linux-kernel - Re: [PATCH 3/6] ftrace/x86_32: Add stack frame pointer to ftrace

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Date:   Thu, 23 Mar 2017 12:07:01 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andy Lutomirski <luto@...capital.net>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 3/6] ftrace/x86_32: Add stack frame pointer to
 ftrace_caller

On Tue, 21 Mar 2017 21:35:05 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:

> From: "Steven Rostedt (VMware)" <rostedt@...dmis.org>
> 
> The function hook ftrace_caller does not create its own stack frame, and
> this causes the ftrace stack trace to miss the first function when doing
> stack traces.
> 
>  # echo schedule:stacktrace > /sys/kernel/tracing/set_ftrace_filter
> 
> Before:
>          <idle>-0     [002] .N..    29.865807: <stack trace>
>  => cpu_startup_entry
>  => start_secondary
>  => startup_32_smp
>            <...>-7     [001] ....    29.866509: <stack trace>
>  => kthread
>  => ret_from_fork
>            <...>-1     [000] ....    29.865377: <stack trace>
>  => poll_schedule_timeout
>  => do_select
>  => core_sys_select
>  => SyS_select
>  => do_fast_syscall_32
>  => entry_SYSENTER_32
> 
> After:
>           <idle>-0     [002] .N..    31.234853: <stack trace>
>  => do_idle
>  => cpu_startup_entry
>  => start_secondary
>  => startup_32_smp
>            <...>-7     [003] ....    31.235140: <stack trace>
>  => rcu_gp_kthread
>  => kthread
>  => ret_from_fork
>            <...>-1819  [000] ....    31.264172: <stack trace>
>  => schedule_hrtimeout_range
>  => poll_schedule_timeout
>  => do_sys_poll
>  => SyS_ppoll
>  => do_fast_syscall_32
>  => entry_SYSENTER_32
> 

Looks good to me.

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

Thank you,

> Reviewed-by: Josh Poimboeuf <jpoimboe@...hat.com>
> Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
> ---
>  arch/x86/kernel/ftrace_32.S | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kernel/ftrace_32.S b/arch/x86/kernel/ftrace_32.S
> index 1889a74823ce..f991e723c3e4 100644
> --- a/arch/x86/kernel/ftrace_32.S
> +++ b/arch/x86/kernel/ftrace_32.S
> @@ -18,12 +18,19 @@ ENTRY(mcount)
>  END(mcount)
>  
>  ENTRY(ftrace_caller)
> +
> +	pushl	%ebp
> +	movl	%esp, %ebp
> +
>  	pushl	%eax
>  	pushl	%ecx
>  	pushl	%edx
>  	pushl	$0				/* Pass NULL as regs pointer */
> -	movl	4*4(%esp), %eax
> -	movl	0x4(%ebp), %edx
> +	movl	5*4(%esp), %eax
> +	/* Copy original ebp into %edx */
> +	movl	4*4(%esp), %edx
> +	/* Get the parent ip */
> +	movl	0x4(%edx), %edx
>  	movl	function_trace_op, %ecx
>  	subl	$MCOUNT_INSN_SIZE, %eax
>  
> @@ -35,6 +42,7 @@ ftrace_call:
>  	popl	%edx
>  	popl	%ecx
>  	popl	%eax
> +	popl	%ebp
>  .Lftrace_ret:
>  #ifdef CONFIG_FUNCTION_GRAPH_TRACER
>  .globl ftrace_graph_call
> -- 
> 2.10.2
> 
> 


-- 
Masami Hiramatsu <mhiramat@...nel.org>