sh: Fix up xchg/cmpxchg corruption with gUSA RB.
gUSA special cases r15 for part of its login/out sequence, meaning that
any parameters need to be explicitly prohibited from accidentally being
assigned that particular register, and the compiler ultimately needs to
use a temporary instead.
Certain configurations have begun generating code paths that do indeed
get allocated r15, resulting in immediate corruption of the exchanged
value. This was observed in (amongst others) exit_mm() code generation
where the xchg_u32 call was immediately corrupting a structure address.
As this is a general gUSA restriction, the rest of the users likewise
need to be updated to ensure sensible constraints.
References: https://bugzilla.stlinux.com/show_bug.cgi?id=11229
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@st.com>
Reviewed-by: Stuart Menefy <stuart.menefy@st.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
diff --git a/arch/sh/include/asm/cmpxchg-grb.h b/arch/sh/include/asm/cmpxchg-grb.h
index 4676bf5..f848dec 100644
--- a/arch/sh/include/asm/cmpxchg-grb.h
+++ b/arch/sh/include/asm/cmpxchg-grb.h
@@ -15,8 +15,9 @@
" mov.l %2, @%1 \n\t" /* store new value */
"1: mov r1, r15 \n\t" /* LOGOUT */
: "=&r" (retval),
- "+r" (m)
- : "r" (val)
+ "+r" (m),
+ "+r" (val) /* inhibit r15 overloading */
+ :
: "memory", "r0", "r1");
return retval;
@@ -36,8 +37,9 @@
" mov.b %2, @%1 \n\t" /* store new value */
"1: mov r1, r15 \n\t" /* LOGOUT */
: "=&r" (retval),
- "+r" (m)
- : "r" (val)
+ "+r" (m),
+ "+r" (val) /* inhibit r15 overloading */
+ :
: "memory" , "r0", "r1");
return retval;
@@ -54,13 +56,14 @@
" nop \n\t"
" mov r15, r1 \n\t" /* r1 = saved sp */
" mov #-8, r15 \n\t" /* LOGIN */
- " mov.l @%1, %0 \n\t" /* load old value */
- " cmp/eq %0, %2 \n\t"
+ " mov.l @%3, %0 \n\t" /* load old value */
+ " cmp/eq %0, %1 \n\t"
" bf 1f \n\t" /* if not equal */
- " mov.l %3, @%1 \n\t" /* store new value */
+ " mov.l %2, @%3 \n\t" /* store new value */
"1: mov r1, r15 \n\t" /* LOGOUT */
- : "=&r" (retval)
- : "r" (m), "r" (old), "r" (new)
+ : "=&r" (retval),
+ "+r" (old), "+r" (new) /* old or new can be r15 */
+ : "r" (m)
: "memory" , "r0", "r1", "t");
return retval;