Signed-off-by: Jason Wessel <[email protected]>
i386-lite.patch
From: Jason Wessel <[email protected]>
CC: [email protected]
Subject: [PATCH] This adds the basic support for i386.
In order to support early debugginer with kgdb when used with kgdb via
rs232 some traps must be initialized sooner rather than later, but it
is safe to always do this. The arch i386 now calls parse_early_param() to
explicitly look at anything marked early_param(). KGDB also adds a
few more notify_die() calls in areas where KGDB needs to take a peek
sometimes. To achieve better back trace results from the debugger
some labels were added to the switch_to macros.
Signed-off-by: Milind Dumbare <[email protected]>
Signed-off-by: Jason Wessel <[email protected]>
---
arch/x86/kernel/Makefile_32 | 1
arch/x86/kernel/kgdb-jmp_32.S | 74 ++++++++++
arch/x86/kernel/kgdb_32.c | 300 ++++++++++++++++++++++++++++++++++++++++++
arch/x86/kernel/setup_32.c | 2
arch/x86/kernel/traps_32.c | 12 +
arch/x86/mm/fault_32.c | 4
include/asm-x86/kdebug_32.h | 1
include/asm-x86/kgdb_32.h | 51 +++++++
lib/Kconfig.kgdb | 2
9 files changed, 442 insertions(+), 5 deletions(-)
create mode 100644 arch/x86/kernel/kgdb-jmp.S
create mode 100644 arch/x86/kernel/kgdb.c
create mode 100644 include/asm-x86/kgdb.h
--- a/arch/x86/kernel/Makefile_32
+++ b/arch/x86/kernel/Makefile_32
@@ -35,6 +35,7 @@ obj-y += sysenter_32.o vsyscall_32.o
obj-$(CONFIG_ACPI_SRAT) += srat_32.o
obj-$(CONFIG_EFI) += efi_32.o efi_stub_32.o
obj-$(CONFIG_DOUBLEFAULT) += doublefault_32.o
+obj-$(CONFIG_KGDB) += kgdb_32.o kgdb-jmp_32.o
obj-$(CONFIG_VM86) += vm86_32.o
obj-$(CONFIG_EARLY_PRINTK) += early_printk.o
obj-$(CONFIG_HPET_TIMER) += hpet.o
--- /dev/null
+++ b/arch/x86/kernel/kgdb-jmp_32.S
@@ -0,0 +1,74 @@
+/*
+ * arch/x86/kernel/kgdb-jmp_32.S
+ *
+ * Save and restore system registers so that within a limited frame we
+ * may have a fault and "jump back" to a known safe location.
+ *
+ * Author: George Anzinger <[email protected]>
+ *
+ * Cribbed from glibc, which carries the following:
+ * Copyright (C) 1996, 1996, 1997, 2000, 2001 Free Software Foundation, Inc.
+ * Copyright (C) 2005 by MontaVista Software.
+ *
+ * This file is licensed under the terms of the GNU General Public License
+ * version 2. This program as licensed "as is" without any warranty of
+ * any kind, whether express or implied.
+ */
+
+#include <linux/linkage.h>
+
+#define PCOFF 0
+#define LINKAGE 4 /* just the return address */
+#define PTR_SIZE 4
+#define PARMS LINKAGE /* no space for saved regs */
+#define JMPBUF PARMS
+#define VAL JMPBUF+PTR_SIZE
+
+#define JB_BX 0
+#define JB_SI 1
+#define JB_DI 2
+#define JB_BP 3
+#define JB_SP 4
+#define JB_PC 5
+
+/* This must be called prior to kgdb_fault_longjmp and
+ * kgdb_fault_longjmp must not be called outside of the context of the
+ * last call to kgdb_fault_setjmp.
