len,
>> +		       unsigned long, prot, unsigned long, flags,
>> +		       unsigned long, fd, unsigned long, pgoff)
>> +{
>> +	/* This should remain 12 even if PAGE_SIZE changes */
>> +	return do_mmap2(addr, len, prot, flags, fd, pgoff << 12, PAGE_SHIFT-12);
>> +}
>> +#endif
>> +
>> SYSCALL_DEFINE6(mmap, unsigned long, addr, size_t, len,
>> 		unsigned long, prot, unsigned long, flags,
>> 		unsigned long, fd, off_t, offset)
>> -- 
>> 2.34.1
> 

Re: [PATCH v4 10/20] powerpc: Use common syscall handler type

[Rohan McLure]

> On 12 Sep 2022, at 8:56 pm, Nicholas Piggin <npiggin@gmail.com> wrote:
> 
> On Wed Aug 24, 2022 at 12:05 PM AEST, Rohan McLure wrote:
>> Cause syscall handlers to be typed as follows when called indirectly
>> throughout the kernel.
>> 
>> typedef long (*syscall_fn)(unsigned long, unsigned long, unsigned long,
>>                           unsigned long, unsigned long, unsigned long);
> 
> The point is... better type checking?
> 
>> 
>> Since both 32 and 64-bit abis allow for at least the first six
>> machine-word length parameters to a function to be passed by registers,
>> even handlers which admit fewer than six parameters may be viewed as
>> having the above type.
>> 
>> Fixup comparisons in VDSO to avoid pointer-integer comparison. Introduce
>> explicit cast on systems with SPUs.
>> 
>> Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
>> ---
>> V1 -> V2: New patch.
>> V2 -> V3: Remove unnecessary cast from const syscall_fn to syscall_fn
>> ---
>> arch/powerpc/include/asm/syscall.h          | 7 +++++--
>> arch/powerpc/include/asm/syscalls.h         | 1 +
>> arch/powerpc/kernel/systbl.c                | 6 +++---
>> arch/powerpc/kernel/vdso.c                  | 4 ++--
>> arch/powerpc/platforms/cell/spu_callbacks.c | 6 +++---
>> 5 files changed, 14 insertions(+), 10 deletions(-)
>> 
>> diff --git a/arch/powerpc/include/asm/syscall.h b/arch/powerpc/include/asm/syscall.h
>> index 25fc8ad9a27a..d2a8dfd5de33 100644
>> --- a/arch/powerpc/include/asm/syscall.h
>> +++ b/arch/powerpc/include/asm/syscall.h
>> @@ -14,9 +14,12 @@
>> #include <linux/sched.h>
>> #include <linux/thread_info.h>
>> 
>> +typedef long (*syscall_fn)(unsigned long, unsigned long, unsigned long,
>> +			   unsigned long, unsigned long, unsigned long);
>> +
>> /* ftrace syscalls requires exporting the sys_call_table */
>> -extern const unsigned long sys_call_table[];
>> -extern const unsigned long compat_sys_call_table[];
>> +extern const syscall_fn sys_call_table[];
>> +extern const syscall_fn compat_sys_call_table[];
> 
> Ah you constify it in this patch. I think the previous patch should have
> kept the const, and it should keep the unsigned long type rather than
> use void *. Either that or do this patch first.
> 
>> static inline int syscall_get_nr(struct task_struct *task, struct pt_regs *regs)
>> {
>> diff --git a/arch/powerpc/include/asm/syscalls.h b/arch/powerpc/include/asm/syscalls.h
>> index 91417dee534e..e979b7593d2b 100644
>> --- a/arch/powerpc/include/asm/syscalls.h
>> +++ b/arch/powerpc/include/asm/syscalls.h
>> @@ -8,6 +8,7 @@
>> #include <linux/types.h>
>> #include <linux/compat.h>
>> 
>> +#include <asm/syscall.h>
>> #ifdef CONFIG_PPC64
>> #include <asm/syscalls_32.h>
>> #endif
> 
> Is this necessary or should be in another patch?

Good spot. This belongs in the patch that produces systbl.c.

