-----Original Message----- From: Sebastian Huber <sebastian.hu...@embedded-brains.de> Sent: Monday, November 16, 2020 07:44 To: Kinsey Moore <kinsey.mo...@oarcorp.com>; devel@rtems.org Subject: Re: [PATCH 2/2] spec/aarch64: Only apply SUBALIGN(4) to ILP32
> On 16/11/2020 14:40, Kinsey Moore wrote: > >> -----Original Message----- >> From: Sebastian Huber<sebastian.hu...@embedded-brains.de> >> Sent: Monday, November 16, 2020 07:35 >> To: Kinsey Moore<kinsey.mo...@oarcorp.com>;devel@rtems.org >> Subject: Re: [PATCH 2/2] spec/aarch64: Only apply SUBALIGN(4) to ILP32 >> >>> On 16/11/2020 14:15, Kinsey Moore wrote: >>> >>>> The SUBALIGN(4) required on rtemsroset and rtemsrwset for ILP32 >>>> builds was previously present on LP64 builds and causes no issues >>>> within RTEMS, but causes relocation/alignment issues when building libbsd. >>>> This restricts those alignment changes to ILP32 builds. >>> Please check it in if you think it is necessary. >>> >>> What troubles me a bit is that these SUBALIGN() stuff is present at all. >>> >>> It also troubles me that the splinkersets01 test case didn't catch this >>> problem. >> That test was what originally caught the problem during development of the >> A53 BSP. This patch isn't the addition of a fix for the alignment problems, >> it's an adjustment of the original fix to be compatible with libbsd's use of >> rtemsroset/rtemsrwset linker sections. > So, this SUBALIGN() is just a workaround for some other problem? It would be > good to document this known issue somewhere, for example a ticket. Is this an > upstream problem in GCC or the GNU linker? Yes, SUBALIGN() is the workaround for ILP32 defaulting to 8 byte alignment in the rtemsroset and rtemsrwset linker sections because RTEMS expects them to default to 4 byte alignment when using 4 byte pointers. I suspect it's an issue in the GNU linker, but I haven't had a chance to track down the root cause. This patch is necessary because while RTEMS works fine with 4 byte alignment in those sections in the context of 8 byte pointers, libbsd puts things other than pointers in those sections and requires the alignment of those sections to exactly match the pointer size. I'll open a ticket for documentation purposes. Kinsey _______________________________________________ devel mailing list devel@rtems.org http://lists.rtems.org/mailman/listinfo/devel
