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Subject[PATCH 2/2] kgdb, mips: add arch support for the kernel's kgdb core
Date
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>
---
arch/mips/Kconfig | 1 +
arch/mips/kernel/Makefile | 1 +
arch/mips/kernel/irq.c | 15 +++
arch/mips/kernel/kgdb.c | 256 +++++++++++++++++++++++++++++++++++++++++++++
arch/mips/kernel/traps.c | 21 ++++
include/asm-mips/kdebug.h | 14 +++-
include/asm-mips/kgdb.h | 54 ++++++++++
7 files changed, 361 insertions(+), 1 deletions(-)
create mode 100644 arch/mips/kernel/kgdb.c
create mode 100644 include/asm-mips/kgdb.h
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 2c75ff3..22f6c43 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -3,6 +3,7 @@ config MIPS
default y
select HAVE_IDE
select HAVE_OPROFILE
+ select HAVE_ARCH_KGDB
# Horrible source of confusion. Die, die, die ...
select EMBEDDED
select RTC_LIB
diff --git a/arch/mips/kernel/Makefile b/arch/mips/kernel/Makefile
index 73ff048..706f939 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 8acba08..4b4007b 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 0000000..3f23b2e
--- /dev/null
+++ b/arch/mips/kernel/kgdb.c
@@ -0,0 +1,256 @@
+/*
+ * arch/mips/kernel/kgdb.c
+ *
+ * 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 <asm/cacheflush.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 */
+};
+
+/* Save the normal trap handlers for user-mode traps. */
+void *saved_vectors[32];
+
+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;
+
+ return;
+}
+
+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++);
+
+ return;
+}
+
+/*
+ * 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;
+
+ return;
+}
+
+/*
+ * 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 = {
+#ifdef CONFIG_CPU_LITTLE_ENDIAN
+ .gdb_bpt_instr = {0xd},
+#else /* ! CONFIG_CPU_LITTLE_ENDIAN */
+ .gdb_bpt_instr = {0x00, 0x00, 0x00, 0x0d},
+#endif
+};
+
+/*
+ * 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)
+{
+ 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 b8ea4e9..426cced 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
diff --git a/include/asm-mips/kdebug.h b/include/asm-mips/kdebug.h
index 6ece1b0..5bf62aa 100644
--- a/include/asm-mips/kdebug.h
+++ b/include/asm-mips/kdebug.h
@@ -1 +1,13 @@
-#include <asm-generic/kdebug.h>
+#ifndef _ASM_MIPS_KDEBUG_H
+#define _ASM_MIPS_KDEBUG_H
+
+#include <linux/notifier.h>
+
+enum die_val {
+ DIE_OOPS = 1,
+ DIE_FP,
+ DIE_TRAP,
+ DIE_RI,
+};
+
+#endif /* _ASM_MIPS_KDEBUG_H */
diff --git a/include/asm-mips/kgdb.h b/include/asm-mips/kgdb.h
new file mode 100644
index 0000000..0e0ed89
--- /dev/null
+++ b/include/asm-mips/kgdb.h
@@ -0,0 +1,54 @@
+#ifdef __KERNEL__
+#ifndef _ASM_KGDB_H_
+#define _ASM_KGDB_H_
+
+#include <asm/sgidefs.h>
+
+#ifndef __ASSEMBLY__
+#if (_MIPS_ISA == _MIPS_ISA_MIPS1) || (_MIPS_ISA == _MIPS_ISA_MIPS2) || \
+ (_MIPS_ISA == _MIPS_ISA_MIPS32)
+
+#define KGDB_GDB_REG_SIZE 32
+
+#elif (_MIPS_ISA == _MIPS_ISA_MIPS3) || (_MIPS_ISA == _MIPS_ISA_MIPS4) || \
+ (_MIPS_ISA == _MIPS_ISA_MIPS64)
+
+#ifdef CONFIG_32BIT
+#define KGDB_GDB_REG_SIZE 32
+#else /* CONFIG_CPU_32BIT */
+#define KGDB_GDB_REG_SIZE 64
+#endif
+#else
+#error "Need to set KGDB_GDB_REG_SIZE for MIPS ISA"
+#endif /* _MIPS_ISA */
+
+#define BUFMAX 2048
+#if (KGDB_GDB_REG_SIZE == 32)
+#define NUMREGBYTES (90*sizeof(u32))
+#define NUMCRITREGBYTES (12*sizeof(u32))
+#else
+#define NUMREGBYTES (90*sizeof(u64))
+#define NUMCRITREGBYTES (12*sizeof(u64))
+#endif
+#define BREAK_INSTR_SIZE 4
+static inline 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");
+}
+#define CACHE_FLUSH_IS_SAFE 0
+
+extern int kgdb_early_setup;
+extern void *saved_vectors[32];
+extern void handle_exception(struct pt_regs *regs);
+extern void trap_low(void);
+extern void breakinst(void);
+
+#endif /* !__ASSEMBLY__ */
+#endif /* _ASM_KGDB_H_ */
+#endif /* __KERNEL__ */
--
1.5.5.1


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