Use the standard regparm=0 calling convention for memcpy and memset when building with clang.
This is a work around for a long standing clang bug (see https://llvm.org/bugs/show_bug.cgi?id=3997) where clang always uses the standard regparm=0 calling convention for any implcit calls to memcpy and memset that it generates (eg for structure assignments and initialization) even if an alternate calling convention such as regparm=3 has been specified. Signed-off-by: Michael Davidson <m...@google.com> --- arch/x86/boot/copy.S | 15 +++++++++++++-- arch/x86/boot/string.h | 13 +++++++++++++ 2 files changed, 26 insertions(+), 2 deletions(-) diff --git a/arch/x86/boot/copy.S b/arch/x86/boot/copy.S index 1eb7d298b47d..57142d1ad0d2 100644 --- a/arch/x86/boot/copy.S +++ b/arch/x86/boot/copy.S @@ -18,6 +18,12 @@ .text GLOBAL(memcpy) +#ifdef __clang__ /* Use normal ABI calling conventions */ + movw 4(%esp), %ax + movw 8(%esp), %dx + movw 12(%esp), %cx +#endif +_memcpy: pushw %si pushw %di movw %ax, %di @@ -34,6 +40,11 @@ GLOBAL(memcpy) ENDPROC(memcpy) GLOBAL(memset) +#ifdef __clang__ /* Use normal ABI calling conventions */ + movw 4(%esp), %ax + movw 8(%esp), %dx + movw 12(%esp), %cx +#endif pushw %di movw %ax, %di movzbl %dl, %eax @@ -52,7 +63,7 @@ GLOBAL(copy_from_fs) pushw %ds pushw %fs popw %ds - calll memcpy + calll _memcpy popw %ds retl ENDPROC(copy_from_fs) @@ -61,7 +72,7 @@ GLOBAL(copy_to_fs) pushw %es pushw %fs popw %es - calll memcpy + calll _memcpy popw %es retl ENDPROC(copy_to_fs) diff --git a/arch/x86/boot/string.h b/arch/x86/boot/string.h index 113588ddb43f..e735cccb3fc8 100644 --- a/arch/x86/boot/string.h +++ b/arch/x86/boot/string.h @@ -6,8 +6,21 @@ #undef memset #undef memcmp +/* + * Use normal ABI calling conventions - i.e. regparm(0) - + * for memcpy() and memset() if we are building the real + * mode setup code with clang since clang may make implicit + * calls to these functions that assume regparm(0). + */ +#if defined(_SETUP) && defined(__clang__) +void __attribute__((regparm(0))) *memcpy(void *dst, const void *src, + size_t len); +void __attribute__((regparm(0))) *memset(void *dst, int c, size_t len); +#else void *memcpy(void *dst, const void *src, size_t len); void *memset(void *dst, int c, size_t len); +#endif + int memcmp(const void *s1, const void *s2, size_t len); /* -- 2.12.0.367.g23dc2f6d3c-goog
