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

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Date:   Fri, 24 Apr 2020 16:38:01 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Josh Poimboeuf <jpoimboe@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-kernel@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] samples/ftrace: Fix asm function ELF annotations

On 4/24/20 1:49 PM, Josh Poimboeuf wrote:
> 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>

Acked-by: Randy Dunlap <rdunlap@...radead.org>
Tested-by: Randy Dunlap <rdunlap@...radead.org>

Thanks.

> ---
>  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"
>  );
>  
> 


-- 
~Randy