Hi Andrew,
Today's linux-next merge of the akpm-current tree got a conflict in:
arch/cris/include/arch-v10/arch/bug.h
between commit:
c8133e59edb0 ("cris: Mark end of BUG() implementation as unreachable")
from the kspp tree and commit:
c5a1e183a75a ("bug.h: work around GCC PR82365 in BUG()")
from the akpm-current tree.
I fixed it up (I just used the akpm-current tree version) and can
carry the fix as necessary. This is now fixed as far as linux-next is
concerned, but any non trivial conflicts should be mentioned to your
upstream maintainer when your tree is submitted for merging. You may
also want to consider cooperating with the maintainer of the conflicting
tree to minimise any particularly complex conflicts.
--
Cheers,
Stephen Rothwell
On Mon, Jan 15, 2018 at 5:57 AM, Stephen Rothwell <[email protected]> wrote:
> Hi Andrew,
>
> Today's linux-next merge of the akpm-current tree got a conflict in:
>
> arch/cris/include/arch-v10/arch/bug.h
>
> between commit:
>
> c8133e59edb0 ("cris: Mark end of BUG() implementation as unreachable")
>
> from the kspp tree and commit:
>
> c5a1e183a75a ("bug.h: work around GCC PR82365 in BUG()")
>
> from the akpm-current tree.
>
> I fixed it up (I just used the akpm-current tree version) and can
> carry the fix as necessary. This is now fixed as far as linux-next is
> concerned, but any non trivial conflicts should be mentioned to your
> upstream maintainer when your tree is submitted for merging. You may
> also want to consider cooperating with the maintainer of the conflicting
> tree to minimise any particularly complex conflicts.
Kees,
it seems you ran into the same issue that I did, and got the same fix
for the first BUG() variant, but I think my version for the second one
is slightly better:
/* This just causes an oops. */
-#define BUG() (*(int *)0 = 0)
+#define BUG() \
+do { \
+ barrier_before_unreachable(); \
+ __builtin_trap(); \
+} while (0)
compared to yours:
/* This just causes an oops. */
-#define BUG() (*(int *)0 = 0)
+#define BUG() \
+do { \
+ (*(int *)0 = 0); \
+ do {} while (1); \
+ unreachable(); \
+} while (0)
which relies on a NULL pointer dereference to trap but otherwise
does the same thing. The easiest solution for the conflict seems to
be that you just drop your patch.
Arnd
On Mon, Jan 15, 2018 at 4:41 AM, Arnd Bergmann <[email protected]> wrote:
> On Mon, Jan 15, 2018 at 5:57 AM, Stephen Rothwell <[email protected]> wrote:
>> Hi Andrew,
>>
>> Today's linux-next merge of the akpm-current tree got a conflict in:
>>
>> arch/cris/include/arch-v10/arch/bug.h
>>
>> between commit:
>>
>> c8133e59edb0 ("cris: Mark end of BUG() implementation as unreachable")
>>
>> from the kspp tree and commit:
>>
>> c5a1e183a75a ("bug.h: work around GCC PR82365 in BUG()")
>>
>> from the akpm-current tree.
>>
>> I fixed it up (I just used the akpm-current tree version) and can
>> carry the fix as necessary. This is now fixed as far as linux-next is
>> concerned, but any non trivial conflicts should be mentioned to your
>> upstream maintainer when your tree is submitted for merging. You may
>> also want to consider cooperating with the maintainer of the conflicting
>> tree to minimise any particularly complex conflicts.
>
> Kees,
>
> it seems you ran into the same issue that I did, and got the same fix
> for the first BUG() variant, but I think my version for the second one
> is slightly better:
>
> /* This just causes an oops. */
> -#define BUG() (*(int *)0 = 0)
> +#define BUG() \
> +do { \
> + barrier_before_unreachable(); \
> + __builtin_trap(); \
> +} while (0)
>
> compared to yours:
>
> /* This just causes an oops. */
> -#define BUG() (*(int *)0 = 0)
> +#define BUG() \
> +do { \
> + (*(int *)0 = 0); \
> + do {} while (1); \
> + unreachable(); \
> +} while (0)
>
> which relies on a NULL pointer dereference to trap but otherwise
> does the same thing. The easiest solution for the conflict seems to
> be that you just drop your patch.
Oh yeah, very nice. Yeah, yours is better. I'll drop mine.
Thanks!
-Kees
--
Kees Cook
Pixel Security