linux-kernel - [Question] About UNWIND_HINT_ENTRY on entry_SYSCALL

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Message-ID: <CAM7-yPTWs8J6sGjcyDrRsXu5APDHm5Kr19G500y=72=FwYCq3g@mail.gmail.com>
Date:   Fri, 25 Nov 2022 19:41:46 +0900
From:   Yun Levi <ppbuk5246@...il.com>
To:     jpoimboe@...nel.org, peterz@...radead.org
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [Question] About UNWIND_HINT_ENTRY on entry_SYSCALL_64.

Hello.

While I try to see the information related to ORC in vmlinux,
I'm trying to find out ORC information related to entry_SYSCALL_64's address.

For this, I've tried to take the following step:
    1. booting the kernel with the "nokaslr" option.
    2. Getting ORC information by "objdump orc dump vmlinux"
    3. cat /proc/kallsyms and check the address of "entry_SYSCALL_64"
          - In my kernel, It's address .text + a00000
    4. Find out related ORC entry gotten in step 2.

But, I couldn't find the reason why entry_SYSCALL_64's orc info isn't
encoded with end =1.
Instead, It was encoded as INVALID ORC entry like:

  .text+a00000: sp:(und) bp:(und) type:call end:0

IIUC, Some of the code is started with UNWIND_HINT_ENTRY or UNWIND_HINT_EMPTY,
it should be encoded with end = 1. But it doesn't.

Am I wrong?

-- 
Sincerely,
Levi