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Commit ff52c3b0 authored by H. Peter Anvin's avatar H. Peter Anvin
Browse files

x86, doc: Clarify the use of asm("%edx") in uaccess.h 

Put in a comment that explains that the use of asm("%edx") in
uaccess.h doesn't actually necessarily mean %edx alone.

Cc: Jamie Lokier <jamie@shareable.org>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: H. J. Lu <hjl.tools@gmail.com>
Link: http://lkml.kernel.org/r/511ACDFB.1050707@zytor.com


Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
parent 3578baae

arch/x86/include/asm/uaccess.h

+8 −1
Original line number Diff line number Diff line
@@ -148,9 +148,16 @@ __typeof__(__builtin_choose_expr(sizeof(x) > sizeof(0UL), 0ULL, 0UL)) 
 *

 * Returns zero on success, or -EFAULT on error.

 * On error, the variable @x is set to zero.

 *

 */

/*

 * 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.

 */

#define get_user(x, ptr)						\

({									\