Re: [PATCH 5/6] ptrace: introduce PTRACE_SET_SYSCALL_INFO request
From: Oleg Nesterov
Date: Thu Jan 09 2025 - 10:23:23 EST
On 01/08, Dmitry V. Levin wrote:
>
> +ptrace_set_syscall_info_entry(struct task_struct *child, struct pt_regs *regs,
> + struct ptrace_syscall_info *info)
> +{
...
> + syscall_set_nr(child, regs, nr);
> + syscall_set_arguments(child, regs, args);
> + if (nr == -1) {
> + /*
> + * When the syscall number is set to -1, the syscall will be
> + * skipped. In this case also set the syscall return value to
> + * -ENOSYS, otherwise on some architectures the corresponding
> + * struct pt_regs field will remain unchanged.
> + *
> + * Note that on some architectures syscall_set_return_value()
> + * modifies one of the struct pt_regs fields also modified by
> + * syscall_set_arguments(), so the former should be called
> + * after the latter.
> + */
> + syscall_set_return_value(child, regs, -ENOSYS, 0);
> + }
This doesn't look nice to me...
We don't need this syscall_set_return_value(ENOSYS) on x86, right?
So perhaps we should move this "if (nr == -1) code into
syscall_set_nr/syscall_set_arguments on those "some architectures" which
actually need it ?
Oleg.