linux-kernel - Re: [tip:x86/pti 19/20] arch/x86/entry/entry_64.o: warning: objtool: paranoid_entry()+0x11: call without frame pointer save/setup

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Date:   Mon, 12 Feb 2018 07:13:51 -0600
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     kbuild test robot <fengguang.wu@...el.com>
Cc:     Dominik Brodowski <linux@...inikbrodowski.net>, kbuild-all@...org,
        linux-kernel@...r.kernel.org, tipbuild@...or.com,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: [tip:x86/pti 19/20] arch/x86/entry/entry_64.o: warning: objtool:
 paranoid_entry()+0x11: call without frame pointer save/setup

On Mon, Feb 12, 2018 at 07:33:27PM +0800, kbuild test robot wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git x86/pti
> head:   5a10e729bc0aa9420a23a70b169eadd229c27bc1
> commit: f09d160992d129b6d8fada7543761d40f5b33596 [19/20] x86/entry/64: Get rid of the ALLOC_PT_GPREGS_ON_STACK and SAVE_AND_CLEAR_REGS macros
> config: x86_64-randconfig-s0-02121550 (attached as .config)
> compiler: gcc-6 (Debian 6.4.0-9) 6.4.0 20171026
> reproduce:
>         git checkout f09d160992d129b6d8fada7543761d40f5b33596
>         # save the attached .config to linux build tree
>         make ARCH=x86_64 
> 
> All warnings (new ones prefixed by >>):
> 
> >> arch/x86/entry/entry_64.o: warning: objtool: paranoid_entry()+0x11: call without frame pointer save/setup
> 
> ---
> 0-DAY kernel test infrastructure                Open Source Technology Center
> https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

Oops, looks like one of my suggested unwind hint changes wasn't so good
for the frame pointer case.  The below should fix it.  I'll submit a
proper patch in a little bit after running it through 0-day.

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index cfbf43366731..1c54204207d8 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -1128,6 +1128,7 @@ idtentry machine_check		do_mce			has_error_code=0	paranoid=1
  * Return: ebx=0: need swapgs on exit, ebx=1: otherwise
  */
 ENTRY(paranoid_entry)
+	UNWIND_HINT_FUNC
 	cld
 	movl	$1, %ebx
 	movl	$MSR_GS_BASE, %ecx
@@ -1141,7 +1142,7 @@ ENTRY(paranoid_entry)
 	SAVE_AND_SWITCH_TO_KERNEL_CR3 scratch_reg=%rax save_reg=%r14
 
 	ret
-ENDPROC(paranoid_entry)
+END(paranoid_entry)
 
 /*
  * "Paranoid" exit path from exception stack.  This is invoked