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SubjectRe: [PATCH 6/6] ftrace/x86: Add save_regs for i386 function calls
(2012/07/03 5:03), Steven Rostedt wrote:
> From: Steven Rostedt <srostedt@redhat.com>
>
> 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@hitachi.com>
> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
> ---
> arch/x86/include/asm/ftrace.h | 2 --
> arch/x86/kernel/entry_32.S | 53 +++++++++++++++++++++++++++++++++++++++++
> arch/x86/kernel/ftrace.c | 4 ----
> 3 files changed, 53 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/include/asm/ftrace.h b/arch/x86/include/asm/ftrace.h
> index fd10faf..2b396cf 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 acd4963..e18ea33 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 +1135,58 @@ ftrace_stub:
> ret
> END(ftrace_caller)
>
> +ENTRY(ftrace_regs_caller)
> + pushf /* push flags before compare */
> + cmpl $0, function_trace_stop
> + jne ftrace_exit
> +
> + subl $8, %esp /* skip ip and 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 14*4(%esp), %eax /* Load return address */
> + pushl %eax /* Save return address (+4) */
> + subl $MCOUNT_INSN_SIZE, %eax
> + movl %eax, 12*4+4(%esp) /* Store IP */
> + movl 13*4+4(%esp), %edx /* Load flags */
> + movl %edx, 14*4+4(%esp) /* Store flags */
> + movl $__KERNEL_CS, %edx
> + movl %edx, 13*4+4(%esp) /* Store CS */
> +
> + movl 0x4(%ebp), %edx
> + lea 4(%esp), %ecx
> + pushl %ecx /* Save pt_regs as 4th parameter */
> + leal function_trace_op, %ecx
> +
> +GLOBAL(ftrace_regs_call)
> + call ftrace_stub
> +
> + addl $4,%esp /* Skip pt_regs */

Hmm, you need to restoring flags here, because
original flags is clobbered by KERNEL_CS.

movl 14*4+4(%esp), %edx
movl %edx, 13*4+4(%esp)

Thank you,

--
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com




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