kgdb,i386: Fix corner case access to ss with NMI watch dog exception

[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / arch / x86 / kernel / kgdb.c

/*
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the
 * Free Software Foundation; either version 2, or (at your option) any
 * later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 */

/*
 * Copyright (C) 2004 Amit S. Kale <amitkale@linsyssoft.com>
 * Copyright (C) 2000-2001 VERITAS Software Corporation.
 * Copyright (C) 2002 Andi Kleen, SuSE Labs
 * Copyright (C) 2004 LinSysSoft Technologies Pvt. Ltd.
 * Copyright (C) 2007 MontaVista Software, Inc.
 * Copyright (C) 2007-2008 Jason Wessel, Wind River Systems, Inc.
 */
/****************************************************************************
 *  Contributor:     Lake Stevens Instrument Division$
 *  Written by:      Glenn Engel $
 *  Updated by:      Amit Kale<akale@veritas.com>
 *  Updated by:      Tom Rini <trini@kernel.crashing.org>
 *  Updated by:      Jason Wessel <jason.wessel@windriver.com>
 *  Modified for 386 by Jim Kingdon, Cygnus Support.
 *  Origianl kgdb, compatibility with 2.1.xx kernel by
 *  David Grothe <dave@gcom.com>
 *  Integrated into 2.2.5 kernel by Tigran Aivazian <tigran@sco.com>
 *  X86_64 changes from Andi Kleen's patch merged by Jim Houston
 */
#include <linux/spinlock.h>
#include <linux/kdebug.h>
#include <linux/string.h>
#include <linux/kernel.h>
#include <linux/ptrace.h>
#include <linux/sched.h>
#include <linux/delay.h>
#include <linux/kgdb.h>
#include <linux/init.h>
#include <linux/smp.h>
#include <linux/nmi.h>

#include <asm/debugreg.h>
#include <asm/apicdef.h>
#include <asm/system.h>

#include <asm/apic.h>

/*
 * Put the error code here just in case the user cares:
 */
static int gdb_x86errcode;

/*
 * Likewise, the vector number here (since GDB only gets the signal
 * number through the usual means, and that's not very specific):
 */
static int gdb_x86vector = -1;

/**
 *      pt_regs_to_gdb_regs - Convert ptrace regs to GDB regs
 *      @gdb_regs: A pointer to hold the registers in the order GDB wants.
 *      @regs: The &struct pt_regs of the current process.
 *
 *      Convert the pt_regs in @regs into the format for registers that
 *      GDB expects, stored in @gdb_regs.
 */
void pt_regs_to_gdb_regs(unsigned long *gdb_regs, struct pt_regs *regs)
{
#ifndef CONFIG_X86_32
        u32 *gdb_regs32 = (u32 *)gdb_regs;
#endif
        gdb_regs[GDB_AX]        = regs->ax;
        gdb_regs[GDB_BX]        = regs->bx;
        gdb_regs[GDB_CX]        = regs->cx;
        gdb_regs[GDB_DX]        = regs->dx;
        gdb_regs[GDB_SI]        = regs->si;
        gdb_regs[GDB_DI]        = regs->di;
        gdb_regs[GDB_BP]        = regs->bp;
        gdb_regs[GDB_PC]        = regs->ip;
#ifdef CONFIG_X86_32
        gdb_regs[GDB_PS]        = regs->flags;
        gdb_regs[GDB_DS]        = regs->ds;
        gdb_regs[GDB_ES]        = regs->es;
        gdb_regs[GDB_CS]        = regs->cs;
        gdb_regs[GDB_FS]        = 0xFFFF;
        gdb_regs[GDB_GS]        = 0xFFFF;
        if (user_mode_vm(regs)) {
                gdb_regs[GDB_SS] = regs->ss;
                gdb_regs[GDB_SP] = regs->sp;
        } else {
                gdb_regs[GDB_SS] = __KERNEL_DS;
                gdb_regs[GDB_SP] = kernel_stack_pointer(regs);
        }
#else
        gdb_regs[GDB_R8]        = regs->r8;
        gdb_regs[GDB_R9]        = regs->r9;
        gdb_regs[GDB_R10]       = regs->r10;
        gdb_regs[GDB_R11]       = regs->r11;
        gdb_regs[GDB_R12]       = regs->r12;
        gdb_regs[GDB_R13]       = regs->r13;
        gdb_regs[GDB_R14]       = regs->r14;
        gdb_regs[GDB_R15]       = regs->r15;
        gdb_regs32[GDB_PS]      = regs->flags;
        gdb_regs32[GDB_CS]      = regs->cs;
        gdb_regs32[GDB_SS]      = regs->ss;
        gdb_regs[GDB_SP]        = kernel_stack_pointer(regs);
#endif
}

