linux-kernel - [PATCH] samples/ftrace: Fix asm function ELF annotations

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Date:   Fri, 24 Apr 2020 15:49:30 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Randy Dunlap <rdunlap@...radead.org>
Subject: [PATCH] samples/ftrace: Fix asm function ELF annotations

Enable objtool coverage for the sample ftrace modules by adding ELF
annotations to the asm trampoline functions.

  samples/ftrace/ftrace-direct.o: warning: objtool: .text+0x0: unreachable instruction
  samples/ftrace/ftrace-direct-modify.o: warning: objtool: .text+0x0: unreachable instruction
  samples/ftrace/ftrace-direct-too.o: warning: objtool: .text+0x0: unreachable instruction

Reported-by: Randy Dunlap <rdunlap@...radead.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
---
 samples/ftrace/ftrace-direct-modify.c | 4 ++++
 samples/ftrace/ftrace-direct-too.c    | 2 ++
 samples/ftrace/ftrace-direct.c        | 2 ++
 3 files changed, 8 insertions(+)

diff --git a/samples/ftrace/ftrace-direct-modify.c b/samples/ftrace/ftrace-direct-modify.c
index e04229d21475..c13a5bc5095b 100644
--- a/samples/ftrace/ftrace-direct-modify.c
+++ b/samples/ftrace/ftrace-direct-modify.c
@@ -20,18 +20,22 @@ static unsigned long my_ip = (unsigned long)schedule;
 
 asm (
 "	.pushsection    .text, \"ax\", @progbits\n"
+"	.type		my_tramp1, @function\n"
 "   my_tramp1:"
 "	pushq %rbp\n"
 "	movq %rsp, %rbp\n"
 "	call my_direct_func1\n"
 "	leave\n"
+"	.size		my_tramp1, .-my_tramp1\n"
 "	ret\n"
+"	.type		my_tramp2, @function\n"
 "   my_tramp2:"
 "	pushq %rbp\n"
 "	movq %rsp, %rbp\n"
 "	call my_direct_func2\n"
 "	leave\n"
 "	ret\n"
+"	.size		my_tramp2, .-my_tramp2\n"
 "	.popsection\n"
 );
 
diff --git a/samples/ftrace/ftrace-direct-too.c b/samples/ftrace/ftrace-direct-too.c
index 27efa5f6ff52..d5c5022be664 100644
--- a/samples/ftrace/ftrace-direct-too.c
+++ b/samples/ftrace/ftrace-direct-too.c
@@ -15,6 +15,7 @@ extern void my_tramp(void *);
 
 asm (
 "	.pushsection    .text, \"ax\", @progbits\n"
+"	.type		my_tramp, @function\n"
 "   my_tramp:"
 "	pushq %rbp\n"
 "	movq %rsp, %rbp\n"
@@ -27,6 +28,7 @@ asm (
 "	popq %rdi\n"
 "	leave\n"
 "	ret\n"
+"	.size		my_tramp, .-my_tramp\n"
 "	.popsection\n"
 );
 
diff --git a/samples/ftrace/ftrace-direct.c b/samples/ftrace/ftrace-direct.c
index a2e3063bd306..63ca06d42c80 100644
--- a/samples/ftrace/ftrace-direct.c
+++ b/samples/ftrace/ftrace-direct.c
@@ -13,6 +13,7 @@ extern void my_tramp(void *);
 
 asm (
 "	.pushsection    .text, \"ax\", @progbits\n"
+"	.type		my_tramp, @function\n"
 "   my_tramp:"
 "	pushq %rbp\n"
 "	movq %rsp, %rbp\n"
@@ -21,6 +22,7 @@ asm (
 "	popq %rdi\n"
 "	leave\n"
 "	ret\n"
+"	.size		my_tramp, .-my_tramp\n"
 "	.popsection\n"
 );
 
-- 
2.21.1