Re: [PATCH v5 3/3] selftests: livepatch: Test livepatching a heavily called syscall

[Petr Mladek]

On Tue 2024-01-09 21:24:56, Marcos Paulo de Souza wrote:
> The test proves that a syscall can be livepatched. It is interesting
> because syscalls are called a tricky way. Also the process gets
> livepatched either when sleeping in the userspace or when entering
> or leaving the kernel space.
> 
> The livepatch is a bit tricky:
>   1. The syscall function name is architecture specific. Also
>      ARCH_HAS_SYSCALL_WRAPPER must be taken in account.
> 
>   2. The syscall must stay working the same way for other processes
>      on the system. It is solved by decrementing a counter only
>      for PIDs of the test processes. It means that the test processes
>      has to call the livepatched syscall at least once.
> 
> The test creates one userspace process per online cpu. The processes
> are calling getpid in a busy loop. The intention is to create random
> locations when the livepatch gets enabled. Nothing is guarantted.
> The magic is in the randomness.
> 
> Reviewed-by: Joe Lawrence <joe.lawrence@xxxxxxxxxx>
> Signed-off-by: Marcos Paulo de Souza <mpdesouza@xxxxxxxx>

Reviewed-by: Petr Mladek <pmladek@xxxxxxxx>

Best Regards,
Petr