[PATCH v4 0/6] Out-of-line static calls for powerpc64 ELF V2

[PATCH v4 0/6] Out-of-line static calls for powerpc64 ELF V2

[Benjamin Gray]

Implementation of out-of-line static calls for PowerPC 64-bit ELF V2 ABI.
Static calls patch an indirect branch into a direct branch at runtime.
Out-of-line specifically has a caller directly call a trampoline, and
the trampoline gets patched to directly call the target.

Previous versions here:
V3: https://lore.kernel.org/all/20221005053234.29312-1-bgray@linux.ibm.com/
V2: https://lore.kernel.org/all/20220926064316.765967-1-bgray@linux.ibm.com/
V1: https://lore.kernel.org/all/20220916062330.430468-1-bgray@linux.ibm.com/
RFC: https://lore.kernel.org/linuxppc-dev/20220901055823.152983-1-bgray@linux.ibm.com/

Still rebased on top of
https://lore.kernel.org/all/0df84a2eea551c1d000c34c36d0c1d23cbe26a97.1664289176.git.christophe.leroy@csgroup.eu/

Changed for V4:

[1/6]
* IS_ENABLED(CONFIG_PPC64) added to patch size condition for better
  compiler optimisation

[2/6]
* Reworded message
* Refactored need r2 save expression. Parens are intentional, C operator
  precedence can be difficult to remember, especially when three different
  kinds are used in a single expression.

Benjamin Gray (6):
  powerpc/code-patching: Implement generic text patching function
  powerpc/module: Handle caller-saved TOC in module linker
  powerpc/module: Optimise nearby branches in ELF V2 ABI stub
  static_call: Move static call selftest to static_call_selftest.c
  powerpc/64: Add support for out-of-line static calls
  powerpc: Add tests for out-of-line static calls

 arch/powerpc/Kconfig                     |  26 ++-
 arch/powerpc/include/asm/code-patching.h |  30 +++
 arch/powerpc/include/asm/static_call.h   |  80 ++++++-
 arch/powerpc/kernel/Makefile             |   4 +-
 arch/powerpc/kernel/module_64.c          |  26 ++-
 arch/powerpc/kernel/static_call.c        | 183 +++++++++++++++-
 arch/powerpc/kernel/static_call_test.c   | 263 +++++++++++++++++++++++
 arch/powerpc/kernel/static_call_test.h   |  56 +++++
 arch/powerpc/lib/code-patching.c         |  73 +++++--
 kernel/Makefile                          |   1 +
 kernel/static_call_inline.c              |  43 ----
 kernel/static_call_selftest.c            |  41 ++++
 12 files changed, 753 insertions(+), 73 deletions(-)
 create mode 100644 arch/powerpc/kernel/static_call_test.c
 create mode 100644 arch/powerpc/kernel/static_call_test.h
 create mode 100644 kernel/static_call_selftest.c


base-commit: 86de6882270620777fe9cc16ece97e9ee407122c
--
2.37.3

[PATCH v4 1/6] powerpc/code-patching: Implement generic text patching function

[Benjamin Gray]

Adds a generic memory patching mechanism for patches of size int or long
bytes.

The patch_instruction function is reimplemented in terms of this
more generic function. This generic implementation allows patching of
arbitrary long data, such as pointers on 64-bit. As a performance
optimisation the patch will unconditionally flush the icache, as
patch_instruction is used significantly more often and in more
performance sensitive contexts (e.g., ftrace activation).

On 32-bit patch_int is marked noinline to prevent a mis-optimisation.
Without noinline, inside patch_branch the compiler may inline all the
way to do_patch_memory, preventing the compiler from inlining
do_patch_memory into patch_int. This would needlessly force patch_int
to be a branch to do_patch_memory.

The 'IS_ENABLED(CONFIG_PPC64) && ' part of the patch size condition
helps GCC inline __patch_memory properly. Only 64-bit requires
doubleword writes anyway, as ints and longs are the same size on 32-bit.

Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
---
 arch/powerpc/include/asm/code-patching.h | 29 ++++++++++
 arch/powerpc/lib/code-patching.c         | 73 ++++++++++++++++++------
 2 files changed, 85 insertions(+), 17 deletions(-)

diff --git a/arch/powerpc/include/asm/code-patching.h b/arch/powerpc/include/asm/code-patching.h
index 3f881548fb61..170bfa848c7c 100644
--- a/arch/powerpc/include/asm/code-patching.h
+++ b/arch/powerpc/include/asm/code-patching.h
@@ -72,7 +72,36 @@ static inline int create_branch(ppc_inst_t *instr, const u32 *addr,
 int create_cond_branch(ppc_inst_t *instr, const u32 *addr,
 		       unsigned long target, int flags);
 int patch_branch(u32 *addr, unsigned long target, int flags);
+
+/* patch_uint and patch_ulong must only be called on addresses where the patch
+ * does not cross a cacheline, otherwise it may not be flushed properly and
+ * mixes of new and stale data may be observed.
+ *
+ * patch_instruction and other instruction patchers automatically satisfy this
+ * requirement due to instruction alignment requirements.
+ */
+
+int patch_uint(void *addr, unsigned int val);
+
+#ifdef CONFIG_PPC64
+
+int patch_ulong(void *addr, unsigned long val);
 int patch_instruction(u32 *addr, ppc_inst_t instr);
+
+#else
+
+static inline int patch_ulong(void *addr, unsigned long val)
+{
+	return patch_uint(addr, val);
+}
+
+static inline int patch_instruction(u32 *addr, ppc_inst_t instr)
+{
+	return patch_uint(addr, ppc_inst_val(instr));
+}
+
+#endif
+
 int raw_patch_instruction(u32 *addr, ppc_inst_t instr);
 
 static inline unsigned long patch_site_addr(s32 *site)
diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
index 125c55e3e148..e41c0ccec79f 100644
--- a/arch/powerpc/lib/code-patching.c
+++ b/arch/powerpc/lib/code-patching.c
@@ -15,20 +15,24 @@
 #include <asm/code-patching.h>
 #include <asm/inst.h>
 
-static int __patch_instruction(u32 *exec_addr, ppc_inst_t instr, u32 *patch_addr)
+static int __patch_memory(void *patch_addr, unsigned long val, void *exec_addr,
+			  bool is_dword)
 {
-	if (!ppc_inst_prefixed(instr)) {
-		u32 val = ppc_inst_val(instr);
-
-		__put_kernel_nofault(patch_addr, &val, u32, failed);
-	} else {
-		u64 val = ppc_inst_as_ulong(instr);
+	/* Prefixed instruction may cross cacheline if cacheline smaller than 64 bytes */
+	BUILD_BUG_ON(IS_ENABLED(CONFIG_PPC64) && L1_CACHE_BYTES < 64);
 
+	if (IS_ENABLED(CONFIG_PPC64) && unlikely(is_dword))
 		__put_kernel_nofault(patch_addr, &val, u64, failed);
-	}
+	else
+		__put_kernel_nofault(patch_addr, &val, u32, failed);
 
-	asm ("dcbst 0, %0; sync; icbi 0,%1; sync; isync" :: "r" (patch_addr),
-							    "r" (exec_addr));
+	/* Assume data is inside a single cacheline */
+	dcbst(patch_addr);
+	mb(); /* sync */
+	/* Flush on the EA that may be executed in case of a non-coherent icache */
+	icbi(exec_addr);
+	mb(); /* sync */
+	isync();
 
 	return 0;
 
@@ -38,7 +42,10 @@ static int __patch_instruction(u32 *exec_addr, ppc_inst_t instr, u32 *patch_addr
 
 int raw_patch_instruction(u32 *addr, ppc_inst_t instr)
 {
-	return __patch_instruction(addr, instr, addr);
+	if (ppc_inst_prefixed(instr))
+		return __patch_memory(addr, ppc_inst_as_ulong(instr), addr, true);
+	else
+		return __patch_memory(addr, ppc_inst_val(instr), addr, false);
 }
 
 static DEFINE_PER_CPU(struct vm_struct *, text_poke_area);
@@ -149,7 +156,7 @@ static void unmap_patch_area(unsigned long addr)
 	flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
 }
 
-static int __do_patch_instruction(u32 *addr, ppc_inst_t instr)
+static int __do_patch_memory(void *addr, unsigned long val, bool is_dword)
 {
 	int err;
 	u32 *patch_addr;
@@ -166,7 +173,7 @@ static int __do_patch_instruction(u32 *addr, ppc_inst_t instr)
 	if (radix_enabled())
 		asm volatile("ptesync": : :"memory");
 
-	err = __patch_instruction(addr, instr, patch_addr);
+	err = __patch_memory(patch_addr, val, addr, is_dword);
 
 	pte_clear(&init_mm, text_poke_addr, pte);
 	flush_tlb_kernel_range(text_poke_addr, text_poke_addr + PAGE_SIZE);
@@ -174,7 +181,7 @@ static int __do_patch_instruction(u32 *addr, ppc_inst_t instr)
 	return err;
 }
 