/**
 *      sleeping_thread_to_gdb_regs - Convert ptrace regs to GDB regs
 *      @gdb_regs: A pointer to hold the registers in the order GDB wants.
 *      @p: The &struct task_struct of the desired process.
 *
 *      Convert the register values of the sleeping process in @p to
 *      the format that GDB expects.
 *      This function is called when kgdb does not have access to the
 *      &struct pt_regs and therefore it should fill the gdb registers
 *      @gdb_regs with what has been saved in &struct thread_struct
 *      thread field during switch_to.
 */
void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *p)
{
#ifndef CONFIG_X86_32
        u32 *gdb_regs32 = (u32 *)gdb_regs;
#endif
        gdb_regs[GDB_AX]        = 0;
        gdb_regs[GDB_BX]        = 0;
        gdb_regs[GDB_CX]        = 0;
        gdb_regs[GDB_DX]        = 0;
        gdb_regs[GDB_SI]        = 0;
        gdb_regs[GDB_DI]        = 0;
        gdb_regs[GDB_BP]        = *(unsigned long *)p->thread.sp;
#ifdef CONFIG_X86_32
        gdb_regs[GDB_DS]        = __KERNEL_DS;
        gdb_regs[GDB_ES]        = __KERNEL_DS;
        gdb_regs[GDB_PS]        = 0;
        gdb_regs[GDB_CS]        = __KERNEL_CS;
        gdb_regs[GDB_PC]        = p->thread.ip;
        gdb_regs[GDB_SS]        = __KERNEL_DS;
        gdb_regs[GDB_FS]        = 0xFFFF;
        gdb_regs[GDB_GS]        = 0xFFFF;
#else
        gdb_regs32[GDB_PS]      = *(unsigned long *)(p->thread.sp + 8);
        gdb_regs32[GDB_CS]      = __KERNEL_CS;
        gdb_regs32[GDB_SS]      = __KERNEL_DS;
        gdb_regs[GDB_PC]        = 0;
        gdb_regs[GDB_R8]        = 0;
        gdb_regs[GDB_R9]        = 0;
        gdb_regs[GDB_R10]       = 0;
        gdb_regs[GDB_R11]       = 0;
        gdb_regs[GDB_R12]       = 0;
        gdb_regs[GDB_R13]       = 0;
        gdb_regs[GDB_R14]       = 0;
        gdb_regs[GDB_R15]       = 0;
#endif
        gdb_regs[GDB_SP]        = p->thread.sp;
}

/**
 *      gdb_regs_to_pt_regs - Convert GDB regs to ptrace regs.
 *      @gdb_regs: A pointer to hold the registers we've received from GDB.
 *      @regs: A pointer to a &struct pt_regs to hold these values in.
 *
 *      Convert the GDB regs in @gdb_regs into the pt_regs, and store them
 *      in @regs.
 */
void gdb_regs_to_pt_regs(unsigned long *gdb_regs, struct pt_regs *regs)
{
#ifndef CONFIG_X86_32
        u32 *gdb_regs32 = (u32 *)gdb_regs;
#endif
        regs->ax                = gdb_regs[GDB_AX];
        regs->bx                = gdb_regs[GDB_BX];
        regs->cx                = gdb_regs[GDB_CX];
        regs->dx                = gdb_regs[GDB_DX];
        regs->si                = gdb_regs[GDB_SI];
        regs->di                = gdb_regs[GDB_DI];
        regs->bp                = gdb_regs[GDB_BP];
        regs->ip                = gdb_regs[GDB_PC];
#ifdef CONFIG_X86_32
        regs->flags             = gdb_regs[GDB_PS];
        regs->ds                = gdb_regs[GDB_DS];
        regs->es                = gdb_regs[GDB_ES];
        regs->cs                = gdb_regs[GDB_CS];
#else
        regs->r8                = gdb_regs[GDB_R8];
        regs->r9                = gdb_regs[GDB_R9];
        regs->r10               = gdb_regs[GDB_R10];
        regs->r11               = gdb_regs[GDB_R11];
        regs->r12               = gdb_regs[GDB_R12];
        regs->r13               = gdb_regs[GDB_R13];
        regs->r14               = gdb_regs[GDB_R14];
        regs->r15               = gdb_regs[GDB_R15];
        regs->flags             = gdb_regs32[GDB_PS];
        regs->cs                = gdb_regs32[GDB_CS];
        regs->ss                = gdb_regs32[GDB_SS];
#endif
}

