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Subject[PATCH] ARM: kprobes: Make __kretprobe_trampoline as a pure asm function
Date
Make __kretprobe_trampoline() as a pure asm function same as the x86
code does. Anyway, it is safe to define the symbol in the asm code
instead of accessing a C symbol from the inline asm.

Without this fix, building arm kernel with GCC-11 may cause below
error.

/tmp/ccIWiggX.s: Assembler messages:
>> /tmp/ccIWiggX.s:22: Error: invalid literal constant: pool needs to be closer

This fixes the error reported by 0day build bot.

Reported-by: kernel test robot <lkp@intel.com>
Fixes: 7e9bf33b8124 ("ARM: kprobes: Make a frame pointer on __kretprobe_trampoline")
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
arch/arm/probes/kprobes/core.c | 57 +++++++++++++++++++++-------------------
1 file changed, 30 insertions(+), 27 deletions(-)

diff --git a/arch/arm/probes/kprobes/core.c b/arch/arm/probes/kprobes/core.c
index 4848404ba51b..51f1438456ae 100644
--- a/arch/arm/probes/kprobes/core.c
+++ b/arch/arm/probes/kprobes/core.c
@@ -373,43 +373,46 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self,
* should be enough for stacktrace from the return handler with or
* without pt_regs.
*/
-void __naked __kprobes __kretprobe_trampoline(void)
-{
- __asm__ __volatile__ (
+asm(
+ ".text\n"
+ ".global __kretprobe_trampoline\n"
+ ".type __kretprobe_trampoline, %function\n"
+ "__kretprobe_trampoline:\n"
#ifdef CONFIG_FRAME_POINTER
- "ldr lr, =__kretprobe_trampoline \n\t"
+ "ldr lr, =__kretprobe_trampoline \n\t"
/* __kretprobe_trampoline makes a framepointer on pt_regs. */
#ifdef CONFIG_CC_IS_CLANG
- "stmdb sp, {sp, lr, pc} \n\t"
- "sub sp, sp, #12 \n\t"
- /* In clang case, pt_regs->ip = lr. */
- "stmdb sp!, {r0 - r11, lr} \n\t"
- /* fp points regs->r11 (fp) */
- "add fp, sp, #44 \n\t"
+ "stmdb sp, {sp, lr, pc} \n\t"
+ "sub sp, sp, #12 \n\t"
+ /* In clang case, pt_regs->ip = lr. */
+ "stmdb sp!, {r0 - r11, lr} \n\t"
+ /* fp points regs->r11 (fp) */
+ "add fp, sp, #44 \n\t"
#else /* !CONFIG_CC_IS_CLANG */
- /* In gcc case, pt_regs->ip = fp. */
- "stmdb sp, {fp, sp, lr, pc} \n\t"
- "sub sp, sp, #16 \n\t"
- "stmdb sp!, {r0 - r11} \n\t"
- /* fp points regs->r15 (pc) */
- "add fp, sp, #60 \n\t"
+ /* In gcc case, pt_regs->ip = fp. */
+ "stmdb sp, {fp, sp, lr, pc} \n\t"
+ "sub sp, sp, #16 \n\t"
+ "stmdb sp!, {r0 - r11} \n\t"
+ /* fp points regs->r15 (pc) */
+ "add fp, sp, #60 \n\t"
#endif /* CONFIG_CC_IS_CLANG */
#else /* !CONFIG_FRAME_POINTER */
- "sub sp, sp, #16 \n\t"
- "stmdb sp!, {r0 - r11} \n\t"
+ "sub sp, sp, #16 \n\t"
+ "stmdb sp!, {r0 - r11} \n\t"
#endif /* CONFIG_FRAME_POINTER */
- "mov r0, sp \n\t"
- "bl trampoline_handler \n\t"
- "mov lr, r0 \n\t"
- "ldmia sp!, {r0 - r11} \n\t"
- "add sp, sp, #16 \n\t"
+ "mov r0, sp \n\t"
+ "bl trampoline_handler \n\t"
+ "mov lr, r0 \n\t"
+ "ldmia sp!, {r0 - r11} \n\t"
+ "add sp, sp, #16 \n\t"
#ifdef CONFIG_THUMB2_KERNEL
- "bx lr \n\t"
+ "bx lr \n\t"
#else
- "mov pc, lr \n\t"
+ "mov pc, lr \n\t"
#endif
- : : : "memory");
-}
+ ".size __kretprobe_trampoline, .-__kretprobe_trampoline\n"
+);
+NOKPROBE_SYMBOL(__kretprobe_trampoline);

/* Called from __kretprobe_trampoline */
static __used __kprobes void *trampoline_handler(struct pt_regs *regs)
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