+ * kgdb_fault_setjmp(int *jmp_buf[6])
+ */
+ENTRY(kgdb_fault_setjmp)
+ movl JMPBUF(%esp), %eax
+
+ /* Save registers. */
+ movl %ebx, (JB_BX*4)(%eax)
+ movl %esi, (JB_SI*4)(%eax)
+ movl %edi, (JB_DI*4)(%eax)
+ /* Save SP as it will be after we return. */
+ leal JMPBUF(%esp), %ecx
+ movl %ecx, (JB_SP*4)(%eax)
+ movl PCOFF(%esp), %ecx /* Save PC we are returning to now. */
+ movl %ecx, (JB_PC*4)(%eax)
+ movl %ebp, (JB_BP*4)(%eax) /* Save caller's frame pointer. */
+
+ /* Restore state so we can now try the access. */
+ movl JMPBUF(%esp), %ecx /* User's jmp_buf in %ecx. */
+ /* Save the return address now. */
+ movl (JB_PC*4)(%ecx), %edx
+ /* Restore registers. */
+ movl $0, %eax
+ movl (JB_SP*4)(%ecx), %esp
+ jmp *%edx /* Jump to saved PC. */
+
+/* kgdb_fault_longjmp(int *jmp_buf[6]) */
+ENTRY(kgdb_fault_longjmp)
+ movl JMPBUF(%esp), %ecx /* User's jmp_buf in %ecx. */
+ /* Save the return address now. */
+ movl (JB_PC*4)(%ecx), %edx
+ /* Restore registers. */
+ movl (JB_BX*4)(%ecx), %ebx
+ movl (JB_SI*4)(%ecx), %esi
+ movl (JB_DI*4)(%ecx), %edi
+ movl (JB_BP*4)(%ecx), %ebp
+ movl $1, %eax
+ movl (JB_SP*4)(%ecx), %esp
+ jmp *%edx /* Jump to saved PC. */
--- /dev/null
+++ b/arch/x86/kernel/kgdb_32.c
@@ -0,0 +1,300 @@
+/*
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2, or (at your option) any
+ * later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ */
+
+/*
+ * Copyright (C) 2000-2001 VERITAS Software Corporation.
+ */
+/*
+ * Contributor: Lake Stevens Instrument Division$
+ * Written by: Glenn Engel $
+ * Updated by: Amit Kale<[email protected]>
+ * Updated by: Tom Rini <[email protected]>
+ * Modified for 386 by Jim Kingdon, Cygnus Support.
+ * Origianl kgdb, compatibility with 2.1.xx kernel by
+ * David Grothe <[email protected]>
+ * Additional support from Tigran Aivazian <[email protected]>
+ */
+
+#include <linux/string.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/smp.h>
+#include <linux/spinlock.h>
+#include <linux/delay.h>
+#include <asm/vm86.h>
+#include <asm/system.h>
+#include <linux/ptrace.h> /* for linux pt_regs struct */
+#include <linux/kgdb.h>
+#include <linux/init.h>
+#include <linux/kdebug.h>
+#include <asm/apicdef.h>
+#include <asm/desc.h>
+
+#include "mach_ipi.h"
+
+/* Put the error code here just in case the user cares. */
+int gdb_i386errcode;
+/* Likewise, the vector number here (since GDB only gets the signal
+ number through the usual means, and that's not very specific). */
+int gdb_i386vector = -1;
+
+void regs_to_gdb_regs(unsigned long *gdb_regs, struct pt_regs *regs)
+{
+ gdb_regs[_EAX] = regs->eax;
+ gdb_regs[_EBX] = regs->ebx;
+ gdb_regs[_ECX] = regs->ecx;
+ gdb_regs[_EDX] = regs->edx;
+ gdb_regs[_ESI] = regs->esi;
+ gdb_regs[_EDI] = regs->edi;
+ gdb_regs[_EBP] = regs->ebp;
+ gdb_regs[_DS] = regs->xds;
+ gdb_regs[_ES] = regs->xes;
+ gdb_regs[_PS] = regs->eflags;
+ gdb_regs[_CS] = regs->xcs;
+ gdb_regs[_PC] = regs->eip;
+ gdb_regs[_ESP] = (int)(®s->esp);
+ gdb_regs[_SS] = __KERNEL_DS;
+ gdb_regs[_FS] = 0xFFFF;
+ gdb_regs[_GS] = 0xFFFF;
+}
+
+/*
+ * Extracts ebp, esp and eip values understandable by gdb from the values
+ * saved by switch_to.
