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authorMikael Pettersson <mikpe@it.uu.se>2013-03-08 18:03:53 +0400
committerGeert Uytterhoeven <geert@linux-m68k.org>2013-05-21 23:29:13 +0400
commite4f2dfbb5e92be4e46c0625f4f8eb101110f756f (patch)
treea9ccf764d085e484d16924c2624b61fb9b02d71a /arch/m68k
parentc7788792a5e7b0d5d7f96d0766b4cb6112d47d75 (diff)
downloadlinux-e4f2dfbb5e92be4e46c0625f4f8eb101110f756f.tar.xz
m68k: implement futex.h to support userspace robust futexes and PI mutexes
Linux/M68K currently doesn't support robust futexes or PI mutexes. The problem is that the futex code needs to perform certain ops (cmpxchg, set, add, or, andn, xor) atomically on user-space addresses, and M68K's lack of a futex.h causes those operations to be unsupported and disabled. This patch adds that support, but only for uniprocessor machines, which is adequate for M68K. For UP it's enough to disable preemption to ensure mutual exclusion (futexes don't need to care about other hardware agents), and the mandatory pagefault_disable() does just that. This patch is closely based on the one I co-wrote for UP ARM back in August 2008. The main change is that this patch uses the C get_user/put_user accessors instead of inline assembly code with exception table fixups. For non-MMU machines the new futex.h simply redirects to the generic futex.h, so there is no functional change for them. Tested on aranym with the glibc-2.17 test suite: no regressions, and a number of mutex/condvar test cases went from failing to succeeding (tst-mutexpi{5,5a,6,9}, tst-cond2[45], tst-robust[1-9], tst-robustpi[1-8]). Also tested with glibc-2.18 HEAD and a local glibc patch to enable PI mutexes: no regressions. Signed-off-by: Mikael Pettersson <mikpe@it.uu.se> Acked-by: Andreas Schwab <schwab@linux-m68k.org> [geert: Added removal of ""generic-y += futex.h"] Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Diffstat (limited to 'arch/m68k')
-rw-r--r--arch/m68k/include/asm/Kbuild1
-rw-r--r--arch/m68k/include/asm/futex.h94
2 files changed, 94 insertions, 1 deletions
diff --git a/arch/m68k/include/asm/Kbuild b/arch/m68k/include/asm/Kbuild
index c7933e41f10d..09d77a862da3 100644
--- a/arch/m68k/include/asm/Kbuild
+++ b/arch/m68k/include/asm/Kbuild
@@ -6,7 +6,6 @@ generic-y += device.h
generic-y += emergency-restart.h
generic-y += errno.h
generic-y += exec.h
-generic-y += futex.h
generic-y += hw_irq.h
generic-y += ioctl.h
generic-y += ipcbuf.h
diff --git a/arch/m68k/include/asm/futex.h b/arch/m68k/include/asm/futex.h
new file mode 100644
index 000000000000..bc868af10c96
--- /dev/null
+++ b/arch/m68k/include/asm/futex.h
@@ -0,0 +1,94 @@
+#ifndef _ASM_M68K_FUTEX_H
+#define _ASM_M68K_FUTEX_H
+
+#ifdef __KERNEL__
+#if !defined(CONFIG_MMU)
+#include <asm-generic/futex.h>
+#else /* CONFIG_MMU */
+
+#include <linux/futex.h>
+#include <linux/uaccess.h>
+#include <asm/errno.h>
+
+static inline int
+futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
+ u32 oldval, u32 newval)
+{
+ u32 val;
+
+ if (unlikely(get_user(val, uaddr) != 0))
+ return -EFAULT;
+
+ if (val == oldval && unlikely(put_user(newval, uaddr) != 0))
+ return -EFAULT;
+
+ *uval = val;
+
+ return 0;
+}
+
+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, ret;
+ u32 tmp;
+
+ if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
+ oparg = 1 << oparg;
+
+ pagefault_disable(); /* implies preempt_disable() */
+
+ ret = -EFAULT;
+ if (unlikely(get_user(oldval, uaddr) != 0))
+ goto out_pagefault_enable;
+
+ ret = 0;
+ tmp = oldval;
+
+ switch (op) {
+ case FUTEX_OP_SET:
+ tmp = oparg;
+ break;
+ case FUTEX_OP_ADD:
+ tmp += oparg;
+ break;
+ case FUTEX_OP_OR:
+ tmp |= oparg;
+ break;
+ case FUTEX_OP_ANDN:
+ tmp &= ~oparg;
+ break;
+ case FUTEX_OP_XOR:
+ tmp ^= oparg;
+ break;
+ default:
+ ret = -ENOSYS;
+ }
+
+ if (ret == 0 && unlikely(put_user(tmp, uaddr) != 0))
+ ret = -EFAULT;
+
+out_pagefault_enable:
+ pagefault_enable(); /* subsumes preempt_enable() */
+
+ if (ret == 0) {
+ 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;
+}
+
+#endif /* CONFIG_MMU */
+#endif /* __KERNEL__ */
+#endif /* _ASM_M68K_FUTEX_H */