> 
>> diff --git a/arch/powerpc/kernel/systbl.c b/arch/powerpc/kernel/systbl.c
>> index 99ffdfef6b9c..b88a9c2a1f50 100644
>> --- a/arch/powerpc/kernel/systbl.c
>> +++ b/arch/powerpc/kernel/systbl.c
>> @@ -21,10 +21,10 @@
>> #define __SYSCALL(nr, entry) [nr] = __powerpc_##entry,
>> #define __powerpc_sys_ni_syscall	sys_ni_syscall
>> #else
>> -#define __SYSCALL(nr, entry) [nr] = entry,
>> +#define __SYSCALL(nr, entry) [nr] = (void *) entry,
>> #endif
> 
> Also perhaps this should have been in the prior pach and this pach
> should change the cast from void to syscall_fn ?

This cast to (void *) kicks in when casting functions with six or fewer
parameters to six-parameter type accepting and returning u64. Sadly I can’t
find a way to avoid -Wcast-function-type even with (__force syscall_fn) short
of an ugly casti to void* here. Any suggestions?

> 
>> 
>> -void *sys_call_table[] = {
>> +const syscall_fn sys_call_table[] = {
>> #ifdef CONFIG_PPC64
>> #include <asm/syscall_table_64.h>
>> #else
>> @@ -35,7 +35,7 @@ void *sys_call_table[] = {
>> #ifdef CONFIG_COMPAT
>> #undef __SYSCALL_WITH_COMPAT
>> #define __SYSCALL_WITH_COMPAT(nr, native, compat)	__SYSCALL(nr, compat)
>> -void *compat_sys_call_table[] = {
>> +const syscall_fn compat_sys_call_table[] = {
>> #include <asm/syscall_table_32.h>
>> };
>> #endif /* CONFIG_COMPAT */
>> diff --git a/arch/powerpc/kernel/vdso.c b/arch/powerpc/kernel/vdso.c
>> index 0da287544054..080c9e7de0c0 100644
>> --- a/arch/powerpc/kernel/vdso.c
>> +++ b/arch/powerpc/kernel/vdso.c
>> @@ -313,10 +313,10 @@ static void __init vdso_setup_syscall_map(void)
>> 	unsigned int i;
>> 
>> 	for (i = 0; i < NR_syscalls; i++) {
>> -		if (sys_call_table[i] != (unsigned long)&sys_ni_syscall)
>> +		if (sys_call_table[i] != (void *)&sys_ni_syscall)
>> 			vdso_data->syscall_map[i >> 5] |= 0x80000000UL >> (i & 0x1f);
>> 		if (IS_ENABLED(CONFIG_COMPAT) &&
>> -		    compat_sys_call_table[i] != (unsigned long)&sys_ni_syscall)
>> +		    compat_sys_call_table[i] != (void *)&sys_ni_syscall)
> 
> Also these.
> 
> Thanks,
> Nick
> 
>> 			vdso_data->compat_syscall_map[i >> 5] |= 0x80000000UL >> (i & 0x1f);
>> 	}
>> }
>> diff --git a/arch/powerpc/platforms/cell/spu_callbacks.c b/arch/powerpc/platforms/cell/spu_callbacks.c
>> index fe0d8797a00a..e780c14c5733 100644
>> --- a/arch/powerpc/platforms/cell/spu_callbacks.c
>> +++ b/arch/powerpc/platforms/cell/spu_callbacks.c
>> @@ -34,15 +34,15 @@
>>  *	mbind, mq_open, ipc, ...
>>  */
>> 
>> -static void *spu_syscall_table[] = {
>> +static const syscall_fn spu_syscall_table[] = {
>> #define __SYSCALL_WITH_COMPAT(nr, entry, compat) __SYSCALL(nr, entry)
>> -#define __SYSCALL(nr, entry) [nr] = entry,
>> +#define __SYSCALL(nr, entry) [nr] = (void *) entry,
>> #include <asm/syscall_table_spu.h>
>> };
>> 
>> long spu_sys_callback(struct spu_syscall_block *s)
>> {
>> -	long (*syscall)(u64 a1, u64 a2, u64 a3, u64 a4, u64 a5, u64 a6);
>> +	syscall_fn syscall;
>> 
>> 	if (s->nr_ret >= ARRAY_SIZE(spu_syscall_table)) {
>> 		pr_debug("%s: invalid syscall #%lld", __func__, s->nr_ret);
>> -- 
>> 2.34.1

