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Message-ID: <CAM7-yPTxgndDR+c1at+y6GngkpKz9h8cFT68cTmdRkcMuGVBQA@mail.gmail.com>
Date: Mon, 28 Nov 2022 14:31:17 +0900
From: Yun Levi <ppbuk5246@...il.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
jpoimboe@...nel.org
Subject: Re: [Question] About UNWIND_HINT_ENTRY on entry_SYSCALL_64.
Thanks Peter and Sorry for the late answer.
I got the same result on the vmlinux.o file when I compiled the recent version.
But when I try to test on some of distribution version of linux, (ex)
debian. and When I try to on vmlinux not on vmlinux.o
I got some different results like below.
$ readelf -Ws /usr/lib/debug/boot/vmlinux-5.18.0-0.deb11.4-amd64 |
grep entry_SYSCALL_64
123448: ffffffff81a00000 404 NOTYPE GLOBAL DEFAULT 1 entry_SYSCALL_64
$ readelf -WS /usr/lib/debug/boot/vmlinux-5.18.0-0.deb11.4-amd64 | grep "\[1\]"
[ 1] .text PROGBITS ffffffff81000000 200000
c01988 00 AX 0 0 4096
123448: ffffffff81a00000 404 NOTYPE GLOBAL DEFAULT 1 entry_SYSCALL_64
123448: ffffffff81a00000 404 NOTYPE GLOBAL DEFAULT 1 entry_SYSCALL_64
$ tools/objtool/objtool --dump=orc
/usr/lib/debug/boot/vmlinux-5.18.0-0.deb11.4-amd64 | grep
"text+a00000"
.text+a00000: sp:(und) bp:(und) type:call end:0
Am I wrong?
Thanks!
On Fri, Nov 25, 2022 at 10:06 PM Peter Zijlstra <peterz@...radead.org> wrote:
>
> On Fri, Nov 25, 2022 at 07:41:46PM +0900, Yun Levi wrote:
> > 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?
>
> $ readelf -Ws defconfig-build/vmlinux.o | grep entry_SYSCALL_64
> 178466: 0000000000000029 0 NOTYPE GLOBAL DEFAULT 18 entry_SYSCALL_64_safe_stack
> 188596: 0000000000000000 422 NOTYPE GLOBAL DEFAULT 18 entry_SYSCALL_64
> 210374: 0000000000000038 0 NOTYPE GLOBAL DEFAULT 18 entry_SYSCALL_64_after_hwframe
>
> $ readelf -WS defconfig-build/vmlinux.o | grep "\[18\]"
> [18] .entry.text PROGBITS 0000000000000000 e59f00 001838 00 AX 0 0 64
>
> $ tools/objtool/objtool --dump=orc defconfig-build/vmlinux.o | grep ".entry.text+0"
> .entry.text+0: sp:(und) bp:(und) type:call end:1
>
>
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