From: "Steven Rostedt (VMware)" 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: -0 [002] .N.. 29.865807: => cpu_startup_entry => start_secondary => startup_32_smp <...>-7 [001] .... 29.866509: => kthread => ret_from_fork <...>-1 [000] .... 29.865377: => poll_schedule_timeout => do_select => core_sys_select => SyS_select => do_fast_syscall_32 => entry_SYSENTER_32 After: -0 [002] .N.. 31.234853: => do_idle => cpu_startup_entry => start_secondary => startup_32_smp <...>-7 [003] .... 31.235140: => rcu_gp_kthread => kthread => ret_from_fork <...>-1819 [000] .... 31.264172: => schedule_hrtimeout_range => poll_schedule_timeout => do_sys_poll => SyS_ppoll => do_fast_syscall_32 => entry_SYSENTER_32 Signed-off-by: Steven Rostedt (VMware) --- 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 4ff30f31f0a5..73d61a62649d 100644 --- a/arch/x86/kernel/ftrace_32.S +++ b/arch/x86/kernel/ftrace_32.S @@ -17,12 +17,19 @@ 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 @@ -34,6 +41,7 @@ ftrace_call: popl %edx popl %ecx popl %eax + popl %ebp .Lftrace_ret: #ifdef CONFIG_FUNCTION_GRAPH_TRACER .globl ftrace_graph_call -- 2.10.2