xen: arm64: xchg and cmpxchg

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Tim Deegan <tim@xen.org>

1 files changed, 115 insertions, 0 deletions

diff --git a/xen/include/asm-arm/arm32/system.h b/xen/include/asm-arm/arm32/system.h
index 13800844b2..276e36343d 100644
--- a/xen/include/asm-arm/arm32/system.h
+++ b/xen/include/asm-arm/arm32/system.h
@@ -18,6 +18,121 @@
 #define smp_rmb()       rmb()
 #define smp_wmb()       wmb()
 
+extern void __bad_xchg(volatile void *, int);
+
+static inline unsigned long __xchg(unsigned long x, volatile void *ptr, int size)
+{
+        unsigned long ret;
+        unsigned int tmp;
+
+        smp_mb();
+
+        switch (size) {
+        case 1:
+                asm volatile("@ __xchg1\n"
+                "1:     ldrexb  %0, [%3]\n"
+                "       strexb  %1, %2, [%3]\n"
+                "       teq     %1, #0\n"
+                "       bne     1b"
+                        : "=&r" (ret), "=&r" (tmp)
+                        : "r" (x), "r" (ptr)
+                        : "memory", "cc");
+                break;
+        case 4:
+                asm volatile("@ __xchg4\n"
+                "1:     ldrex   %0, [%3]\n"
+                "       strex   %1, %2, [%3]\n"
+                "       teq     %1, #0\n"
+                "       bne     1b"
+                        : "=&r" (ret), "=&r" (tmp)
+                        : "r" (x), "r" (ptr)
+                        : "memory", "cc");
+                break;
+        default:
+                __bad_xchg(ptr, size), ret = 0;
+                break;
+        }
+        smp_mb();
+
+        return ret;
+}
+
+/*
+ * Atomic compare and exchange.  Compare OLD with MEM, if identical,
+ * store NEW in MEM.  Return the initial value in MEM.  Success is
+ * indicated by comparing RETURN with OLD.
+ */
+
+extern void __bad_cmpxchg(volatile void *ptr, int size);
+
+static always_inline unsigned long __cmpxchg(
+    volatile void *ptr, unsigned long old, unsigned long new, int size)
+{
+    unsigned long /*long*/ oldval, res;
+
+    switch (size) {
+    case 1:
+        do {
+            asm volatile("@ __cmpxchg1\n"
+                         "       ldrexb  %1, [%2]\n"
+                         "       mov     %0, #0\n"
+                         "       teq     %1, %3\n"
+                         "       strexbeq %0, %4, [%2]\n"
+                         : "=&r" (res), "=&r" (oldval)
+                         : "r" (ptr), "Ir" (old), "r" (new)
+                         : "memory", "cc");
+        } while (res);
+        break;
+    case 2:
+        do {
+            asm volatile("@ __cmpxchg2\n"
+                         "       ldrexh  %1, [%2]\n"
+                         "       mov     %0, #0\n"
+                         "       teq     %1, %3\n"
+                         "       strexheq %0, %4, [%2]\n"
+                         : "=&r" (res), "=&r" (oldval)
+                         : "r" (ptr), "Ir" (old), "r" (new)
+                         : "memory", "cc");
+        } while (res);
+        break;
+    case 4:
+        do {
+            asm volatile("@ __cmpxchg4\n"
+                         "       ldrex   %1, [%2]\n"
+                         "       mov     %0, #0\n"
+                         "       teq     %1, %3\n"
+                         "       strexeq %0, %4, [%2]\n"
+                         : "=&r" (res), "=&r" (oldval)
+                         : "r" (ptr), "Ir" (old), "r" (new)
+                         : "memory", "cc");
+        } while (res);
+        break;
+#if 0
+    case 8:
+        do {
+            asm volatile("@ __cmpxchg8\n"
+                         "       ldrexd   %1, [%2]\n"
+                         "       mov      %0, #0\n"
+                         "       teq      %1, %3\n"
+                         "       strexdeq %0, %4, [%2]\n"
+                         : "=&r" (res), "=&r" (oldval)
+                         : "r" (ptr), "Ir" (old), "r" (new)
+                         : "memory", "cc");
+        } while (res);
+        break;
+#endif
+    default:
+        __bad_cmpxchg(ptr, size);
+        oldval = 0;
+    }
+
+    return oldval;
+}
+
+#define cmpxchg(ptr,o,n)                                                \
+    ((__typeof__(*(ptr)))__cmpxchg((ptr),(unsigned long)(o),            \
+                                   (unsigned long)(n),sizeof(*(ptr))))
+
 #endif
 /*
  * Local variables: