From 5f5db591326779a80cfe490c5d6b6ce9fac08b31 Mon Sep 17 00:00:00 2001 From: jia zhang Date: Sun, 23 Nov 2008 22:47:10 +0800 Subject: [PATCH] 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 Acked-by: Alexander van Heukelum Signed-off-by: Ingo Molnar --- arch/x86/kernel/entry_32.S | 1 + arch/x86/kernel/entry_64.S | 1 + 2 files changed, 2 insertions(+) diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S index 28b597ef9ca..f6402c4ba10 100644 --- a/arch/x86/kernel/entry_32.S +++ b/arch/x86/kernel/entry_32.S @@ -1051,6 +1051,7 @@ ENTRY(kernel_thread_helper) 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 ddeeb105258..4a16bf31c78 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -1172,6 +1172,7 @@ child_rip: # exit mov %eax, %edi call do_exit + ud2 # padding for call trace CFI_ENDPROC ENDPROC(child_rip) -- 2.20.1