[MIPS] kgdb: add arch support for the kernel's kgdb core

The new kgdb architecture specific handler registers and unregisters
dynamically for exceptions depending on when you configure a kgdb I/O
driver.

Aside from initializing the exceptions earlier in the boot process,
kgdb should have no impact on a device when it is compiled in so long
as an I/O module is not configured for use.

There have been quite a number of contributors during the existence of
this patch (see arch/mips/kernel/kgdb.c).  Most recently Jason
re-wrote the mips kgdb logic to use the die notification handlers.

Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

4 files changed, 318 insertions, 0 deletions

diff --git a/arch/mips/kernel/Makefile b/arch/mips/kernel/Makefile
index 73ff048eaa55..706f93974797 100644
--- a/arch/mips/kernel/Makefile
+++ b/arch/mips/kernel/Makefile
@@ -71,6 +71,7 @@ obj-$(CONFIG_MIPS32_COMPAT)	+= linux32.o ptrace32.o signal32.o
 obj-$(CONFIG_MIPS32_N32)        += binfmt_elfn32.o scall64-n32.o signal_n32.o
 obj-$(CONFIG_MIPS32_O32)        += binfmt_elfo32.o scall64-o32.o
 
+obj-$(CONFIG_KGDB)              += kgdb.o
 obj-$(CONFIG_PROC_FS)           += proc.o
 
 obj-$(CONFIG_64BIT)             += cpu-bugs64.o
diff --git a/arch/mips/kernel/irq.c b/arch/mips/kernel/irq.c
index 8acba0880d9f..4b4007b3083a 100644
--- a/arch/mips/kernel/irq.c
+++ b/arch/mips/kernel/irq.c
@@ -21,11 +21,16 @@
 #include <linux/sched.h>
 #include <linux/seq_file.h>
 #include <linux/kallsyms.h>
+#include <linux/kgdb.h>
 
 #include <asm/atomic.h>
 #include <asm/system.h>
 #include <asm/uaccess.h>
 
+#ifdef CONFIG_KGDB
+int kgdb_early_setup;
+#endif
+
 static unsigned long irq_map[NR_IRQS / BITS_PER_LONG];
 
 int allocate_irqno(void)
@@ -130,8 +135,18 @@ void __init init_IRQ(void)
 {
         int i;
 
+#ifdef CONFIG_KGDB
+        if (kgdb_early_setup)
+                return;
+#endif
+
         for (i = 0; i < NR_IRQS; i++)
                 set_irq_noprobe(i);
 
