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From: Ard Biesheuvel <ardb@kernel.org>
To: linux@armlinux.org.uk, linux-arm-kernel@lists.infradead.org
Cc: Ard Biesheuvel <ardb@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
	Linus Walleij <linus.walleij@linaro.org>,
	Nick Desaulniers <ndesaulniers@google.com>
Subject: [PATCH 6/8] ARM: ftrace: enable HAVE_FUNCTION_GRAPH_FP_TEST
Date: Tue, 25 Jan 2022 16:36:54 +0100	[thread overview]
Message-ID: <20220125153656.1802079-7-ardb@kernel.org> (raw)
In-Reply-To: <20220125153656.1802079-1-ardb@kernel.org>

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 --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;
 
-- 
2.30.2


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  parent reply	other threads:[~2022-01-25 15:53 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-25 15:36 [PATCH 0/8] ARM: ftrace fixes and cleanups Ard Biesheuvel
2022-01-25 15:36 ` [PATCH 1/8] ARM: ftrace: ensure that ADR take Thumb bit into account Ard Biesheuvel
2022-01-25 19:14   ` Nick Desaulniers
2022-02-02 23:53   ` Linus Walleij
2022-01-25 15:36 ` [PATCH 2/8] ARM: ftrace: use ADD not POP to counter PUSH at entry Ard Biesheuvel
2022-01-25 19:23   ` Nick Desaulniers
2022-02-02 23:59   ` Linus Walleij
2022-01-25 15:36 ` [PATCH 3/8] ARM: ftrace: use trampolines to keep .init.text in branching range Ard Biesheuvel
2022-01-25 20:20   ` Nick Desaulniers
2022-02-03  0:12   ` Linus Walleij
2022-01-25 15:36 ` [PATCH 4/8] ARM: ftrace: avoid redundant loads or clobbering IP Ard Biesheuvel
2022-01-25 15:36 ` [PATCH 5/8] ARM: ftrace: avoid unnecessary literal loads Ard Biesheuvel
2022-01-25 20:27   ` Nick Desaulniers
2022-01-25 15:36 ` Ard Biesheuvel [this message]
2022-01-25 15:36 ` [PATCH 7/8] ARM: unwind: track location of LR value in stack frame Ard Biesheuvel
2022-01-25 15:36 ` [PATCH 8/8] ARM: ftrace: enable the graph tracer with the EABI unwinder Ard Biesheuvel

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