x86, debug: remove the confusing entry in call trace
Impact: improve backtrace quality
avoid the confusion in call trace because of the lack of padding at the
tail of function.
When do_exit gets called, the return address behind call instruction is
pushed into stack. If something get wrong in do_exit, for x86_64, the
entry "kernel_execve +0x00/0xXX" rather than "child_rip +0xYY/0xZZ" is
in the call trace.
That looks confusing, so add a u2d to make the return address still part
of the original call site. (This also catches any instances of us returning
from that function somehow.)
Signed-off-by: jia zhang <jia.zhang2008@gmail.com>
Acked-by: Alexander van Heukelum <heukelum@fastmail.fm>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
index 28b597e..f6402c4 100644
--- a/arch/x86/kernel/entry_32.S
+++ b/arch/x86/kernel/entry_32.S
@@ -1051,6 +1051,7 @@
push %eax
CFI_ADJUST_CFA_OFFSET 4
call do_exit
+ ud2 # padding for call trace
CFI_ENDPROC
ENDPROC(kernel_thread_helper)
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index ddeeb10..4a16bf3 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -1172,6 +1172,7 @@
# exit
mov %eax, %edi
call do_exit
+ ud2 # padding for call trace
CFI_ENDPROC
ENDPROC(child_rip)
