FRV: Add support for emulation of userspace atomic ops [try #2]

Use traps 120-126 to emulate atomic cmpxchg32, xchg32, and XOR-, OR-, AND-, SUB-
and ADD-to-memory operations for userspace.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 254 insertions, 1 deletions

diff --git a/arch/frv/kernel/entry-table.S b/arch/frv/kernel/entry-table.S
index d3b9253d862a..bf35f33e48c9 100644
--- a/arch/frv/kernel/entry-table.S
+++ b/arch/frv/kernel/entry-table.S
@@ -316,8 +316,14 @@ __trap_fixup_kernel_data_tlb_miss:
         .section        .trap.vector
         .org            TBR_TT_TRAP0 >> 2
         .long           system_call
-        .rept           126
+        .rept           119
         .long           __entry_unsupported_trap
         .endr
+
+        # userspace atomic op emulation, traps 120-126
+        .rept           7
+        .long           __entry_atomic_op
+        .endr
+        
         .org            TBR_TT_BREAK >> 2
         .long           __entry_debug_exception
diff --git a/arch/frv/kernel/entry.S b/arch/frv/kernel/entry.S
index f36d7f4a7c25..b8a4b94779b1 100644
--- a/arch/frv/kernel/entry.S
+++ b/arch/frv/kernel/entry.S
@@ -656,6 +656,26 @@ __entry_debug_exception:
 
 ###############################################################################
 #
+# handle atomic operation emulation for userspace
+#
+###############################################################################
+        .globl          __entry_atomic_op
+__entry_atomic_op:
+        LEDS            0x6012
+        sethi.p         %hi(atomic_operation),gr5
+        setlo           %lo(atomic_operation),gr5
+        movsg           esfr1,gr8
+        movsg           epcr0,gr9
+        movsg           esr0,gr10
+
+        # now that we've accessed the exception regs, we can enable exceptions
+        movsg           psr,gr4
+        ori             gr4,#PSR_ET,gr4
+        movgs           gr4,psr
+        jmpl            @(gr5,gr0)      ; call atomic_operation(esfr1,epcr0,esr0)
+
+###############################################################################
+#
 # handle media exception
 #
 ###############################################################################
diff --git a/arch/frv/kernel/traps.c b/arch/frv/kernel/traps.c
index 2e6098c85578..2f7e66877f3b 100644
--- a/arch/frv/kernel/traps.c
+++ b/arch/frv/kernel/traps.c
@@ -102,6 +102,233 @@ asmlinkage void illegal_instruction(unsigned long esfr1, unsigned long epcr0, un
 
