Bug Report: Unaligned Access in BGP Code on ARMv7 Platforms

[nick]

Sorry for the long response time.

Here is the requested output:

> Program received signal SIGBUS, Bus error.
> 0x00056fc0 in bgp_get_prefix (path_id=0, net=0xb6f0709c, c=0xb6ee9bc0) 
> at proto/bgp/attrs.c:1710
> 1710    proto/bgp/attrs.c: No such file or directory.
> (gdb) p sizeof(struct mblock)
> $1 = 16
> (gdb) p px
> $2 = (struct bgp_prefix *) 0xb6eac01c
> (gdb) p (uintptr_t)px % 4
> $3 = 0
> (gdb) p (uintptr_t)px % 8
> $4 = 4

On 12/6/24 3:16 AM, Ondrej Zajicek wrote:
> On Thu, Dec 05, 2024 at 11:35:13PM +0100, nick via Bird-users wrote:
>> Dear BIRD Community,
>>
>> I am writing to report a bug observed in the BGP implementation on ARMv7
>> platforms, which results in a SIGBUS error due to unaligned memory access in
>> the NEON assembler code. I debugged this issue on version 2.15.1 of BIRD.
>>
>> The root cause appears to be insufficient alignment of memory allocated for
>> structures, specifically in this line:
>>
>> ```c
>> px = mb_alloc(c->pool, sizeof(struct bgp_prefix) + net->length);
>> ```
> Hello
>
> Thanks for the report, can you get from your crash the pointer / aligment of
> 'px' and also get sizeof(struct mblock) in your build?
>