+ * thread.esp points to ebp. flags and ebp are pushed in switch_to hence esp
+ * prior to entering switch_to is 8 greater then the value that is saved.
+ * If switch_to changes, change following code appropriately.
+ */
+void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *p)
+{
+ gdb_regs[_EAX] = 0;
+ gdb_regs[_EBX] = 0;
+ gdb_regs[_ECX] = 0;
+ gdb_regs[_EDX] = 0;
+ gdb_regs[_ESI] = 0;
+ gdb_regs[_EDI] = 0;
+ gdb_regs[_EBP] = *(unsigned long *)p->thread.esp;
+ gdb_regs[_DS] = __KERNEL_DS;
+ gdb_regs[_ES] = __KERNEL_DS;
+ gdb_regs[_PS] = 0;
+ gdb_regs[_CS] = __KERNEL_CS;
+ gdb_regs[_PC] = p->thread.eip;
+ gdb_regs[_ESP] = p->thread.esp;
+ gdb_regs[_SS] = __KERNEL_DS;
+ gdb_regs[_FS] = 0xFFFF;
+ gdb_regs[_GS] = 0xFFFF;
+}
+
+void gdb_regs_to_regs(unsigned long *gdb_regs, struct pt_regs *regs)
+{
+ regs->eax = gdb_regs[_EAX];
+ regs->ebx = gdb_regs[_EBX];
+ regs->ecx = gdb_regs[_ECX];
+ regs->edx = gdb_regs[_EDX];
+ regs->esi = gdb_regs[_ESI];
+ regs->edi = gdb_regs[_EDI];
+ regs->ebp = gdb_regs[_EBP];
+ regs->xds = gdb_regs[_DS];
+ regs->xes = gdb_regs[_ES];
+ regs->eflags = gdb_regs[_PS];
+ regs->xcs = gdb_regs[_CS];
+ regs->eip = gdb_regs[_PC];
+}
+
+static struct hw_breakpoint {
+ unsigned enabled;
+ unsigned type;
+ unsigned len;
+ unsigned addr;
+} breakinfo[4] = {
+ { .enabled = 0 },
+ { .enabled = 0 },
+ { .enabled = 0 },
+ { .enabled = 0 },
+};
+
+void kgdb_disable_hw_debug(struct pt_regs *regs)
+{
+ /* Disable hardware debugging while we are in kgdb */
+ asm volatile ("movl %0,%%db7": /* no output */ :"r" (0));
+}
+
+void kgdb_post_master_code(struct pt_regs *regs, int e_vector, int err_code)
+{
+ /* Master processor is completely in the debugger */
+ gdb_i386vector = e_vector;
+ gdb_i386errcode = err_code;
+}
+
+#ifdef CONFIG_SMP
+void kgdb_roundup_cpus(unsigned long flags)
+{
+ send_IPI_allbutself(APIC_DM_NMI);
+}
+#endif
+
+int kgdb_arch_handle_exception(int e_vector, int signo,
+ int err_code, char *remcom_in_buffer,
+ char *remcom_out_buffer,
+ struct pt_regs *linux_regs)
+{
+ long addr;
+ char *ptr;
+ int newPC;
+ int dr6;
+
+ switch (remcom_in_buffer[0]) {
+ case 'c':
+ case 's':
+ /* try to read optional parameter, pc unchanged if no parm */
+ ptr = &remcom_in_buffer[1];
+ if (kgdb_hex2long(&ptr, &addr))
+ linux_regs->eip = addr;
+ newPC = linux_regs->eip;
+
+ /* clear the trace bit */
+ linux_regs->eflags &= ~TF_MASK;
+ atomic_set(&cpu_doing_single_step, -1);
+
+ /* set the trace bit if we're stepping */
+ if (remcom_in_buffer[0] == 's') {
+ linux_regs->eflags |= TF_MASK;
+ debugger_step = 1;
+ atomic_set(&cpu_doing_single_step,
+ raw_smp_processor_id());
+ }
+
+ asm volatile ("movl %%db6, %0\n":"=r" (dr6));
+ if (!(dr6 & 0x4000)) {
+ long breakno;
+ for (breakno = 0; breakno < 4; ++breakno) {