static struct hw_breakpoint {
        unsigned                enabled;
        unsigned                type;
        unsigned                len;
        unsigned long           addr;
} breakinfo[4];

static void kgdb_correct_hw_break(void)
{
        unsigned long dr7;
        int correctit = 0;
        int breakbit;
        int breakno;

        get_debugreg(dr7, 7);
        for (breakno = 0; breakno < 4; breakno++) {
                breakbit = 2 << (breakno << 1);
                if (!(dr7 & breakbit) && breakinfo[breakno].enabled) {
                        correctit = 1;
                        dr7 |= breakbit;
                        dr7 &= ~(0xf0000 << (breakno << 2));
                        dr7 |= ((breakinfo[breakno].len << 2) |
                                 breakinfo[breakno].type) <<
                               ((breakno << 2) + 16);
                        set_debugreg(breakinfo[breakno].addr, breakno);

                } else {
                        if ((dr7 & breakbit) && !breakinfo[breakno].enabled) {
                                correctit = 1;
                                dr7 &= ~breakbit;
                                dr7 &= ~(0xf0000 << (breakno << 2));
                        }
                }
        }
        if (correctit)
                set_debugreg(dr7, 7);
}

static int
kgdb_remove_hw_break(unsigned long addr, int len, enum kgdb_bptype bptype)
{
        int i;

        for (i = 0; i < 4; i++)
                if (breakinfo[i].addr == addr && breakinfo[i].enabled)
                        break;
        if (i == 4)
                return -1;

        breakinfo[i].enabled = 0;

        return 0;
}

static void kgdb_remove_all_hw_break(void)
{
        int i;

        for (i = 0; i < 4; i++)
                memset(&breakinfo[i], 0, sizeof(struct hw_breakpoint));
}

static int
kgdb_set_hw_break(unsigned long addr, int len, enum kgdb_bptype bptype)
{
        unsigned type;
        int i;

        for (i = 0; i < 4; i++)
                if (!breakinfo[i].enabled)
                        break;
        if (i == 4)
                return -1;

        switch (bptype) {
        case BP_HARDWARE_BREAKPOINT:
                type = 0;
                len  = 1;
                break;
        case BP_WRITE_WATCHPOINT:
                type = 1;
                break;
        case BP_ACCESS_WATCHPOINT:
                type = 3;
                break;
        default:
                return -1;
        }

        if (len == 1 || len == 2 || len == 4)
                breakinfo[i].len  = len - 1;
        else
                return -1;

        breakinfo[i].enabled = 1;
        breakinfo[i].addr = addr;
        breakinfo[i].type = type;

        return 0;
}

/**
 *      kgdb_disable_hw_debug - Disable hardware debugging while we in kgdb.
 *      @regs: Current &struct pt_regs.
 *
 *      This function will be called if the particular architecture must
 *      disable hardware debugging while it is processing gdb packets or
 *      handling exception.
 */
void kgdb_disable_hw_debug(struct pt_regs *regs)
{
        /* Disable hardware debugging while we are in kgdb: */
        set_debugreg(0UL, 7);
}

/**
 *      kgdb_post_primary_code - Save error vector/code numbers.
 *      @regs: Original pt_regs.
 *      @e_vector: Original error vector.
 *      @err_code: Original error code.
 *
 *      This is needed on architectures which support SMP and KGDB.
 *      This function is called after all the slave cpus have been put
 *      to a know spin state and the primary CPU has control over KGDB.
 */
void kgdb_post_primary_code(struct pt_regs *regs, int e_vector, int err_code)
{
        /* primary processor is completely in the debugger */
        gdb_x86vector = e_vector;
        gdb_x86errcode = err_code;
}

