From 953f534a7ed6b725d4f101d2949393acc9262880 Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Tue, 25 Jan 2022 11:20:49 +0100 Subject: [PATCH] ARM: ftrace: enable HAVE_FUNCTION_GRAPH_FP_TEST 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 Reviewed-by: Steven Rostedt (Google) --- arch/arm/include/asm/ftrace.h | 2 ++ arch/arm/kernel/entry-ftrace.S | 2 +- arch/arm/kernel/ftrace.c | 5 +++++ 3 files changed, 8 insertions(+), 1 deletion(-) diff --git a/arch/arm/include/asm/ftrace.h b/arch/arm/include/asm/ftrace.h index a4dbac07e4ef..b4f5fab6b04e 100644 --- a/arch/arm/include/asm/ftrace.h +++ b/arch/arm/include/asm/ftrace.h @@ -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 diff --git a/arch/arm/kernel/entry-ftrace.S b/arch/arm/kernel/entry-ftrace.S index 99720064a4c5..bbfa0954c385 100644 --- a/arch/arm/kernel/entry-ftrace.S +++ b/arch/arm/kernel/entry-ftrace.S @@ -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} diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c index 74d3913f5590..ea2396900c7d 100644 --- a/arch/arm/kernel/ftrace.c +++ b/arch/arm/kernel/ftrace.c @@ -233,6 +233,11 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr, if (unlikely(atomic_read(¤t->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; -- 2.25.1