+ if (dr6 & (1 << breakno) &&
+ breakinfo[breakno].type == 0) {
+ /* Set restore flag */
+ linux_regs->eflags |= X86_EFLAGS_RF;
+ break;
+ }
+ }
+ }
+ asm volatile ("movl %0, %%db6\n"::"r" (0));
+
+ return (0);
+ } /* switch */
+ /* 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 notifier_block *self, unsigned long cmd,
+ void *ptr)
+{
+ struct die_args *args = ptr;
+ struct pt_regs *regs = args->regs;
+
+ switch (cmd) {
+ case DIE_NMI:
+ if (atomic_read(&debugger_active)) {
+ /* KGDB CPU roundup */
+ kgdb_nmihook(raw_smp_processor_id(), regs);
+ return NOTIFY_STOP;
+ }
+ return NOTIFY_DONE;
+ case DIE_NMI_IPI:
+ if (atomic_read(&debugger_active)) {
+ /* KGDB CPU roundup */
+ if (kgdb_nmihook(raw_smp_processor_id(), regs))
+ return NOTIFY_DONE;
+ return NOTIFY_STOP;
+ }
+ return NOTIFY_DONE;
+ case DIE_NMIWATCHDOG:
+ if (atomic_read(&debugger_active)) {
+ /* KGDB CPU roundup */
+ kgdb_nmihook(raw_smp_processor_id(), regs);
+ return NOTIFY_STOP;
+ }
+ /* Enter debugger */
+ break;
+ case DIE_DEBUG:
+ if (atomic_read(&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_may_fault) {
+ kgdb_fault_longjmp(kgdb_fault_jmp_regs);
+ return NOTIFY_STOP;
+ }
+
+ if (kgdb_handle_exception(args->trapnr, args->signr,
+ args->err, regs))
+ return NOTIFY_DONE;
+
+ return NOTIFY_STOP;
+}
+
+static struct notifier_block kgdb_notifier = {
+ .notifier_call = kgdb_notify,
+};
+
+int kgdb_arch_init(void)
+{
+ register_die_notifier(&kgdb_notifier);
+ return 0;
+}
+
+/*
+ * 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->eip - 1)) {
+ regs->eip -= 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 = {
+ .gdb_bpt_instr = {0xcc},
+};
--- a/arch/x86/kernel/setup_32.c
+++ b/arch/x86/kernel/setup_32.c
@@ -113,6 +113,7 @@ EXPORT_SYMBOL(ist_info);
#endif
extern void early_cpu_init(void);
+extern void early_trap_init(void);
extern int root_mountflags;
unsigned long saved_videomode;
@@ -503,6 +504,7 @@ void __init setup_arch(char **cmdline_p)
memcpy(&boot_cpu_data, &new_cpu_data, sizeof(new_cpu_data));
pre_setup_arch_hook();
early_cpu_init();
+ early_trap_init();
/*
* FIXME: This isn't an official loader_type right
--- a/arch/x86/kernel/traps_32.c
+++ b/arch/x86/kernel/traps_32.c
@@ -895,6 +895,7 @@ fastcall void __kprobes do_debug(struct
*/
clear_dr7:
set_debugreg(0, 7);
+ notify_die(DIE_DEBUG, "debug2", regs, condition, error_code, SIGTRAP);
return;
debug_vm86:
@@ -1160,6 +1161,12 @@ static void __init set_task_gate(unsigne
_set_gate(n, DESCTYPE_TASK, (void *)0, (gdt_entry<<3));
}
+/* Some traps need to be set early. */
+void __init early_trap_init(void) {
+ set_intr_gate(1, &debug);
+ set_system_intr_gate(3, &int3); /* int3 can be called from all */
+ set_intr_gate(14, &page_fault);
+}
