[PATCHv2 00/19] arm64: invoke syscalls with pt_regs

[PATCHv2 00/19] arm64: invoke syscalls with pt_regs

[Mark Rutland]

This series reworks arm64's syscall handling to minimize the propagation
of user-controlled register values into speculated code paths. As with
x86 [1], a wrapper is generated for each syscall, which extracts the
argument from a struct pt_regs. During kernel entry from userspace,
registers are zeroed.

The arm64 kernel code directly invokes some syscalls which the x86 code
doesn't, so I've added ksys_* wrappers for these, following the x86
example. The rest of the series is arm64-specific.

I've pushed the series out to my arm64/syscall-regs branch [2] on
kernel.org.

Since v1 [3]:
* Rebase atop of arm64 for-next/core (for SSBD conflicts)
* Move ksys_personality logic into <linux/syscalls.h>
* Move kcompat_sys_* wrappers to <linux/compat.h>
* Fix scno bounds check to use unisgned comparison
* Fix sve_user_reset() call in el0_svc_handler()
* Add BUILD_BUG() to the !CONFIG_ARM64_SVE stubs
* Accumulate acked-by / reviewed-by tags

Thanks,
Mark.

[1] https://lkml.kernel.org/r/20180330093720.6780-1-linux@dominikbrodowski.net
[2] git://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git
[3] https://lkml.kernel.org/r/20180514094640.27569-1-mark.rutland@arm.com

Mark Rutland (19):
  arm64: consistently use unsigned long for thread flags
  arm64: move SCTLR_EL{1,2} assertions to <asm/sysreg.h>
  arm64: introduce sysreg_clear_set()
  arm64: kill config_sctlr_el1()
  arm64: kill change_cpacr()
  arm64: move sve_user_{enable,disable} to <asm/fpsimd.h>
  arm64: remove sigreturn wrappers
  arm64: convert raw syscall invocation to C
  arm64: convert syscall trace logic to C
  arm64: convert native/compat syscall entry to C
  arm64: don't reload GPRs after apply_ssbd
  arm64: zero GPRs upon entry from EL0
  kernel: add ksys_personality()
  kernel: add kcompat_sys_{f,}statfs64()
  arm64: remove in-kernel call to sys_personality()
  arm64: use {COMPAT,}SYSCALL_DEFINE0 for sigreturn
  arm64: use SYSCALL_DEFINE6() for mmap
  arm64: convert compat wrappers to C
  arm64: implement syscall wrappers

 arch/arm64/Kconfig                       |   1 +
 arch/arm64/include/asm/fpsimd.h          |  17 +++-
 arch/arm64/include/asm/syscall_wrapper.h |  80 +++++++++++++++++
 arch/arm64/include/asm/sysreg.h          |  33 ++++---
 arch/arm64/include/asm/unistd32.h        |  26 +++---
 arch/arm64/kernel/Makefile               |   5 +-
 arch/arm64/kernel/armv8_deprecated.c     |   8 +-
 arch/arm64/kernel/cpu_errata.c           |   3 +-
 arch/arm64/kernel/entry.S                | 145 ++++---------------------------
 arch/arm64/kernel/entry32.S              | 121 --------------------------
 arch/arm64/kernel/fpsimd.c               |  19 ----
 arch/arm64/kernel/signal.c               |   5 +-
 arch/arm64/kernel/signal32.c             |   6 +-
 arch/arm64/kernel/sys.c                  |  19 ++--
 arch/arm64/kernel/sys32.c                | 127 ++++++++++++++++++++++++---
 arch/arm64/kernel/syscall.c              | 114 ++++++++++++++++++++++++
 arch/arm64/kernel/traps.c                |   4 +-
 arch/arm64/mm/fault.c                    |   2 +-
 fs/statfs.c                              |  14 ++-
 include/linux/compat.h                   |  11 +++
 include/linux/syscalls.h                 |  11 +++
 21 files changed, 437 insertions(+), 334 deletions(-)
 create mode 100644 arch/arm64/include/asm/syscall_wrapper.h
 delete mode 100644 arch/arm64/kernel/entry32.S
 create mode 100644 arch/arm64/kernel/syscall.c

-- 
2.11.0

[PATCHv2 14/19] kernel: add kcompat_sys_{f,}statfs64()

[Mark Rutland]

Using this helper allows us to avoid the in-kernel calls to the
compat_sys_{f,}statfs64() sycalls, as are necessary for parameter
mangling in arm64's compat handling.