Re: [PATCH v4 11/20] powerpc: Add ZEROIZE_GPRS macros for register clears

[Rohan McLure]

> On 12 Sep 2022, at 9:09 pm, Nicholas Piggin <npiggin@gmail.com> wrote:
> 
> On Wed Aug 24, 2022 at 12:05 PM AEST, Rohan McLure wrote:
>> Macros for restoring and saving registers to and from the stack exist.
>> Provide macros with the same interface for clearing a range of gprs by
>> setting each register's value in that range to zero.
> 
> Can I bikeshed this a bit more and ask if you would change the order?
> 
> Saving and restoring macros are incidental, and are neither the change
> nor the reson for it. I think the changelog reads better if you state
> the change (or the problem) up front.
> 
> Provid register zeroing macros ... follow the same convention as
> existing register stack save/restore macros ... will be used in later
> change to zero registers.

Thanks for the suggestion, that should read better.

> 
> Or not, if you disagree.
> 
> Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
> 
>> The resulting macros are called ZEROIZE_GPRS and ZEROIZE_NVGPRS, keeping
>> with the naming of the accompanying restore and save macros, and usage
>> of zeroize to describe this operation elsewhere in the kernel.
>> 
>> Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
>> ---
>> V1 -> V2: Change 'ZERO' usage in naming to 'NULLIFY', a more obvious verb
>> V2 -> V3: Change 'NULLIFY' usage in naming to 'ZEROIZE', which has
>> precedent in kernel and explicitly specifies that we are zeroing.
>> V3 -> V4: Update commit message to use zeroize.
>> ---
>> arch/powerpc/include/asm/ppc_asm.h | 22 ++++++++++++++++++++++
>> 1 file changed, 22 insertions(+)
>> 
>> diff --git a/arch/powerpc/include/asm/ppc_asm.h b/arch/powerpc/include/asm/ppc_asm.h
>> index 83c02f5a7f2a..b95689ada59c 100644
>> --- a/arch/powerpc/include/asm/ppc_asm.h
>> +++ b/arch/powerpc/include/asm/ppc_asm.h
>> @@ -33,6 +33,20 @@
>> 	.endr
>> .endm
>> 
>> +/*
>> + * This expands to a sequence of register clears for regs start to end
>> + * inclusive, of the form:
>> + *
>> + *   li rN, 0
>> + */
>> +.macro ZEROIZE_REGS start, end
>> +	.Lreg=\start
>> +	.rept (\end - \start + 1)
>> +	li	.Lreg, 0
>> +	.Lreg=.Lreg+1
>> +	.endr
>> +.endm
>> +
>> /*
>>  * Macros for storing registers into and loading registers from
>>  * exception frames.
>> @@ -49,6 +63,14 @@
>> #define REST_NVGPRS(base)		REST_GPRS(13, 31, base)
>> #endif
>> 
>> +#define	ZEROIZE_GPRS(start, end)	ZEROIZE_REGS start, end
>> +#ifdef __powerpc64__
>> +#define	ZEROIZE_NVGPRS()		ZEROIZE_GPRS(14, 31)
>> +#else
>> +#define	ZEROIZE_NVGPRS()		ZEROIZE_GPRS(13, 31)
>> +#endif
>> +#define	ZEROIZE_GPR(n)			ZEROIZE_GPRS(n, n)
>> +
>> #define SAVE_GPR(n, base)		SAVE_GPRS(n, n, base)
>> #define REST_GPR(n, base)		REST_GPRS(n, n, base)
>> 
>> -- 
>> 2.34.1
> 

Re: [PATCH v4 19/20] powerpc/64s: Clear gprs on interrupt routine entry in Book3S

[Rohan McLure]