#ifdef CONFIG_SMP
/**
 *      kgdb_roundup_cpus - Get other CPUs into a holding pattern
 *      @flags: Current IRQ state
 *
 *      On SMP systems, we need to get the attention of the other CPUs
 *      and get them be in a known state.  This should do what is needed
 *      to get the other CPUs to call kgdb_wait(). Note that on some arches,
 *      the NMI approach is not used for rounding up all the CPUs. For example,
 *      in case of MIPS, smp_call_function() is used to roundup CPUs. In
 *      this case, we have to make sure that interrupts are enabled before
 *      calling smp_call_function(). The argument to this function is
 *      the flags that will be used when restoring the interrupts. There is
 *      local_irq_save() call before kgdb_roundup_cpus().
 *
 *      On non-SMP systems, this is not called.
 */
void kgdb_roundup_cpus(unsigned long flags)
{
        apic->send_IPI_allbutself(APIC_DM_NMI);
}
#endif

/**
 *      kgdb_arch_handle_exception - Handle architecture specific GDB packets.
 *      @vector: The error vector of the exception that happened.
 *      @signo: The signal number of the exception that happened.
 *      @err_code: The error code of the exception that happened.
 *      @remcom_in_buffer: The buffer of the packet we have read.
 *      @remcom_out_buffer: The buffer of %BUFMAX bytes to write a packet into.
 *      @regs: The &struct pt_regs of the current process.
 *
 *      This function MUST handle the 'c' and 's' command packets,
 *      as well packets to set / remove a hardware breakpoint, if used.
 *      If there are additional packets which the hardware needs to handle,
 *      they are handled here.  The code should return -1 if it wants to
 *      process more packets, and a %0 or %1 if it wants to exit from the
 *      kgdb callback.
 */
int kgdb_arch_handle_exception(int e_vector, int signo, int err_code,
                               char *remcomInBuffer, char *remcomOutBuffer,
                               struct pt_regs *linux_regs)
{
        unsigned long addr;
        unsigned long dr6;
        char *ptr;
        int newPC;

        switch (remcomInBuffer[0]) {
        case 'c':
        case 's':
                /* try to read optional parameter, pc unchanged if no parm */
                ptr = &remcomInBuffer[1];
                if (kgdb_hex2long(&ptr, &addr))
                        linux_regs->ip = addr;
        case 'D':
        case 'k':
                newPC = linux_regs->ip;

                /* clear the trace bit */
                linux_regs->flags &= ~X86_EFLAGS_TF;
                atomic_set(&kgdb_cpu_doing_single_step, -1);

                /* set the trace bit if we're stepping */
                if (remcomInBuffer[0] == 's') {
                        linux_regs->flags |= X86_EFLAGS_TF;
                        kgdb_single_step = 1;
                        atomic_set(&kgdb_cpu_doing_single_step,
                                   raw_smp_processor_id());
                }

                get_debugreg(dr6, 6);
                if (!(dr6 & 0x4000)) {
                        int breakno;

                        for (breakno = 0; breakno < 4; breakno++) {
                                if (dr6 & (1 << breakno) &&
                                    breakinfo[breakno].type == 0) {
                                        /* Set restore flag: */
                                        linux_regs->flags |= X86_EFLAGS_RF;
                                        break;
                                }
                        }
                }
                set_debugreg(0UL, 6);
                kgdb_correct_hw_break();

                return 0;
        }

        /* this means that we do not want to exit from the handler: */
        return -1;
}

static inline int
single_step_cont(struct pt_regs *regs, struct die_args *args)
{
        /*
         * Single step exception from kernel space to user space so
         * eat the exception and continue the process:
         */
        printk(KERN_ERR "KGDB: trap/step from kernel to user space, "
                        "resuming...\n");
        kgdb_arch_handle_exception(args->trapnr, args->signr,
                                   args->err, "c", "", regs);
        /*
         * Reset the BS bit in dr6 (pointed by args->err) to
         * denote completion of processing
         */
        (*(unsigned long *)ERR_PTR(args->err)) &= ~DR_STEP;

        return NOTIFY_STOP;
}

static int was_in_debug_nmi[NR_CPUS];