-int patch_instruction(u32 *addr, ppc_inst_t instr)
+static int do_patch_memory(void *addr, unsigned long val, bool is_dword)
 {
 	int err;
 	unsigned long flags;
@@ -186,15 +193,47 @@ int patch_instruction(u32 *addr, ppc_inst_t instr)
 	 */
 	if (!IS_ENABLED(CONFIG_STRICT_KERNEL_RWX) ||
 	    !static_branch_likely(&poking_init_done))
-		return raw_patch_instruction(addr, instr);
+		return __patch_memory(addr, val, addr, is_dword);
 
 	local_irq_save(flags);
-	err = __do_patch_instruction(addr, instr);
+	err = __do_patch_memory(addr, val, is_dword);
 	local_irq_restore(flags);
 
 	return err;
 }
-NOKPROBE_SYMBOL(patch_instruction);
+
+#ifdef CONFIG_PPC64
+
+int patch_uint(void *addr, unsigned int val)
+{
+	return do_patch_memory(addr, val, false);
+}
+NOKPROBE_SYMBOL(patch_uint)
+
+int patch_ulong(void *addr, unsigned long val)
+{
+	return do_patch_memory(addr, val, true);
+}
+NOKPROBE_SYMBOL(patch_ulong)
+
+int patch_instruction(u32 *addr, ppc_inst_t instr)
+{
+	if (ppc_inst_prefixed(instr))
+		return patch_ulong(addr, ppc_inst_as_ulong(instr));
+	else
+		return patch_uint(addr, ppc_inst_val(instr));
+}
+NOKPROBE_SYMBOL(patch_instruction)
+
+#else
+
+noinline int patch_uint(void *addr, unsigned int val)
+{
+	return do_patch_memory(addr, val, false);
+}
+NOKPROBE_SYMBOL(patch_uint)
+
+#endif
 
 int patch_branch(u32 *addr, unsigned long target, int flags)
 {
-- 
2.37.3

[PATCH v4 2/6] powerpc/module: Handle caller-saved TOC in module linker

[Benjamin Gray]

A function symbol may set a value in the st_other field to indicate
the TOC should be treated as caller-saved. The linker should ensure the
current TOC is saved before calling it and restore the TOC afterwards,
much like external calls.

This is necessary for supporting V2 ABI static calls that do not
preserve the TOC.

Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
---
 arch/powerpc/kernel/module_64.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
index 7e45dc98df8a..83a6f6e22e3b 100644
--- a/arch/powerpc/kernel/module_64.c
+++ b/arch/powerpc/kernel/module_64.c
@@ -55,6 +55,12 @@ static unsigned int local_entry_offset(const Elf64_Sym *sym)
 	 * of function and try to derive r2 from it). */
 	return PPC64_LOCAL_ENTRY_OFFSET(sym->st_other);
 }
+
+static bool need_r2save_stub(unsigned char st_other)
+{
+	return (st_other & STO_PPC64_LOCAL_MASK) == (1 << STO_PPC64_LOCAL_BIT);
+}
+
 #else
 
 static func_desc_t func_desc(unsigned long addr)
@@ -66,6 +72,11 @@ static unsigned int local_entry_offset(const Elf64_Sym *sym)
 	return 0;
 }
 
+static bool need_r2save_stub(unsigned char st_other)
+{
+	return false;
+}
+
 void *dereference_module_function_descriptor(struct module *mod, void *ptr)
 {
 	if (ptr < (void *)mod->arch.start_opd ||
@@ -632,7 +643,8 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
 		case R_PPC_REL24:
 			/* FIXME: Handle weak symbols here --RR */
 			if (sym->st_shndx == SHN_UNDEF ||
-			    sym->st_shndx == SHN_LIVEPATCH) {
+			    sym->st_shndx == SHN_LIVEPATCH ||
+			    need_r2save_stub(sym->st_other)) {
 				/* External: go via stub */
 				value = stub_for_addr(sechdrs, value, me,
 						strtab + sym->st_name);
-- 
2.37.3

[PATCH v4 3/6] powerpc/module: Optimise nearby branches in ELF V2 ABI stub

[Benjamin Gray]

Inserts a direct branch to the stub target when possible, replacing the
mtctr/btctr sequence.

The load into r12 could potentially be skipped too, but that change
would need to refactor the arguments to indicate that the address
does not have a separate local entry point.

This helps the static call implementation, where modules calling their
own trampolines are called through this stub and the trampoline is
easily within range of a direct branch.

Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: Andrew Donnellan <ajd@linux.ibm.com>
---
 arch/powerpc/kernel/module_64.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
index 83a6f6e22e3b..3a90043b006c 100644
--- a/arch/powerpc/kernel/module_64.c
+++ b/arch/powerpc/kernel/module_64.c
@@ -141,6 +141,12 @@ static u32 ppc64_stub_insns[] = {
 	PPC_RAW_BCTR(),
 };
 
+#ifdef CONFIG_PPC64_ELF_ABI_V1
+#define PPC64_STUB_MTCTR_OFFSET 5
+#else
+#define PPC64_STUB_MTCTR_OFFSET 4
+#endif
+
 /* Count how many different 24-bit relocations (different symbol,
    different addend) */
 static unsigned int count_relocs(const Elf64_Rela *rela, unsigned int num)
@@ -426,6 +432,7 @@ static inline int create_stub(const Elf64_Shdr *sechdrs,
 			      struct module *me,
 			      const char *name)
 {
+	int err;
 	long reladdr;
 	func_desc_t desc;
 	int i;
@@ -439,6 +446,11 @@ static inline int create_stub(const Elf64_Shdr *sechdrs,
 			return 0;
 	}
 
+	/* Replace indirect branch sequence with direct branch where possible */
+	err = patch_branch(&entry->jump[PPC64_STUB_MTCTR_OFFSET], addr, 0);
+	if (err && err != -ERANGE)
+		return 0;
+
 	/* Stub uses address relative to r2. */
 	reladdr = (unsigned long)entry - my_r2(sechdrs, me);
 	if (reladdr > 0x7FFFFFFF || reladdr < -(0x80000000L)) {
-- 
2.37.3

[PATCH v4 4/6] static_call: Move static call selftest to static_call_selftest.c

[Benjamin Gray]

These tests are out-of-line only, so moving them to the
their own file allows them to be run when an arch does
not implement inline static calls.

Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
Reviewed-by: Andrew Donnellan <ajd@linux.ibm.com>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 kernel/Makefile               |  1 +
 kernel/static_call_inline.c   | 43 -----------------------------------
 kernel/static_call_selftest.c | 41 +++++++++++++++++++++++++++++++++
 3 files changed, 42 insertions(+), 43 deletions(-)
 create mode 100644 kernel/static_call_selftest.c

diff --git a/kernel/Makefile b/kernel/Makefile
index 318789c728d3..8ce8beaa3cc0 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -113,6 +113,7 @@ obj-$(CONFIG_KCSAN) += kcsan/
 obj-$(CONFIG_SHADOW_CALL_STACK) += scs.o
 obj-$(CONFIG_HAVE_STATIC_CALL) += static_call.o
 obj-$(CONFIG_HAVE_STATIC_CALL_INLINE) += static_call_inline.o
+obj-$(CONFIG_STATIC_CALL_SELFTEST) += static_call_selftest.o
 obj-$(CONFIG_CFI_CLANG) += cfi.o
 
 obj-$(CONFIG_PERF_EVENTS) += events/
diff --git a/kernel/static_call_inline.c b/kernel/static_call_inline.c
index dc5665b62814..64d04d054698 100644
--- a/kernel/static_call_inline.c
+++ b/kernel/static_call_inline.c
@@ -498,46 +498,3 @@ int __init static_call_init(void)
 	return 0;
 }
 early_initcall(static_call_init);
-
-#ifdef CONFIG_STATIC_CALL_SELFTEST
-
-static int func_a(int x)
-{
-	return x+1;
-}
-
-static int func_b(int x)
-{
-	return x+2;
-}
-
-DEFINE_STATIC_CALL(sc_selftest, func_a);
-
-static struct static_call_data {
-      int (*func)(int);
-      int val;
-      int expect;
-} static_call_data [] __initdata = {
-      { NULL,   2, 3 },
-      { func_b, 2, 4 },
-      { func_a, 2, 3 }
-};
-
-static int __init test_static_call_init(void)
-{
-      int i;
-
-      for (i = 0; i < ARRAY_SIZE(static_call_data); i++ ) {
-	      struct static_call_data *scd = &static_call_data[i];
-
-              if (scd->func)
-                      static_call_update(sc_selftest, scd->func);
-
-              WARN_ON(static_call(sc_selftest)(scd->val) != scd->expect);
-      }
-
-      return 0;
-}
-early_initcall(test_static_call_init);
-
-#endif /* CONFIG_STATIC_CALL_SELFTEST */
diff --git a/kernel/static_call_selftest.c b/kernel/static_call_selftest.c
new file mode 100644
index 000000000000..246ad89f64eb
--- /dev/null
+++ b/kernel/static_call_selftest.c
@@ -0,0 +1,41 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/static_call.h>
+
+static int func_a(int x)
+{
+	return x+1;
+}
+
+static int func_b(int x)
+{
+	return x+2;
+}
+
+DEFINE_STATIC_CALL(sc_selftest, func_a);
+
+static struct static_call_data {
+	int (*func)(int);
+	int val;
+	int expect;
+} static_call_data [] __initdata = {
+	{ NULL,   2, 3 },
+	{ func_b, 2, 4 },
+	{ func_a, 2, 3 }
+};
+
+static int __init test_static_call_init(void)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(static_call_data); i++ ) {
+		struct static_call_data *scd = &static_call_data[i];
+
+		if (scd->func)
+			static_call_update(sc_selftest, scd->func);
+
+		WARN_ON(static_call(sc_selftest)(scd->val) != scd->expect);
+	}
+
+	return 0;
+}
+early_initcall(test_static_call_init);
-- 
2.37.3

[PATCH v4 5/6] powerpc/64: Add support for out-of-line static calls

[Benjamin Gray]

Implement static call support for 64 bit V2 ABI. This requires making
sure the TOC is kept correct across kernel-module boundaries. As a
secondary concern, it tries to use the local entry point of a target
wherever possible. It does so by checking if both tramp & target are
kernel code, and falls back to detecting the common global entry point
patterns if modules are involved. Detecting the global entry point is
also required for setting the local entry point as the trampoline
target: if we cannot detect the local entry point, then we need to
convservatively initialise r12 and use the global entry point.

