linux-kernel - [RFC PATCH v1 0/1] Call forget_syscall() if different than execve*()

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Date:   Mon,  9 May 2022 16:19:56 +0100
From:   Francis Laniel <flaniel@...ux.microsoft.com>
To:     linux-arm-kernel@...ts.infradead.org
Cc:     linux-trace-devel@...r.kernel.org,
        Francis Laniel <flaniel@...ux.microsoft.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Peter Collingbourne <pcc@...gle.com>,
        Mark Brown <broonie@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Daniel Kiss <daniel.kiss@....com>,
        Kees Cook <keescook@...omium.org>, linux-kernel@...r.kernel.org
Subject: [RFC PATCH v1 0/1] Call forget_syscall() if different than execve*()

Hi.

First, I hope you are fine and the same for your relatives.

With this contribution, I enabled using syscalls:sys_exit_execve and
syscalls:sys_exit_execveat as tracepoints on arm64.
Indeed, before this contribution, the above tracepoint would not print their
information as syscall number was set to -1 by calling forget_syscall().

Now, forget_syscall() is called only if previous syscall number was different
than __NR_execve and __NR_execveat.
I tested it by compiling a kernel for arm64 and running it within a VM:
# Perf was compiled with linux kernel source.
root@...arm64:~# perf record -ag -e 'syscalls:sys_exit_execve' -e 'syscalls:sys_enter_execve' &
[1] 263
root@...arm64:~# ls
perf.data  share
root@...arm64:~# fg
perf record -ag -e 'syscalls:sys_exit_execve' -e 'syscalls:sys_enter_execve'
^C[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.061 MB perf.data (2 samples) ]
root@...arm64:~# perf script
bash   264 [000]    66.220187: syscalls:sys_enter_execve: filename: 0xaaab05d9d
...
# Below line does not appear with this patch.
ls   264 [000]    66.226848:  syscalls:sys_exit_execve: 0x0
...

Nonetheless, this contribution is not perfect, hence I marked it as RFC.
First, I am not really sure if this is safe to not call forget_syscall() all the
time, even though I did not have problem while testing it.
Then, by including <asm-generic/unistd.h> to the modified file I ended with
some warnings at compile time:

So, if you see any way to improve this contribution, feel free to share!

Francis Laniel (1):
  arm64: Forget syscall if different from execve*()

 arch/arm64/include/asm/processor.h | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

Best regards and thank you in advance.
-- 
2.25.1