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x86, asm: Fix a compilation issue with clang

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Clang does not support the "shortcut" we're taking here for gcc (see below).
The patch uses the macro _ASM_DX to do the job.

From arch/x86/include/asm/uaccess.h:
/*
 * Careful: we have to cast the result to the type of the pointer
 * for sign reasons.
 *
 * The use of %edx as the register specifier is a bit of a
 * simplification, as gcc only cares about it as the starting point
 * and not size: for a 64-bit value it will use %ecx:%edx on 32 bits
 * (%ecx being the next register in gcc's x86 register sequence), and
 * %rdx on 64 bits.
 */

[ hpa: I consider this a compatibility bug in clang as this reflects a
  bit of a misunderstanding about how register strings are used by
  gcc, but the workaround is straightforward and there is no
  particular reason to not do it. ]

Signed-off-by: Jan-Simon Möller <dl9pf@gmx.de>
Link: http://lkml.kernel.org/r/1377803585-5913-3-git-send-email-dl9pf@gmx.de
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
This commit is contained in:
Jan-Simon Möller 2013-08-29 21:13:05 +02:00 committed by H. Peter Anvin
parent 3e9b2327b5
commit bdfc017eea
1 changed files with 1 additions and 1 deletions
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2
arch/x86/include/asm/uaccess.h
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@ -162,7 +162,7 @@ __typeof__(__builtin_choose_expr(sizeof(x) > sizeof(0UL), 0ULL, 0UL))
#define get_user(x, ptr) \
({ \
int __ret_gu; \
register __inttype(*(ptr)) __val_gu asm("%edx"); \
register __inttype(*(ptr)) __val_gu asm("%"_ASM_DX); \
__chk_user_ptr(ptr); \
might_fault(); \
asm volatile("call __get_user_%P3" \