| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <02930c55-6423-4db4-b6f3-b783c572c121@intel.com>
Date: Mon, 22 Jul 2024 16:15:56 +0300
From: Adrian Hunter <adrian.hunter@...el.com>
To: duchangbin <changbin.du@...wei.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Namhyung Kim <namhyung@...nel.org>, Nathan Chancellor <nathan@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
"Liang, Kan" <kan.liang@...ux.intel.com>,
Nick Desaulniers <ndesaulniers@...gle.com>, Bill Wendling
<morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>,
"linux-perf-users@...r.kernel.org" <linux-perf-users@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"llvm@...ts.linux.dev" <llvm@...ts.linux.dev>,
"Wanghui (OS Kernel Lab, Beijing)" <hw.huiwang@...wei.com>
Subject: Re: [PATCH v5 1/8] perf: support specify vdso path in cmdline
On 22/07/24 15:19, duchangbin wrote:
> On Thu, Jul 18, 2024 at 08:02:16PM +0300, Adrian Hunter wrote:
>> On 2/07/24 07:18, Changbin Du wrote:
>>> The vdso dumped from process memory (in buildid-cache) lacks debugging
>>> info. To annotate vdso symbols with source lines we need specify a
>>> debugging version.
>>>
>>> For x86, we can find them from your local build as
>>> arch/x86/entry/vdso/vdso{32,64}.so.dbg. Or they may reside in
>>> /lib/modules/<version>/vdso/vdso{32,64}.so on Ubuntu. But notice that
>>> the buildid has to match.
>>>
>>> $ sudo perf record -a
>>> $ sudo perf report --objdump=llvm-objdump \
>>> --vdso arch/x86/entry/vdso/vdso64.so.dbg,arch/x86/entry/vdso/vdso32.so.dbg
>>>
>>> Samples: 17K of event 'cycles:P', 4000 Hz, Event count (approx.): 1760
>>> __vdso_clock_gettime /work/linux-host/arch/x86/entry/vdso/vdso64.so.d
>>> Percent│ movq -48(%rbp),%rsi
>>> │ testq %rax,%rax
>>> │ ; return vread_hvclock();
>>> │ movq %rax,%rdx
>>> │ ; if (unlikely(!vdso_cycles_ok(cycles)))
>>> │ ↑ js eb
>>> │ ↑ jmp 74
>>> │ ; ts->tv_sec = vdso_ts->sec;
>>> 0.02 │147: leaq 2(%rbx),%rax
>>> │ shlq $4, %rax
>>> │ addq %r10,%rax
>>> │ ; while ((seq = READ_ONCE(vd->seq)) & 1) {
>>> 9.38 │152: movl (%r10),%ecx
>>>
>>> When doing cross platform analysis, we also need specify the vdso path if
>>> we are interested in its symbols.
>>>
>>
>> Just realized this is about objdump. Sorry for not getting that
>> earlier.
>>
>> Like perf tools, objdump follows the paradigm of attempting to
>> locate and use debug info transparently. However, objdump looks
>> at the installed debug info in /usr/lib/debug/.build-id/
>>
>> For example, if the debug file is copied (or linked) there, then
>> objdump or llvm-objdump will find it:
>>
>> $ llvm-objdump-18 -dS ~/.debug/\[vdso\]/cf702469f4637840fd6ba1a8d8a628ff83253d04/vdso | head -20
>>
>> ~/.debug/[vdso]/cf702469f4637840fd6ba1a8d8a628ff83253d04/vdso: file format elf64-x86-64
>>
>> Disassembly of section .text:
>>
>> 00000000000006d0 <.text>:
>> 6d0: 48 8d 3d 29 d9 ff ff leaq -0x26d7(%rip), %rdi # 0xffffffffffffe000
>> 6d7: eb 19 jmp 0x6f2 <.text+0x22>
>> 6d9: 4c 8b 0d 28 d9 ff ff movq -0x26d8(%rip), %r9 # 0xffffffffffffe008
>> 6e0: 4c 8b 05 29 d9 ff ff movq -0x26d7(%rip), %r8 # 0xffffffffffffe010
>> 6e7: 0f 01 f9 rdtscp
>> 6ea: 66 90 nop
>> 6ec: 8b 0f movl (%rdi), %ecx
>> 6ee: 39 ce cmpl %ecx, %esi
>> 6f0: 74 0e je 0x700 <.text+0x30>
>> 6f2: 8b 37 movl (%rdi), %esi
>> 6f4: 85 f6 testl %esi, %esi
>> 6f6: 75 e1 jne 0x6d9 <.text+0x9>
>> 6f8: 48 c7 c0 ff ff ff ff movq $-0x1, %rax
>> 6ff: c3 retq
>> $ sudo ln -s /lib/modules/6.9.2-local/build/arch/x86/entry/vdso/vdso64.so.dbg /usr/lib/debug/.build-id/cf/702469f4637840fd6ba1a8d8a628ff83253d04.debug
>> $ llvm-objdump-18 -dS ~/.debug/\[vdso\]/cf702469f4637840fd6ba1a8d8a628ff83253d04/vdso | head -20
>>
>> ~/.debug/[vdso]/cf702469f4637840fd6ba1a8d8a628ff83253d04/vdso: file format elf64-x86-64
>>
>> Disassembly of section .text:
>>
>> 00000000000006d0 <vread_hvclock>:
>> ; hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg,
>> 6d0: 48 8d 3d 29 d9 ff ff leaq -0x26d7(%rip), %rdi # 0xffffffffffffe000 <hvclock_page>
>> 6d7: eb 19 jmp 0x6f2 <vread_hvclock+0x22>
>> ; scale = READ_ONCE(tsc_pg->tsc_scale);
>> 6d9: 4c 8b 0d 28 d9 ff ff movq -0x26d8(%rip), %r9 # 0xffffffffffffe008 <hvclock_page+0x8>
>> ; offset = READ_ONCE(tsc_pg->tsc_offset);
>> 6e0: 4c 8b 05 29 d9 ff ff movq -0x26d7(%rip), %r8 # 0xffffffffffffe010 <hvclock_page+0x10>
>> ; asm volatile(ALTERNATIVE_2("rdtsc",
>> 6e7: 0f 31 rdtsc
>> 6e9: 90 nop
>> 6ea: 90 nop
>> 6eb: 90 nop
>> ; } while (READ_ONCE(tsc_pg->tsc_sequence) != sequence);
>> 6ec: 8b 0f movl (%rdi), %ecx
>> $
>>
>> Would that solve your problem?
