On 14/06/17 21:04, Michael Ellerman wrote:
> Alexey Kardashevskiy <a...@ozlabs.ru> writes:
>
>> When trapped on WARN_ON(), report_bug() is expected to return
>> BUG_TRAP_TYPE_WARN so the caller could increment NIP by 4 and continue.
>> The __builtin_constant_p() path of the PPC's WARN_ON() calls (indirectly)
>> __WARN_FLAGS() which has BUGFLAG_WARNING set, however the other branch
>> does not which makes report_bug() report a bug rather than a warning.
>>
>> Fixes: 19d436268dde95389 ("debug: Add _ONCE() logic to report_bug()")
>> Signed-off-by: Alexey Kardashevskiy <a...@ozlabs.ru>
>> ---
>>
>> Actually 19d436268dde95389 replaced __WARN_TAINT() with __WARN_FLAGS()
>> and lost BUGFLAG_TAINT() and this is not in the commit log so it is
>> unclear:
>> 1) why
>
> I think the rename is because previously the argument was a taint value,
> whereas now it is a flags value (which is a superset of taint).
>
>> 2) whether this particular patch should be doing
>> BUGFLAG_WARNING|BUGFLAG_TAINT(TAINT_WARN)
>> or
>> BUGFLAG_WARNING|(flags)
>
> There is no flags here so the latter won't work AFAICS.
>
>> Any ideas? Thanks.
>
> Your patch looks correct to me. I assume it works?
Yes, it does.
>
>
> The bug isn't introduced by 19d436268dde ("debug: Add _ONCE() logic to
> report_bug()") as far as I can see.
>
> If you check out that revision you see that BUGFLAG_TAINT still contains
> BUGFLAG_WARNING:
>
> #define BUGFLAG_TAINT(taint) (BUGFLAG_WARNING | ((taint) << 8))
>
> But that was removed in f26dee15103f ("debug: Avoid setting
> BUGFLAG_WARNING twice"). So I think the Fixes: tag should point at that
> commit.
Ah, you're right. Should I repost the patch with the updated "fixes:" clause?
>
> cheers
>
>> diff --git a/arch/powerpc/include/asm/bug.h b/arch/powerpc/include/asm/bug.h
>> index f2c562a0a427..0151af6c2a50 100644
>> --- a/arch/powerpc/include/asm/bug.h
>> +++ b/arch/powerpc/include/asm/bug.h
>> @@ -104,7 +104,7 @@
>> "1: "PPC_TLNEI" %4,0\n" \
>> _EMIT_BUG_ENTRY \
>> : : "i" (__FILE__), "i" (__LINE__), \
>> - "i" (BUGFLAG_TAINT(TAINT_WARN)), \
>> + "i" (BUGFLAG_WARNING|BUGFLAG_TAINT(TAINT_WARN)),\
>> "i" (sizeof(struct bug_entry)), \
>> "r" (__ret_warn_on)); \
>> } \
>> --
>> 2.11.0
--
Alexey
