Re: [RFC][PATCH 2/4 v4] ftrace/x86: Add save_regs for i386 functioncalls

[Steven Rostedt]

On Fri, 2012-07-13 at 14:47 -0400, Steven Rostedt wrote:

Masami, can you give your Reviewed-by tag for this version? Or is there
something else needing to be fixed?

Thanks!

-- Steve

> From: Steven Rostedt <srostedt@xxxxxxxxxx>
> Date: Tue, 5 Jun 2012 20:00:11 -0400
> Subject: [PATCH] ftrace/x86: Add save_regs for i386 function calls
> 
> Add saving full regs for function tracing on i386.
> The saving of regs was influenced by patches sent out by
> Masami Hiramatsu.
> 
> Cc: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
> Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
> ---
>  arch/x86/include/asm/ftrace.h |    2 -
>  arch/x86/kernel/entry_32.S    |   68 +++++++++++++++++++++++++++++++++++++++++
>  arch/x86/kernel/ftrace.c      |    4 --
>  3 files changed, 68 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/include/asm/ftrace.h b/arch/x86/include/asm/ftrace.h
> index a847501..a6cae0c 100644
> --- a/arch/x86/include/asm/ftrace.h
> +++ b/arch/x86/include/asm/ftrace.h
> @@ -40,10 +40,8 @@
>  
>  #ifdef CONFIG_DYNAMIC_FTRACE
>  #define ARCH_SUPPORTS_FTRACE_OPS 1
> -#ifdef CONFIG_X86_64
>  #define ARCH_SUPPORTS_FTRACE_SAVE_REGS
>  #endif
> -#endif
>  
>  #ifndef __ASSEMBLY__
>  extern void mcount(void);
> diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
> index 5da11d1..46caa56 100644
> --- a/arch/x86/kernel/entry_32.S
> +++ b/arch/x86/kernel/entry_32.S
> @@ -1123,6 +1123,7 @@ ftrace_call:
>  	popl %edx
>  	popl %ecx
>  	popl %eax
> +ftrace_ret:
>  #ifdef CONFIG_FUNCTION_GRAPH_TRACER
>  .globl ftrace_graph_call
>  ftrace_graph_call:
> @@ -1134,6 +1135,73 @@ ftrace_stub:
>  	ret
>  END(ftrace_caller)
>  
> +ENTRY(ftrace_regs_caller)
> +	pushf	/* push flags before compare (in cs location) */
> +	cmpl $0, function_trace_stop
> +	jne ftrace_restore_flags
> +
> +	/*
> +	 * i386 does not save SS and ESP when coming from kernel.
> +	 * Instead, to get sp, &regs->sp is used (see ptrace.h).
> +	 * Unfortunately, that means eflags must be at the same location
> +	 * as the current return ip is. We move the return ip into the
> +	 * ip location, and move flags into the return ip location.
> +	 */
> +	pushl 4(%esp)	/* save return ip into ip slot */
> +	subl $MCOUNT_INSN_SIZE, (%esp)	/* Adjust ip */
> +
> +	pushl $0	/* Load 0 into orig_ax */
> +	pushl %gs
> +	pushl %fs
> +	pushl %es
> +	pushl %ds
> +	pushl %eax
> +	pushl %ebp
> +	pushl %edi
> +	pushl %esi
> +	pushl %edx
> +	pushl %ecx
> +	pushl %ebx
> +
> +	movl 13*4(%esp), %eax	/* Get the saved flags */
> +	movl %eax, 14*4(%esp)	/* Move saved flags into regs->flags location */
> +				/* clobbering return ip */
> +	movl $__KERNEL_CS,13*4(%esp)
> +
> +	movl 12*4(%esp), %eax	/* Load ip (1st parameter) */
> +	movl 0x4(%ebp), %edx	/* Load parent ip (2cd parameter) */
> +	lea  (%esp), %ecx
> +	pushl %ecx		/* Save pt_regs as 4th parameter */
> +	leal function_trace_op, %ecx /* Save ftrace_pos in 3rd parameter */
> +
> +GLOBAL(ftrace_regs_call)
> +	call ftrace_stub
> +
> +	addl $4, %esp		/* Skip pt_regs */
> +	movl 14*4(%esp), %eax	/* Move flags back into cs */
> +	movl %eax, 13*4(%esp)	/* Needed to keep addl from modifying flags */
> +	movl 12*4(%esp), %eax	/* Get return ip from regs->ip */
> +	addl $MCOUNT_INSN_SIZE, %eax
> +	movl %eax, 14*4(%esp)	/* Put return ip back for ret */
> +
> +	popl %ebx
> +	popl %ecx
> +	popl %edx
> +	popl %esi
> +	popl %edi
> +	popl %ebp
> +	popl %eax
> +	popl %ds
> +	popl %es
> +	popl %fs
> +	popl %gs
> +	addl $8, %esp		/* Skip orig_ax and ip */
> +	popf			/* Pop flags at end (no addl to corrupt flags) */
> +	jmp ftrace_ret
> +
> +ftrace_restore_flags:
> +	popf
> +	jmp  ftrace_stub
>  #else /* ! CONFIG_DYNAMIC_FTRACE */
>  
>  ENTRY(mcount)
> diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
> index b90eb1a..1d41402 100644
> --- a/arch/x86/kernel/ftrace.c
> +++ b/arch/x86/kernel/ftrace.c
> @@ -206,7 +206,6 @@ static int
>  ftrace_modify_code(unsigned long ip, unsigned const char *old_code,
>  		   unsigned const char *new_code);
>  
> -#ifdef ARCH_SUPPORTS_FTRACE_SAVE_REGS
>  /*
>   * Should never be called:
>   *  As it is only called by __ftrace_replace_code() which is called by
> @@ -221,7 +220,6 @@ int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
>  	WARN_ON(1);
>  	return -EINVAL;
>  }
> -#endif
>  
>  int ftrace_update_ftrace_func(ftrace_func_t func)
>  {
> @@ -237,7 +235,6 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
>  
>  	ret = ftrace_modify_code(ip, old, new);
>  
> -#ifdef ARCH_SUPPORTS_FTRACE_SAVE_REGS
>  	/* Also update the regs callback function */
>  	if (!ret) {
>  		ip = (unsigned long)(&ftrace_regs_call);
> @@ -245,7 +242,6 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
>  		new = ftrace_call_replace(ip, (unsigned long)func);
>  		ret = ftrace_modify_code(ip, old, new);
>  	}
> -#endif
>  
>  	atomic_dec(&modifying_ftrace_code);
>  


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