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.

Link: http://lkml.kernel.org/r/20120711195745.379060003@goodmis.org
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/arch/x86/include/asm/ftrace.h b/arch/x86/include/asm/ftrace.h
index a8475014c4ad5ee070f8d0f4c477284788c88854..a6cae0c1720cdcd66f27724c0b8fd6a52a013c82 100644 (file)
--- 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 5da11d1b85ae3dd8d897c468c65cd31ddb578fc6..46caa5649a5e92178c129d414ea4f899c9121101 100644 (file)
--- 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 b90eb1a13071bcf4aab93855101b0c6865176ae7..1d414029f1d800ff67ae21bd2e74794ad06efa32 100644 (file)
--- 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);