         arch_init_irq();
+
+#ifdef CONFIG_KGDB
+        if (!kgdb_early_setup)
+                kgdb_early_setup = 1;
+#endif
 }
diff --git a/arch/mips/kernel/kgdb.c b/arch/mips/kernel/kgdb.c
new file mode 100644
index 000000000000..c5a8b2d21ca4
--- /dev/null
+++ b/arch/mips/kernel/kgdb.c
@@ -0,0 +1,281 @@
+/*
+ *  Originally written by Glenn Engel, Lake Stevens Instrument Division
+ *
+ *  Contributed by HP Systems
+ *
+ *  Modified for Linux/MIPS (and MIPS in general) by Andreas Busse
+ *  Send complaints, suggestions etc. to <andy@waldorf-gmbh.de>
+ *
+ *  Copyright (C) 1995 Andreas Busse
+ *
+ *  Copyright (C) 2003 MontaVista Software Inc.
+ *  Author: Jun Sun, jsun@mvista.com or jsun@junsun.net
+ *
+ *  Copyright (C) 2004-2005 MontaVista Software Inc.
+ *  Author: Manish Lachwani, mlachwani@mvista.com or manish@koffee-break.com
+ *
+ *  Copyright (C) 2007-2008 Wind River Systems, Inc.
+ *  Author/Maintainer: Jason Wessel, jason.wessel@windriver.com
+ *
+ *  This file is licensed under the terms of the GNU General Public License
+ *  version 2. This program is licensed "as is" without any warranty of any
+ *  kind, whether express or implied.
+ */
+
+#include <linux/ptrace.h>               /* for linux pt_regs struct */
+#include <linux/kgdb.h>
+#include <linux/kdebug.h>
+#include <linux/sched.h>
+#include <asm/inst.h>
+#include <asm/fpu.h>
+#include <asm/cacheflush.h>
+#include <asm/processor.h>
+#include <asm/sigcontext.h>
+
+static struct hard_trap_info {
+        unsigned char tt;       /* Trap type code for MIPS R3xxx and R4xxx */
+        unsigned char signo;    /* Signal that we map this trap into */
+} hard_trap_info[] = {
+        { 6, SIGBUS },          /* instruction bus error */
+        { 7, SIGBUS },          /* data bus error */
+        { 9, SIGTRAP },         /* break */
+/*      { 11, SIGILL }, */      /* CPU unusable */
+        { 12, SIGFPE },         /* overflow */
+        { 13, SIGTRAP },        /* trap */
+        { 14, SIGSEGV },        /* virtual instruction cache coherency */
+        { 15, SIGFPE },         /* floating point exception */
+        { 23, SIGSEGV },        /* watch */
+        { 31, SIGSEGV },        /* virtual data cache coherency */
+        { 0, 0}                 /* Must be last */
+};
+
+void arch_kgdb_breakpoint(void)
+{
+        __asm__ __volatile__(
+                ".globl breakinst\n\t"
+                ".set\tnoreorder\n\t"
+                "nop\n"
+                "breakinst:\tbreak\n\t"
+                "nop\n\t"
+                ".set\treorder");
+}
+
+static void kgdb_call_nmi_hook(void *ignored)
+{
+        kgdb_nmicallback(raw_smp_processor_id(), (void *)0);
+}
+
+void kgdb_roundup_cpus(unsigned long flags)
+{
+        local_irq_enable();
+        smp_call_function(kgdb_call_nmi_hook, NULL, NULL);
+        local_irq_disable();
+}
+
+static int compute_signal(int tt)
+{
+        struct hard_trap_info *ht;
+
+        for (ht = hard_trap_info; ht->tt && ht->signo; ht++)
+                if (ht->tt == tt)
+                        return ht->signo;
+
+        return SIGHUP;          /* default for things we don't know about */
+}
+
+void pt_regs_to_gdb_regs(unsigned long *gdb_regs, struct pt_regs *regs)
+{
+        int reg;
+
+#if (KGDB_GDB_REG_SIZE == 32)
+        u32 *ptr = (u32 *)gdb_regs;
+#else
+        u64 *ptr = (u64 *)gdb_regs;
+#endif
+
+        for (reg = 0; reg < 32; reg++)
+                *(ptr++) = regs->regs[reg];
+
+        *(ptr++) = regs->cp0_status;
+        *(ptr++) = regs->lo;
+        *(ptr++) = regs->hi;
+        *(ptr++) = regs->cp0_badvaddr;
+        *(ptr++) = regs->cp0_cause;
+        *(ptr++) = regs->cp0_epc;
+
+        /* FP REGS */
+        if (!(current && (regs->cp0_status & ST0_CU1)))
+                return;
+
+        save_fp(current);
+        for (reg = 0; reg < 32; reg++)
+                *(ptr++) = current->thread.fpu.fpr[reg];
+}
+
+void gdb_regs_to_pt_regs(unsigned long *gdb_regs, struct pt_regs *regs)
+{
+        int reg;
+
+#if (KGDB_GDB_REG_SIZE == 32)
+        const u32 *ptr = (u32 *)gdb_regs;
+#else
+        const u64 *ptr = (u64 *)gdb_regs;
+#endif
+
+        for (reg = 0; reg < 32; reg++)
+                regs->regs[reg] = *(ptr++);
+
+        regs->cp0_status = *(ptr++);
+        regs->lo = *(ptr++);
+        regs->hi = *(ptr++);
+        regs->cp0_badvaddr = *(ptr++);
+        regs->cp0_cause = *(ptr++);
+        regs->cp0_epc = *(ptr++);
+
+        /* FP REGS from current */
+        if (!(current && (regs->cp0_status & ST0_CU1)))
+                return;
+
