Date: Mon, 16 Jul 2018 18:21:30 +0000 (UTC) From: Andrew Turner <andrew@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r336349 - head/sys/sys Message-ID: <201807161821.w6GILULx052749@repo.freebsd.org>
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Author: andrew Date: Mon Jul 16 18:21:29 2018 New Revision: 336349 URL: https://svnweb.freebsd.org/changeset/base/336349 Log: Don't use the static keyword with DPCPU defines in arm64 modules. On arm64 compiler will create PC-relative loads and stores for static data. This means it doesn't emit a relocation. Unfortunately the in-kernel linker expects there to be one for DPCPU defines so it can modify its value so the code will use the correct DPCPU region. To workaround the lack of a relocation with static data remove it when building modules on arm64. The kernel is unaffected as it doesn't rely on modifying these relocations to find the data. PR: 225684 Reported by: Johannes Lundberg <johalun0@gmail.com> Reported by: Jose Luis Duran <jlduran@gmail.com> Reported by: Greg V <greg@unrelenting.technology> Reviewed by: bz Sponsored by: ABT Systems Ltd Differential Revision: https://reviews.freebsd.org/D16145 Modified: head/sys/sys/pcpu.h Modified: head/sys/sys/pcpu.h ============================================================================== --- head/sys/sys/pcpu.h Mon Jul 16 15:39:33 2018 (r336348) +++ head/sys/sys/pcpu.h Mon Jul 16 18:21:29 2018 (r336349) @@ -84,8 +84,26 @@ extern uintptr_t dpcpu_off[]; /* struct _hack is to stop this from being used with the static keyword. */ #define DPCPU_DEFINE(t, n) \ struct _hack; t DPCPU_NAME(n) __section(DPCPU_SETNAME) __used +#if defined(KLD_MODULE) && defined(__aarch64__) +/* + * On some architectures the compiler will use PC-relative load to + * find the address of DPCPU data with the static keyword. We then + * use this to find the offset of the data in a per-CPU region. + * This works for in the kernel as we can allocate the space ahead + * of time, however modules need to allocate a sepatate space and + * then use relocations to fix the address of the data. As + * PC-relative data doesn't have a relocation there is nothing for + * the kernel module linker to fix so data is accessed from the + * wrong location. + * + * This is a workaround until a better solution can be found. +*/ #define DPCPU_DEFINE_STATIC(t, n) \ + t DPCPU_NAME(n) __section(DPCPU_SETNAME) __used +#else +#define DPCPU_DEFINE_STATIC(t, n) \ static t DPCPU_NAME(n) __section(DPCPU_SETNAME) __used +#endif /* * Accessors with a given base.
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