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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>
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2 changed files with 3 additions and 1 deletions
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@ -32,6 +32,7 @@
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#define _ASM_ADD __ASM_SIZE(add)
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#define _ASM_SUB __ASM_SIZE(sub)
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#define _ASM_XADD __ASM_SIZE(xadd)
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#define _ASM_MUL __ASM_SIZE(mul)
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#define _ASM_AX __ASM_REG(ax)
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#define _ASM_BX __ASM_REG(bx)
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@ -5,6 +5,7 @@
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* kernel starts. This file is included in the compressed kernel and
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* normally linked in the regular.
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*/
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#include <asm/asm.h>
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#include <asm/kaslr.h>
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#include <asm/msr.h>
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#include <asm/archrandom.h>
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@ -79,7 +80,7 @@ unsigned long kaslr_get_random_long(const char *purpose)
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}
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/* Circular multiply for better bit diffusion */
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asm("mul %3"
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asm(_ASM_MUL "%3"
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: "=a" (random), "=d" (raw)
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: "a" (random), "rm" (mix_const));
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random += raw;
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