[PARISC] Use FIXUP_BRANCH_CLOBBER to asm clobber list

Joel Soete noticed correctly that the fixup's clobbers must be listed
as the ASM clobbers. FIXUP_BRANCH in unaligned.c has a new macro which
lists all the clobbers in the fixup, we use this throughout the file
to simplify the process of listing clobbers in the future.

A missing "r1" clobber is added to our uaccess.h for the 64-bit
__put_kernel_asm. Interestingly this is a pretty serious bug since gcc
generates pretty good use of r1 as a temporary and the uses of
__put_kernel_asm are varied and dangerous if r1 is scratched during
an invalid write.

Signed-off-by: Joel Soete <soete.joel@tiscali.be>
Signed-off-by: Carlos O'Donell <carlos@parisc-linux.org>
Signed-off-by: Kyle McMartin <kyle@parisc-linux.org>

1 files changed, 7 insertions, 2 deletions

diff --git a/include/asm-parisc/uaccess.h b/include/asm-parisc/uaccess.h
index f6c417c8c484..d973e8b3466c 100644
--- a/include/asm-parisc/uaccess.h
+++ b/include/asm-parisc/uaccess.h
@@ -172,7 +172,11 @@ struct exception_data {
 /*
  * The "__put_user/kernel_asm()" macros tell gcc they read from memory
  * instead of writing. This is because they do not write to any memory
- * gcc knows about, so there are no aliasing issues.
+ * gcc knows about, so there are no aliasing issues. These macros must
+ * also be aware that "fixup_put_user_skip_[12]" are executed in the
+ * context of the fault, and any registers used there must be listed
+ * as clobbers. In this case only "r1" is used by the current routines.
+ * r8/r9 are already listed as err/val.
  */
 
 #ifdef __LP64__
@@ -183,7 +187,8 @@ struct exception_data {
                 "\t.dword\t1b,fixup_put_user_skip_1\n"      \
                 "\t.previous"                               \
                 : "=r"(__pu_err)                            \
-                : "r"(ptr), "r"(x), "0"(__pu_err))
+                : "r"(ptr), "r"(x), "0"(__pu_err)           \
+                : "r1")
 
 #define __put_user_asm(stx,x,ptr)                           \
         __asm__ __volatile__ (                              \