| From foo@baz Mon Apr 9 17:09:24 CEST 2018 |
| From: Matthias Kaehlcke <mka@chromium.org> |
| Date: Mon, 1 May 2017 15:47:41 -0700 |
| Subject: x86/mm/kaslr: Use the _ASM_MUL macro for multiplication to work around Clang incompatibility |
| |
| From: Matthias Kaehlcke <mka@chromium.org> |
| |
| |
| [ Upstream commit 121843eb02a6e2fa30aefab64bfe183c97230c75 ] |
| |
| 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> |
| Signed-off-by: Sasha Levin <alexander.levin@microsoft.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| arch/x86/include/asm/asm.h | 1 + |
| arch/x86/lib/kaslr.c | 3 ++- |
| 2 files changed, 3 insertions(+), 1 deletion(-) |
| |
| --- 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) |
| --- 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(cons |
| } |
| |
| /* Circular multiply for better bit diffusion */ |
| - asm("mul %3" |
| + asm(_ASM_MUL "%3" |
| : "=a" (random), "=d" (raw) |
| : "a" (random), "rm" (mix_const)); |
| random += raw; |