sh: nmi_debug support.

This implements support for NMI debugging that was shamelessly copied
from the avr32 port. A bit of special magic is needed in the interrupt
exception path given that the NMI exception handler is stubbed in to the
regular exception handling table despite being reported in INTEVT. So we
mangle the lookup and kick off an EXPEVT-style exception dispatch from
the INTEVT path for exceptions that do_IRQ() has no chance of handling.
As a result, we also drop the evt2irq() conversion from the do_IRQ() path
and just do it in assembly.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

9 files changed, 133 insertions, 9 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 7936b801fe6a..76c355214dc3 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1514,7 +1514,7 @@ and is between 256 and 4096 characters. It is defined in the file
                         of returning the full 64-bit number.
                         The default is to return 64-bit inode numbers.
 
-        nmi_debug=      [KNL,AVR32] Specify one or more actions to take
+        nmi_debug=      [KNL,AVR32,SH] Specify one or more actions to take
                         when a NMI is triggered.
                         Format: [state][,regs][,debounce][,die]
 
diff --git a/arch/sh/include/asm/kdebug.h b/arch/sh/include/asm/kdebug.h
index 0b9f896f203c..985219f9759e 100644
--- a/arch/sh/include/asm/kdebug.h
+++ b/arch/sh/include/asm/kdebug.h
@@ -4,6 +4,7 @@
 /* Grossly misnamed. */
 enum die_val {
         DIE_TRAP,
+        DIE_NMI,
         DIE_OOPS,
 };
 
diff --git a/arch/sh/include/asm/system.h b/arch/sh/include/asm/system.h
index 6b272238a46e..b5c5acdc8c0e 100644
--- a/arch/sh/include/asm/system.h
+++ b/arch/sh/include/asm/system.h
@@ -169,7 +169,7 @@ BUILD_TRAP_HANDLER(breakpoint);
 BUILD_TRAP_HANDLER(singlestep);
 BUILD_TRAP_HANDLER(fpu_error);
 BUILD_TRAP_HANDLER(fpu_state_restore);
-BUILD_TRAP_HANDLER(unwinder);
+BUILD_TRAP_HANDLER(nmi);
 
 #ifdef CONFIG_BUG
 extern void handle_BUG(struct pt_regs *);
diff --git a/arch/sh/kernel/Makefile b/arch/sh/kernel/Makefile
index f37cf02ad9be..a2d0a40f3848 100644
--- a/arch/sh/kernel/Makefile
+++ b/arch/sh/kernel/Makefile
@@ -10,9 +10,10 @@ CFLAGS_REMOVE_ftrace.o = -pg
 endif
 
 obj-y   := debugtraps.o dumpstack.o idle.o io.o io_generic.o irq.o      \
-           machvec.o process_$(BITS).o ptrace_$(BITS).o setup.o         \
-           signal_$(BITS).o sys_sh.o sys_sh$(BITS).o syscalls_$(BITS).o \
-           time.o topology.o traps.o traps_$(BITS).o unwinder.o
+           machvec.o nmi_debug.o process_$(BITS).o ptrace_$(BITS).o     \
+           setup.o signal_$(BITS).o sys_sh.o sys_sh$(BITS).o            \
+           syscalls_$(BITS).o time.o topology.o traps.o                 \
+           traps_$(BITS).o unwinder.o
 
 obj-y                           += cpu/
 obj-$(CONFIG_VSYSCALL)          += vsyscall/
diff --git a/arch/sh/kernel/cpu/sh3/entry.S b/arch/sh/kernel/cpu/sh3/entry.S
index aebd33d18ff7..d1142d365925 100644
--- a/arch/sh/kernel/cpu/sh3/entry.S
+++ b/arch/sh/kernel/cpu/sh3/entry.S
@@ -532,7 +532,33 @@ ENTRY(handle_interrupt)
         mov.l   2f, r4
         mov.l   3f, r9
         mov.l   @r4, r4         ! pass INTEVT vector as arg0
+
+        shlr2   r4
+        shlr    r4
+        mov     r4, r0          ! save vector->jmp table offset for later
+
+        shlr2   r4              ! vector to IRQ# conversion
+        add     #-0x10, r4
+
+        cmp/pz  r4              ! is it a valid IRQ?
+        bt      10f
+
+        /*
+         * We got here as a result of taking the INTEVT path for something
+         * that isn't a valid hard IRQ, therefore we bypass the do_IRQ()
+         * path and special case the event dispatch instead.  This is the
+         * expected path for the NMI (and any other brilliantly implemented
+         * exception), which effectively wants regular exception dispatch
+         * but is unfortunately reported through INTEVT rather than
+         * EXPEVT.  Grr.
+         */
+        mov.l   6f, r9
+        mov.l   @(r0, r9), r9
         jmp     @r9
+         mov    r15, r8         ! trap handlers take saved regs in r8
+
+10:
+        jmp     @r9             ! Off to do_IRQ() we go.
          mov    r15, r5         ! pass saved registers as arg1
 