> On 12 Sep 2022, at 10:15 pm, Nicholas Piggin <npiggin@gmail.com> wrote:
> 
> On Wed Aug 24, 2022 at 12:05 PM AEST, Rohan McLure wrote:
>> Zero GPRS r0, r2-r11, r14-r31, on entry into the kernel for all
>> other interrupt sources to limit influence of user-space values
>> in potential speculation gadgets. The remaining gprs are overwritten by
>> entry macros to interrupt handlers, irrespective of whether or not a
>> given handler consumes these register values.
>> 
>> Prior to this commit, r14-r31 are restored on a per-interrupt basis at
>> exit, but now they are always restored. Remove explicit REST_NVGPRS
>> invocations as non-volatiles must now always be restored. 32-bit systems
>> do not clear user registers on interrupt, and continue to depend on the
>> return value of interrupt_exit_user_prepare to determine whether or not
>> to restore non-volatiles.
>> 
>> The mmap_bench benchmark in selftests should rapidly invoke pagefaults.
>> See ~0.8% performance regression with this mitigation, but this
>> indicates the worst-case performance due to heavier-weight interrupt
>> handlers.
> 
> Ow, my heart :(
> 
> Are we not keeping a CONFIG option to rid ourselves of this vile
> performance robbing thing? Are we getting rid of the whole
> _TIF_RESTOREALL thing too, or does PPC32 want to keep it?

I see no reason not to include a CONFIG option for this 
mitigation here other than simplicity. Any suggestions for a name?
I’m thinking PPC64_SANITIZE_INTERRUPTS. Defaults on Book3E_64, optional
on Book3S_64.

>> 
>> Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
>> ---
>> V1 -> V2: Add benchmark data
>> V2 -> V3: Use ZEROIZE_GPR{,S} macro renames, clarify
>> interrupt_exit_user_prepare changes in summary.
>> ---
>> arch/powerpc/kernel/exceptions-64s.S | 21 ++++++++-------------
>> arch/powerpc/kernel/interrupt_64.S   |  9 ++-------
>> 2 files changed, 10 insertions(+), 20 deletions(-)
>> 
>> diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
>> index a3b51441b039..038e42fb2182 100644
>> --- a/arch/powerpc/kernel/exceptions-64s.S
>> +++ b/arch/powerpc/kernel/exceptions-64s.S
>> @@ -502,6 +502,7 @@ DEFINE_FIXED_SYMBOL(\name\()_common_real, text)
>> 	std	r10,0(r1)		/* make stack chain pointer	*/
>> 	std	r0,GPR0(r1)		/* save r0 in stackframe	*/
>> 	std	r10,GPR1(r1)		/* save r1 in stackframe	*/
>> +	ZEROIZE_GPR(0)
>> 
>> 	/* Mark our [H]SRRs valid for return */
>> 	li	r10,1
>> @@ -538,14 +539,18 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
>> 	ld	r10,IAREA+EX_R10(r13)
>> 	std	r9,GPR9(r1)
>> 	std	r10,GPR10(r1)
>> +	ZEROIZE_GPRS(9, 10)
> 
> You use 9/10 right afterwards, this'd have to move down to where
> you zero r11 at least.
> 
>> 	ld	r9,IAREA+EX_R11(r13)	/* move r11 - r13 to stackframe	*/
>> 	ld	r10,IAREA+EX_R12(r13)
>> 	ld	r11,IAREA+EX_R13(r13)
>> 	std	r9,GPR11(r1)
>> 	std	r10,GPR12(r1)
>> 	std	r11,GPR13(r1)
>> +	/* keep r12 ([H]SRR1/MSR), r13 (PACA) for interrupt routine */
>> +	ZEROIZE_GPR(11)
> 
> Kernel always has to keep r13 so no need to comment that. Keeping r11,
> is that for those annoying fp_unavailable etc handlers?
> 
> There's probably not much a user can do with this, given they're set
> from the MSR. Use can influence some bits of its MSR though. So long
> as we're being paranoid, you could add an IOPTION to retain r11 only for
> the handlers that need it, or have them load it from MSR and zero it
> here.

Good suggestion. Presume you’re referring to r12 here. I might go the
IOPTION route.

