yes Zhangin

please find the complete patch
====================================================================
diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c
index 7955409..df72738 100644
--- a/arch/mips/kernel/process.c
+++ b/arch/mips/kernel/process.c
@@ -290,12 +290,45 @@ static inline int is_sp_move_ins(union
mips_instruction *ip)
  return 0;
 }

+#ifdef CONFIG_DYNAMIC_FTRACE
+/*
+ * To create the jal <> instruction from mcount.
+ * taken from:
+ * - arch/mips/kernel/ftrace.c
+ */
+#define ADDR_MASK 0x03ffffff    /*  op_code|addr : 31...26|25 ....0 */
+#define JAL 0x0c000000      /* jump & link: ip --> ra, jump to target */
+#define INSN_JAL(addr)  \
+      ((unsigned int)(JAL | (((addr) >> 2) & ADDR_MASK)))
+
+/*
+ * We assume jal <mcount>/<ftrace_caller> to be present in
+ * first JAL_MAX_OFFSET instructions.
+ * Increment this, if its otherwise
+ */
+#define JAL_MAX_OFFSET 16U
+#define MCOUNT_STACK_INST 0x27bdfff8 /* addiu   sp,sp,-8 */
+
+/*
+ * If Dynamic Ftrace is enabled, ftrace_caller is the trace function.
+ * Otherwise its - mcount
+ */
+extern void  ftrace_caller(void);
+#endif /* CONFIG_DYNAMIC_FTRACE */
+
 static int get_frame_info(struct mips_frame_info *info)
 {
  union mips_instruction *ip = info->func;
  unsigned max_insns = info->func_size / sizeof(union mips_instruction);
  unsigned i;

+#ifdef CONFIG_DYNAMIC_FTRACE
+ unsigned max_prolog_inst = max_insns;
+ int jal_found = 0;
+ /* instruction corresponding to jal <_mcount>/<ftrace_caller> */
+ int jal_mcount = 0;
+#endif
+
  info->pc_offset = -1;
  info->frame_size = 0;

@@ -306,6 +339,28 @@ static int get_frame_info(struct mips_frame_info *info)
   max_insns = 128U; /* unknown function size */
  max_insns = min(128U, max_insns);

+#ifdef CONFIG_DYNAMIC_FTRACE
+ max_prolog_inst = min(JAL_MAX_OFFSET, max_prolog_inst);
+ jal_mcount = INSN_JAL((unsigned)&ftrace_caller);
+
+ for (i = 0; i < max_prolog_inst; i++, ip++) {
+  if ((*(int *)ip == jal_mcount) ||
+    /*
+     * for dyn ftrace, the code initially has 0.
+     * so we check whether the next instruction is
+     * addiu   sp,sp,-8
+     */
+    (!(*(int *)ip) &&
+     (*(int *)(ip + 1) == MCOUNT_STACK_INST))
+     ) {
+   jal_found = 1;
+   break;
+  }
+ }
+ /* restore the ip to start of function */
+ ip = info->func;
+#endif
+
  for (i = 0; i < max_insns; i++, ip++) {

   if (is_jal_jalr_jr_ins(ip))
@@ -321,6 +376,18 @@ static int get_frame_info(struct mips_frame_info *info)
    break;
   }
  }
+#ifdef CONFIG_DYNAMIC_FTRACE
+ /*
+  * to offset the effect of:
+  * addiu   sp,sp,-8
+  */
+ if (jal_found) {
+  if (info->frame_size)
+   info->frame_size += 8;
+  if (info->pc_offset >= 0)
+   info->pc_offset += 8 / sizeof(long);
+ }
+#endif
  if (info->frame_size && info->pc_offset >= 0) /* nested */
   return 0;
  if (info->pc_offset < 0) /* leaf */
-- 
1.7.8.4

====================================================================

On Thu, Aug 9, 2012 at 9:41 PM, Wu Zhangjin <wuzhangjin@gmail.com> wrote:

