linux-kernel - Re: [PATCH] samples: ftrace: Include the nospec-branch.h only for x86

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Date:   Fri, 3 Feb 2023 10:22:39 +0900
From:   Masami Hiramatsu (Google) <mhiramat@...nel.org>
To:     Song Shuai <suagrfillet@...il.com>
Cc:     rostedt@...dmis.org, mark.rutland@....com, peterz@...radead.org,
        jpoimboe@...nel.org, tglx@...utronix.de,
        linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH] samples: ftrace: Include the nospec-branch.h only for
 x86

On Mon, 30 Jan 2023 16:59:54 +0800
Song Shuai <suagrfillet@...il.com> wrote:

> When other architectures without the nospec functionality write their
> direct-call functions of samples/ftrace/*.c, the including of
> asm/nospec-branch.h must be taken care to fix the no header file found
> error in building process.
> 
> This commit (ee3e2469b346 "x86/ftrace: Make it call depth tracking aware")
> file-globally includes asm/nospec-branch.h providing CALL_DEPTH_ACCOUNT
> for only x86 direct-call functions.
> 
> It seems better to move the including to `#ifdef CONFIG_X86_64`.
> 
> Signed-off-by: Song Shuai <suagrfillet@...il.com>

This looks good to me since nospec-branch.h is used only for x86 asm macro.
(s390 also has "nospec-branch.h" file but that doesn't provide such macro,
so this change will not affect it.)

Reviewed-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>

Thank you,

> ---
>  samples/ftrace/ftrace-direct-modify.c       | 2 +-
>  samples/ftrace/ftrace-direct-multi-modify.c | 2 +-
>  samples/ftrace/ftrace-direct-multi.c        | 2 +-
>  samples/ftrace/ftrace-direct-too.c          | 2 +-
>  samples/ftrace/ftrace-direct.c              | 2 +-
>  5 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/samples/ftrace/ftrace-direct-modify.c b/samples/ftrace/ftrace-direct-modify.c
> index de5a0f67f320..d93abbcb1f4c 100644
> --- a/samples/ftrace/ftrace-direct-modify.c
> +++ b/samples/ftrace/ftrace-direct-modify.c
> @@ -3,7 +3,6 @@
>  #include <linux/kthread.h>
>  #include <linux/ftrace.h>
>  #include <asm/asm-offsets.h>
> -#include <asm/nospec-branch.h>
>  
>  extern void my_direct_func1(void);
>  extern void my_direct_func2(void);
> @@ -26,6 +25,7 @@ static unsigned long my_ip = (unsigned long)schedule;
>  #ifdef CONFIG_X86_64
>  
>  #include <asm/ibt.h>
> +#include <asm/nospec-branch.h>
>  
>  asm (
>  "	.pushsection    .text, \"ax\", @progbits\n"
> diff --git a/samples/ftrace/ftrace-direct-multi-modify.c b/samples/ftrace/ftrace-direct-multi-modify.c
> index a825dbd2c9cf..b58c594efb51 100644
> --- a/samples/ftrace/ftrace-direct-multi-modify.c
> +++ b/samples/ftrace/ftrace-direct-multi-modify.c
> @@ -3,7 +3,6 @@
>  #include <linux/kthread.h>
>  #include <linux/ftrace.h>
>  #include <asm/asm-offsets.h>
> -#include <asm/nospec-branch.h>
>  
>  extern void my_direct_func1(unsigned long ip);
>  extern void my_direct_func2(unsigned long ip);
> @@ -24,6 +23,7 @@ extern void my_tramp2(void *);
>  #ifdef CONFIG_X86_64
>  
>  #include <asm/ibt.h>
> +#include <asm/nospec-branch.h>
>  
>  asm (
>  "	.pushsection    .text, \"ax\", @progbits\n"
> diff --git a/samples/ftrace/ftrace-direct-multi.c b/samples/ftrace/ftrace-direct-multi.c
> index d955a2650605..c27cf130c319 100644
> --- a/samples/ftrace/ftrace-direct-multi.c
> +++ b/samples/ftrace/ftrace-direct-multi.c
> @@ -5,7 +5,6 @@
>  #include <linux/ftrace.h>
>  #include <linux/sched/stat.h>
>  #include <asm/asm-offsets.h>
> -#include <asm/nospec-branch.h>
>  
>  extern void my_direct_func(unsigned long ip);
>  
> @@ -19,6 +18,7 @@ extern void my_tramp(void *);
>  #ifdef CONFIG_X86_64
>  
>  #include <asm/ibt.h>
> +#include <asm/nospec-branch.h>
>  
>  asm (
>  "	.pushsection    .text, \"ax\", @progbits\n"
> diff --git a/samples/ftrace/ftrace-direct-too.c b/samples/ftrace/ftrace-direct-too.c
> index e13fb59a2b47..8139dce2a31c 100644
> --- a/samples/ftrace/ftrace-direct-too.c
> +++ b/samples/ftrace/ftrace-direct-too.c
> @@ -4,7 +4,6 @@
>  #include <linux/mm.h> /* for handle_mm_fault() */
>  #include <linux/ftrace.h>
>  #include <asm/asm-offsets.h>
> -#include <asm/nospec-branch.h>
>  
>  extern void my_direct_func(struct vm_area_struct *vma,
>  			   unsigned long address, unsigned int flags);
> @@ -21,6 +20,7 @@ extern void my_tramp(void *);
>  #ifdef CONFIG_X86_64
>  
>  #include <asm/ibt.h>
> +#include <asm/nospec-branch.h>
>  
>  asm (
>  "	.pushsection    .text, \"ax\", @progbits\n"
> diff --git a/samples/ftrace/ftrace-direct.c b/samples/ftrace/ftrace-direct.c
> index 1f769d0db20f..1d3d307ca33d 100644
> --- a/samples/ftrace/ftrace-direct.c
> +++ b/samples/ftrace/ftrace-direct.c
> @@ -4,7 +4,6 @@
>  #include <linux/sched.h> /* for wake_up_process() */
>  #include <linux/ftrace.h>
>  #include <asm/asm-offsets.h>
> -#include <asm/nospec-branch.h>
>  
>  extern void my_direct_func(struct task_struct *p);
>  
> @@ -18,6 +17,7 @@ extern void my_tramp(void *);
>  #ifdef CONFIG_X86_64
>  
>  #include <asm/ibt.h>
> +#include <asm/nospec-branch.h>
>  
>  asm (
>  "	.pushsection    .text, \"ax\", @progbits\n"
> -- 
> 2.20.1
> 


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>