> 
> Thanks,
> Nick
> 
>> 
>> 	SAVE_NVGPRS(r1)
>> +	ZEROIZE_NVGPRS()
>> 
>> 	.if IDAR
>> 	.if IISIDE
>> @@ -577,8 +582,8 @@ BEGIN_FTR_SECTION
>> END_FTR_SECTION_IFSET(CPU_FTR_CFAR)
>> 	ld	r10,IAREA+EX_CTR(r13)
>> 	std	r10,_CTR(r1)
>> -	std	r2,GPR2(r1)		/* save r2 in stackframe	*/
>> -	SAVE_GPRS(3, 8, r1)		/* save r3 - r8 in stackframe   */
>> +	SAVE_GPRS(2, 8, r1)		/* save r2 - r8 in stackframe   */
>> +	ZEROIZE_GPRS(2, 8)
>> 	mflr	r9			/* Get LR, later save to stack	*/
>> 	ld	r2,PACATOC(r13)		/* get kernel TOC into r2	*/
>> 	std	r9,_LINK(r1)
>> @@ -696,6 +701,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_CFAR)
>> 	mtlr	r9
>> 	ld	r9,_CCR(r1)
>> 	mtcr	r9
>> +	REST_NVGPRS(r1)
>> 	REST_GPRS(2, 13, r1)
>> 	REST_GPR(0, r1)
>> 	/* restore original r1. */
>> @@ -1368,11 +1374,6 @@ ALT_MMU_FTR_SECTION_END_IFCLR(MMU_FTR_TYPE_RADIX)
>> 	b	interrupt_return_srr
>> 
>> 1:	bl	do_break
>> -	/*
>> -	 * do_break() may have changed the NV GPRS while handling a breakpoint.
>> -	 * If so, we need to restore them with their updated values.
>> -	 */
>> -	REST_NVGPRS(r1)
>> 	b	interrupt_return_srr
>> 
>> 
>> @@ -1598,7 +1599,6 @@ EXC_COMMON_BEGIN(alignment_common)
>> 	GEN_COMMON alignment
>> 	addi	r3,r1,STACK_FRAME_OVERHEAD
>> 	bl	alignment_exception
>> -	REST_NVGPRS(r1) /* instruction emulation may change GPRs */
>> 	b	interrupt_return_srr
>> 
>> 
>> @@ -1708,7 +1708,6 @@ EXC_COMMON_BEGIN(program_check_common)
>> .Ldo_program_check:
>> 	addi	r3,r1,STACK_FRAME_OVERHEAD
>> 	bl	program_check_exception
>> -	REST_NVGPRS(r1) /* instruction emulation may change GPRs */
>> 	b	interrupt_return_srr
>> 
>> 
>> @@ -2139,7 +2138,6 @@ EXC_COMMON_BEGIN(emulation_assist_common)
>> 	GEN_COMMON emulation_assist
>> 	addi	r3,r1,STACK_FRAME_OVERHEAD
>> 	bl	emulation_assist_interrupt
>> -	REST_NVGPRS(r1) /* instruction emulation may change GPRs */
>> 	b	interrupt_return_hsrr
>> 
>> 
>> @@ -2457,7 +2455,6 @@ EXC_COMMON_BEGIN(facility_unavailable_common)
>> 	GEN_COMMON facility_unavailable
>> 	addi	r3,r1,STACK_FRAME_OVERHEAD
>> 	bl	facility_unavailable_exception
>> -	REST_NVGPRS(r1) /* instruction emulation may change GPRs */
>> 	b	interrupt_return_srr
>> 
>> 
>> @@ -2485,7 +2482,6 @@ EXC_COMMON_BEGIN(h_facility_unavailable_common)
>> 	GEN_COMMON h_facility_unavailable
>> 	addi	r3,r1,STACK_FRAME_OVERHEAD
>> 	bl	facility_unavailable_exception
>> -	REST_NVGPRS(r1) /* XXX Shouldn't be necessary in practice */
>> 	b	interrupt_return_hsrr
>> 
>> 
>> @@ -2711,7 +2707,6 @@ EXC_COMMON_BEGIN(altivec_assist_common)
>> 	addi	r3,r1,STACK_FRAME_OVERHEAD
>> #ifdef CONFIG_ALTIVEC
>> 	bl	altivec_assist_exception
>> -	REST_NVGPRS(r1) /* instruction emulation may change GPRs */
>> #else
>> 	bl	unknown_exception
>> #endif
>> diff --git a/arch/powerpc/kernel/interrupt_64.S b/arch/powerpc/kernel/interrupt_64.S
>> index ad302ad93433..f9ee93e3a0d3 100644
>> --- a/arch/powerpc/kernel/interrupt_64.S
>> +++ b/arch/powerpc/kernel/interrupt_64.S
>> @@ -432,9 +432,6 @@ interrupt_return_\srr\()_user: /* make backtraces match the _kernel variant */
>> _ASM_NOKPROBE_SYMBOL(interrupt_return_\srr\()_user)
>> 	addi	r3,r1,STACK_FRAME_OVERHEAD
>> 	bl	interrupt_exit_user_prepare
>> -	cmpdi	r3,0
>> -	bne-	.Lrestore_nvgprs_\srr
>> -.Lrestore_nvgprs_\srr\()_cont:
>> 	std	r1,PACA_EXIT_SAVE_R1(r13) /* save r1 for restart */
>> #ifdef CONFIG_PPC_BOOK3S
>> .Linterrupt_return_\srr\()_user_rst_start:
>> @@ -448,6 +445,7 @@ _ASM_NOKPROBE_SYMBOL(interrupt_return_\srr\()_user)
>> 	stb	r11,PACAIRQHAPPENED(r13) # clear out possible HARD_DIS
>> 
>> .Lfast_user_interrupt_return_\srr\():
>> +	REST_NVGPRS(r1)
>> #ifdef CONFIG_PPC_BOOK3S
>> 	.ifc \srr,srr
>> 	lbz	r4,PACASRR_VALID(r13)
>> @@ -517,10 +515,6 @@ ALT_FTR_SECTION_END_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS)
>> 	b	.	/* prevent speculative execution */
>> .Linterrupt_return_\srr\()_user_rst_end:
>> 
>> -.Lrestore_nvgprs_\srr\():
>> -	REST_NVGPRS(r1)
>> -	b	.Lrestore_nvgprs_\srr\()_cont
>> -
>> #ifdef CONFIG_PPC_BOOK3S
>> interrupt_return_\srr\()_user_restart:
>> _ASM_NOKPROBE_SYMBOL(interrupt_return_\srr\()_user_restart)
>> @@ -561,6 +555,7 @@ _ASM_NOKPROBE_SYMBOL(interrupt_return_\srr\()_kernel)
>> 1:
>> 
>> .Lfast_kernel_interrupt_return_\srr\():
>> +	REST_NVGPRS(r1)
>> 	cmpdi	cr1,r3,0
>> #ifdef CONFIG_PPC_BOOK3S
>> 	.ifc \srr,srr
>> -- 
>> 2.34.1

