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| author | Matthias Kaehlcke <mka@chromium.org> | 2017-05-01 15:47:41 -0700 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2017-05-05 08:31:05 +0200 |
| commit | 121843eb02a6e2fa30aefab64bfe183c97230c75 (patch) | |
| tree | 72e56dafd21ade241842af08ec79b13a76178b5b | |
| parent | fc5f9d5f151c9fff21d3d1d2907b888a5aec3ff7 (diff) | |
| download | lwn-121843eb02a6e2fa30aefab64bfe183c97230c75.tar.gz lwn-121843eb02a6e2fa30aefab64bfe183c97230c75.zip | |
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
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>
| -rw-r--r-- | arch/x86/include/asm/asm.h | 1 | ||||
| -rw-r--r-- | arch/x86/lib/kaslr.c | 3 |
2 files changed, 3 insertions, 1 deletions
diff --git a/arch/x86/include/asm/asm.h b/arch/x86/include/asm/asm.h index 7acb51c49fec..7a9df3beb89b 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) diff --git a/arch/x86/lib/kaslr.c b/arch/x86/lib/kaslr.c index 5761a4f19455..ab2d1d73e9e7 100644 --- a/arch/x86/lib/kaslr.c +++ b/arch/x86/lib/kaslr.c @@ -5,6 +5,7 @@ * kernel starts. This file is included in the compressed kernel and * normally linked in the regular. */ +#include <asm/asm.h> #include <asm/kaslr.h> #include <asm/msr.h> #include <asm/archrandom.h> @@ -79,7 +80,7 @@ unsigned long kaslr_get_random_long(const char *purpose) } /* Circular multiply for better bit diffusion */ - asm("mul %3" + asm(_ASM_MUL "%3" : "=a" (random), "=d" (raw) : "a" (random), "rm" (mix_const)); random += raw; |