From d99582a829e63c1a86b5fae20ff853aa4f0a9bc2 Mon Sep 17 00:00:00 2001 From: andrew Date: Mon, 16 Jul 2018 18:21:29 +0000 Subject: [PATCH] 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 Reported by: Jose Luis Duran Reported by: Greg V Reviewed by: bz Sponsored by: ABT Systems Ltd Differential Revision: https://reviews.freebsd.org/D16145 --- sys/sys/pcpu.h | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/sys/sys/pcpu.h b/sys/sys/pcpu.h index cba9d6e89797..9057cab20698 100644 --- a/sys/sys/pcpu.h +++ b/sys/sys/pcpu.h @@ -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.