 ENTRY(exception_none)
diff --git a/arch/sh/kernel/cpu/sh3/ex.S b/arch/sh/kernel/cpu/sh3/ex.S
index e5a0de39a2db..46610c35c232 100644
--- a/arch/sh/kernel/cpu/sh3/ex.S
+++ b/arch/sh/kernel/cpu/sh3/ex.S
@@ -48,9 +48,7 @@ ENTRY(exception_handling_table)
         .long   system_call     ! Unconditional Trap     /* 160 */
         .long   exception_error ! reserved_instruction (filled by trap_init) /* 180 */
         .long   exception_error ! illegal_slot_instruction (filled by trap_init) /*1A0*/
-ENTRY(nmi_slot)
-        .long   kgdb_handle_exception   /* 1C0 */       ! Allow trap to debugger
-ENTRY(user_break_point_trap)
+        .long   nmi_trap_handler        /* 1C0 */       ! Allow trap to debugger
         .long   break_point_trap        /* 1E0 */
 
         /*
diff --git a/arch/sh/kernel/irq.c b/arch/sh/kernel/irq.c
index d1053392e287..60f8af4497c7 100644
--- a/arch/sh/kernel/irq.c
+++ b/arch/sh/kernel/irq.c
@@ -114,7 +114,7 @@ asmlinkage int do_IRQ(unsigned int irq, struct pt_regs *regs)
 #endif
 
         irq_enter();
-        irq = irq_demux(evt2irq(irq));
+        irq = irq_demux(irq);
 
 #ifdef CONFIG_IRQSTACKS
         curctx = (union irq_ctx *)current_thread_info();
diff --git a/arch/sh/kernel/nmi_debug.c b/arch/sh/kernel/nmi_debug.c
new file mode 100644
index 000000000000..ff0abbd1e652
--- /dev/null
+++ b/arch/sh/kernel/nmi_debug.c
@@ -0,0 +1,77 @@
+/*
+ * Copyright (C) 2007 Atmel Corporation
+ *
+ * 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.
+ */
+#include <linux/delay.h>
+#include <linux/kdebug.h>
+#include <linux/notifier.h>
+#include <linux/sched.h>
+#include <linux/hardirq.h>
+
+enum nmi_action {
+        NMI_SHOW_STATE  = 1 << 0,
+        NMI_SHOW_REGS   = 1 << 1,
+        NMI_DIE         = 1 << 2,
+        NMI_DEBOUNCE    = 1 << 3,
+};
+
+static unsigned long nmi_actions;
+
+static int nmi_debug_notify(struct notifier_block *self,
+                unsigned long val, void *data)
+{
+        struct die_args *args = data;
+
+        if (likely(val != DIE_NMI))
+                return NOTIFY_DONE;
+
+        if (nmi_actions & NMI_SHOW_STATE)
+                show_state();
+        if (nmi_actions & NMI_SHOW_REGS)
+                show_regs(args->regs);
+        if (nmi_actions & NMI_DEBOUNCE)
+                mdelay(10);
+        if (nmi_actions & NMI_DIE)
+                return NOTIFY_BAD;
+
+        return NOTIFY_OK;
+}
+
+static struct notifier_block nmi_debug_nb = {
+        .notifier_call = nmi_debug_notify,
+};
+
+static int __init nmi_debug_setup(char *str)
+{
+        char *p, *sep;
+
+        register_die_notifier(&nmi_debug_nb);
+
+        if (*str != '=')
+                return 0;
+
+        for (p = str + 1; *p; p = sep + 1) {
+                sep = strchr(p, ',');
+                if (sep)
+                        *sep = 0;
+                if (strcmp(p, "state") == 0)
+                        nmi_actions |= NMI_SHOW_STATE;
+                else if (strcmp(p, "regs") == 0)
+                        nmi_actions |= NMI_SHOW_REGS;
+                else if (strcmp(p, "debounce") == 0)
+                        nmi_actions |= NMI_DEBOUNCE;
+                else if (strcmp(p, "die") == 0)
+                        nmi_actions |= NMI_DIE;
+                else
+                        printk(KERN_WARNING "NMI: Unrecognized action `%s'\n",
+                                p);
+                if (!sep)
+                        break;
+        }
+
+        return 0;
+}
+__setup("nmi_debug", nmi_debug_setup);
diff --git a/arch/sh/kernel/traps.c b/arch/sh/kernel/traps.c
index f69bd968fcca..a8396f36bd14 100644
--- a/arch/sh/kernel/traps.c
+++ b/arch/sh/kernel/traps.c
@@ -5,6 +5,7 @@
 #include <linux/signal.h>
 #include <linux/sched.h>
 #include <linux/uaccess.h>
+#include <linux/hardirq.h>
 #include <asm/unwinder.h>
 #include <asm/system.h>
 
@@ -91,3 +92,23 @@ BUILD_TRAP_HANDLER(bug)
 
         force_sig(SIGTRAP, current);
 }
+
+BUILD_TRAP_HANDLER(nmi)
+{
+        TRAP_HANDLER_DECL;
+
+        nmi_enter();
+
+        switch (notify_die(DIE_NMI, "NMI", regs, 0, vec & 0xff, SIGINT)) {
+        case NOTIFY_OK:
+        case NOTIFY_STOP:
+                break;
+        case NOTIFY_BAD:
+                die("Fatal Non-Maskable Interrupt", regs, SIGINT);
+        default:
+                printk(KERN_ALERT "Got NMI, but nobody cared. Ignoring...\n");
+                break;
+        }
+
+        nmi_exit();
+}