The trampolines are marked with `.localentry NAME, 1` to make the
linker save and restore the TOC on each call to the trampoline. This
allows the trampoline to safely target functions with different TOC
values.

However this directive also implies the TOC is not initialised on entry
to the trampoline. The kernel TOC is easily found in the PACA, but not
an arbitrary module TOC. Therefore the trampoline implementation depends
on whether it's in the kernel or not. If in the kernel, we initialise
the TOC using the PACA. If in a module, we have to initialise the TOC
with zero context, so it's quite expensive.

Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/powerpc/Kconfig                     |  14 ++-
 arch/powerpc/include/asm/code-patching.h |   1 +
 arch/powerpc/include/asm/static_call.h   |  80 +++++++++++++-
 arch/powerpc/kernel/Makefile             |   3 +-
 arch/powerpc/kernel/static_call.c        | 130 +++++++++++++++++++++--
 5 files changed, 216 insertions(+), 12 deletions(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 4c466acdc70d..962e36ec34ec 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -102,6 +102,18 @@ config GENERIC_HWEIGHT
 	bool
 	default y
 
+config TOOLCHAIN_SUPPORTS_LOCALENTRY1
+	bool
+	depends on PPC64_ELF_ABI_V2
+	default y if LD_VERSION >= 23200 || LLD_VERSION >= 110000
+	help
+	  A section of the ELF symbol st_other field can be given the value 1
+	  using the directive '.localentry NAME, 1' to mean the local and global
+	  entry points are the same, and r2 should be treated as caller-saved.
+
+	  Older versions of Clang and binutils do not recognise this form of the
+	  directive and will error if it is used.
+
 config PPC
 	bool
 	default y
@@ -248,7 +260,7 @@ config PPC
 	select HAVE_SOFTIRQ_ON_OWN_STACK
 	select HAVE_STACKPROTECTOR		if PPC32 && $(cc-option,-mstack-protector-guard=tls -mstack-protector-guard-reg=r2)
 	select HAVE_STACKPROTECTOR		if PPC64 && $(cc-option,-mstack-protector-guard=tls -mstack-protector-guard-reg=r13)
-	select HAVE_STATIC_CALL			if PPC32
+	select HAVE_STATIC_CALL			if PPC32 || (PPC64_ELF_ABI_V2 && TOOLCHAIN_SUPPORTS_LOCALENTRY1)
 	select HAVE_SYSCALL_TRACEPOINTS
 	select HAVE_VIRT_CPU_ACCOUNTING
 	select HUGETLB_PAGE_SIZE_VARIABLE	if PPC_BOOK3S_64 && HUGETLB_PAGE
diff --git a/arch/powerpc/include/asm/code-patching.h b/arch/powerpc/include/asm/code-patching.h
index 170bfa848c7c..cb4629e55e57 100644
--- a/arch/powerpc/include/asm/code-patching.h
+++ b/arch/powerpc/include/asm/code-patching.h
@@ -152,6 +152,7 @@ int translate_branch(ppc_inst_t *instr, const u32 *dest, const u32 *src);
 bool is_conditional_branch(ppc_inst_t instr);
 
 #define OP_RT_RA_MASK	0xffff0000UL
+#define OP_SI_MASK	0x0000ffffUL
 #define LIS_R2		(PPC_RAW_LIS(_R2, 0))
 #define ADDIS_R2_R12	(PPC_RAW_ADDIS(_R2, _R12, 0))
 #define ADDI_R2_R2	(PPC_RAW_ADDI(_R2, _R2, 0))
diff --git a/arch/powerpc/include/asm/static_call.h b/arch/powerpc/include/asm/static_call.h
index de1018cc522b..3d6e82200cb7 100644
--- a/arch/powerpc/include/asm/static_call.h
+++ b/arch/powerpc/include/asm/static_call.h
@@ -2,12 +2,75 @@
 #ifndef _ASM_POWERPC_STATIC_CALL_H
 #define _ASM_POWERPC_STATIC_CALL_H
 
+#ifdef CONFIG_PPC64_ELF_ABI_V2
+
+#ifdef MODULE
+
+#define __PPC_SCT(name, inst)					\
+	asm(".pushsection .text, \"ax\"				\n"	\
+	    ".align 6						\n"	\
+	    ".globl " STATIC_CALL_TRAMP_STR(name) "		\n"	\
+	    ".localentry " STATIC_CALL_TRAMP_STR(name) ", 1	\n"	\
+	    STATIC_CALL_TRAMP_STR(name) ":			\n"	\
+	    "	mflr	11					\n"	\
+	    "	bcl	20, 31, $+4				\n"	\
+	    "0:	mflr	12					\n"	\
+	    "	mtlr	11					\n"	\
+	    "	addi	12, 12, (" STATIC_CALL_TRAMP_STR(name) " - 0b)	\n"	\
+	    "	addis 2, 12, (.TOC.-" STATIC_CALL_TRAMP_STR(name) ")@ha	\n"	\
+	    "	addi 2, 2, (.TOC.-" STATIC_CALL_TRAMP_STR(name) ")@l	\n"	\
+	    "	" inst "					\n"	\
+	    "	ld	12, (2f - " STATIC_CALL_TRAMP_STR(name) ")(12)	\n"	\
+	    "	mtctr	12					\n"	\
+	    "	bctr						\n"	\
+	    "1:	li	3, 0					\n"	\
+	    "	blr						\n"	\
+	    ".balign 8						\n"	\
+	    "2:	.8byte 0					\n"	\
+	    ".type " STATIC_CALL_TRAMP_STR(name) ", @function	\n"	\
+	    ".size " STATIC_CALL_TRAMP_STR(name) ", . - " STATIC_CALL_TRAMP_STR(name) " \n" \
+	    ".popsection					\n")
+
+#else /* KERNEL */
+
+#define __PPC_SCT(name, inst)					\
+	asm(".pushsection .text, \"ax\"				\n"	\
+	    ".align 5						\n"	\
+	    ".globl " STATIC_CALL_TRAMP_STR(name) "		\n"	\
+	    ".localentry " STATIC_CALL_TRAMP_STR(name) ", 1	\n"	\
+	    STATIC_CALL_TRAMP_STR(name) ":			\n"	\
+	    "	ld	2, 16(13)				\n"	\
+	    "	" inst "					\n"	\
+	    "	addis	12, 2, 2f@toc@ha			\n"	\
+	    "	ld	12, 2f@toc@l(12)			\n"	\
+	    "	mtctr	12					\n"	\
+	    "	bctr						\n"	\
+	    "1:	li	3, 0					\n"	\
+	    "	blr						\n"	\
+	    ".balign 8						\n"	\
+	    "2:	.8byte 0					\n"	\
+	    ".type " STATIC_CALL_TRAMP_STR(name) ", @function	\n"	\
+	    ".size " STATIC_CALL_TRAMP_STR(name) ", . - " STATIC_CALL_TRAMP_STR(name) " \n" \
+	    ".popsection					\n")
+
+#endif /* MODULE */
+
+#define PPC_SCT_INST_MODULE		28		/* Offset of instruction to update */
+#define PPC_SCT_RET0_MODULE		44		/* Offset of label 1 */
+#define PPC_SCT_DATA_MODULE		56		/* Offset of label 2 (aligned) */
+
+#define PPC_SCT_INST_KERNEL		4		/* Offset of instruction to update */
+#define PPC_SCT_RET0_KERNEL		24		/* Offset of label 1 */
+#define PPC_SCT_DATA_KERNEL		32		/* Offset of label 2 (aligned) */
+
+#elif defined(CONFIG_PPC32)
+
 #define __PPC_SCT(name, inst)					\
 	asm(".pushsection .text, \"ax\"				\n"	\
 	    ".align 5						\n"	\
 	    ".globl " STATIC_CALL_TRAMP_STR(name) "		\n"	\
 	    STATIC_CALL_TRAMP_STR(name) ":			\n"	\
-	    inst "						\n"	\
+	    "	" inst "					\n"	\
 	    "	lis	12,2f@ha				\n"	\
 	    "	lwz	12,2f@l(12)				\n"	\
 	    "	mtctr	12					\n"	\
@@ -19,11 +82,20 @@
 	    ".size " STATIC_CALL_TRAMP_STR(name) ", . - " STATIC_CALL_TRAMP_STR(name) " \n" \
 	    ".popsection					\n")
 
-#define PPC_SCT_RET0		20		/* Offset of label 1 */
-#define PPC_SCT_DATA		28		/* Offset of label 2 */
+#define PPC_SCT_INST_MODULE		0		/* Offset of instruction to update */
+#define PPC_SCT_RET0_MODULE		20		/* Offset of label 1 */
+#define PPC_SCT_DATA_MODULE		28		/* Offset of label 2 */
+
+#define PPC_SCT_INST_KERNEL		PPC_SCT_INST_MODULE
+#define PPC_SCT_RET0_KERNEL		PPC_SCT_RET0_MODULE
+#define PPC_SCT_DATA_KERNEL		PPC_SCT_DATA_MODULE
+
+#else /* !CONFIG_PPC64_ELF_ABI_V2 && !CONFIG_PPC32 */
+#error "Unsupported ABI"
+#endif /* CONFIG_PPC64_ELF_ABI_V2 */
 