static int __kgdb_notify(struct die_args *args, unsigned long cmd)
{
        struct pt_regs *regs = args->regs;

        switch (cmd) {
        case DIE_NMI:
                if (atomic_read(&kgdb_active) != -1) {
                        /* KGDB CPU roundup */
                        kgdb_nmicallback(raw_smp_processor_id(), regs);
                        was_in_debug_nmi[raw_smp_processor_id()] = 1;
                        touch_nmi_watchdog();
                        return NOTIFY_STOP;
                }
                return NOTIFY_DONE;

        case DIE_NMI_IPI:
                /* Just ignore, we will handle the roundup on DIE_NMI. */
                return NOTIFY_DONE;

        case DIE_NMIUNKNOWN:
                if (was_in_debug_nmi[raw_smp_processor_id()]) {
                        was_in_debug_nmi[raw_smp_processor_id()] = 0;
                        return NOTIFY_STOP;
                }
                return NOTIFY_DONE;

        case DIE_NMIWATCHDOG:
                if (atomic_read(&kgdb_active) != -1) {
                        /* KGDB CPU roundup: */
                        kgdb_nmicallback(raw_smp_processor_id(), regs);
                        return NOTIFY_STOP;
                }
                /* Enter debugger: */
                break;

        case DIE_DEBUG:
                if (atomic_read(&kgdb_cpu_doing_single_step) ==
                    raw_smp_processor_id()) {
                        if (user_mode(regs))
                                return single_step_cont(regs, args);
                        break;
                } else if (test_thread_flag(TIF_SINGLESTEP))
                        /* This means a user thread is single stepping
                         * a system call which should be ignored
                         */
                        return NOTIFY_DONE;
                /* fall through */
        default:
                if (user_mode(regs))
                        return NOTIFY_DONE;
        }

        if (kgdb_handle_exception(args->trapnr, args->signr, args->err, regs))
                return NOTIFY_DONE;

        /* Must touch watchdog before return to normal operation */
        touch_nmi_watchdog();
        return NOTIFY_STOP;
}

static int
kgdb_notify(struct notifier_block *self, unsigned long cmd, void *ptr)
{
        unsigned long flags;
        int ret;

        local_irq_save(flags);
        ret = __kgdb_notify(ptr, cmd);
        local_irq_restore(flags);

        return ret;
}

static struct notifier_block kgdb_notifier = {
        .notifier_call  = kgdb_notify,

        /*
         * Lowest-prio notifier priority, we want to be notified last:
         */
        .priority       = -INT_MAX,
};

/**
 *      kgdb_arch_init - Perform any architecture specific initalization.
 *
 *      This function will handle the initalization of any architecture
 *      specific callbacks.
 */
int kgdb_arch_init(void)
{
        return register_die_notifier(&kgdb_notifier);
}

/**
 *      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);
}

/**
 *
 *      kgdb_skipexception - Bail out of KGDB when we've been triggered.
 *      @exception: Exception vector number
 *      @regs: Current &struct pt_regs.
 *
 *      On some architectures we need to skip a breakpoint exception when
 *      it occurs after a breakpoint has been removed.
 *
 * Skip an int3 exception when it occurs after a breakpoint has been
 * removed. Backtrack eip by 1 since the int3 would have caused it to
 * increment by 1.
 */
int kgdb_skipexception(int exception, struct pt_regs *regs)
{
        if (exception == 3 && kgdb_isremovedbreak(regs->ip - 1)) {
                regs->ip -= 1;
                return 1;
        }
        return 0;
}

unsigned long kgdb_arch_pc(int exception, struct pt_regs *regs)
{
        if (exception == 3)
                return instruction_pointer(regs) - 1;
        return instruction_pointer(regs);
}

struct kgdb_arch arch_kgdb_ops = {
        /* Breakpoint instruction: */
        .gdb_bpt_instr          = { 0xcc },
        .flags                  = KGDB_HW_BREAKPOINT,
        .set_hw_breakpoint      = kgdb_set_hw_break,
        .remove_hw_breakpoint   = kgdb_remove_hw_break,
        .remove_all_hw_break    = kgdb_remove_all_hw_break,
        .correct_hw_break       = kgdb_correct_hw_break,
};