From cafc5bc76374ba807d570055be4e217572d33a49 Mon Sep 17 00:00:00 2001 From: Matthias Kaehlcke Date: Fri, 5 May 2017 09:50:49 -0700 Subject: [PATCH] BACKPORT: x86/mm/kaslr: Use the _ASM_MUL macro for multiplication to work around Clang incompatibility 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 Upstream commit: 121843eb02a6 Change-Id: I53f51839705dabeb6c950d1def3a45881294129c Signed-off-by: Matthias Kaehlcke Cc: Grant Grundler Cc: Greg Hackmann Cc: Kees Cook Cc: Linus Torvalds Cc: Michael Davidson Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/20170501224741.133938-1-mka@chromium.org Signed-off-by: Ingo Molnar Signed-off-by: Greg Hackmann --- arch/x86/boot/compressed/aslr.c | 2 +- arch/x86/include/asm/asm.h | 1 + 2 files changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/boot/compressed/aslr.c b/arch/x86/boot/compressed/aslr.c index 6a9b96b4624d..4a5fbd2da658 100644 --- a/arch/x86/boot/compressed/aslr.c +++ b/arch/x86/boot/compressed/aslr.c @@ -94,7 +94,7 @@ static unsigned long get_random_long(void) } /* Circular multiply for better bit diffusion */ - asm("mul %3" + asm(_ASM_MUL "%3" : "=a" (random), "=d" (raw) : "a" (random), "rm" (mix_const)); random += raw; diff --git a/arch/x86/include/asm/asm.h b/arch/x86/include/asm/asm.h index 189679aba703..1f16ec50abeb 100644 --- a/arch/x86/include/asm/asm.h +++ b/arch/x86/include/asm/asm.h @@ -32,6 +32,7 @@ #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)