 #define ARCH_DEFINE_STATIC_CALL_TRAMP(name, func)	__PPC_SCT(name, "b " #func)
 #define ARCH_DEFINE_STATIC_CALL_NULL_TRAMP(name)	__PPC_SCT(name, "blr")
-#define ARCH_DEFINE_STATIC_CALL_RET0_TRAMP(name)	__PPC_SCT(name, "b .+20")
+#define ARCH_DEFINE_STATIC_CALL_RET0_TRAMP(name)	__PPC_SCT(name, "b 1f")
 
 #endif /* _ASM_POWERPC_STATIC_CALL_H */
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index 06d2d1f78f71..a30d0d0f5499 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -128,8 +128,9 @@ extra-y				+= vmlinux.lds
 
 obj-$(CONFIG_RELOCATABLE)	+= reloc_$(BITS).o
 
-obj-$(CONFIG_PPC32)		+= entry_32.o setup_32.o early_32.o static_call.o
+obj-$(CONFIG_PPC32)		+= entry_32.o setup_32.o early_32.o
 obj-$(CONFIG_PPC64)		+= dma-iommu.o iommu.o
+obj-$(CONFIG_HAVE_STATIC_CALL)	+= static_call.o
 obj-$(CONFIG_KGDB)		+= kgdb.o
 obj-$(CONFIG_BOOTX_TEXT)	+= btext.o
 obj-$(CONFIG_SMP)		+= smp.o
diff --git a/arch/powerpc/kernel/static_call.c b/arch/powerpc/kernel/static_call.c
index 863a7aa24650..9211b2e189bb 100644
--- a/arch/powerpc/kernel/static_call.c
+++ b/arch/powerpc/kernel/static_call.c
@@ -1,33 +1,151 @@
 // SPDX-License-Identifier: GPL-2.0
+#include <linux/bitops.h>
 #include <linux/memory.h>
 #include <linux/static_call.h>
 
 #include <asm/code-patching.h>
 
+static long sign_extend_long(unsigned long value, int index)
+{
+	if (sizeof(long) == 8)
+		return sign_extend64(value, index);
+	else
+		return sign_extend32(value, index);
+}
+
+static void *ppc_function_toc(u32 *func)
+{
+	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2)) {
+		/* There are two common global entry sequences we handle below
+		 *
+		 * 1. addis r2, r12, SI1
+		 *    addi r2, SI2
+		 *
+		 * 2. lis r2, SI1
+		 *    addi r2, SI2
+		 *
+		 * Where r12 contains the global entry point address (it is otherwise
+		 * uninitialised, so doesn't matter what value we use if this is not
+		 * a separate global entry point).
+		 *
+		 * Here we simulate running the given sequence and return the result it
+		 * would calculate. If the sequence is not recognised we return NULL.
+		 */
+		u32 insn1 = *func;
+		u32 insn2 = *(func + 1);
+		unsigned long op_regs1 = insn1 & OP_RT_RA_MASK;
+		unsigned long op_regs2 = insn2 & OP_RT_RA_MASK;
+		unsigned long si1 = insn1 & OP_SI_MASK;
+		unsigned long si2 = insn2 & OP_SI_MASK;
+		unsigned long imm1 = sign_extend_long(si1 << 16, 31);
+		unsigned long imm2 = sign_extend_long(si2, 15);
+		unsigned long addr = 0;
+
+		/* Simulate the first instruction */
+		if (op_regs1 == ADDIS_R2_R12)
+			addr += (unsigned long)func + imm1;
+		else if (op_regs1 == LIS_R2)
+			addr += imm1;
+		else
+			return NULL;
+
+		/* Simulate the second instruction */
+		if (op_regs2 == ADDI_R2_R2)
+			addr += imm2;
+		else
+			return NULL;
+
+		return (void *)addr;
+	}
+
+	return NULL;
+}
+
+static bool shares_toc(void *func1, void *func2)
+{
+	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2)) {
+		void *func1_toc;
+		void *func2_toc;
+
+		if (func1 == NULL || func2 == NULL)
+			return false;
+
+		/* Assume the kernel only uses a single TOC */
+		if (core_kernel_text((unsigned long)func1) &&
+		    core_kernel_text((unsigned long)func2))
+			return true;
+
+		/* Fall back to calculating the TOC from common patterns
+		 * if modules are involved
+		 */
+		func1_toc = ppc_function_toc(func1);
+		func2_toc = ppc_function_toc(func2);
+		return func1_toc != NULL && func2_toc != NULL && func1_toc == func2_toc;
+	}
+
+	return true;
+}
+
+static void *get_inst_addr(void *tramp)
+{
+	return tramp + (core_kernel_text((unsigned long)tramp)
+				? PPC_SCT_INST_KERNEL
+				: PPC_SCT_INST_MODULE);
+}
+
+static void *get_ret0_addr(void *tramp)
+{
+	return tramp + (core_kernel_text((unsigned long)tramp)
+				? PPC_SCT_RET0_KERNEL
+				: PPC_SCT_RET0_MODULE);
+}
+
+static void *get_data_addr(void *tramp)
+{
+	return tramp + (core_kernel_text((unsigned long) tramp)
+				? PPC_SCT_DATA_KERNEL
+				: PPC_SCT_DATA_MODULE);
+}
+
 void arch_static_call_transform(void *site, void *tramp, void *func, bool tail)
 {
 	int err;
 	bool is_ret0 = (func == __static_call_return0);
-	unsigned long target = (unsigned long)(is_ret0 ? tramp + PPC_SCT_RET0 : func);
-	bool is_short = is_offset_in_branch_range((long)target - (long)tramp);
+	bool is_short;
+	void *target = is_ret0 ? get_ret0_addr(tramp) : func;
+	void *tramp_inst = get_inst_addr(tramp);
 
 	if (!tramp)
 		return;
 
+	if (is_ret0)
+		is_short = true;
+	else if (shares_toc(tramp, target))
+		is_short = is_offset_in_branch_range(
+			(long)ppc_function_entry(target) - (long)tramp_inst);
+	else
+		/* Combine out-of-range with not sharing a TOC. Though it's possible
+		 * an out-of-range target shares a TOC, handling this separately
+		 * complicates the trampoline. It's simpler to always use the global
+		 * entry point in this case.
+		 */
+		is_short = false;
+
 	mutex_lock(&text_mutex);
 
 	if (func && !is_short) {
-		err = patch_instruction(tramp + PPC_SCT_DATA, ppc_inst(target));
+		err = patch_ulong(get_data_addr(tramp), (unsigned long)target);
 		if (err)
 			goto out;
 	}
 
 	if (!func)
-		err = patch_instruction(tramp, ppc_inst(PPC_RAW_BLR()));
+		err = patch_instruction(tramp_inst, ppc_inst(PPC_RAW_BLR()));
 	else if (is_short)
-		err = patch_branch(tramp, target, 0);
+		err = patch_branch(tramp_inst, ppc_function_entry(target), 0);
 	else
-		err = patch_instruction(tramp, ppc_inst(PPC_RAW_NOP()));
+		err = patch_instruction(tramp_inst, ppc_inst(PPC_RAW_NOP()));
+
 out:
 	mutex_unlock(&text_mutex);
 
-- 
2.37.3

[PATCH v4 6/6] powerpc: Add tests for out-of-line static calls

[Benjamin Gray]

KUnit tests for the various combinations of caller/trampoline/target and
kernel/module. They must be run from a module loaded at runtime to
guarantee they have a different TOC to the kernel (64-bit ELF V2) and
increase the chance of testing the non-direct branch path of the
trampoline.

For 64-bit ELF V2 ABI the tests try to mitigate the chance of panicking
by restoring the TOC after every static call. Not all possible errors
can be caught by this (we can't stop a trampoline from using a bad TOC
itself), but it makes certain errors easier to debug.

Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
---
 arch/powerpc/Kconfig                   |  12 ++
 arch/powerpc/kernel/Makefile           |   1 +
 arch/powerpc/kernel/static_call.c      |  53 +++++
 arch/powerpc/kernel/static_call_test.c | 263 +++++++++++++++++++++++++
 arch/powerpc/kernel/static_call_test.h |  56 ++++++
 5 files changed, 385 insertions(+)
 create mode 100644 arch/powerpc/kernel/static_call_test.c
 create mode 100644 arch/powerpc/kernel/static_call_test.h

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 962e36ec34ec..5b9d5fa96a9e 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -1035,6 +1035,18 @@ config PPC_RTAS_FILTER
 	  Say Y unless you know what you are doing and the filter is causing
 	  problems for you.
 
