Re: [PATCH v7 1/6] arm64: ptrace: add PTRACE_SET_SYSCALL

AKASHI Takahiro
2014-11-06T02:40:28Z

Hi Will, Kees

#Sorry for this late ping,

On 10/09/2014 06:23 PM, Will Deacon wrote:
> On Wed, Oct 08, 2014 at 04:30:18PM +0100, Kees Cook wrote:
>> On Wed, Oct 8, 2014 at 9:13 AM, Will Deacon <will.deacon@arm.com> wrote:
>>> On Thu, Oct 02, 2014 at 10:46:11AM +0100, AKASHI Takahiro wrote:
>>>> diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
>>>> index fe63ac5..2842f9f 100644
>>>> --- a/arch/arm64/kernel/ptrace.c
>>>> +++ b/arch/arm64/kernel/ptrace.c
>>>> @@ -1082,7 +1082,19 @@ const struct user_regset_view *task_user_regset_view(struct task_struct *task)
>>>> long arch_ptrace(struct task_struct *child, long request,
>>>> unsigned long addr, unsigned long data)
>>>> {
>>>> - return ptrace_request(child, request, addr, data);
>>>> + int ret;
>>>> +
>>>> + switch (request) {
>>>> + case PTRACE_SET_SYSCALL:
>>>> + task_pt_regs(child)->syscallno = data;
>>>> + ret = 0;
>>>> + break;
>>>> + default:
>>>> + ret = ptrace_request(child, request, addr, data);
>>>> + break;
>>>> + }
>>>> +
>>>> + return ret;
>>>> }
>>>
>>> I still don't understand why this needs to be in arch-specific code. Can't
>>> we implement this in generic code and get architectures to implement
>>> something like syscall_set_nr if they want the generic interface?
>>
>> Personally, I'd rather see this land as-is in the arm64 tree, and then
>> later optimize PTRACE_SET_SYSCALL out of arm/ and arm64/, especially
>> since only these architectures implement this at the moment.
>
> Why? It should be really straightforward to do this in core code from the
> get-go and experience shows that, if we don't do it now, it will never
> happen.

How should I deal with this issue? I would be able to go either way.

Other than that, I will submit v8 patch series with a few very minor updates:
- use compat_uint_t in struct compat_siginfo
- use a new call interface of secure_computing(void)
- modify and clarify comments in syscall_trace_enter()

Thanks,
-Takahiro AKASHI

>> This is my plan for the asm-generic seccomp.h too -- I'd rather avoid
>> touching other architectures in this series, as it's easier to review
>> this way. Then we can optimize the code in a separate series, which
>> will have those changes isolated, etc.
>
> But this doesn't need to touch any other architectures...
>
> Will
>