Re: [PATCH v4 19/20] powerpc/64s: Clear gprs on interrupt routine entry in Book3S

[Nicholas Piggin]

On Thu Sep 15, 2022 at 4:55 PM AEST, Rohan McLure wrote:
>
>
> > On 12 Sep 2022, at 10:15 pm, Nicholas Piggin <npiggin@gmail.com> wrote:
> > 
> > On Wed Aug 24, 2022 at 12:05 PM AEST, Rohan McLure wrote:
> >> Zero GPRS r0, r2-r11, r14-r31, on entry into the kernel for all
> >> other interrupt sources to limit influence of user-space values
> >> in potential speculation gadgets. The remaining gprs are overwritten by
> >> entry macros to interrupt handlers, irrespective of whether or not a
> >> given handler consumes these register values.
> >> 
> >> Prior to this commit, r14-r31 are restored on a per-interrupt basis at
> >> exit, but now they are always restored. Remove explicit REST_NVGPRS
> >> invocations as non-volatiles must now always be restored. 32-bit systems
> >> do not clear user registers on interrupt, and continue to depend on the
> >> return value of interrupt_exit_user_prepare to determine whether or not
> >> to restore non-volatiles.
> >> 
> >> The mmap_bench benchmark in selftests should rapidly invoke pagefaults.
> >> See ~0.8% performance regression with this mitigation, but this
> >> indicates the worst-case performance due to heavier-weight interrupt
> >> handlers.
> > 
> > Ow, my heart :(
> > 
> > Are we not keeping a CONFIG option to rid ourselves of this vile
> > performance robbing thing? Are we getting rid of the whole
> > _TIF_RESTOREALL thing too, or does PPC32 want to keep it?
>
> I see no reason not to include a CONFIG option for this 
> mitigation here other than simplicity. Any suggestions for a name?
> I’m thinking PPC64_SANITIZE_INTERRUPTS. Defaults on Book3E_64, optional
> on Book3S_64.