>>
>> Notably, later versions of llvm-objdump have an option
>> --debug-file-directory which makes it possible to
>> have the debug info in a directory owned by the user,
>> for example:
>>
>> $ sudo rm /usr/lib/debug/.build-id/cf/702469f4637840fd6ba1a8d8a628ff83253d04.debug
>> $ llvm-objdump-18 -dS ~/.debug/\[vdso\]/cf702469f4637840fd6ba1a8d8a628ff83253d04/vdso | head -20
>>
>> ~/.debug/[vdso]/cf702469f4637840fd6ba1a8d8a628ff83253d04/vdso: file format elf64-x86-64
>>
>> Disassembly of section .text:
>>
>> 00000000000006d0 <.text>:
>> 6d0: 48 8d 3d 29 d9 ff ff leaq -0x26d7(%rip), %rdi # 0xffffffffffffe000
>> 6d7: eb 19 jmp 0x6f2 <.text+0x22>
>> 6d9: 4c 8b 0d 28 d9 ff ff movq -0x26d8(%rip), %r9 # 0xffffffffffffe008
>> 6e0: 4c 8b 05 29 d9 ff ff movq -0x26d7(%rip), %r8 # 0xffffffffffffe010
>> 6e7: 0f 01 f9 rdtscp
>> 6ea: 66 90 nop
>> 6ec: 8b 0f movl (%rdi), %ecx
>> 6ee: 39 ce cmpl %ecx, %esi
>> 6f0: 74 0e je 0x700 <.text+0x30>
>> 6f2: 8b 37 movl (%rdi), %esi
>> 6f4: 85 f6 testl %esi, %esi
>> 6f6: 75 e1 jne 0x6d9 <.text+0x9>
>> 6f8: 48 c7 c0 ff ff ff ff movq $-0x1, %rax
>> 6ff: c3 retq
>> $ mkdir -p /tmp/debug/.build-id/cf/
>> $ ln -s /lib/modules/6.9.2-local/build/arch/x86/entry/vdso/vdso64.so.dbg /tmp/debug/.build-id/cf/702469f4637840fd6ba1a8d8a628ff83253d04.debug
>> $ llvm-objdump-18 --debug-file-directory /tmp/debug -dS ~/.debug/\[vdso\]/cf702469f4637840fd6ba1a8d8a628ff83253d04/vdso | head -20
>>
>> ~/.debug/[vdso]/cf702469f4637840fd6ba1a8d8a628ff83253d04/vdso: file format elf64-x86-64
>>
>> Disassembly of section .text:
>>
>> 00000000000006d0 <vread_hvclock>:
>> ; hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg,
>> 6d0: 48 8d 3d 29 d9 ff ff leaq -0x26d7(%rip), %rdi # 0xffffffffffffe000 <hvclock_page>
>> 6d7: eb 19 jmp 0x6f2 <vread_hvclock+0x22>
>> ; scale = READ_ONCE(tsc_pg->tsc_scale);
>> 6d9: 4c 8b 0d 28 d9 ff ff movq -0x26d8(%rip), %r9 # 0xffffffffffffe008 <hvclock_page+0x8>
>> ; offset = READ_ONCE(tsc_pg->tsc_offset);
>> 6e0: 4c 8b 05 29 d9 ff ff movq -0x26d7(%rip), %r8 # 0xffffffffffffe010 <hvclock_page+0x10>
>> ; asm volatile(ALTERNATIVE_2("rdtsc",
>> 6e7: 0f 31 rdtsc
>> 6e9: 90 nop
>> 6ea: 90 nop
>> 6eb: 90 nop
>> ; } while (READ_ONCE(tsc_pg->tsc_sequence) != sequence);
>> 6ec: 8b 0f movl (%rdi), %ecx
>> $
>>
> Yes, not only llvm-objdump. I can see other tools also can handle this and even
> can download from online by Debuginfod.
> - perf can search debugging info there if HAVE_DEBUGINFOD_SUPPORT.
> - gdb can search debugging info there and download via Debuginfod if not exist.
>
> While above requires debugging files are placed correctly in
> /usr/lib/debug/.build-id/. For vdso mostly you need to copy it manully.
>
> The target of this series is to handle it transparently, espacially for locally
> built kernels.
Passing the file name to perf tool doesn't seem transparent.
For locally built kernels, maybe there should be a make target for it.
There seems to be "vdso_install" for the stripped binary.
Powered by blists - more mailing lists