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Don't use the static keyword with DPCPU defines in arm64 modules.

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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
This commit is contained in:
andrew 2018-07-16 18:21:29 +00:00
parent 8b7eda763d
commit d99582a829
1 changed files with 18 additions and 0 deletions
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18
sys/sys/pcpu.h
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@ -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.