When using the clang integrated assembler, we get a reference to __force_order that should normally get ignored in a few rare cases:
ERROR: modpost: "__force_order" [drivers/cpufreq/powernow-k6.ko] undefined! Add a 'static' definition so any file in which this happens can have a local copy. Signed-off-by: Arnd Bergmann <a...@arndb.de> --- arch/x86/boot/compressed/pgtable_64.c | 2 ++ arch/x86/include/asm/special_insns.h | 7 +++++++ 2 files changed, 9 insertions(+) diff --git a/arch/x86/boot/compressed/pgtable_64.c b/arch/x86/boot/compressed/pgtable_64.c index c8862696a47b..8595194cea41 100644 --- a/arch/x86/boot/compressed/pgtable_64.c +++ b/arch/x86/boot/compressed/pgtable_64.c @@ -12,7 +12,9 @@ * It is not referenced from the code, but GCC < 5 with -fPIE would fail * due to an undefined symbol. Define it to make these ancient GCCs work. */ +#ifndef CONFIG_CC_IS_CLANG unsigned long __force_order; +#endif #define BIOS_START_MIN 0x20000U /* 128K, less than this is insane */ #define BIOS_START_MAX 0x9f000U /* 640K, absolute maximum */ diff --git a/arch/x86/include/asm/special_insns.h b/arch/x86/include/asm/special_insns.h index 82436cb04ccf..7081e587c1ea 100644 --- a/arch/x86/include/asm/special_insns.h +++ b/arch/x86/include/asm/special_insns.h @@ -16,8 +16,15 @@ * A memory clobber would solve the problem, but would prevent reordering of * all loads stores around it, which can hurt performance. Solution is to * use a variable and mimic reads and writes to it to enforce serialization + * + * Clang sometimes fails to kill the reference to the dummy variable, so + * provide an actual copy. */ +#ifdef CONFIG_CC_IS_CLANG +static unsigned long __force_order; +#else extern unsigned long __force_order; +#endif void native_write_cr0(unsigned long val); -- 2.26.2
