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futex.c

/* futex.c: futex operations
 *
 * Copyright (C) 2005 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/futex.h>
#include <linux/uaccess.h>
#include <asm/futex.h>
#include <asm/errno.h>

/*
 * the various futex operations; MMU fault checking is ignored under no-MMU
 * conditions
 */
static inline int atomic_futex_op_xchg_set(int oparg, int __user *uaddr, int *_oldval)
{
      int oldval, ret;

      asm("0:                                   \n"
          " orcc        gr0,gr0,gr0,icc3  \n"   /* set ICC3.Z */
          " ckeq        icc3,cc7          \n"
          "1:     ld.p        %M0,%1                  \n"   /* LD.P/ORCR must be atomic */
          " orcr        cc7,cc7,cc3       \n"   /* set CC3 to true */
          "2:     cst.p       %3,%M0            ,cc3,#1     \n"
          " corcc       gr29,gr29,gr0     ,cc3,#1     \n"   /* clear ICC3.Z if store happens */
          " beq         icc3,#0,0b        \n"
          " setlos            0,%2              \n"
          "3:                                   \n"
          ".subsection 2                        \n"
          "4:     setlos            %5,%2             \n"
          " bra         3b                \n"
          ".previous                            \n"
          ".section __ex_table,\"a\"                  \n"
          " .balign           8                 \n"
          " .long       1b,4b             \n"
          " .long       2b,4b             \n"
          ".previous"
          : "+U"(*uaddr), "=&r"(oldval), "=&r"(ret), "=r"(oparg)
          : "3"(oparg), "i"(-EFAULT)
          : "memory", "cc7", "cc3", "icc3"
          );

      *_oldval = oldval;
      return ret;
}

static inline int atomic_futex_op_xchg_add(int oparg, int __user *uaddr, int *_oldval)
{
      int oldval, ret;

      asm("0:                                   \n"
          " orcc        gr0,gr0,gr0,icc3  \n"   /* set ICC3.Z */
          " ckeq        icc3,cc7          \n"
          "1:     ld.p        %M0,%1                  \n"   /* LD.P/ORCR must be atomic */
          " orcr        cc7,cc7,cc3       \n"   /* set CC3 to true */
          " add         %1,%3,%3          \n"
          "2:     cst.p       %3,%M0            ,cc3,#1     \n"
          " corcc       gr29,gr29,gr0     ,cc3,#1     \n"   /* clear ICC3.Z if store happens */
          " beq         icc3,#0,0b        \n"
          " setlos            0,%2              \n"
          "3:                                   \n"
          ".subsection 2                        \n"
          "4:     setlos            %5,%2             \n"
          " bra         3b                \n"
          ".previous                            \n"
          ".section __ex_table,\"a\"                  \n"
          " .balign           8                 \n"
          " .long       1b,4b             \n"
          " .long       2b,4b             \n"
          ".previous"
          : "+U"(*uaddr), "=&r"(oldval), "=&r"(ret), "=r"(oparg)
          : "3"(oparg), "i"(-EFAULT)
          : "memory", "cc7", "cc3", "icc3"
          );

      *_oldval = oldval;
      return ret;
}

static inline int atomic_futex_op_xchg_or(int oparg, int __user *uaddr, int *_oldval)
{
      int oldval, ret;

      asm("0:                                   \n"
          " orcc        gr0,gr0,gr0,icc3  \n"   /* set ICC3.Z */
          " ckeq        icc3,cc7          \n"
          "1:     ld.p        %M0,%1                  \n"   /* LD.P/ORCR must be atomic */
          " orcr        cc7,cc7,cc3       \n"   /* set CC3 to true */
          " or          %1,%3,%3          \n"
          "2:     cst.p       %3,%M0            ,cc3,#1     \n"
          " corcc       gr29,gr29,gr0     ,cc3,#1     \n"   /* clear ICC3.Z if store happens */
          " beq         icc3,#0,0b        \n"
          " setlos            0,%2              \n"
          "3:                                   \n"
          ".subsection 2                        \n"
          "4:     setlos            %5,%2             \n"
          " bra         3b                \n"
          ".previous                            \n"
          ".section __ex_table,\"a\"                  \n"
          " .balign           8                 \n"
          " .long       1b,4b             \n"
          " .long       2b,4b             \n"
          ".previous"
          : "+U"(*uaddr), "=&r"(oldval), "=&r"(ret), "=r"(oparg)
          : "3"(oparg), "i"(-EFAULT)
          : "memory", "cc7", "cc3", "icc3"
          );

