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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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