Re: [PATCH] ptrace RSE bug

[Petr Tesarik <ptesarik@suse.cz>]

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Shaohua Li wrote:
> On Thu, 2007-09-06 at 15:59 +0200, Petr Tesarik wrote:
>>[...]
>> So, what happens if upon syscall entry notification the debugger
>> modifies the part of the RBS (in user-space) which corresponds to the
>> arguments of that syscall? Currently, the syscall takes the modified
>> arguments, but with your change it would still take the stale data
>> from
>> the kernel RBS.
> The patch does sync from user RBS to kernel RBS just after syscall trace
> enter. this is an exception I said doing sync just before syscall
> return. I thought this covers your case, no?

Ah, I'm sorry, I missed that part of the patch. Well, if we have to do a
sync on every syscall_trace_enter() and syscall_trace_leave(), then the
only cases where introducing TIF_RESTORE_RSE saves us a duplicate sync
seems to be in the clone/fork and exit paths. In other words, it's
probably not worth the added complexity. But since you have written the
whole complex thing already, I have no objections against it.

Regards,
Petr Tesarik
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