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Date: Thu, 19 Jul 2012 08:52:24 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc: linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
Andrew Morton <akpm@...ux-foundation.org>,
Thomas Gleixner <tglx@...utronix.de>,
Frederic Weisbecker <fweisbec@...il.com>,
"H. Peter Anvin" <hpa@...or.com>, yrl.pp-manager.tt@...achi.com
Subject: Re: Re: [RFC][PATCH 2/4 v4] ftrace/x86: Add save_regs for i386
function calls
On Thu, 2012-07-19 at 11:20 +0900, Masami Hiramatsu wrote:
> (2012/07/19 0:59), Steven Rostedt wrote:
> > 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?
>
> No, that is OK for me. I've just missed that...
>
> Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
>
> Thank you!
>
Thanks! Except I have one more version. Someone offlist gave me some
ideas.
Here's the diff from the previous patch.
diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
index 46caa56..ca5a146 100644
--- a/arch/x86/kernel/entry_32.S
+++ b/arch/x86/kernel/entry_32.S
@@ -1169,10 +1169,9 @@ ENTRY(ftrace_regs_caller)
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 */
+ movl 0x4(%ebp), %edx /* Load parent ip (2nd parameter) */
leal function_trace_op, %ecx /* Save ftrace_pos in 3rd parameter */
+ pushl %esp /* Save pt_regs as 4th parameter */
GLOBAL(ftrace_regs_call)
call ftrace_stub
@@ -1195,8 +1194,8 @@ GLOBAL(ftrace_regs_call)
popl %es
popl %fs
popl %gs
- addl $8, %esp /* Skip orig_ax and ip */
- popf /* Pop flags at end (no addl to corrupt flags) */
+ lea 8(%esp), %esp /* Skip orig_ax and ip */
+ popf /* Pop flags at end */
jmp ftrace_ret
ftrace_restore_flags:
Because we no longer have that 4 byte offset on the stack when we need
to load the 4th parameter, we can just load the current stack pointer
into the stack (pushl %esp), without the save to %ecx step.
also, because lea is faster than add (and doesn't even modify flags), I
changed the last part to use lea instead of addl.
Can you give your reviewed-by tag for this too? I'd like to push this
out today so we can still make 3.6.
Thanks!
-- Steve
here's the full patch:
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..ca5a146 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 +1135,72 @@ 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, ®s->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 (2nd parameter) */
+ leal function_trace_op, %ecx /* Save ftrace_pos in 3rd parameter */
+ pushl %esp /* Save pt_regs as 4th 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
+ lea 8(%esp), %esp /* Skip orig_ax and ip */
+ popf /* Pop flags at end */
+ 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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