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

Francis Laniel
2022-05-09T15:20:25Z

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@vm-arm64:~# perf record -ag -e 'syscalls:sys_exit_execve' -e 'syscalls:sys_enter_execve' &
[1] 263
root@vm-arm64:~# ls
perf.data share
root@vm-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@vm-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