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SubjectRe: [PATCH] more sanity checks in Dwarf2 unwinder
>>  	while (unwind(info) == 0 && UNW_PC(info)) {
>> n++;
>> oad->ops->address(oad->data, UNW_PC(info));
>> if (arch_unw_user_mode(info))
>> break;
>> + if ((sp & ~(PAGE_SIZE - 1)) == (UNW_SP(info) & ~(PAGE_SIZE - 1))
>> + && sp > UNW_SP(info))
>> + break;
>
>Hmm, but that wouldn't catch the case when the SP is completely
>corrupted for some reason.
>Maybe it would be better to just run a brute force check here like
>the old in_exception_stack(). Similar on x86-64.

Correct. Even though I know Linus disagrees here, I'm not sure
I want to do this, as my ultimate goal would be to eliminate the
hand-crafted linking (which we know got broken a few times on
x86-64, because it's so easy to forget about).
Not the least of the reasons for this is that this increases the
chances of stucks.

>> + if (UNW_PC(frame) % state.codeAlign
>> + || UNW_SP(frame) % sleb128abs(state.dataAlign)
>> + || (pc == UNW_PC(frame) && sp == UNW_SP(frame)))
>> + return -EIO;
>
>Would it be possible to add printks for the EIOs? We want to know
>when dwarf2 is corrupted.

Certainly, will be a follow-up patch.

Jan
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