+config PPC_STATIC_CALL_KUNIT_TEST
+	tristate "KUnit tests for static calls"
+	default KUNIT_ALL_TESTS
+	depends on HAVE_STATIC_CALL && KUNIT && m
+	help
+	  Tests for static calls across all combinations of caller/trampoline/target
+	  being kernel/module. On ELF ABI V2 the tests check the TOC is kept consistent.
+
+	  Must be built as a module and loaded at runtime to ensure the module has
+	  a different TOC to the kernel and make it likely that non-direct branch
+	  path of the trampoline is tested.
+
 endmenu
 
 config ISA_DMA_API
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index a30d0d0f5499..22c07e3d34df 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -131,6 +131,7 @@ obj-$(CONFIG_RELOCATABLE)	+= reloc_$(BITS).o
 obj-$(CONFIG_PPC32)		+= entry_32.o setup_32.o early_32.o
 obj-$(CONFIG_PPC64)		+= dma-iommu.o iommu.o
 obj-$(CONFIG_HAVE_STATIC_CALL)	+= static_call.o
+obj-$(CONFIG_PPC_STATIC_CALL_KUNIT_TEST)	+= static_call_test.o
 obj-$(CONFIG_KGDB)		+= kgdb.o
 obj-$(CONFIG_BOOTX_TEXT)	+= btext.o
 obj-$(CONFIG_SMP)		+= smp.o
diff --git a/arch/powerpc/kernel/static_call.c b/arch/powerpc/kernel/static_call.c
index 9211b2e189bb..44957ba91e3f 100644
--- a/arch/powerpc/kernel/static_call.c
+++ b/arch/powerpc/kernel/static_call.c
@@ -153,3 +153,56 @@ void arch_static_call_transform(void *site, void *tramp, void *func, bool tail)
 		panic("%s: patching failed %pS at %pS\n", __func__, func, tramp);
 }
 EXPORT_SYMBOL_GPL(arch_static_call_transform);
+
+
+#if IS_MODULE(CONFIG_PPC_STATIC_CALL_KUNIT_TEST)
+
+#include "static_call_test.h"
+
+int ppc_sc_kernel_target_1(struct kunit *test)
+{
+	toc_fixup(test);
+	return 1;
+}
+
+int ppc_sc_kernel_target_2(struct kunit *test)
+{
+	toc_fixup(test);
+	return 2;
+}
+
+DEFINE_STATIC_CALL(ppc_sc_kernel, ppc_sc_kernel_target_1);
+
+int ppc_sc_kernel_call(struct kunit *test)
+{
+	return PROTECTED_SC(test, int, static_call(ppc_sc_kernel)(test));
+}
+
+int ppc_sc_kernel_call_indirect(struct kunit *test, int (*fn)(struct kunit *test))
+{
+	return PROTECTED_SC(test, int, fn(test));
+}
+
+long ppc_sc_kernel_target_big(struct kunit *test, long a, long b, long c, long d,
+			      long e, long f, long g, long h, long i)
+{
+	toc_fixup(test);
+	KUNIT_EXPECT_EQ(test, a, b);
+	KUNIT_EXPECT_EQ(test, a, c);
+	KUNIT_EXPECT_EQ(test, a, d);
+	KUNIT_EXPECT_EQ(test, a, e);
+	KUNIT_EXPECT_EQ(test, a, f);
+	KUNIT_EXPECT_EQ(test, a, g);
+	KUNIT_EXPECT_EQ(test, a, h);
+	KUNIT_EXPECT_EQ(test, a, i);
+	return ~a;
+}
+
+EXPORT_SYMBOL_GPL(ppc_sc_kernel_target_1);
+EXPORT_SYMBOL_GPL(ppc_sc_kernel_target_2);
+EXPORT_SYMBOL_GPL(ppc_sc_kernel_target_big);
+EXPORT_STATIC_CALL_GPL(ppc_sc_kernel);
+EXPORT_SYMBOL_GPL(ppc_sc_kernel_call);
+EXPORT_SYMBOL_GPL(ppc_sc_kernel_call_indirect);
+
+#endif /* IS_MODULE(CONFIG_PPC_STATIC_CALL_KUNIT_TEST) */
diff --git a/arch/powerpc/kernel/static_call_test.c b/arch/powerpc/kernel/static_call_test.c
new file mode 100644
index 000000000000..10a09ef455cf
--- /dev/null
+++ b/arch/powerpc/kernel/static_call_test.c
@@ -0,0 +1,263 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include "static_call_test.h"
+
+#include <linux/kconfig.h>
+#include <linux/module.h>
+#include <linux/static_call.h>
+
+/* Tests to ensure correctness in a variety of cases for static calls.
+ *
+ * The tests focus on ensuring the TOC is kept consistent across the
+ * module-kernel boundary, as compilers can't see that a trampoline
+ * defined locally to a caller might be jumping to a function with a
+ * different TOC. So it's important that these tests are compiled as
+ * a module to ensure the TOC will be different to the kernel's.
+ */
+
+#ifdef CONFIG_PPC64_ELF_ABI_V2
+
+/* Utils to hold a copy of the old register values while we test.
+ *
+ * We can't use the KUnit init/exit hooks because when the hooks and
+ * test cases return they will be in the KUnit context that doesn't know
+ * we've reserved and modified some non-volatile registers.
+ */
+
+static void *saved_registers[2];
+
+static void init_testcase(struct kunit *test)
+{
+	saved_registers[0] = actual_toc;
+	saved_registers[1] = module_toc;
+	module_toc = current_toc;
+	KUNIT_ASSERT_PTR_NE(test, module_toc, (void *)get_paca()->kernel_toc);
+}
+
+static void exit_testcase(void)
+{
+	actual_toc = saved_registers[0];
+	module_toc = saved_registers[1];
+}
+
+#else
+
+static void init_testcase(struct kunit *test) {}
+static void exit_testcase(void) {}
+
+#endif  /* CONFIG_PPC64_ELF_ABI_V2 */
+
+static int module_target_11(struct kunit *test)
+{
+	toc_fixup(test);
+	return 11;
+}
+
+static int module_target_12(struct kunit *test)
+{
+	toc_fixup(test);
+	return 12;
+}
+
+DEFINE_STATIC_CALL(module_sc, module_target_11);
+
+DEFINE_STATIC_CALL_RET0(module_sc_ret0, int(void));
+DEFINE_STATIC_CALL_NULL(module_sc_null, int(int));
+
+static int add_one(int *val)
+{
+	return (*val)++;
+}
+
+static void null_function_test(struct kunit *test)
+{
+	int val = 0;
+
+	init_testcase(test);
+
+	/* Check argument unconditionally evaluated */
+	static_call_cond(module_sc_null)(add_one(&val));
+	KUNIT_ASSERT_EQ(test, 1, val);
+
+	exit_testcase();
+}
+
+static void return_zero_test(struct kunit *test)
+{
+	int ret;
+
+	init_testcase(test);
+
+	ret = PROTECTED_SC(test, int, static_call(module_sc_ret0)());
+	KUNIT_ASSERT_EQ(test, 0, ret);
+
+	static_call_update(ppc_sc_kernel, (void *)__static_call_return0);
+	ret = PROTECTED_SC(test, int, static_call(ppc_sc_kernel)(test));
+	KUNIT_ASSERT_EQ(test, 0, ret);
+
+	static_call_update(module_sc, (void *)__static_call_return0);
+	ret = PROTECTED_SC(test, int, static_call(module_sc)(test));
+	KUNIT_ASSERT_EQ(test, 0, ret);
+
+	exit_testcase();
+}
+
+static void kernel_kernel_kernel_test(struct kunit *test)
+{
+	init_testcase(test);
+
+	static_call_update(ppc_sc_kernel, ppc_sc_kernel_target_1);
+	KUNIT_ASSERT_EQ(test, 1, ppc_sc_kernel_call(test));
+
+	static_call_update(ppc_sc_kernel, ppc_sc_kernel_target_2);
+	KUNIT_ASSERT_EQ(test, 2, ppc_sc_kernel_call(test));
+
+	exit_testcase();
+}
+
+static void kernel_kernel_module_test(struct kunit *test)
+{
+	init_testcase(test);
+
+	static_call_update(ppc_sc_kernel, module_target_11);
+	KUNIT_ASSERT_EQ(test, 11, ppc_sc_kernel_call(test));
+
+	static_call_update(ppc_sc_kernel, module_target_12);
+	KUNIT_ASSERT_EQ(test, 12, ppc_sc_kernel_call(test));
+
+	exit_testcase();
+}
+
+static void kernel_module_kernel_test(struct kunit *test)
+{
+	init_testcase(test);
+
+	static_call_update(module_sc, ppc_sc_kernel_target_1);
+	KUNIT_ASSERT_EQ(test, 1, ppc_sc_kernel_call_indirect(test, static_call(module_sc)));
+
+	static_call_update(module_sc, ppc_sc_kernel_target_2);
+	KUNIT_ASSERT_EQ(test, 2, ppc_sc_kernel_call_indirect(test, static_call(module_sc)));
+
+	exit_testcase();
+}
+
+static void kernel_module_module_test(struct kunit *test)
+{
+	init_testcase(test);
+
+	static_call_update(module_sc, module_target_11);
+	KUNIT_ASSERT_EQ(test, 11, ppc_sc_kernel_call_indirect(test, static_call(module_sc)));
+
+	static_call_update(module_sc, module_target_12);
+	KUNIT_ASSERT_EQ(test, 12, ppc_sc_kernel_call_indirect(test, static_call(module_sc)));
+
+	exit_testcase();
+}
+
+static void module_kernel_kernel_test(struct kunit *test)
+{
+	int ret;
+
+	init_testcase(test);
+
+	static_call_update(ppc_sc_kernel, ppc_sc_kernel_target_1);
+	ret = PROTECTED_SC(test, int, static_call(ppc_sc_kernel)(test));
+	KUNIT_ASSERT_EQ(test, 1, ret);
+
+	static_call_update(ppc_sc_kernel, ppc_sc_kernel_target_2);
+	ret = PROTECTED_SC(test, int, static_call(ppc_sc_kernel)(test));
+	KUNIT_ASSERT_EQ(test, 2, ret);
+
+	exit_testcase();
+}
+
+static void module_kernel_module_test(struct kunit *test)
+{
+	int ret;
+
+	init_testcase(test);
+
+	static_call_update(ppc_sc_kernel, module_target_11);
+	ret = PROTECTED_SC(test, int, static_call(ppc_sc_kernel)(test));
+	KUNIT_ASSERT_EQ(test, 11, ret);
+
+	static_call_update(ppc_sc_kernel, module_target_12);
+	ret = PROTECTED_SC(test, int, static_call(ppc_sc_kernel)(test));
+	KUNIT_ASSERT_EQ(test, 12, ret);
+
+	exit_testcase();
+}
+
+static void module_module_kernel_test(struct kunit *test)
+{
+	int ret;
+
+	init_testcase(test);
+
+	static_call_update(module_sc, ppc_sc_kernel_target_1);
+	ret = PROTECTED_SC(test, int, static_call(module_sc)(test));
+	KUNIT_ASSERT_EQ(test, 1, ret);
+
+	static_call_update(module_sc, ppc_sc_kernel_target_2);
+	ret = PROTECTED_SC(test, int, static_call(module_sc)(test));
+	KUNIT_ASSERT_EQ(test, 2, ret);
+
+	exit_testcase();
+}
+
+static void module_module_module_test(struct kunit *test)
+{
+	int ret;
+
+	init_testcase(test);
+
+	static_call_update(module_sc, module_target_11);
+	ret = PROTECTED_SC(test, int, static_call(module_sc)(test));
+	KUNIT_ASSERT_EQ(test, 11, ret);
+
+	static_call_update(module_sc, module_target_12);
+	ret = PROTECTED_SC(test, int, static_call(module_sc)(test));
+	KUNIT_ASSERT_EQ(test, 12, ret);
+
+	exit_testcase();
+}
+
+DEFINE_STATIC_CALL(module_sc_stack_params, ppc_sc_kernel_target_big);
+
+static void stack_parameters_test(struct kunit *test)
+{
+	long m = -0x87654321;
+	long ret;
+
+	init_testcase(test);
+
+	ret = PROTECTED_SC(test, long,
+		static_call(module_sc_stack_params)(test, m, m, m, m, m, m, m, m, m));
+	KUNIT_ASSERT_EQ(test, ~m, ret);
+
+	exit_testcase();
+}
+
+static struct kunit_case static_call_test_cases[] = {
+	KUNIT_CASE(null_function_test),
+	KUNIT_CASE(return_zero_test),
+	KUNIT_CASE(stack_parameters_test),
+	KUNIT_CASE(kernel_kernel_kernel_test),
+	KUNIT_CASE(kernel_kernel_module_test),
+	KUNIT_CASE(kernel_module_kernel_test),
+	KUNIT_CASE(kernel_module_module_test),
+	KUNIT_CASE(module_kernel_kernel_test),
+	KUNIT_CASE(module_kernel_module_test),
+	KUNIT_CASE(module_module_kernel_test),
+	KUNIT_CASE(module_module_module_test),
+	{}
+};
+
+static struct kunit_suite ppc_static_call_test_suite = {
+	.name = "ppc-static-call",
+	.test_cases = static_call_test_cases,
+};
+kunit_test_suite(ppc_static_call_test_suite);
+
+MODULE_AUTHOR("Benjamin Gray <bgray@linux.ibm.com>");
+MODULE_LICENSE("GPL");
diff --git a/arch/powerpc/kernel/static_call_test.h b/arch/powerpc/kernel/static_call_test.h
new file mode 100644
index 000000000000..71b5bc52c099
--- /dev/null
+++ b/arch/powerpc/kernel/static_call_test.h
@@ -0,0 +1,56 @@
+#ifndef _POWERPC_STATIC_CALL_TEST_
+#define _POWERPC_STATIC_CALL_TEST_
+
+#include <kunit/test.h>
+
+DECLARE_STATIC_CALL(ppc_sc_kernel, int(struct kunit *test));
+int ppc_sc_kernel_target_1(struct kunit *test);
+int ppc_sc_kernel_target_2(struct kunit *test);
+long ppc_sc_kernel_target_big(struct kunit *test, long a, long b, long c, long d,
+			      long e, long f, long g, long h, long i);
+int ppc_sc_kernel_call(struct kunit *test);
+int ppc_sc_kernel_call_indirect(struct kunit *test, int(*fn)(struct kunit *test));
+
+#ifdef CONFIG_PPC64_ELF_ABI_V2
+
+/* Reserve these registers for testing so that a TOC error
+ * doesn't necessarily crash the whole kernel.
+ *
+ * The tests ensure the contents are restored before returning.
+ */
+register void *current_toc asm ("r2");
+register void *actual_toc asm ("r14");  /* Copy of TOC before fixup */
+register void *module_toc asm ("r15");
+
+#ifdef MODULE
+
+#define toc_fixup(test) \
+	actual_toc = current_toc; \
+	current_toc = module_toc; \
+	KUNIT_EXPECT_PTR_EQ(test, module_toc, actual_toc)
+
+#else /* KERNEL */
+
+#define toc_fixup(test) \
+	actual_toc = current_toc; \
+	current_toc = (void *)get_paca()->kernel_toc; \
+	KUNIT_EXPECT_PTR_EQ(test, (void *)get_paca()->kernel_toc, actual_toc)
+
+#endif /* MODULE */
+
+#define PROTECTED_SC(test, ret_type, call) \
+({ \
+	ret_type ret; \
+	ret = call; \
+	toc_fixup(test); \
+	ret; \
+})
+
+#else
+
+#define toc_fixup(test) {}
+#define PROTECTED_SC(test, ret_type, call) call
+
+#endif /* CONFIG_PPC64_ELF_ABI_V2 */
+
+#endif /* _POWERPC_STATIC_CALL_TEST_ */
-- 
2.37.3