void __init trap_init(void)
{
@@ -1176,10 +1183,8 @@ void __init trap_init(void)
#endif
set_trap_gate(0,÷_error);
- set_intr_gate(1,&debug);
set_intr_gate(2,&nmi);
- set_system_intr_gate(3, &int3); /* int3/4 can be called from all */
- set_system_gate(4,&overflow);
+ set_system_gate(4, &overflow); /* int4/5 can be called from all */
set_trap_gate(5,&bounds);
set_trap_gate(6,&invalid_op);
set_trap_gate(7,&device_not_available);
@@ -1189,7 +1194,6 @@ void __init trap_init(void)
set_trap_gate(11,&segment_not_present);
set_trap_gate(12,&stack_segment);
set_trap_gate(13,&general_protection);
- set_intr_gate(14,&page_fault);
set_trap_gate(15,&spurious_interrupt_bug);
set_trap_gate(16,&coprocessor_error);
set_trap_gate(17,&alignment_check);
--- a/arch/x86/mm/fault_32.c
+++ b/arch/x86/mm/fault_32.c
@@ -517,6 +517,10 @@ no_context:
if (is_prefetch(regs, address, error_code))
return;
+ if (notify_die(DIE_PAGE_FAULT_NO_CONTEXT, "no context", regs,
+ error_code, 14, SIGSEGV) == NOTIFY_STOP)
+ return;
+
/*
* Oops. The kernel tried to access some bad page. We'll have to
* terminate things with extreme prejudice.
--- a/include/asm-x86/kdebug_32.h
+++ b/include/asm-x86/kdebug_32.h
@@ -28,6 +28,7 @@ enum die_val {
DIE_CALL,
DIE_NMI_IPI,
DIE_PAGE_FAULT,
+ DIE_PAGE_FAULT_NO_CONTEXT,
};
#endif
--- /dev/null
+++ b/include/asm-x86/kgdb_32.h
@@ -0,0 +1,51 @@
+#ifdef __KERNEL__
+#ifndef _ASM_KGDB_H_
+#define _ASM_KGDB_H_
+
+#include <asm-generic/kgdb.h>
+
+/*
+ * Copyright (C) 2001-2004 Amit S. Kale
+ */
+
+/************************************************************************/
+/* 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
+
+/* Number of bytes of registers. */
+#define NUMREGBYTES 64
+/* Number of bytes of registers we need to save for a setjmp/longjmp. */
+#define NUMCRITREGBYTES 24
+
+/*
+ * 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.
+ */
+enum regnames { _EAX, /* 0 */
+ _ECX, /* 1 */
+ _EDX, /* 2 */
+ _EBX, /* 3 */
+ _ESP, /* 4 */
+ _EBP, /* 5 */
+ _ESI, /* 6 */
+ _EDI, /* 7 */
+ _PC, /* 8 also known as eip */
+ _PS, /* 9 also known as eflags */
+ _CS, /* 10 */
+ _SS, /* 11 */
+ _DS, /* 12 */
+ _ES, /* 13 */
+ _FS, /* 14 */
+ _GS /* 15 */
+};
+
+#define BREAKPOINT() asm(" int $3");
+#define BREAK_INSTR_SIZE 1
+#define CACHE_FLUSH_IS_SAFE 1
+#endif /* _ASM_KGDB_H_ */
+#endif /* __KERNEL__ */
--- a/lib/Kconfig.kgdb
+++ b/lib/Kconfig.kgdb
@@ -13,7 +13,7 @@ config UNWIND_INFO
config KGDB
bool "KGDB: kernel debugging with remote gdb"
select WANT_EXTRA_DEBUG_INFORMATION
- depends on DEBUG_KERNEL
+ depends on DEBUG_KERNEL && (X86)
help
If you say Y here, it will be possible to remotely debug the
kernel using gdb. Documentation of kernel debugger is available
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