Commit 121843eb authored by Matthias Kaehlcke's avatar Matthias Kaehlcke Committed by Ingo Molnar

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

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: default avatarMatthias Kaehlcke <>
Cc: Grant Grundler <>
Cc: Greg Hackmann <>
Cc: Kees Cook <>
Cc: Linus Torvalds <>
Cc: Michael Davidson <>
Cc: Peter Zijlstra <>
Cc: Thomas Gleixner <>
Link: default avatarIngo Molnar <>
parent fc5f9d5f
......@@ -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)
......@@ -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;
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