Following the example of ksys_* functions, kcompat_sys_* functions are
intended to be a drop-in replacement for their compat_sys_*
counterparts, with the same calling convention.

This is necessary to enable conversion of arm64's syscall handling to
use pt_regs wrappers.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Dominik Brodowski <linux@dominikbrodowski.net>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
---
 fs/statfs.c            | 14 ++++++++++++--
 include/linux/compat.h | 11 +++++++++++
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/fs/statfs.c b/fs/statfs.c
index 5b2a24f0f263..f0216629621d 100644
--- a/fs/statfs.c
+++ b/fs/statfs.c
@@ -335,7 +335,7 @@ static int put_compat_statfs64(struct compat_statfs64 __user *ubuf, struct kstat
 	return 0;
 }
 
-COMPAT_SYSCALL_DEFINE3(statfs64, const char __user *, pathname, compat_size_t, sz, struct compat_statfs64 __user *, buf)
+int kcompat_sys_statfs64(const char __user * pathname, compat_size_t sz, struct compat_statfs64 __user * buf)
 {
 	struct kstatfs tmp;
 	int error;
@@ -349,7 +349,12 @@ COMPAT_SYSCALL_DEFINE3(statfs64, const char __user *, pathname, compat_size_t, s
 	return error;
 }
 
-COMPAT_SYSCALL_DEFINE3(fstatfs64, unsigned int, fd, compat_size_t, sz, struct compat_statfs64 __user *, buf)
+COMPAT_SYSCALL_DEFINE3(statfs64, const char __user *, pathname, compat_size_t, sz, struct compat_statfs64 __user *, buf)
+{
+	return kcompat_sys_statfs64(pathname, sz, buf);
+}
+
+int kcompat_sys_fstatfs64(unsigned int fd, compat_size_t sz, struct compat_statfs64 __user * buf)
 {
 	struct kstatfs tmp;
 	int error;
@@ -363,6 +368,11 @@ COMPAT_SYSCALL_DEFINE3(fstatfs64, unsigned int, fd, compat_size_t, sz, struct co
 	return error;
 }
 
+COMPAT_SYSCALL_DEFINE3(fstatfs64, unsigned int, fd, compat_size_t, sz, struct compat_statfs64 __user *, buf)
+{
+	return kcompat_sys_fstatfs64(fd, sz, buf);
+}
+
 /*
  * This is a copy of sys_ustat, just dealing with a structure layout.
  * Given how simple this syscall is that apporach is more maintainable
diff --git a/include/linux/compat.h b/include/linux/compat.h
index 081281ad5772..6cecf9f11d6b 100644
--- a/include/linux/compat.h
+++ b/include/linux/compat.h
@@ -1013,6 +1013,17 @@ static inline struct compat_timeval ns_to_compat_timeval(s64 nsec)
 	return ctv;
 }
 
+/*
+ * Kernel code should not call compat syscalls (i.e., compat_sys_xyzyyz())
+ * directly.  Instead, use one of the functions which work equivalently, such
+ * as the kcompat_sys_xyzyyz() functions prototyped below.
+ */
+
+int kcompat_sys_statfs64(const char __user * pathname, compat_size_t sz,
+		     struct compat_statfs64 __user * buf);
+int kcompat_sys_fstatfs64(unsigned int fd, compat_size_t sz,
+			  struct compat_statfs64 __user * buf);
+
 #else /* !CONFIG_COMPAT */
 
 #define is_compat_task() (0)
-- 
2.11.0