[tip:x86/asm] x86/ftrace: Add stack frame pointer to ftrace_caller

[tip-bot for Steven Rostedt (VMware)]

Commit-ID:  e6928e58d4d4a02f88838945f792c107623314ac
Gitweb:     http://git.kernel.org/tip/e6928e58d4d4a02f88838945f792c107623314ac
Author:     Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
AuthorDate: Thu, 23 Mar 2017 10:33:50 -0400
Committer:  Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Fri, 24 Mar 2017 10:14:07 +0100

x86/ftrace: Add stack frame pointer to ftrace_caller

The function hook ftrace_caller does not create its own stack frame, and
this causes the ftrace stack trace to miss the first function when doing
stack traces.

 # echo schedule:stacktrace > /sys/kernel/tracing/set_ftrace_filter

Before:
         <idle>-0     [002] .N..    29.865807: <stack trace>
 => cpu_startup_entry
 => start_secondary
 => startup_32_smp
           <...>-7     [001] ....    29.866509: <stack trace>
 => kthread
 => ret_from_fork
           <...>-1     [000] ....    29.865377: <stack trace>
 => poll_schedule_timeout
 => do_select
 => core_sys_select
 => SyS_select
 => do_fast_syscall_32
 => entry_SYSENTER_32

After:
          <idle>-0     [002] .N..    31.234853: <stack trace>
 => do_idle
 => cpu_startup_entry
 => start_secondary
 => startup_32_smp
           <...>-7     [003] ....    31.235140: <stack trace>
 => rcu_gp_kthread
 => kthread
 => ret_from_fork
           <...>-1819  [000] ....    31.264172: <stack trace>
 => schedule_hrtimeout_range
 => poll_schedule_timeout
 => do_sys_poll
 => SyS_ppoll
 => do_fast_syscall_32
 => entry_SYSENTER_32

Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Reviewed-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Reviewed-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Reviewed-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/20170323143445.771707773@xxxxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

---
 arch/x86/kernel/ftrace_32.S | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/ftrace_32.S b/arch/x86/kernel/ftrace_32.S
index 2b160f2..a4e2872 100644
--- a/arch/x86/kernel/ftrace_32.S
+++ b/arch/x86/kernel/ftrace_32.S
@@ -16,12 +16,19 @@ ENTRY(mcount)
 END(mcount)
 
 ENTRY(ftrace_caller)
+
+	pushl	%ebp
+	movl	%esp, %ebp
+
 	pushl	%eax
 	pushl	%ecx
 	pushl	%edx
 	pushl	$0				/* Pass NULL as regs pointer */
-	movl	4*4(%esp), %eax
-	movl	0x4(%ebp), %edx
+	movl	5*4(%esp), %eax
+	/* Copy original ebp into %edx */
+	movl	4*4(%esp), %edx
+	/* Get the parent ip */
+	movl	0x4(%edx), %edx
 	movl	function_trace_op, %ecx
 	subl	$MCOUNT_INSN_SIZE, %eax
 
@@ -33,6 +40,7 @@ ftrace_call:
 	popl	%edx
 	popl	%ecx
 	popl	%eax
+	popl	%ebp
 .Lftrace_ret:
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 .globl ftrace_graph_call