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ARM: ftrace: enable HAVE_FUNCTION_GRAPH_FP_TEST

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Fix the frame pointer handling in the function graph tracer entry and
exit code so we can enable HAVE_FUNCTION_GRAPH_FP_TEST. Instead of using
FP directly (which will have different values between the entry and exit
pieces of the function graph tracer), use the value of SP at entry and
exit, as we can derive the former value from the frame pointer.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Ard Biesheuvel 2022-01-25 11:20:49 +01:00
parent 65aa7e342a
commit 953f534a7e
3 changed files with 8 additions and 1 deletions
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2
arch/arm/include/asm/ftrace.h
View File

@ -2,6 +2,8 @@
#ifndef _ASM_ARM_FTRACE
#define _ASM_ARM_FTRACE
#define HAVE_FUNCTION_GRAPH_FP_TEST
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
#define ARCH_SUPPORTS_FTRACE_OPS 1
#endif

2
arch/arm/kernel/entry-ftrace.S
View File

@ -247,7 +247,7 @@ ENDPROC(ftrace_graph_regs_caller)
.globl return_to_handler
return_to_handler:
stmdb sp!, {r0-r3}
mov r0, fp @ frame pointer
add r0, sp, #16 @ sp at exit of instrumented routine
bl ftrace_return_to_handler
mov lr, r0 @ r0 has real ret addr
ldmia sp!, {r0-r3}

5
arch/arm/kernel/ftrace.c
View File

@ -233,6 +233,11 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
if (unlikely(atomic_read(&current->tracing_graph_pause)))
return;
if (IS_ENABLED(CONFIG_UNWINDER_FRAME_POINTER)) {
/* FP points one word below parent's top of stack */
frame_pointer += 4;
}
old = *parent;
*parent = return_hooker;