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SubjectRe: [PATCH 4/6] x86/coredump: use core regs, rather that TIF_IA32 flag
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On 06/07/2016 01:43 AM, Oleg Nesterov wrote:
> On 06/06, Oleg Nesterov wrote:
>>
>> On 06/01, Dmitry Safonov wrote:
>>>
>>> static int fill_thread_core_info(struct elf_thread_core_info *t,
>>> const struct user_regset_view *view,
>>> - long signr, size_t *total)
>>> + long signr, size_t *total,
>>> + struct pt_regs *regs __maybe_unused)
>>> {
>>> unsigned int i;
>>>
>>> @@ -1652,11 +1653,11 @@ static int fill_thread_core_info(struct elf_thread_core_info *t,
>>> */
>>> fill_prstatus(&t->prstatus, t->task, signr);
>>> (void) view->regsets[0].get(t->task, &view->regsets[0],
>>> - 0, PR_REG_SIZE(t->prstatus.pr_reg),
>>> + 0, PR_REG_SIZE(t->prstatus.pr_reg, regs),
>>
>> Hmm. I don't understand this... Note that this "regs" argument has nothing
>> to do with t->task if the process is multithreaded,
>>
>>> @@ -1772,7 +1773,8 @@ static int fill_note_info(struct elfhdr *elf, int phdrs,
>>> * Now fill in each thread's information.
>>> */
>>> for (t = info->thread; t != NULL; t = t->next)
>>> - if (!fill_thread_core_info(t, view, siginfo->si_signo, &info->size))
>>> + if (!fill_thread_core_info(t, view, siginfo->si_signo,
>>> + &info->size, regs))
>>
>> fill_note_info(..., args) is called with args = task_pt_regs(dumper_thread).
>
> forgot to mention... yes, this matches the fact we use a single "view"
> for all threads, and we get it via task_user_regset_view(dump_task).
>
> But this change (imo) adds even more confusion, and without the next patch
> the logic looks "obviously wrong", becauase PR_REG_SIZE/etc look at
> dumper_thread->cs while task_user_regset_view() checks thread flags.
>
> Anyway I fail to understand these macros... Say, PR_REG_SIZE(S). Can't we
> kill it and use regsets[0].n * regsets[0].size instead ? These numbers
> should match whatever we do, if we call ->get().
>

Thanks, the idea of dropping PR_REG_SIZE looks better than my patch!
I'll try to drop those macros for the next revision.

--
Regards,
Dmitry Safonov

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