4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Matthias Kaehlcke mka@chromium.org
commit 121843eb02a6e2fa30aefab64bfe183c97230c75 upstream.
The constraint "rm" allows the compiler to put mix_const into memory. When the input operand is a memory location then MUL needs an operand size suffix, since Clang can't infer the multiplication width from the operand.
Add and use the _ASM_MUL macro which determines the operand size and resolves to the NUL instruction with the corresponding suffix.
This fixes the following error when building with clang:
CC arch/x86/lib/kaslr.o /tmp/kaslr-dfe1ad.s: Assembler messages: /tmp/kaslr-dfe1ad.s:182: Error: no instruction mnemonic suffix given and no register operands; can't size instruction
Signed-off-by: Matthias Kaehlcke mka@chromium.org Cc: Grant Grundler grundler@chromium.org Cc: Greg Hackmann ghackmann@google.com Cc: Kees Cook keescook@chromium.org Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Michael Davidson md@google.com Cc: Peter Zijlstra peterz@infradead.org Cc: Thomas Gleixner tglx@linutronix.de Link: http://lkml.kernel.org/r/20170501224741.133938-1-mka@chromium.org Signed-off-by: Ingo Molnar mingo@kernel.org [nc: Apply to aslr.c in get_random_long as the kaslr shift didn't happen until 4.8 in commit d899a7d146a2] Signed-off-by: Nathan Chancellor natechancellor@gmail.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/boot/compressed/aslr.c | 3 ++- arch/x86/include/asm/asm.h | 1 + 2 files changed, 3 insertions(+), 1 deletion(-)
--- a/arch/x86/boot/compressed/aslr.c +++ b/arch/x86/boot/compressed/aslr.c @@ -1,5 +1,6 @@ #include "misc.h"
+#include <asm/asm.h> #include <asm/msr.h> #include <asm/archrandom.h> #include <asm/e820.h> @@ -94,7 +95,7 @@ static unsigned long get_random_long(voi }
/* Circular multiply for better bit diffusion */ - asm("mul %3" + asm(_ASM_MUL "%3" : "=a" (random), "=d" (raw) : "a" (random), "rm" (mix_const)); random += raw; --- a/arch/x86/include/asm/asm.h +++ b/arch/x86/include/asm/asm.h @@ -34,6 +34,7 @@ #define _ASM_ADD __ASM_SIZE(add) #define _ASM_SUB __ASM_SIZE(sub) #define _ASM_XADD __ASM_SIZE(xadd) +#define _ASM_MUL __ASM_SIZE(mul)
#define _ASM_AX __ASM_REG(ax) #define _ASM_BX __ASM_REG(bx)