 /*****************************************************************************/
 /*
+ * handle atomic operations with errors
+ * - arguments in gr8, gr9, gr10
+ * - original memory value placed in gr5
+ * - replacement memory value placed in gr9
+ */
+asmlinkage void atomic_operation(unsigned long esfr1, unsigned long epcr0,
+                                 unsigned long esr0)
+{
+        static DEFINE_SPINLOCK(atomic_op_lock);
+        unsigned long x, y, z, *p;
+        mm_segment_t oldfs;
+        siginfo_t info;
+        int ret;
+
+        y = 0;
+        z = 0;
+
+        oldfs = get_fs();
+        if (!user_mode(__frame))
+                set_fs(KERNEL_DS);
+
+        switch (__frame->tbr & TBR_TT) {
+                /* TIRA gr0,#120
+                 * u32 __atomic_user_cmpxchg32(u32 *ptr, u32 test, u32 new)
+                 */
+        case TBR_TT_ATOMIC_CMPXCHG32:
+                p = (unsigned long *) __frame->gr8;
+                x = __frame->gr9;
+                y = __frame->gr10;
+
+                for (;;) {
+                        ret = get_user(z, p);
+                        if (ret < 0)
+                                goto error;
+
+                        if (z != x)
+                                goto done;
+
+                        spin_lock_irq(&atomic_op_lock);
+
+                        if (__get_user(z, p) == 0) {
+                                if (z != x)
+                                        goto done2;
+
+                                if (__put_user(y, p) == 0)
+                                        goto done2;
+                                goto error2;
+                        }
+
+                        spin_unlock_irq(&atomic_op_lock);
+                }
+
+                /* TIRA gr0,#121
+                 * u32 __atomic_kernel_xchg32(void *v, u32 new)
+                 */
+        case TBR_TT_ATOMIC_XCHG32:
+                p = (unsigned long *) __frame->gr8;
+                y = __frame->gr9;
+
+                for (;;) {
+                        ret = get_user(z, p);
+                        if (ret < 0)
+                                goto error;
+
+                        spin_lock_irq(&atomic_op_lock);
+
+                        if (__get_user(z, p) == 0) {
+                                if (__put_user(y, p) == 0)
+                                        goto done2;
+                                goto error2;
+                        }
+
+                        spin_unlock_irq(&atomic_op_lock);
+                }
+
+                /* TIRA gr0,#122
+                 * ulong __atomic_kernel_XOR_return(ulong i, ulong *v)
+                 */
+        case TBR_TT_ATOMIC_XOR:
+                p = (unsigned long *) __frame->gr8;
+                x = __frame->gr9;
+
+                for (;;) {
+                        ret = get_user(z, p);
+                        if (ret < 0)
+                                goto error;
+
+                        spin_lock_irq(&atomic_op_lock);
+
+                        if (__get_user(z, p) == 0) {
+                                y = x ^ z;
+                                if (__put_user(y, p) == 0)
+                                        goto done2;
+                                goto error2;
+                        }
+
+                        spin_unlock_irq(&atomic_op_lock);
+                }
+
+                /* TIRA gr0,#123
+                 * ulong __atomic_kernel_OR_return(ulong i, ulong *v)
+                 */
+        case TBR_TT_ATOMIC_OR:
+                p = (unsigned long *) __frame->gr8;
+                x = __frame->gr9;
+
+                for (;;) {
+                        ret = get_user(z, p);
+                        if (ret < 0)
+                                goto error;
+
+                        spin_lock_irq(&atomic_op_lock);
+
+                        if (__get_user(z, p) == 0) {
+                                y = x ^ z;
+                                if (__put_user(y, p) == 0)
+                                        goto done2;
+                                goto error2;
+                        }
+
+                        spin_unlock_irq(&atomic_op_lock);
+                }
+
+                /* TIRA gr0,#124
+                 * ulong __atomic_kernel_AND_return(ulong i, ulong *v)
+                 */
+        case TBR_TT_ATOMIC_AND:
+                p = (unsigned long *) __frame->gr8;
+                x = __frame->gr9;
+
+                for (;;) {
+                        ret = get_user(z, p);
+                        if (ret < 0)
+                                goto error;
+
+                        spin_lock_irq(&atomic_op_lock);
+
+                        if (__get_user(z, p) == 0) {
+                                y = x & z;
+                                if (__put_user(y, p) == 0)
+                                        goto done2;
+                                goto error2;
+                        }
+
+                        spin_unlock_irq(&atomic_op_lock);
+                }
+
+                /* TIRA gr0,#125
+                 * int __atomic_user_sub_return(atomic_t *v, int i)
+                 */
+        case TBR_TT_ATOMIC_SUB:
+                p = (unsigned long *) __frame->gr8;
+                x = __frame->gr9;
+
+                for (;;) {
+                        ret = get_user(z, p);
+                        if (ret < 0)
+                                goto error;
+
+                        spin_lock_irq(&atomic_op_lock);
+
+                        if (__get_user(z, p) == 0) {
+                                y = z - x;
+                                if (__put_user(y, p) == 0)
+                                        goto done2;
+                                goto error2;
+                        }
+
+                        spin_unlock_irq(&atomic_op_lock);
+                }
+
+                /* TIRA gr0,#126
+                 * int __atomic_user_add_return(atomic_t *v, int i)
+                 */
+        case TBR_TT_ATOMIC_ADD:
+                p = (unsigned long *) __frame->gr8;
+                x = __frame->gr9;
+
+                for (;;) {
+                        ret = get_user(z, p);
+                        if (ret < 0)
+                                goto error;
+
+                        spin_lock_irq(&atomic_op_lock);
+
+                        if (__get_user(z, p) == 0) {
+                                y = z + x;
+                                if (__put_user(y, p) == 0)
+                                        goto done2;
+                                goto error2;
+                        }
+
+                        spin_unlock_irq(&atomic_op_lock);
+                }
+
+        default:
+                BUG();
+        }
+
+done2:
+        spin_unlock_irq(&atomic_op_lock);
+done:
+        if (!user_mode(__frame))
+                set_fs(oldfs);
+        __frame->gr5 = z;
+        __frame->gr9 = y;
+        return;
+
+error2:
+        spin_unlock_irq(&atomic_op_lock);
+error:
+        if (!user_mode(__frame))
+                set_fs(oldfs);
+        __frame->pc -= 4;
+
+        die_if_kernel("-- Atomic Op Error --\n");
+
+        info.si_signo   = SIGSEGV;
+        info.si_code    = SEGV_ACCERR;
+        info.si_errno   = 0;
+        info.si_addr    = (void *) __frame->pc;
+
+        force_sig_info(info.si_signo, &info, current);
+}
+
+/*****************************************************************************/
+/*
  *
  */
 asmlinkage void media_exception(unsigned long msr0, unsigned long msr1)