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authorJohn David Anglin <dave.anglin@bell.net>2014-12-14 10:49:11 -0500
committerHelge Deller <deller@gmx.de>2014-12-26 17:47:01 +0100
commit45db07382a5c78b0c43b3b0002b63757fb60e873 (patch)
tree63d86170ec09f9d9181f40dd6caa091271b5116d
parentb2776bf7149bddd1f4161f14f79520f17fc1d71d (diff)
downloadlinux-45db07382a5c78b0c43b3b0002b63757fb60e873.tar.gz
parisc: fix out-of-register compiler error in ldcw inline assembler function
The __ldcw macro has a problem when its argument needs to be reloaded from memory. The output memory operand and the input register operand both need to be reloaded using a register in class R1_REGS when generating 64-bit code. This fails because there's only a single register in the class. Instead, use a memory clobber. This also makes the __ldcw macro a compiler memory barrier. Signed-off-by: John David Anglin <dave.anglin@bell.net> Cc: <stable@vger.kernel.org> [3.13+] Signed-off-by: Helge Deller <deller@gmx.de>
-rw-r--r--arch/parisc/include/asm/ldcw.h13
1 files changed, 10 insertions, 3 deletions
diff --git a/arch/parisc/include/asm/ldcw.h b/arch/parisc/include/asm/ldcw.h
index d2d11b7055ba..8121aa6db2ff 100644
--- a/arch/parisc/include/asm/ldcw.h
+++ b/arch/parisc/include/asm/ldcw.h
@@ -33,11 +33,18 @@
#endif /*!CONFIG_PA20*/
-/* LDCW, the only atomic read-write operation PA-RISC has. *sigh*. */
+/* LDCW, the only atomic read-write operation PA-RISC has. *sigh*.
+ We don't explicitly expose that "*a" may be written as reload
+ fails to find a register in class R1_REGS when "a" needs to be
+ reloaded when generating 64-bit PIC code. Instead, we clobber
+ memory to indicate to the compiler that the assembly code reads
+ or writes to items other than those listed in the input and output
+ operands. This may pessimize the code somewhat but __ldcw is
+ usually used within code blocks surrounded by memory barriors. */
#define __ldcw(a) ({ \
unsigned __ret; \
- __asm__ __volatile__(__LDCW " 0(%2),%0" \
- : "=r" (__ret), "+m" (*(a)) : "r" (a)); \
+ __asm__ __volatile__(__LDCW " 0(%1),%0" \
+ : "=r" (__ret) : "r" (a) : "memory"); \
__ret; \
})