Re: [PATCH v4 1/6] powerpc/code-patching: Implement generic text patching function

[Andrew Donnellan]

On Mon, 2022-10-10 at 11:29 +1100, Benjamin Gray wrote:
> Adds a generic memory patching mechanism for patches of size int or
> long
> bytes.
> 
> The patch_instruction function is reimplemented in terms of this
> more generic function. This generic implementation allows patching of
> arbitrary long data, such as pointers on 64-bit. As a performance
> optimisation the patch will unconditionally flush the icache, as
> patch_instruction is used significantly more often and in more
> performance sensitive contexts (e.g., ftrace activation).
> 
> On 32-bit patch_int is marked noinline to prevent a mis-optimisation.
> Without noinline, inside patch_branch the compiler may inline all the
> way to do_patch_memory, preventing the compiler from inlining
> do_patch_memory into patch_int. This would needlessly force patch_int
> to be a branch to do_patch_memory.
> 
> The 'IS_ENABLED(CONFIG_PPC64) && ' part of the patch size condition
> helps GCC inline __patch_memory properly. Only 64-bit requires
> doubleword writes anyway, as ints and longs are the same size on 32-
> bit.
> 
> Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>

It looks like this needs rebasing.

Otherwise I gave this a read over and didn't spot anything, but I'll
hold off on a reviewed-by tag until it's rebased.