> Hi, Akhilesh
>
> Thanks very much for your work.
>
> Seems this patch has lost something, can you send a full one?
>
> Best Regards,
> Wu Zhangjin
>
> On Thu, Aug 9, 2012 at 9:53 PM, Akhilesh Kumar <akhilesh.lxr@gmail.com>
> wrote:
> > Hi Ralf,
> >
> >
> > Sub:- Bug  unable to retrive backtrace when HAVE_FUNCTION_TRACER is
> enable.
> > I send this bug and bug fix long back, I am resending this patch again
> for
> > review.
> >
> > Please review below patch if you agree I will regenerate this patch and
> with
> > you.
> >
> > ====[ backtrace testing ]===========
> > Testing a backtrace from process context.
> > The following trace is a kernel self test and not a bug!
> > Testing a backtrace.
> > The following trace is a kernel self test and not a bug!
> > Call Trace:
> > [<80295134>] dump_stack+0x8/0x34
> > [<c0946060>] backtrace_regression_test+0x60/0x94 [sisc_backtrcae]
> > [<800004f0>] do_one_initcall+0xf0/0x1d0
> > [<80060954>] sys_init_module+0x19c8/0x1c60
> > [<8000a418>] stack_done+0x20/0x40
> > output befor patch when HAVE_FUNCTION_TRACER is enable
> > ---------------------------------------------------------------------
> > #> insmod backtrace.ko
> > ====[ backtrace testing ]===========
> > Testing a backtrace from process context.
> > The following trace is a kernel self test and not a bug!
> > Testing a backtrace.
> > The following trace is a kernel self test and not a bug!
> > Call Trace:
> > [<802e5164>] dump_stack+0x1c/0x50
> > [<802e5164>] dump_stack+0x1c/0x50
> > ====[ end of backtrace testing ]====
> > ------------------------------------------------------
> > above shows the wrong back trcae
> > output after patch when HAVE_FUNCTION_TRACER is enable
> > ----------------------------------------------------------------------
> > ====[ backtrace testing ]===========
> > Testing a backtrace from process context.
> > The following trace is a kernel self test and not a bug!
> > Testing a backtrace.
> > The following trace is a kernel self test and not a bug!
> > Call Trace:
> > [<802eb1a4>] dump_stack+0x20/0x54
> > [<c003405c>] backtrace_test_timer+0x5c/0x74 [sisc_backtrcae]
> > [<c00340dc>] init_module+0x68/0xa0 [sisc_backtrcae]
> > [<80000508>] do_one_initcall+0x108/0x1f0
> > [<8006d4c4>] sys_init_module+0x1a10/0x1c74
> > [<8000b038>] stack_done+0x20/0x40
> > ------------------------------------------------------------------
> > get_frame_info() is used to fetch the frame information from the
> > function.
> > However,
> > 1. this function just considers the first stack adjustment for frame
> > size.
> > 2. On finding the save_lr instruction, it returns.
> > It doesn't handle the ftrace condition.
> > If Dynamic Frace "CONFIG_DYNAMIC_FTRACE" is enabled, the instrumentation
> > code is:
> >  - jal <ftrace_caller>
> >  - addiu sp,sp,-8
> > Thus, the current Frame Size of function is increased by 8 for Ftrace.
> > Signed-off-by: Akhilesh Kumar <akhilesh.lxr@gmail.com>
> > ---
> >  arch/mips/kernel/process.c |   67
> > ++++++++++++++++++++++++++++++++++++++++++++
> >  1 files changed, 67 insertions(+), 0 deletions(-)
> > diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c
> > index 7955409..df72738 100644
> > --- a/arch/mips/kernel/process.c
> > +++ b/arch/mips/kernel/process.c
> > @@ -290,12 +290,45 @@  static inline int is_sp_move_ins(union
> > mips_instruction *ip)
> >   return 0;
> >  }
> > +#ifdef CONFIG_DYNAMIC_FTRACE
> > +/*
> > + * To create the jal <> instruction from mcount.
> > + * taken from:
> > + * - arch/mips/kernel/ftrace.c
> > + */
> > +#define ADDR_MASK 0x03ffffff    /*  op_code|addr : 31...26|25 ....0 */
> > +#define JAL 0x0c000000      /* jump & link: ip --> ra, jump to target */
> > +#define INSN_JAL(addr)  \
> > +      ((unsigned int)(JAL | (((addr) >> 2) & ADDR_MASK)))
> > +
> > +/*
> > + * We assume jal <mcount>/<ftrace_caller> to be present in
> > + * first JAL_MAX_OFFSET instructions.
> > + * Increment this, if its otherwise
> > + */
> > +#define JAL_MAX_OFFSET 16U
> > +#define MCOUNT_STACK_INST 0x27bdfff8 /* addiu   sp,sp,-8 */
> > +
> > +/*
> > + * If Dynamic Ftrace is enabled, ftrace_caller is the trace function.
> > + * Otherwise its - mcount
> > + */
> > +extern void  ftrace_caller(void);
> > +#endif /* CONFIG_DYNAMIC_FTRACE */
> > +
> >  static int get_frame_info(struct mips_frame_info *info)
> >  {
> >   union mips_instruction *ip = info->func;
> >   unsigned max_insns = info->func_size / sizeof(union mips_instruction);
> >   unsigned i;
> > +#ifdef CONFIG_DYNAMIC_FTRACE
> > + unsigned max_prolog_inst = max_insns;
> > + int jal_found = 0;
> > + /* instruction corresponding to jal <_mcount>/<ftrace_caller> */
> > + int jal_mcount = 0;
> > +#endif
> > +
> >   info->pc_offset = -1;
> >   info->frame_size = 0;
>