Commit-ID: f69fa9a91f60fff6f2d8b658b7d84d235d9d89b7
Gitweb: http://git.kernel.org/tip/f69fa9a91f60fff6f2d8b658b7d84d235d9d89b7
Author: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
AuthorDate: Thu, 29 Aug 2013 13:34:50 -0700
Committer: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
CommitDate: Thu, 29 Aug 2013 13:34:50 -0700
x86, doc: Update uaccess.h comment to reflect clang changes
Update comment in uaccess.h to reflect the changes for clang support:
gcc only cares about the base register (most architectures don't
encode the size of the operation in the operands like x86 does, and so
it is treated effectively like a register number), whereas clang tries
to enforce the size -- but not for register pairs.
Link: http://lkml.kernel.org/r/1377803585-5913-3-git-send-email-dl9pf@xxxxxx
Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
Cc: Jan-Simon Möller <dl9pf@xxxxxx>
---
arch/x86/include/asm/uaccess.h | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index f715fee..5838fa9 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -153,11 +153,14 @@ __typeof__(__builtin_choose_expr(sizeof(x) > sizeof(0UL), 0ULL, 0UL))
* 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
+ * The use of _ASM_DX 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.
+ *
+ * Clang/LLVM cares about the size of the register, but still wants
+ * the base register for something that ends up being a pair.
*/
#define get_user(x, ptr) \
({ \
--
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