ARC: Futex support

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

1 files changed, 151 insertions, 0 deletions

diff --git a/arch/arc/include/asm/futex.h b/arch/arc/include/asm/futex.h
new file mode 100644
index 000000000000..4dc64ddebece
--- /dev/null
+++ b/arch/arc/include/asm/futex.h
@@ -0,0 +1,151 @@
+/*
+ * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
+ *
+ * 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.
+ *
+ * Vineetg: August 2010: From Android kernel work
+ */
+
+#ifndef _ASM_FUTEX_H
+#define _ASM_FUTEX_H
+
+#include <linux/futex.h>
+#include <linux/preempt.h>
+#include <linux/uaccess.h>
+#include <asm/errno.h>
+
+#define __futex_atomic_op(insn, ret, oldval, uaddr, oparg)\
+                                                        \
+        __asm__ __volatile__(                           \
+        "1:     ld  %1, [%2]                    \n"     \
+                insn                            "\n"    \
+        "2:     st  %0, [%2]                    \n"     \
+        "       mov %0, 0                       \n"     \
+        "3:                                     \n"     \
+        "       .section .fixup,\"ax\"          \n"     \
+        "       .align  4                       \n"     \
+        "4:     mov %0, %4                      \n"     \
+        "       b   3b                          \n"     \
+        "       .previous                       \n"     \
+        "       .section __ex_table,\"a\"       \n"     \
+        "       .align  4                       \n"     \
+        "       .word   1b, 4b                  \n"     \
+        "       .word   2b, 4b                  \n"     \
+        "       .previous                       \n"     \
+                                                        \
+        : "=&r" (ret), "=&r" (oldval)                   \
+        : "r" (uaddr), "r" (oparg), "ir" (-EFAULT)      \
+        : "cc", "memory")
+
+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;
+
+        if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
+                oparg = 1 << oparg;
+
+        if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))
+                return -EFAULT;
+
+        pagefault_disable();    /* implies preempt_disable() */
+
+        switch (op) {
+        case FUTEX_OP_SET:
+                __futex_atomic_op("mov %0, %3", ret, oldval, uaddr, oparg);
+                break;
+        case FUTEX_OP_ADD:
+                __futex_atomic_op("add %0, %1, %3", ret, oldval, uaddr, oparg);
+                break;
+        case FUTEX_OP_OR:
+                __futex_atomic_op("or  %0, %1, %3", ret, oldval, uaddr, oparg);
+                break;
+        case FUTEX_OP_ANDN:
+                __futex_atomic_op("bic %0, %1, %3", ret, oldval, uaddr, oparg);
+                break;
+        case FUTEX_OP_XOR:
+                __futex_atomic_op("xor %0, %1, %3", ret, oldval, uaddr, 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;
+}
+
+/* Compare-xchg with preemption disabled.
+ *  Notes:
+ *      -Best-Effort: Exchg happens only if compare succeeds.
+ *          If compare fails, returns; leaving retry/looping to upper layers
+ *      -successful cmp-xchg: return orig value in @addr (same as cmp val)
+ *      -Compare fails: return orig value in @addr
+ *      -user access r/w fails: return -EFAULT
+ */
+static inline int
+futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, u32 oldval,
+                                        u32 newval)
+{
+        u32 val;
+
+        if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))
+                return -EFAULT;
+
+        pagefault_disable();    /* implies preempt_disable() */
+
+        /* TBD : can use llock/scond */
+        __asm__ __volatile__(
+        "1:     ld    %0, [%3]  \n"
+        "       brne  %0, %1, 3f        \n"
+        "2:     st    %2, [%3]  \n"
+        "3:     \n"
+        "       .section .fixup,\"ax\"  \n"
+        "4:     mov %0, %4      \n"
+        "       b   3b  \n"
+        "       .previous       \n"
+        "       .section __ex_table,\"a\"       \n"
+        "       .align  4       \n"
+        "       .word   1b, 4b  \n"
+        "       .word   2b, 4b  \n"
+        "       .previous\n"
+        : "=&r"(val)
+        : "r"(oldval), "r"(newval), "r"(uaddr), "ir"(-EFAULT)
+        : "cc", "memory");
+
+        pagefault_enable();     /* subsumes preempt_enable() */
+
+        *uval = val;
+        return val;
+}
+
+#endif