x86: kgdb support

simplified and streamlined kgdb support on x86, both 32-bit and 64-bit,
based on patch from:

  Subject: kgdb: core-lite
  From: Jason Wessel <jason.wessel@windriver.com>

[ and countless other authors - see the patch for details. ]

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Jan Kiszka <jan.kiszka@web.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>

4 files changed, 500 insertions, 0 deletions

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 6c70fed0f9a0..5c4c8d7a46cc 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -23,6 +23,7 @@ config X86
         select HAVE_KPROBES
         select HAVE_KRETPROBES
         select HAVE_KVM if ((X86_32 && !X86_VOYAGER && !X86_VISWS && !X86_NUMAQ) || X86_64)
+        select HAVE_ARCH_KGDB
 
 
 config GENERIC_LOCKBREAK
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 4eb5ce841106..4a4260c7f672 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -66,6 +66,7 @@ obj-$(CONFIG_MODULES)		+= module_$(BITS).o
 obj-$(CONFIG_ACPI_SRAT)         += srat_32.o
 obj-$(CONFIG_EFI)               += efi.o efi_$(BITS).o efi_stub_$(BITS).o
 obj-$(CONFIG_DOUBLEFAULT)       += doublefault_32.o
+obj-$(CONFIG_KGDB)              += kgdb.o
 obj-$(CONFIG_VM86)              += vm86_32.o
 obj-$(CONFIG_EARLY_PRINTK)      += early_printk.o
 
diff --git a/arch/x86/kernel/kgdb.c b/arch/x86/kernel/kgdb.c
new file mode 100644
index 000000000000..37194d6374d8
--- /dev/null
+++ b/arch/x86/kernel/kgdb.c
@@ -0,0 +1,417 @@
+/*
+ * 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 <asm/apicdef.h>
+#include <asm/system.h>
+
+#ifdef CONFIG_X86_32
+# include <mach_ipi.h>
+#else
+# include <asm/mach_apic.h>
+#endif
+
+/*
+ * 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)
+{
+        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_PS]        = regs->flags;
+        gdb_regs[GDB_PC]        = regs->ip;
+#ifdef CONFIG_X86_32
+        gdb_regs[GDB_DS]        = regs->ds;
+        gdb_regs[GDB_ES]        = regs->es;
+        gdb_regs[GDB_CS]        = regs->cs;
+        gdb_regs[GDB_SS]        = __KERNEL_DS;
+        gdb_regs[GDB_FS]        = 0xFFFF;
+        gdb_regs[GDB_GS]        = 0xFFFF;
+#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;
+#endif
+        gdb_regs[GDB_SP]        = regs->sp;
+}
+
+/**
+ *      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)
+{
+        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_regs[GDB_PS]        = *(unsigned long *)(p->thread.sp + 8);
+        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)
+{
+        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->flags             = gdb_regs[GDB_PS];
+        regs->ip                = gdb_regs[GDB_PC];
+#ifdef CONFIG_X86_32
+        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];
+#endif
+}
+
+/**
+ *      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)
+{
+        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;
+        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;
+                newPC = linux_regs->ip;
+
+                /* clear the trace bit */
+                linux_regs->flags &= ~TF_MASK;
+                atomic_set(&kgdb_cpu_doing_single_step, -1);
+
+                /* set the trace bit if we're stepping */
+                if (remcomInBuffer[0] == 's') {
+                        linux_regs->flags |= TF_MASK;
+                        kgdb_single_step = 1;
+                        if (kgdb_contthread) {
+                                atomic_set(&kgdb_cpu_doing_single_step,
+                                           raw_smp_processor_id());
+                        }
+                }
+
+                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);
+
+        return NOTIFY_STOP;
+}
+
+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);
+                        return NOTIFY_STOP;
+                }
+                return NOTIFY_DONE;
+
+        case DIE_NMI_IPI:
+                if (atomic_read(&kgdb_active) != -1) {
+                        /* KGDB CPU roundup: */
+                        if (kgdb_nmicallback(raw_smp_processor_id(), regs))
+                                return NOTIFY_DONE;
+                        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() &&
+                        user_mode(regs))
+                        return single_step_cont(regs, args);
+                /* fall through */
+        default:
+                if (user_mode(regs))
+                        return NOTIFY_DONE;
+        }
+
+        if (kgdb_handle_exception(args->trapnr, args->signr, args->err, regs))
+                return NOTIFY_DONE;
+
+        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 },
+};
diff --git a/include/asm-x86/kgdb.h b/include/asm-x86/kgdb.h
new file mode 100644
index 000000000000..484c47554f3b
--- /dev/null
+++ b/include/asm-x86/kgdb.h
@@ -0,0 +1,81 @@
+#ifndef _ASM_KGDB_H_
+#define _ASM_KGDB_H_
+
+/*
+ * Copyright (C) 2001-2004 Amit S. Kale
+ * Copyright (C) 2008 Wind River Systems, Inc.
+ */
+
+/*
+ * BUFMAX defines the maximum number of characters in inbound/outbound
+ * buffers at least NUMREGBYTES*2 are needed for register packets
+ * Longer buffer is needed to list all threads
+ */
+#define BUFMAX                  1024
+
+/*
+ *  Note that this register image is in a different order than
+ *  the register image that Linux produces at interrupt time.
+ *
+ *  Linux's register image is defined by struct pt_regs in ptrace.h.
+ *  Just why GDB uses a different order is a historical mystery.
+ */
+#ifdef CONFIG_X86_32
+enum regnames {
+        GDB_AX,                 /* 0 */
+        GDB_CX,                 /* 1 */
+        GDB_DX,                 /* 2 */
+        GDB_BX,                 /* 3 */
+        GDB_SP,                 /* 4 */
+        GDB_BP,                 /* 5 */
+        GDB_SI,                 /* 6 */
+        GDB_DI,                 /* 7 */
+        GDB_PC,                 /* 8 also known as eip */
+        GDB_PS,                 /* 9 also known as eflags */
+        GDB_CS,                 /* 10 */
+        GDB_SS,                 /* 11 */
+        GDB_DS,                 /* 12 */
+        GDB_ES,                 /* 13 */
+        GDB_FS,                 /* 14 */
+        GDB_GS,                 /* 15 */
+};
+#else /* ! CONFIG_X86_32 */
+enum regnames {
+        GDB_AX,                 /* 0 */
+        GDB_DX,                 /* 1 */
+        GDB_CX,                 /* 2 */
+        GDB_BX,                 /* 3 */
+        GDB_SI,                 /* 4 */
+        GDB_DI,                 /* 5 */
+        GDB_BP,                 /* 6 */
+        GDB_SP,                 /* 7 */
+        GDB_R8,                 /* 8 */
+        GDB_R9,                 /* 9 */
+        GDB_R10,                /* 10 */
+        GDB_R11,                /* 11 */
+        GDB_R12,                /* 12 */
+        GDB_R13,                /* 13 */
+        GDB_R14,                /* 14 */
+        GDB_R15,                /* 15 */
+        GDB_PC,                 /* 16 */
+        GDB_PS,                 /* 17 */
+};
+#endif /* CONFIG_X86_32 */
+
+/*
+ * Number of bytes of registers:
+ */
+#ifdef CONFIG_X86_32
+# define NUMREGBYTES            64
+#else
+# define NUMREGBYTES            ((GDB_PS+1)*8)
+#endif
+
+static inline void arch_kgdb_breakpoint(void)
+{
+        asm("   int $3");
+}
+#define BREAK_INSTR_SIZE        1
+#define CACHE_FLUSH_IS_SAFE     1
+
+#endif                          /* _ASM_KGDB_H_ */