INTERRUPT_SANITIZE_REGISTERS perhaps?

>
> >> 
> >> Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
> >> ---
> >> V1 -> V2: Add benchmark data
> >> V2 -> V3: Use ZEROIZE_GPR{,S} macro renames, clarify
> >> interrupt_exit_user_prepare changes in summary.
> >> ---
> >> arch/powerpc/kernel/exceptions-64s.S | 21 ++++++++-------------
> >> arch/powerpc/kernel/interrupt_64.S   |  9 ++-------
> >> 2 files changed, 10 insertions(+), 20 deletions(-)
> >> 
> >> diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
> >> index a3b51441b039..038e42fb2182 100644
> >> --- a/arch/powerpc/kernel/exceptions-64s.S
> >> +++ b/arch/powerpc/kernel/exceptions-64s.S
> >> @@ -502,6 +502,7 @@ DEFINE_FIXED_SYMBOL(\name\()_common_real, text)
> >> 	std	r10,0(r1)		/* make stack chain pointer	*/
> >> 	std	r0,GPR0(r1)		/* save r0 in stackframe	*/
> >> 	std	r10,GPR1(r1)		/* save r1 in stackframe	*/
> >> +	ZEROIZE_GPR(0)
> >> 
> >> 	/* Mark our [H]SRRs valid for return */
> >> 	li	r10,1
> >> @@ -538,14 +539,18 @@ END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
> >> 	ld	r10,IAREA+EX_R10(r13)
> >> 	std	r9,GPR9(r1)
> >> 	std	r10,GPR10(r1)
> >> +	ZEROIZE_GPRS(9, 10)
> > 
> > You use 9/10 right afterwards, this'd have to move down to where
> > you zero r11 at least.
> > 
> >> 	ld	r9,IAREA+EX_R11(r13)	/* move r11 - r13 to stackframe	*/
> >> 	ld	r10,IAREA+EX_R12(r13)
> >> 	ld	r11,IAREA+EX_R13(r13)
> >> 	std	r9,GPR11(r1)
> >> 	std	r10,GPR12(r1)
> >> 	std	r11,GPR13(r1)
> >> +	/* keep r12 ([H]SRR1/MSR), r13 (PACA) for interrupt routine */
> >> +	ZEROIZE_GPR(11)
> > 
> > Kernel always has to keep r13 so no need to comment that. Keeping r11,
> > is that for those annoying fp_unavailable etc handlers?
> > 
> > There's probably not much a user can do with this, given they're set
> > from the MSR. Use can influence some bits of its MSR though. So long
> > as we're being paranoid, you could add an IOPTION to retain r11 only for
> > the handlers that need it, or have them load it from MSR and zero it
> > here.
>
> Good suggestion. Presume you’re referring to r12 here. I might go the
> IOPTION route.

Yeah r12, I think you need it because some of those assembly handlers
expect it there to check SRR1 bits. Having an IOPTION is probably good
and it documents that quirk of those handlers. That's bitten me before.

Thanks,
Nick

Re: [PATCH v4 10/20] powerpc: Use common syscall handler type

[Nicholas Piggin]