> ---
>  arch/powerpc/include/asm/code-patching.h | 29 ++++++++++
>  arch/powerpc/lib/code-patching.c         | 73 ++++++++++++++++++----
> --
>  2 files changed, 85 insertions(+), 17 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/code-patching.h
> b/arch/powerpc/include/asm/code-patching.h
> index 3f881548fb61..170bfa848c7c 100644
> --- a/arch/powerpc/include/asm/code-patching.h
> +++ b/arch/powerpc/include/asm/code-patching.h
> @@ -72,7 +72,36 @@ static inline int create_branch(ppc_inst_t *instr,
> const u32 *addr,
>  int create_cond_branch(ppc_inst_t *instr, const u32 *addr,
>                        unsigned long target, int flags);
>  int patch_branch(u32 *addr, unsigned long target, int flags);
> +
> +/* patch_uint and patch_ulong must only be called on addresses where
> the patch
> + * does not cross a cacheline, otherwise it may not be flushed
> properly and
> + * mixes of new and stale data may be observed.
> + *
> + * patch_instruction and other instruction patchers automatically
> satisfy this
> + * requirement due to instruction alignment requirements.
> + */
> +
> +int patch_uint(void *addr, unsigned int val);
> +
> +#ifdef CONFIG_PPC64
> +
> +int patch_ulong(void *addr, unsigned long val);
>  int patch_instruction(u32 *addr, ppc_inst_t instr);
> +
> +#else
> +
> +static inline int patch_ulong(void *addr, unsigned long val)
> +{
> +       return patch_uint(addr, val);
> +}
> +
> +static inline int patch_instruction(u32 *addr, ppc_inst_t instr)
> +{
> +       return patch_uint(addr, ppc_inst_val(instr));
> +}
> +
> +#endif
> +
>  int raw_patch_instruction(u32 *addr, ppc_inst_t instr);
>  
>  static inline unsigned long patch_site_addr(s32 *site)
> diff --git a/arch/powerpc/lib/code-patching.c
> b/arch/powerpc/lib/code-patching.c
> index 125c55e3e148..e41c0ccec79f 100644
> --- a/arch/powerpc/lib/code-patching.c
> +++ b/arch/powerpc/lib/code-patching.c
> @@ -15,20 +15,24 @@
>  #include <asm/code-patching.h>
>  #include <asm/inst.h>
>  
> -static int __patch_instruction(u32 *exec_addr, ppc_inst_t instr, u32
> *patch_addr)
> +static int __patch_memory(void *patch_addr, unsigned long val, void
> *exec_addr,
> +                         bool is_dword)
>  {
> -       if (!ppc_inst_prefixed(instr)) {
> -               u32 val = ppc_inst_val(instr);
> -
> -               __put_kernel_nofault(patch_addr, &val, u32, failed);
> -       } else {
> -               u64 val = ppc_inst_as_ulong(instr);
> +       /* Prefixed instruction may cross cacheline if cacheline
> smaller than 64 bytes */
> +       BUILD_BUG_ON(IS_ENABLED(CONFIG_PPC64) && L1_CACHE_BYTES <
> 64);
>  
> +       if (IS_ENABLED(CONFIG_PPC64) && unlikely(is_dword))
>                 __put_kernel_nofault(patch_addr, &val, u64, failed);
> -       }
> +       else
> +               __put_kernel_nofault(patch_addr, &val, u32, failed);
>  
> -       asm ("dcbst 0, %0; sync; icbi 0,%1; sync; isync" :: "r"
> (patch_addr),
> -                                                           "r"
> (exec_addr));
> +       /* Assume data is inside a single cacheline */
> +       dcbst(patch_addr);
> +       mb(); /* sync */
> +       /* Flush on the EA that may be executed in case of a non-
> coherent icache */
> +       icbi(exec_addr);
> +       mb(); /* sync */
> +       isync();
>  
>         return 0;
>  
> @@ -38,7 +42,10 @@ static int __patch_instruction(u32 *exec_addr,
> ppc_inst_t instr, u32 *patch_addr
>  
>  int raw_patch_instruction(u32 *addr, ppc_inst_t instr)
>  {
> -       return __patch_instruction(addr, instr, addr);
> +       if (ppc_inst_prefixed(instr))
> +               return __patch_memory(addr, ppc_inst_as_ulong(instr),
> addr, true);
> +       else
> +               return __patch_memory(addr, ppc_inst_val(instr),
> addr, false);
>  }
>  
>  static DEFINE_PER_CPU(struct vm_struct *, text_poke_area);
> @@ -149,7 +156,7 @@ static void unmap_patch_area(unsigned long addr)
>         flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
>  }
>  
> -static int __do_patch_instruction(u32 *addr, ppc_inst_t instr)
> +static int __do_patch_memory(void *addr, unsigned long val, bool
> is_dword)
>  {
>         int err;
>         u32 *patch_addr;
> @@ -166,7 +173,7 @@ static int __do_patch_instruction(u32 *addr,
> ppc_inst_t instr)
>         if (radix_enabled())
>                 asm volatile("ptesync": : :"memory");
>  
> -       err = __patch_instruction(addr, instr, patch_addr);
> +       err = __patch_memory(patch_addr, val, addr, is_dword);
>  
>         pte_clear(&init_mm, text_poke_addr, pte);
>         flush_tlb_kernel_range(text_poke_addr, text_poke_addr +
> PAGE_SIZE);
> @@ -174,7 +181,7 @@ static int __do_patch_instruction(u32 *addr,
> ppc_inst_t instr)
>         return err;
>  }
>  
> -int patch_instruction(u32 *addr, ppc_inst_t instr)
> +static int do_patch_memory(void *addr, unsigned long val, bool
> is_dword)
>  {
>         int err;
>         unsigned long flags;
> @@ -186,15 +193,47 @@ int patch_instruction(u32 *addr, ppc_inst_t
> instr)
>          */
>         if (!IS_ENABLED(CONFIG_STRICT_KERNEL_RWX) ||
>             !static_branch_likely(&poking_init_done))
> -               return raw_patch_instruction(addr, instr);
> +               return __patch_memory(addr, val, addr, is_dword);
>  
>         local_irq_save(flags);
> -       err = __do_patch_instruction(addr, instr);
> +       err = __do_patch_memory(addr, val, is_dword);
>         local_irq_restore(flags);
>  
>         return err;
>  }
> -NOKPROBE_SYMBOL(patch_instruction);
> +
> +#ifdef CONFIG_PPC64
> +
> +int patch_uint(void *addr, unsigned int val)
> +{
> +       return do_patch_memory(addr, val, false);
> +}
> +NOKPROBE_SYMBOL(patch_uint)
> +
> +int patch_ulong(void *addr, unsigned long val)
> +{
> +       return do_patch_memory(addr, val, true);
> +}
> +NOKPROBE_SYMBOL(patch_ulong)
> +
> +int patch_instruction(u32 *addr, ppc_inst_t instr)
> +{
> +       if (ppc_inst_prefixed(instr))
> +               return patch_ulong(addr, ppc_inst_as_ulong(instr));
> +       else
> +               return patch_uint(addr, ppc_inst_val(instr));
> +}
> +NOKPROBE_SYMBOL(patch_instruction)
> +
> +#else
> +
> +noinline int patch_uint(void *addr, unsigned int val)
> +{
> +       return do_patch_memory(addr, val, false);
> +}
> +NOKPROBE_SYMBOL(patch_uint)
> +
> +#endif
>  
>  int patch_branch(u32 *addr, unsigned long target, int flags)
>  {

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

Re: [PATCH v4 1/6] powerpc/code-patching: Implement generic text patching function

[Andrew Donnellan]

On Mon, 2022-10-10 at 15:45 +1100, Andrew Donnellan wrote:
> On Mon, 2022-10-10 at 11:29 +1100, Benjamin Gray wrote:
> > Adds a generic memory patching mechanism for patches of size int or
> > long
> > bytes.
> > 
> > The patch_instruction function is reimplemented in terms of this
> > more generic function. This generic implementation allows patching
> > of
> > arbitrary long data, such as pointers on 64-bit. As a performance
> > optimisation the patch will unconditionally flush the icache, as
> > patch_instruction is used significantly more often and in more
> > performance sensitive contexts (e.g., ftrace activation).
> > 
> > On 32-bit patch_int is marked noinline to prevent a mis-
> > optimisation.
> > Without noinline, inside patch_branch the compiler may inline all
> > the
> > way to do_patch_memory, preventing the compiler from inlining
> > do_patch_memory into patch_int. This would needlessly force
> > patch_int
> > to be a branch to do_patch_memory.
> > 
> > The 'IS_ENABLED(CONFIG_PPC64) && ' part of the patch size condition
> > helps GCC inline __patch_memory properly. Only 64-bit requires
> > doubleword writes anyway, as ints and longs are the same size on
> > 32-
> > bit.
> > 
> > Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
> 
> It looks like this needs rebasing.

Alternatively, I just need to learn to read cover letters properly and
notice that this is based off another series...

> 
> Otherwise I gave this a read over and didn't spot anything, but I'll
> hold off on a reviewed-by tag until it's rebased.
> 

