3.18-stable review patch. If anyone has any objections, please let me know.
------------------
From: John David Anglin <dave.anglin@xxxxxxxx>
commit 45db07382a5c78b0c43b3b0002b63757fb60e873 upstream.
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@xxxxxxxx>
Signed-off-by: Helge Deller <deller@xxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/parisc/include/asm/ldcw.h | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)
--- 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; \
})
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