arm64: Atomic operations

This patch introduces the atomic, mutex and futex operations. Many
atomic operations use the load-acquire and store-release operations
which imply barriers, avoiding the need for explicit DMB.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
Acked-by: Olof Johansson <olof@lixom.net>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>

1 files changed, 136 insertions, 0 deletions

diff --git a/arch/arm64/include/asm/futex.h b/arch/arm64/include/asm/futex.h
new file mode 100644
index 000000000000..3468ae8439fa
--- /dev/null
+++ b/arch/arm64/include/asm/futex.h
@@ -0,0 +1,136 @@
+/*
+ * Copyright (C) 2012 ARM Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#ifndef __ASM_FUTEX_H
+#define __ASM_FUTEX_H
+
+#ifdef __KERNEL__
+
+#include <linux/futex.h>
+#include <linux/uaccess.h>
+#include <asm/errno.h>
+
+#define __futex_atomic_op(insn, ret, oldval, uaddr, tmp, oparg)         \
+        asm volatile(                                                   \
+"1:     ldaxr   %w1, %2\n"                                              \
+        insn "\n"                                                       \
+"2:     stlxr   %w3, %w0, %2\n"                                         \
+"       cbnz    %w3, 1b\n"                                              \
+"3:\n"                                                                  \
+"       .pushsection .fixup,\"ax\"\n"                                   \
+"4:     mov     %w0, %w5\n"                                             \
+"       b       3b\n"                                                   \
+"       .popsection\n"                                                  \
+"       .pushsection __ex_table,\"a\"\n"                                \
+"       .align  3\n"                                                    \
+"       .quad   1b, 4b, 2b, 4b\n"                                       \
+"       .popsection\n"                                                  \
+        : "=&r" (ret), "=&r" (oldval), "+Q" (*uaddr), "=&r" (tmp)       \
+        : "r" (oparg), "Ir" (-EFAULT)                                   \
+        : "cc")
+
+static inline int
+futex_atomic_op_inuser (int encoded_op, u32 __user *uaddr)
+{
+        int op = (encoded_op >> 28) & 7;
+        int cmp = (encoded_op >> 24) & 15;
+        int oparg = (encoded_op << 8) >> 20;
+        int cmparg = (encoded_op << 20) >> 20;
+        int oldval = 0, ret, tmp;
+
+        if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
+                oparg = 1 << oparg;
+
+        if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
+                return -EFAULT;
+
+        pagefault_disable();    /* implies preempt_disable() */
+
+        switch (op) {
+        case FUTEX_OP_SET:
+                __futex_atomic_op("mov  %w0, %w4",
+                                  ret, oldval, uaddr, tmp, oparg);
+                break;
+        case FUTEX_OP_ADD:
+                __futex_atomic_op("add  %w0, %w1, %w4",
+                                  ret, oldval, uaddr, tmp, oparg);
+                break;
+        case FUTEX_OP_OR:
+                __futex_atomic_op("orr  %w0, %w1, %w4",
+                                  ret, oldval, uaddr, tmp, oparg);
+                break;
+        case FUTEX_OP_ANDN:
+                __futex_atomic_op("and  %w0, %w1, %w4",
+                                  ret, oldval, uaddr, tmp, ~oparg);
+                break;
+        case FUTEX_OP_XOR:
+                __futex_atomic_op("eor  %w0, %w1, %w4",
+                                  ret, oldval, uaddr, tmp, oparg);
+                break;
+        default:
+                ret = -ENOSYS;
+        }
+
+        pagefault_enable();     /* subsumes preempt_enable() */
+
+        if (!ret) {
+                switch (cmp) {
+                case FUTEX_OP_CMP_EQ: ret = (oldval == cmparg); break;
+                case FUTEX_OP_CMP_NE: ret = (oldval != cmparg); break;
+                case FUTEX_OP_CMP_LT: ret = (oldval < cmparg); break;
+                case FUTEX_OP_CMP_GE: ret = (oldval >= cmparg); break;
+                case FUTEX_OP_CMP_LE: ret = (oldval <= cmparg); break;
+                case FUTEX_OP_CMP_GT: ret = (oldval > cmparg); break;
+                default: ret = -ENOSYS;
+                }
+        }
+        return ret;
+}
+
+static inline int
+futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
+                              u32 oldval, u32 newval)
+{
+        int ret = 0;
+        u32 val, tmp;
+
+        if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
+                return -EFAULT;
+
+        asm volatile("// futex_atomic_cmpxchg_inatomic\n"
+"1:     ldaxr   %w1, %2\n"
+"       sub     %w3, %w1, %w4\n"
+"       cbnz    %w3, 3f\n"
+"2:     stlxr   %w3, %w5, %2\n"
+"       cbnz    %w3, 1b\n"
+"3:\n"
+"       .pushsection .fixup,\"ax\"\n"
+"4:     mov     %w0, %w6\n"
+"       b       3b\n"
+"       .popsection\n"
+"       .pushsection __ex_table,\"a\"\n"
+"       .align  3\n"
+"       .quad   1b, 4b, 2b, 4b\n"
+"       .popsection\n"
+        : "+r" (ret), "=&r" (val), "+Q" (*uaddr), "=&r" (tmp)
+        : "r" (oldval), "r" (newval), "Ir" (-EFAULT)
+        : "cc", "memory");
+
+        *uval = val;
+        return ret;
+}
+
+#endif /* __KERNEL__ */
+#endif /* __ASM_FUTEX_H */