Message-ID: <CAH0uvojUEXiT2mk1pknLS1nc-gA3Py+AjmEW22ETiCCyOLLr8Q@mail.gmail.com>
Date: Tue, 17 Sep 2024 10:37:52 -0700
From: Howard Chu <howardchu95@...il.com>
To: Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
Cc: James Clark <james.clark@...aro.org>, Arnaldo Carvalho de Melo <acme@...nel.org>, 
	Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
	Alan Maguire <alan.maguire@...cle.com>, Jiri Olsa <jolsa@...nel.org>, 
	Kan Liang <kan.liang@...ux.intel.com>, Namhyung Kim <namhyung@...nel.org>, 
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, 
	linux-perf-users <linux-perf-users@...r.kernel.org>
Subject: Re: [PATCH 1/1] perf build: Require at least clang 16.0.6 to build
 BPF skeletons

Hello James and Arnaldo,

On Fri, Sep 13, 2024 at 3:42 AM Arnaldo Carvalho de Melo
<arnaldo.melo@...il.com> wrote:
>
>
>
> On Fri, Sep 13, 2024, 7:20 AM James Clark <james.clark@...aro.org> wrote:
>>
>>
>>
>> On 12/09/2024 15:50, Arnaldo Carvalho de Melo wrote:
>> > On Thu, Sep 12, 2024 at 03:40:32PM +0100, James Clark wrote:
>> >> On 11/09/2024 13:24, Arnaldo Carvalho de Melo wrote:
>> >>> Howard reported problems using perf features that use BPF:
>> >
>> >>>     perf $ clang -v
>> >>>     Debian clang version 15.0.6
>> >>>     Target: x86_64-pc-linux-gnu
>> >>>     Thread model: posix
>> >>>     InstalledDir: /bin
>> >>>     Found candidate GCC installation: /bin/../lib/gcc/x86_64-linux-gnu/12
>> >>>     Selected GCC installation: /bin/../lib/gcc/x86_64-linux-gnu/12
>> >>>     Candidate multilib: .;@m64
>> >>>     Selected multilib: .;@m64
>> >>>     perf $ ./perf trace -e write --max-events=1
>> >>>     libbpf: prog 'sys_enter_rename': BPF program load failed: Permission denied
>> >>>     libbpf: prog 'sys_enter_rename': -- BEGIN PROG LOAD LOG --
>> >>>     0: R1=ctx() R10=fp0
>> >>>
>> >>> But it works with:
>> >>>
>> >>>     perf $ clang -v
>> >>>     Debian clang version 16.0.6 (15~deb12u1)
>> >>>     Target: x86_64-pc-linux-gnu
>> >>>     Thread model: posix
>> >>>     InstalledDir: /bin
>> >>>     Found candidate GCC installation: /bin/../lib/gcc/x86_64-linux-gnu/12
>> >>>     Selected GCC installation: /bin/../lib/gcc/x86_64-linux-gnu/12
>> >>>     Candidate multilib: .;@m64
>> >>>     Selected multilib: .;@m64
>> >>>     perf $ ./perf trace -e write --max-events=1
>> >>>          0.000 ( 0.009 ms): gmain/1448 write(fd: 4, buf: \1\0\0\0\0\0\0\0, count: 8)                         = 8 (kworker/0:0-eve)
>> >>>     perf $
>> >>>
>> >>> So lets make that the required version, if you happen to have a slightly
>> >>> older version where this work, please report so that we can adjust the
>> >>> minimum required version.
>> >
>> >> I wasn't able to reproduce the issue with either of these versions. But I
>> >> suppose it could be an issue with only 15.0.6.
>> >
>> > Interesting, that complicates things, probably the best way then is to
>> > try to build it, if it fails, mention that 15.0.6 is known to be
>> > problematic and suggest working versions?
>> >
>> > - Arnaldo
>>
>> I still wasn't able to reproduce it with 15.0.6. And I double checked
>> with V=1 that the build was using the right clang. I suppose it could be
>> a build configuration issue, or maybe with a different kernel version?
>
>
> Howard? If not reproducible we can revert it.
>
> - Arnaldo
>
>
>>
>> $  uname --kernel-release
>> 6.8.0-76060800daily20240311-generic
>>
>> $ ../../llvm-project/build/bin/clang -v
>> clang version 15.0.6 (https://github.com/llvm/llvm-project.git
>> 088f33605d8a61ff519c580a71b1dd57d16a03f8)
>> Target: x86_64-unknown-linux-gnu
>> Thread model: posix
>> InstalledDir: /home/james/workspace/linux/linux/../../llvm-project/build/bin
>> Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/11
>> Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/12
>> Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/12
>> Candidate multilib: .;@m64
>> Selected multilib: .;@m64
>>
>> $ git log
>> commit 003265bb6f028d7bcd7cbd92d6ba2b4e26382796
>> (perf-tools-next/perf-tools-next)
>>
>> $ make O=../build/local/ CLANG=../../llvm-project/build/bin/clang -C \
>>    tools/perf
>>
>> $ perf trace -e write --max-events=1
>>
>>       0.000 ( 0.026 ms): gnome-shell/5454 write(fd: 5, buf:
>>         0x7fffa102d9b0, count: 8)                           = 8

Thanks for the effort! But this output seems to be unaugmented? I
think you are testing the perf/perf-tools-next branch that's slightly
older (perf mem: Fix the wrong reference in parse_record_events()
003265bb6f028d7bcd7cbd92d6ba2b4e26382796), and I think that doesn't
have the new perf trace feature yet...

That's why the perf trace output looks like:

>> $ perf trace -e write --max-events=1
>>
>>       0.000 ( 0.026 ms): gnome-shell/5454 write(fd: 5, buf:
>>         0x7fffa102d9b0, count: 8)

With the new buffer augmentation it should look like this:

perf $ ./perf trace -e write --max-events=1
     0.000 ( 0.011 ms): gmain/1408 write(fd: 4, buf: \1\0\0\0\0\0\0\0,
count: 8)                         =

The new perf trace can be found on
https://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/
perf-tools-next

perf $ git log
commit 1de5b5dcb8353f36581c963df2d359a5f151a0be (HEAD ->
struct-aug-arnaldo-2, perf/perf-tools-next)

Also, if you want to test the clang, you may want to checkout to the
commit before the clang-16 guard (otherwise you can't test different
clang version).

perf $ git log --oneline
1de5b5dcb835 (HEAD -> struct-aug-arnaldo-2, perf/perf-tools-next) perf
trace: Mark the 'head' arg in the set_robust_list syscall as coming
from user space
0c1019e3463b perf trace: Mark the 'rseq' arg in the rseq syscall as
coming from user space
edf3ce0ed38e perf env: Find correct branch counter info on hybrid
9953807c9e01 perf evlist: Print hint for group
eb9b9a6f5ab3 tools: Drop nonsensical -O6
89c0a55e550e perf pmu: To info add event_type_desc
f08cc258431d perf evsel: Add accessor for tool_event
925320737ae2 perf pmus: Fake PMU clean up
d3d5c1a00fcd perf list: Avoid potential out of bounds memory read
4ae354d73a8e perf help: Fix a typo ("bellow")
74298dd8acb8 perf ftrace: Detect whether ftrace is enabled on system
83420d5f5863 perf test shell probe_vfs_getname: Remove extraneous '='
from probe line number regex
9327f0ecad48 perf build: Require at least clang 16.0.6 to build BPF
skeletons. **********[[[[[[[[[[[[!!!!(This is the clang
guard)]]]]]]]]]]*****
4c1af9bf97eb perf trace: If a syscall arg is marked as 'const', assume
it is coming _from_ userspace
e37b315c17df perf parse-events: Remove duplicated include in parse-events.c

My machine is debian 12, and I cannot build perf trace with the new
augmentation feature on clang-13, clang-14, and clang-15.

perf $ uname -r
6.11.0-061100rc7-generic

perf $ git log
commit 4c1af9bf97eb56d069421c3233ce61608458d5c8 (HEAD)

perf $ make CLANG=/bin/clang-13 && ./perf trace -e write --max-events=1
...
libbpf: prog 'sys_enter': BPF program load failed: Invalid argument
libbpf: prog 'sys_enter': -- BEGIN PROG LOAD LOG --
0: R1=ctx() R10=fp0
; int sys_enter(struct syscall_enter_args *args) @
augmented_raw_syscalls.bpf.c:509
0: (bf) r7 = r1                       ; R1=ctx() R7_w=ctx()


perf $ make CLANG=/bin/clang-14 && ./perf trace -e write --max-events=1
...
libbpf: prog 'sys_enter': BPF program load failed: Invalid argument
libbpf: prog 'sys_enter': -- BEGIN PROG LOAD LOG --
0: R1=ctx() R10=fp0
; int sys_enter(struct syscall_enter_args *args) @
augmented_raw_syscalls.bpf.c:509


perf $ make CLANG=/bin/clang-15 && ./perf trace -e write --max-events=1
libbpf: prog 'sys_enter': BPF program load failed: Invalid argument
libbpf: prog 'sys_enter': -- BEGIN PROG LOAD LOG --
0: R1=ctx() R10=fp0


perf $ make CLANG=/bin/clang-16 && ./perf trace -e write --max-events=1
     0.000 ( 0.010 ms): gmain/1408 write(fd: 4, buf: \1\0\0\0\0\0\0\0,
count: 8)                         =


Anyway thank you so much, I'll try to reproduce it on Ubuntu, like you
mentioned.

Thanks,
Howard


>>

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