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Date:   Thu, 4 Aug 2022 15:06:23 -0700
From:   Josh Poimboeuf <jpoimboe@kernel.org>
To:     Chen Zhongjin <chenzhongjin@huawei.com>
Cc:     linux-kernel@vger.kernel.org, x86@kernel.org,
        linux-arch@vger.kernel.org, peterz@infradead.org,
        tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
        dave.hansen@linux.intel.com, hpa@zytor.com, mbenes@suse.cz
Subject: Re: [PATCH] Revert "x86/unwind/orc: Don't skip the first frame for
 inactive tasks"
Message-ID: <20220804220623.a2s7ucblryudm63m@treble>
References: <20220727031506.59322-1-chenzhongjin@huawei.com>
 <20220804045518.bfhe3rxhpkxzn4hk@treble>
 <5ee1dfb5-fa70-d412-43c2-3e90ee057eec@huawei.com>
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On Thu, Aug 04, 2022 at 03:27:39PM +0800, Chen Zhongjin wrote:
> I believe disassemble show_stack in vmlinux and if we have:
> 
>     push   %rbp
> 
>     mov    %rsp,%rbp
> 
>     ... (no regs pushed to stack)
> 
>     callq  <show_trace_log_lvl>
> 
> This can be reproduced.

Weird, that's what I have.  This is GCC 12.1.

ffffffff81056de0 <show_stack>:
ffffffff81056de0:	e8 0b 43 05 00       	call   ffffffff810ab0f0 <__fentry__>
ffffffff81056de5:	55                   	push   %rbp
ffffffff81056de6:	48 83 05 b2 0f c9 02 01 	addq   $0x1,0x2c90fb2(%rip)        # ffffffff83ce7da0 <__gcov0.show_stack>
ffffffff81056dee:	48 89 e5             	mov    %rsp,%rbp
ffffffff81056df1:	48 85 ff             	test   %rdi,%rdi
ffffffff81056df4:	74 41                	je     ffffffff81056e37 <show_stack+0x57>
ffffffff81056df6:	48 85 f6             	test   %rsi,%rsi
ffffffff81056df9:	0f 85 c2 24 15 01    	jne    ffffffff821a92c1 <show_stack.cold+0xd>
ffffffff81056dff:	65 48 8b 04 25 c0 bd 01 00 	mov    %gs:0x1bdc0,%rax
ffffffff81056e08:	48 39 c7             	cmp    %rax,%rdi
ffffffff81056e0b:	0f 85 a3 24 15 01    	jne    ffffffff821a92b4 <show_stack.cold>
ffffffff81056e11:	48 83 05 af 0f c9 02 01 	addq   $0x1,0x2c90faf(%rip)        # ffffffff83ce7dc8 <__gcov0.show_stack+0x28>
ffffffff81056e19:	48 89 ee             	mov    %rbp,%rsi
ffffffff81056e1c:	48 89 d1             	mov    %rdx,%rcx
ffffffff81056e1f:	48 89 f2             	mov    %rsi,%rdx
ffffffff81056e22:	31 f6                	xor    %esi,%esi
ffffffff81056e24:	e8 8e 20 15 01       	call   ffffffff821a8eb7 <show_trace_log_lvl>
ffffffff81056e29:	48 83 05 9f 0f c9 02 01 	addq   $0x1,0x2c90f9f(%rip)        # ffffffff83ce7dd0 <__gcov0.show_stack+0x30>
ffffffff81056e31:	5d                   	pop    %rbp
ffffffff81056e32:	e9 49 b2 5a 01       	jmp    ffffffff82602080 <__x86_return_thunk>
ffffffff81056e37:	48 83 05 69 0f c9 02 01 	addq   $0x1,0x2c90f69(%rip)        # ffffffff83ce7da8 <__gcov0.show_stack+0x8>
ffffffff81056e3f:	65 48 8b 3c 25 c0 bd 01 00 	mov    %gs:0x1bdc0,%rdi
ffffffff81056e48:	eb ac                	jmp    ffffffff81056df6 <show_stack+0x16>
ffffffff81056e4a:	66 0f 1f 44 00 00    	nopw   0x0(%rax,%rax,1)

-- 
Josh