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

> > ---
> >  arch/powerpc/include/asm/code-patching.h | 29 ++++++++++
> >  arch/powerpc/lib/code-patching.c         | 73 ++++++++++++++++++--
> > --
> > --
> >  2 files changed, 85 insertions(+), 17 deletions(-)
> > 
> > diff --git a/arch/powerpc/include/asm/code-patching.h
> > b/arch/powerpc/include/asm/code-patching.h
> > index 3f881548fb61..170bfa848c7c 100644
> > --- a/arch/powerpc/include/asm/code-patching.h
> > +++ b/arch/powerpc/include/asm/code-patching.h
> > @@ -72,7 +72,36 @@ static inline int create_branch(ppc_inst_t
> > *instr,
> > const u32 *addr,
> >  int create_cond_branch(ppc_inst_t *instr, const u32 *addr,
> >                        unsigned long target, int flags);
> >  int patch_branch(u32 *addr, unsigned long target, int flags);
> > +
> > +/* patch_uint and patch_ulong must only be called on addresses
> > where
> > the patch
> > + * does not cross a cacheline, otherwise it may not be flushed
> > properly and
> > + * mixes of new and stale data may be observed.
> > + *
> > + * patch_instruction and other instruction patchers automatically
> > satisfy this
> > + * requirement due to instruction alignment requirements.
> > + */
> > +
> > +int patch_uint(void *addr, unsigned int val);
> > +
> > +#ifdef CONFIG_PPC64
> > +
> > +int patch_ulong(void *addr, unsigned long val);
> >  int patch_instruction(u32 *addr, ppc_inst_t instr);
> > +
> > +#else
> > +
> > +static inline int patch_ulong(void *addr, unsigned long val)
> > +{
> > +       return patch_uint(addr, val);
> > +}
> > +
> > +static inline int patch_instruction(u32 *addr, ppc_inst_t instr)
> > +{
> > +       return patch_uint(addr, ppc_inst_val(instr));
> > +}
> > +
> > +#endif
> > +
> >  int raw_patch_instruction(u32 *addr, ppc_inst_t instr);
> >  
> >  static inline unsigned long patch_site_addr(s32 *site)
> > diff --git a/arch/powerpc/lib/code-patching.c
> > b/arch/powerpc/lib/code-patching.c
> > index 125c55e3e148..e41c0ccec79f 100644
> > --- a/arch/powerpc/lib/code-patching.c
> > +++ b/arch/powerpc/lib/code-patching.c
> > @@ -15,20 +15,24 @@
> >  #include <asm/code-patching.h>
> >  #include <asm/inst.h>
> >  
> > -static int __patch_instruction(u32 *exec_addr, ppc_inst_t instr,
> > u32
> > *patch_addr)
> > +static int __patch_memory(void *patch_addr, unsigned long val,
> > void
> > *exec_addr,
> > +                         bool is_dword)
> >  {
> > -       if (!ppc_inst_prefixed(instr)) {
> > -               u32 val = ppc_inst_val(instr);
> > -
> > -               __put_kernel_nofault(patch_addr, &val, u32,
> > failed);
> > -       } else {
> > -               u64 val = ppc_inst_as_ulong(instr);
> > +       /* Prefixed instruction may cross cacheline if cacheline
> > smaller than 64 bytes */
> > +       BUILD_BUG_ON(IS_ENABLED(CONFIG_PPC64) && L1_CACHE_BYTES <
> > 64);
> >  
> > +       if (IS_ENABLED(CONFIG_PPC64) && unlikely(is_dword))
> >                 __put_kernel_nofault(patch_addr, &val, u64,
> > failed);
> > -       }
> > +       else
> > +               __put_kernel_nofault(patch_addr, &val, u32,
> > failed);
> >  
> > -       asm ("dcbst 0, %0; sync; icbi 0,%1; sync; isync" :: "r"
> > (patch_addr),
> > -                                                           "r"
> > (exec_addr));
> > +       /* Assume data is inside a single cacheline */
> > +       dcbst(patch_addr);
> > +       mb(); /* sync */
> > +       /* Flush on the EA that may be executed in case of a non-
> > coherent icache */
> > +       icbi(exec_addr);
> > +       mb(); /* sync */
> > +       isync();
> >  
> >         return 0;
> >  
> > @@ -38,7 +42,10 @@ static int __patch_instruction(u32 *exec_addr,
> > ppc_inst_t instr, u32 *patch_addr
> >  
> >  int raw_patch_instruction(u32 *addr, ppc_inst_t instr)
> >  {
> > -       return __patch_instruction(addr, instr, addr);
> > +       if (ppc_inst_prefixed(instr))
> > +               return __patch_memory(addr,
> > ppc_inst_as_ulong(instr),
> > addr, true);
> > +       else
> > +               return __patch_memory(addr, ppc_inst_val(instr),
> > addr, false);
> >  }
> >  
> >  static DEFINE_PER_CPU(struct vm_struct *, text_poke_area);
> > @@ -149,7 +156,7 @@ static void unmap_patch_area(unsigned long
> > addr)
> >         flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
> >  }
> >  
> > -static int __do_patch_instruction(u32 *addr, ppc_inst_t instr)
> > +static int __do_patch_memory(void *addr, unsigned long val, bool
> > is_dword)
> >  {
> >         int err;
> >         u32 *patch_addr;
> > @@ -166,7 +173,7 @@ static int __do_patch_instruction(u32 *addr,
> > ppc_inst_t instr)
> >         if (radix_enabled())
> >                 asm volatile("ptesync": : :"memory");
> >  
> > -       err = __patch_instruction(addr, instr, patch_addr);
> > +       err = __patch_memory(patch_addr, val, addr, is_dword);
> >  
> >         pte_clear(&init_mm, text_poke_addr, pte);
> >         flush_tlb_kernel_range(text_poke_addr, text_poke_addr +
> > PAGE_SIZE);
> > @@ -174,7 +181,7 @@ static int __do_patch_instruction(u32 *addr,
> > ppc_inst_t instr)
> >         return err;
> >  }
> >  
> > -int patch_instruction(u32 *addr, ppc_inst_t instr)
> > +static int do_patch_memory(void *addr, unsigned long val, bool
> > is_dword)
> >  {
> >         int err;
> >         unsigned long flags;
> > @@ -186,15 +193,47 @@ int patch_instruction(u32 *addr, ppc_inst_t
> > instr)
> >          */
> >         if (!IS_ENABLED(CONFIG_STRICT_KERNEL_RWX) ||
> >             !static_branch_likely(&poking_init_done))
> > -               return raw_patch_instruction(addr, instr);
> > +               return __patch_memory(addr, val, addr, is_dword);
> >  
> >         local_irq_save(flags);
> > -       err = __do_patch_instruction(addr, instr);
> > +       err = __do_patch_memory(addr, val, is_dword);
> >         local_irq_restore(flags);
> >  
> >         return err;
> >  }
> > -NOKPROBE_SYMBOL(patch_instruction);
> > +
> > +#ifdef CONFIG_PPC64
> > +
> > +int patch_uint(void *addr, unsigned int val)
> > +{
> > +       return do_patch_memory(addr, val, false);
> > +}
> > +NOKPROBE_SYMBOL(patch_uint)
> > +
> > +int patch_ulong(void *addr, unsigned long val)
> > +{
> > +       return do_patch_memory(addr, val, true);
> > +}
> > +NOKPROBE_SYMBOL(patch_ulong)
> > +
> > +int patch_instruction(u32 *addr, ppc_inst_t instr)
> > +{
> > +       if (ppc_inst_prefixed(instr))
> > +               return patch_ulong(addr, ppc_inst_as_ulong(instr));
> > +       else
> > +               return patch_uint(addr, ppc_inst_val(instr));
> > +}
> > +NOKPROBE_SYMBOL(patch_instruction)
> > +
> > +#else
> > +
> > +noinline int patch_uint(void *addr, unsigned int val)
> > +{
> > +       return do_patch_memory(addr, val, false);
> > +}
> > +NOKPROBE_SYMBOL(patch_uint)
> > +
> > +#endif
> >  
> >  int patch_branch(u32 *addr, unsigned long target, int flags)
> >  {
> 

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

Re: [PATCH v4 2/6] powerpc/module: Handle caller-saved TOC in module linker

[Andrew Donnellan]

On Mon, 2022-10-10 at 11:29 +1100, Benjamin Gray wrote:
> > A function symbol may set a value in the st_other field to indicate
> > the TOC should be treated as caller-saved. The linker should
> > ensure> the
> > current TOC is saved before calling it and restore the TOC>
> > afterwards,
> > much like external calls.

As I suggested on the last revision, worth mentioning here that it's
the '.localentry <NAME>, 1' directive we're talking about here.

> > 
> > This is necessary for supporting V2 ABI static calls that do not
> > preserve the TOC.
> > 
> > Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
> > ---
> >  arch/powerpc/kernel/module_64.c | 14 +++++++++++++-
> >  1 file changed, 13 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/powerpc/kernel/module_64.c>
> > b/arch/powerpc/kernel/module_64.c
> > index 7e45dc98df8a..83a6f6e22e3b 100644
> > --- a/arch/powerpc/kernel/module_64.c
> > +++ b/arch/powerpc/kernel/module_64.c
> > @@ -55,6 +55,12 @@ static unsigned int local_entry_offset(const>
> > Elf64_Sym *sym)
> >          * of function and try to derive r2 from it). */
> >         return PPC64_LOCAL_ENTRY_OFFSET(sym->st_other);
> >  }
> > +
> > +static bool need_r2save_stub(unsigned char st_other)
> > +{
> > +       return (st_other & STO_PPC64_LOCAL_MASK) == (1 <<>
> > STO_PPC64_LOCAL_BIT);
> > +}
> > +
> >  #else
> >  
> >  static func_desc_t func_desc(unsigned long addr)
> > @@ -66,6 +72,11 @@ static unsigned int local_entry_offset(const>
> > Elf64_Sym *sym)
> >         return 0;
> >  }
> >  
> > +static bool need_r2save_stub(unsigned char st_other)
> > +{
> > +       return false;
> > +}
> > +
> >  void *dereference_module_function_descriptor(struct module *mod,>
> > void *ptr)
> >  {
> >         if (ptr < (void *)mod->arch.start_opd ||
> > @@ -632,7 +643,8 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
> >                 case R_PPC_REL24:
> >                         /* FIXME: Handle weak symbols here --RR */
> >                         if (sym->st_shndx == SHN_UNDEF ||
> > -                           sym->st_shndx == SHN_LIVEPATCH) {
> > +                           sym->st_shndx == SHN_LIVEPATCH ||
> > +                           need_r2save_stub(sym->st_other)) {
> >                                 /* External: go via stub */

Perhaps this comment should be updated to mention that there are non-
external but external-like calls?

Otherwise

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

> >                                 value = stub_for_addr(sechdrs,
> > value,> me,
> >                                                 strtab +> sym-
> > >st_name);

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

Re: [PATCH v4 2/6] powerpc/module: Handle caller-saved TOC in module linker

[Benjamin Gray]

On Tue, 2022-10-25 at 13:10 +1100, Andrew Donnellan wrote:
> On Mon, 2022-10-10 at 11:29 +1100, Benjamin Gray wrote:
> > > A function symbol may set a value in the st_other field to
> > > indicate
> > > the TOC should be treated as caller-saved. The linker should
> > > ensure> the
> > > current TOC is saved before calling it and restore the TOC>
> > > afterwards,
> > > much like external calls.
> 
> As I suggested on the last revision, worth mentioning here that it's
> the '.localentry <NAME>, 1' directive we're talking about here.

Ah right, whoops. Added "For example, GCC and Clang support a
'.localentry <NAME>, 1' directive to set this explicitly in assembly."

The exact method for doing this seems to be nonstandard (GCC supports
arbitrary value in 1--7, Clang special cases only 1), so originally I
was avoiding specifying how it is set.

> > > @@ -632,7 +643,8 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,
> > >                 case R_PPC_REL24:
> > >                         /* FIXME: Handle weak symbols here --RR
> > > */
> > >                         if (sym->st_shndx == SHN_UNDEF ||
> > > -                           sym->st_shndx == SHN_LIVEPATCH) {
> > > +                           sym->st_shndx == SHN_LIVEPATCH ||
> > > +                           need_r2save_stub(sym->st_other)) {
> > >                                 /* External: go via stub */
> 
> Perhaps this comment should be updated to mention that there are non-
> external but external-like calls?
> 
> Otherwise
> 
> Reviewed-by: Andrew Donnellan <ajd@linux.ibm.com>

Updated to "/* May use different / not preserve TOC: go via stub */",
will add your reviewed-by in the next version. For now I'll wait for
any other feedback before sending it.
> >