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On Sun, Jan 09, 2022 at 05:58:44AM -0800, Huacai Chen wrote:<br>
> > > With @chenhuacai's [latest patch](https://github.com/xen0n/linux/commit/593f8c0180fc1056e3ea0ca91ce9a8096f40b7ef), every test passes except this:<br>
> > <br>
> > Yes, this looks plausible.<br>
> > <br>
> > As I said earlier, another problem with the current implementation of `do_syscall` is that unlike other architectures, here the ptracer cannot change the first syscall argument because it is currently stored in `regs->orig_a0` which is out of reach of ptracers. What do you think about exposing `regs->orig_a0` to ptracers?<br>
> <br>
> Exposing orig_a0 means modifying user_pt_regs, gpr_get(), gpr_set() and all tracers (gdb, strace, etc) and don't need to overriding arch_syscall_enter_tracehook(), right?<br>
<br>
Yes, exposing orig_a0 means modifying user_pt_regs, gpr_get(), gpr_set(),<br>
and all tracers.<br>
This would allow to do<br>
        regs->regs[4] = -ENOSYS;<br>
in do_syscall() right before the syscall_enter_from_user_mode()<br>
invocation, and there won't be any need to override<br>
arch_syscall_enter_tracehook() then.<br>


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