+        for (reg = 0; reg < 32; reg++)
+                current->thread.fpu.fpr[reg] = *(ptr++);
+        restore_fp(current);
+}
+
+/*
+ * Similar to regs_to_gdb_regs() except that process is sleeping and so
+ * we may not be able to get all the info.
+ */
+void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *p)
+{
+        int reg;
+        struct thread_info *ti = task_thread_info(p);
+        unsigned long ksp = (unsigned long)ti + THREAD_SIZE - 32;
+        struct pt_regs *regs = (struct pt_regs *)ksp - 1;
+#if (KGDB_GDB_REG_SIZE == 32)
+        u32 *ptr = (u32 *)gdb_regs;
+#else
+        u64 *ptr = (u64 *)gdb_regs;
+#endif
+
+        for (reg = 0; reg < 16; reg++)
+                *(ptr++) = regs->regs[reg];
+
+        /* S0 - S7 */
+        for (reg = 16; reg < 24; reg++)
+                *(ptr++) = regs->regs[reg];
+
+        for (reg = 24; reg < 28; reg++)
+                *(ptr++) = 0;
+
+        /* GP, SP, FP, RA */
+        for (reg = 28; reg < 32; reg++)
+                *(ptr++) = regs->regs[reg];
+
+        *(ptr++) = regs->cp0_status;
+        *(ptr++) = regs->lo;
+        *(ptr++) = regs->hi;
+        *(ptr++) = regs->cp0_badvaddr;
+        *(ptr++) = regs->cp0_cause;
+        *(ptr++) = regs->cp0_epc;
+}
+
+/*
+ * Calls linux_debug_hook before the kernel dies. If KGDB is enabled,
+ * then try to fall into the debugger
+ */
+static int kgdb_mips_notify(struct notifier_block *self, unsigned long cmd,
+                            void *ptr)
+{
+        struct die_args *args = (struct die_args *)ptr;
+        struct pt_regs *regs = args->regs;
+        int trap = (regs->cp0_cause & 0x7c) >> 2;
+
+        if (fixup_exception(regs))
+                return NOTIFY_DONE;
+
+        /* Userpace events, ignore. */
+        if (user_mode(regs))
+                return NOTIFY_DONE;
+
+        if (atomic_read(&kgdb_active) != -1)
+                kgdb_nmicallback(smp_processor_id(), regs);
+
+        if (kgdb_handle_exception(trap, compute_signal(trap), 0, regs))
+                return NOTIFY_DONE;
+
+        if (atomic_read(&kgdb_setting_breakpoint))
+                if ((trap == 9) && (regs->cp0_epc == (unsigned long)breakinst))
+                        regs->cp0_epc += 4;
+
+        /* In SMP mode, __flush_cache_all does IPI */
+        local_irq_enable();
+        __flush_cache_all();
+
+        return NOTIFY_STOP;
+}
+
+static struct notifier_block kgdb_notifier = {
+        .notifier_call = kgdb_mips_notify,
+};
+
+/*
+ * Handle the 's' and 'c' commands
+ */
+int kgdb_arch_handle_exception(int vector, int signo, int err_code,
+                               char *remcom_in_buffer, char *remcom_out_buffer,
+                               struct pt_regs *regs)
+{
+        char *ptr;
+        unsigned long address;
+        int cpu = smp_processor_id();
+
+        switch (remcom_in_buffer[0]) {
+        case 's':
+        case 'c':
+                /* handle the optional parameter */
+                ptr = &remcom_in_buffer[1];
+                if (kgdb_hex2long(&ptr, &address))
+                        regs->cp0_epc = address;
+
+                atomic_set(&kgdb_cpu_doing_single_step, -1);
+                if (remcom_in_buffer[0] == 's')
+                        if (kgdb_contthread)
+                                atomic_set(&kgdb_cpu_doing_single_step, cpu);
+
+                return 0;
+        }
+
+        return -1;
+}
+
+struct kgdb_arch arch_kgdb_ops;
+
+/*
+ * We use kgdb_early_setup so that functions we need to call now don't
+ * cause trouble when called again later.
+ */
+int kgdb_arch_init(void)
+{
+        union mips_instruction insn = {
+                .r_format = {
+                        .opcode = spec_op,
+                        .func   = break_op,
+                }
+        };
+        memcpy(arch_kgdb_ops.gdb_bpt_instr, insn.byte, BREAK_INSTR_SIZE);
+
+        register_die_notifier(&kgdb_notifier);
+
+        return 0;
+}
+
+/*
+ *      kgdb_arch_exit - Perform any architecture specific uninitalization.
+ *
+ *      This function will handle the uninitalization of any architecture
+ *      specific callbacks, for dynamic registration and unregistration.
+ */
+void kgdb_arch_exit(void)
+{
+        unregister_die_notifier(&kgdb_notifier);
+}
diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index b8ea4e9d0d87..426cced1e9dc 100644
--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -23,6 +23,8 @@
 #include <linux/bootmem.h>
 #include <linux/interrupt.h>
 #include <linux/ptrace.h>
+#include <linux/kgdb.h>
+#include <linux/kdebug.h>
 
