[patch 5/6] lightweight robust futexes: i386

From: Ingo Molnar
Date: Tue Feb 21 2006 - 03:47:13 EST



i386: add the futex_atomic_cmpxchg_inuser() assembly implementation, and
wire up the new syscalls.

Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Arjan van de Ven <arjan@xxxxxxxxxxxxx>
Acked-by: Ulrich Drepper <drepper@xxxxxxxxxx>

----

arch/i386/kernel/syscall_table.S | 2 ++
include/asm-i386/futex.h | 23 ++++++++++++++++++++++-
include/asm-i386/unistd.h | 4 +++-
3 files changed, 27 insertions(+), 2 deletions(-)

Index: linux/arch/i386/kernel/syscall_table.S
===================================================================
--- linux.orig/arch/i386/kernel/syscall_table.S
+++ linux/arch/i386/kernel/syscall_table.S
@@ -310,3 +310,5 @@ ENTRY(sys_call_table)
.long sys_pselect6
.long sys_ppoll
.long sys_unshare /* 310 */
+ .long sys_set_robust_list
+ .long sys_get_robust_list
Index: linux/include/asm-i386/futex.h
===================================================================
--- linux.orig/include/asm-i386/futex.h
+++ linux/include/asm-i386/futex.h
@@ -107,7 +107,28 @@ futex_atomic_op_inuser (int encoded_op,
static inline int
futex_atomic_cmpxchg_inuser(int __user *uaddr, int oldval, int newval)
{
- return -ENOSYS;
+ if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))
+ return -EFAULT;
+
+ __asm__ __volatile__(
+ "1: " LOCK_PREFIX "cmpxchgl %3, %1 \n"
+
+ "2: .section .fixup, \"ax\" \n"
+ "3: mov %2, %0 \n"
+ " jmp 2b \n"
+ " .previous \n"
+
+ " .section __ex_table, \"a\" \n"
+ " .align 8 \n"
+ " .long 1b,3b \n"
+ " .previous \n"
+
+ : "=a" (oldval), "=m" (*uaddr)
+ : "i" (-EFAULT), "r" (newval), "0" (oldval)
+ : "memory"
+ );
+
+ return oldval;
}

#endif
Index: linux/include/asm-i386/unistd.h
===================================================================
--- linux.orig/include/asm-i386/unistd.h
+++ linux/include/asm-i386/unistd.h
@@ -316,8 +316,10 @@
#define __NR_pselect6 308
#define __NR_ppoll 309
#define __NR_unshare 310
+#define __NR_set_robust_list 311
+#define __NR_get_robust_list 312

-#define NR_syscalls 311
+#define NR_syscalls 313

/*
* user-visible error numbers are in the range -1 - -128: see
-
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