      *_oldval = oldval;
      return ret;
}

static inline int atomic_futex_op_xchg_and(int oparg, int __user *uaddr, int *_oldval)
{
      int oldval, ret;

      asm("0:                                   \n"
          " orcc        gr0,gr0,gr0,icc3  \n"   /* set ICC3.Z */
          " ckeq        icc3,cc7          \n"
          "1:     ld.p        %M0,%1                  \n"   /* LD.P/ORCR must be atomic */
          " orcr        cc7,cc7,cc3       \n"   /* set CC3 to true */
          " and         %1,%3,%3          \n"
          "2:     cst.p       %3,%M0            ,cc3,#1     \n"
          " corcc       gr29,gr29,gr0     ,cc3,#1     \n"   /* clear ICC3.Z if store happens */
          " beq         icc3,#0,0b        \n"
          " setlos            0,%2              \n"
          "3:                                   \n"
          ".subsection 2                        \n"
          "4:     setlos            %5,%2             \n"
          " bra         3b                \n"
          ".previous                            \n"
          ".section __ex_table,\"a\"                  \n"
          " .balign           8                 \n"
          " .long       1b,4b             \n"
          " .long       2b,4b             \n"
          ".previous"
          : "+U"(*uaddr), "=&r"(oldval), "=&r"(ret), "=r"(oparg)
          : "3"(oparg), "i"(-EFAULT)
          : "memory", "cc7", "cc3", "icc3"
          );

      *_oldval = oldval;
      return ret;
}

static inline int atomic_futex_op_xchg_xor(int oparg, int __user *uaddr, int *_oldval)
{
      int oldval, ret;

      asm("0:                                   \n"
          " orcc        gr0,gr0,gr0,icc3  \n"   /* set ICC3.Z */
          " ckeq        icc3,cc7          \n"
          "1:     ld.p        %M0,%1                  \n"   /* LD.P/ORCR must be atomic */
          " orcr        cc7,cc7,cc3       \n"   /* set CC3 to true */
          " xor         %1,%3,%3          \n"
          "2:     cst.p       %3,%M0            ,cc3,#1     \n"
          " corcc       gr29,gr29,gr0     ,cc3,#1     \n"   /* clear ICC3.Z if store happens */
          " beq         icc3,#0,0b        \n"
          " setlos            0,%2              \n"
          "3:                                   \n"
          ".subsection 2                        \n"
          "4:     setlos            %5,%2             \n"
          " bra         3b                \n"
          ".previous                            \n"
          ".section __ex_table,\"a\"                  \n"
          " .balign           8                 \n"
          " .long       1b,4b             \n"
          " .long       2b,4b             \n"
          ".previous"
          : "+U"(*uaddr), "=&r"(oldval), "=&r"(ret), "=r"(oparg)
          : "3"(oparg), "i"(-EFAULT)
          : "memory", "cc7", "cc3", "icc3"
          );

      *_oldval = oldval;
      return ret;
}

/*****************************************************************************/
/*
 * do the futex operations
 */
int futex_atomic_op_inuser(int encoded_op, int __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();

      switch (op) {
      case FUTEX_OP_SET:
            ret = atomic_futex_op_xchg_set(oparg, uaddr, &oldval);
            break;
      case FUTEX_OP_ADD:
            ret = atomic_futex_op_xchg_add(oparg, uaddr, &oldval);
            break;
      case FUTEX_OP_OR:
            ret = atomic_futex_op_xchg_or(oparg, uaddr, &oldval);
            break;
      case FUTEX_OP_ANDN:
            ret = atomic_futex_op_xchg_and(~oparg, uaddr, &oldval);
            break;
      case FUTEX_OP_XOR:
            ret = atomic_futex_op_xchg_xor(oparg, uaddr, &oldval);
            break;
      default:
            ret = -ENOSYS;
            break;
      }

      pagefault_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; break;
            }
      }

      return ret;

} /* end futex_atomic_op_inuser() */

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