 #include <asm/bootinfo.h>
 #include <asm/branch.h>
@@ -425,6 +427,10 @@ asmlinkage void do_be(struct pt_regs *regs)
         printk(KERN_ALERT "%s bus error, epc == %0*lx, ra == %0*lx\n",
                data ? "Data" : "Instruction",
                field, regs->cp0_epc, field, regs->regs[31]);
+        if (notify_die(DIE_OOPS, "bus error", regs, SIGBUS, 0, 0)
+            == NOTIFY_STOP)
+                return;
+
         die_if_kernel("Oops", regs);
         force_sig(SIGBUS, current);
 }
@@ -623,6 +629,9 @@ asmlinkage void do_fpe(struct pt_regs *regs, unsigned long fcr31)
 {
         siginfo_t info;
 
+        if (notify_die(DIE_FP, "FP exception", regs, SIGFPE, 0, 0)
+            == NOTIFY_STOP)
+                return;
         die_if_kernel("FP exception in kernel code", regs);
 
         if (fcr31 & FPU_CSR_UNI_X) {
@@ -682,6 +691,9 @@ static void do_trap_or_bp(struct pt_regs *regs, unsigned int code,
         siginfo_t info;
         char b[40];
 
+        if (notify_die(DIE_TRAP, str, regs, code, 0, 0) == NOTIFY_STOP)
+                return;
+
         /*
          * A short test says that IRIX 5.3 sends SIGTRAP for all trap
          * insns, even for trap and break codes that indicate arithmetic
@@ -762,6 +774,10 @@ asmlinkage void do_ri(struct pt_regs *regs)
         unsigned int opcode = 0;
         int status = -1;
 
+        if (notify_die(DIE_RI, "RI Fault", regs, SIGSEGV, 0, 0)
+            == NOTIFY_STOP)
+                return;
+
         die_if_kernel("Reserved instruction in kernel code", regs);
 
         if (unlikely(compute_return_epc(regs) < 0))
@@ -1537,6 +1553,11 @@ void __init trap_init(void)
         extern char except_vec4;
         unsigned long i;
 
+#if defined(CONFIG_KGDB)
+        if (kgdb_early_setup)
+                return; /* Already done */
+#endif
+
         if (cpu_has_veic || cpu_has_vint)
                 ebase = (unsigned long) alloc_bootmem_low_pages(0x200 + VECTORSPACING*64);
         else