On Thu Sep 15, 2022 at 3:45 PM AEST, Rohan McLure wrote:
>
>
> > On 12 Sep 2022, at 8:56 pm, Nicholas Piggin <npiggin@gmail.com> wrote:
> > 
> > On Wed Aug 24, 2022 at 12:05 PM AEST, Rohan McLure wrote:
> >> Cause syscall handlers to be typed as follows when called indirectly
> >> throughout the kernel.
> >> 
> >> typedef long (*syscall_fn)(unsigned long, unsigned long, unsigned long,
> >>                           unsigned long, unsigned long, unsigned long);
> > 
> > The point is... better type checking?
> > 
> >> 
> >> Since both 32 and 64-bit abis allow for at least the first six
> >> machine-word length parameters to a function to be passed by registers,
> >> even handlers which admit fewer than six parameters may be viewed as
> >> having the above type.
> >> 
> >> Fixup comparisons in VDSO to avoid pointer-integer comparison. Introduce
> >> explicit cast on systems with SPUs.
> >> 
> >> Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
> >> ---
> >> V1 -> V2: New patch.
> >> V2 -> V3: Remove unnecessary cast from const syscall_fn to syscall_fn
> >> ---
> >> arch/powerpc/include/asm/syscall.h          | 7 +++++--
> >> arch/powerpc/include/asm/syscalls.h         | 1 +
> >> arch/powerpc/kernel/systbl.c                | 6 +++---
> >> arch/powerpc/kernel/vdso.c                  | 4 ++--
> >> arch/powerpc/platforms/cell/spu_callbacks.c | 6 +++---
> >> 5 files changed, 14 insertions(+), 10 deletions(-)
> >> 
> >> diff --git a/arch/powerpc/include/asm/syscall.h b/arch/powerpc/include/asm/syscall.h
> >> index 25fc8ad9a27a..d2a8dfd5de33 100644
> >> --- a/arch/powerpc/include/asm/syscall.h
> >> +++ b/arch/powerpc/include/asm/syscall.h
> >> @@ -14,9 +14,12 @@
> >> #include <linux/sched.h>
> >> #include <linux/thread_info.h>
> >> 
> >> +typedef long (*syscall_fn)(unsigned long, unsigned long, unsigned long,
> >> +			   unsigned long, unsigned long, unsigned long);
> >> +
> >> /* ftrace syscalls requires exporting the sys_call_table */
> >> -extern const unsigned long sys_call_table[];
> >> -extern const unsigned long compat_sys_call_table[];
> >> +extern const syscall_fn sys_call_table[];
> >> +extern const syscall_fn compat_sys_call_table[];
> > 
> > Ah you constify it in this patch. I think the previous patch should have
> > kept the const, and it should keep the unsigned long type rather than
> > use void *. Either that or do this patch first.
> > 
> >> static inline int syscall_get_nr(struct task_struct *task, struct pt_regs *regs)
> >> {
> >> diff --git a/arch/powerpc/include/asm/syscalls.h b/arch/powerpc/include/asm/syscalls.h
> >> index 91417dee534e..e979b7593d2b 100644
> >> --- a/arch/powerpc/include/asm/syscalls.h
> >> +++ b/arch/powerpc/include/asm/syscalls.h
> >> @@ -8,6 +8,7 @@
> >> #include <linux/types.h>
> >> #include <linux/compat.h>
> >> 
> >> +#include <asm/syscall.h>
> >> #ifdef CONFIG_PPC64
> >> #include <asm/syscalls_32.h>
> >> #endif
> > 
> > Is this necessary or should be in another patch?
>
> Good spot. This belongs in the patch that produces systbl.c.
>
> > 
> >> diff --git a/arch/powerpc/kernel/systbl.c b/arch/powerpc/kernel/systbl.c
> >> index 99ffdfef6b9c..b88a9c2a1f50 100644
> >> --- a/arch/powerpc/kernel/systbl.c
> >> +++ b/arch/powerpc/kernel/systbl.c
> >> @@ -21,10 +21,10 @@
> >> #define __SYSCALL(nr, entry) [nr] = __powerpc_##entry,
> >> #define __powerpc_sys_ni_syscall	sys_ni_syscall
> >> #else
> >> -#define __SYSCALL(nr, entry) [nr] = entry,
> >> +#define __SYSCALL(nr, entry) [nr] = (void *) entry,
> >> #endif
> > 
> > Also perhaps this should have been in the prior pach and this pach
> > should change the cast from void to syscall_fn ?
>
> This cast to (void *) kicks in when casting functions with six or fewer

Right, I was just wondering if it needs to be in the previous patch
because that's where you changed the type from unsigned long to void *.
Maybe there's some reason it's not required, I didn't entirely follow
all the macro expansion.

> parameters to six-parameter type accepting and returning u64. Sadly I can’t
> find a way to avoid -Wcast-function-type even with (__force syscall_fn) short
> of an ugly casti to void* here. Any suggestions?

Ah okay. I think __force is a sparse specific attribute. Not sure if
gcc/clang can do it. There is a diag thing which maybe can turn off
warnings selectively, but if (void *) is turning off the warning
selectively then there would be no benefit to using it :) That's fine to
keep using void *.

Thanks,
Nick