diff mbox series

[6/8] ARM: ftrace: enable HAVE_FUNCTION_GRAPH_FP_TEST

Message ID 20220125153656.1802079-7-ardb@kernel.org (mailing list archive)
State New, archived
Headers show
Series ARM: ftrace fixes and cleanups | expand

Commit Message

Ard Biesheuvel Jan. 25, 2022, 3:36 p.m. UTC 
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>
---
 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 mbox series

Patch

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 d2326794fd09..988525b274e3 100644
--- a/arch/arm/kernel/ftrace.c
+++ b/arch/arm/kernel/ftrace.c
@@ -220,6 +220,11 @@  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;