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Subject[PATCH 5/6, fixed] reliable stack trace support (i386)
These are the i386-specific pieces to enable reliable stack traces. This is
going to be even more useful once CFI annotations get added to he assembly
code, namely to entry.S.

Signed-off-by: Jan Beulich <jbeulich@novell.com>

Index: unwind-2.6.17-rc5/arch/i386/kernel/entry.S
===================================================================
--- unwind-2.6.17-rc5.orig/arch/i386/kernel/entry.S 2006-05-26 09:01:15.000000000 +0200
+++ unwind-2.6.17-rc5/arch/i386/kernel/entry.S 2006-05-30 09:35:00.000000000 +0200
@@ -663,6 +663,35 @@ ENTRY(spurious_interrupt_bug)
pushl $do_spurious_interrupt_bug
jmp error_code

+#ifdef CONFIG_STACK_UNWIND
+ENTRY(arch_unwind_init_running)
+ movl 4(%esp), %edx
+ movl (%esp), %ecx
+ leal 4(%esp), %eax
+ movl %ebx, EBX(%edx)
+ xorl %ebx, %ebx
+ movl %ebx, ECX(%edx)
+ movl %ebx, EDX(%edx)
+ movl %esi, ESI(%edx)
+ movl %edi, EDI(%edx)
+ movl %ebp, EBP(%edx)
+ movl %ebx, EAX(%edx)
+ movl $__USER_DS, DS(%edx)
+ movl $__USER_DS, ES(%edx)
+ movl %ebx, ORIG_EAX(%edx)
+ movl %ecx, EIP(%edx)
+ movl 12(%esp), %ecx
+ movl $__KERNEL_CS, CS(%edx)
+ movl %ebx, EFLAGS(%edx)
+ movl %eax, OLDESP(%edx)
+ movl 8(%esp), %eax
+ movl %ecx, 8(%esp)
+ movl EBX(%edx), %ebx
+ movl $__KERNEL_DS, OLDSS(%edx)
+ jmpl *%eax
+ENDPROC(arch_unwind_init_running)
+#endif
+
.section .rodata,"a"
#include "syscall_table.S"

Index: unwind-2.6.17-rc5/arch/i386/kernel/process.c
===================================================================
--- unwind-2.6.17-rc5.orig/arch/i386/kernel/process.c 2006-05-26 09:01:15.000000000 +0200
+++ unwind-2.6.17-rc5/arch/i386/kernel/process.c 2006-05-30 09:35:00.000000000 +0200
@@ -312,7 +312,7 @@ void show_regs(struct pt_regs * regs)
cr3 = read_cr3();
cr4 = read_cr4_safe();
printk("CR0: %08lx CR2: %08lx CR3: %08lx CR4: %08lx\n", cr0, cr2, cr3, cr4);
- show_trace(NULL, &regs->esp);
+ show_trace(NULL, regs, &regs->esp);
}

/*
Index: unwind-2.6.17-rc5/arch/i386/kernel/traps.c
===================================================================
--- unwind-2.6.17-rc5.orig/arch/i386/kernel/traps.c 2006-05-26 09:01:15.000000000 +0200
+++ unwind-2.6.17-rc5/arch/i386/kernel/traps.c 2006-05-30 09:35:00.000000000 +0200
@@ -28,6 +28,7 @@
#include <linux/utsname.h>
#include <linux/kprobes.h>
#include <linux/kexec.h>
+#include <linux/unwind.h>

#ifdef CONFIG_EISA
#include <linux/ioport.h>
@@ -47,7 +48,7 @@
#include <asm/desc.h>
#include <asm/i387.h>
#include <asm/nmi.h>
-
+#include <asm/unwind.h>
#include <asm/smp.h>
#include <asm/arch_hooks.h>
#include <asm/kdebug.h>
@@ -164,14 +165,43 @@ static inline unsigned long print_contex
return ebp;
}

-static void show_trace_log_lvl(struct task_struct *task,
+static asmlinkage void show_trace_unwind(struct unwind_frame_info *info, void *log_lvl)
+{
+ int printed = 0; /* nr of entries already printed on current line */
+
+ while (unwind(info) == 0 && UNW_PC(info)) {
+ printed = print_addr_and_symbol(UNW_PC(info), log_lvl, printed);
+ if (arch_unw_user_mode(info))
+ break;
+ }
+ if (printed)
+ printk("\n");
+}
+
+static void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs,
unsigned long *stack, char *log_lvl)
{
unsigned long ebp;
+ struct unwind_frame_info info;

if (!task)
task = current;

+ if (regs) {
+ if (unwind_init_frame_info(&info, task, regs) == 0) {
+ show_trace_unwind(&info, log_lvl);
+ return;
+ }
+ } else if (task == current) {
+ if (unwind_init_running(&info, show_trace_unwind, log_lvl) == 0)
+ return;
+ } else {
+ if (unwind_init_blocked(&info, task) == 0) {
+ show_trace_unwind(&info, log_lvl);
+ return;
+ }
+ }
+
if (task == current) {
/* Grab ebp right from our regs */
asm ("movl %%ebp, %0" : "=r" (ebp) : );
@@ -192,13 +222,13 @@ static void show_trace_log_lvl(struct ta
}
}

-void show_trace(struct task_struct *task, unsigned long * stack)
+void show_trace(struct task_struct *task, struct pt_regs *regs, unsigned long * stack)
{
- show_trace_log_lvl(task, stack, "");
+ show_trace_log_lvl(task, regs, stack, "");
}

-static void show_stack_log_lvl(struct task_struct *task, unsigned long *esp,
- char *log_lvl)
+static void show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs,
+ unsigned long *esp, char *log_lvl)
{
unsigned long *stack;
int i;
@@ -219,13 +249,13 @@ static void show_stack_log_lvl(struct ta
printk("%08lx ", *stack++);
}
printk("\n%sCall Trace:\n", log_lvl);
- show_trace_log_lvl(task, esp, log_lvl);
+ show_trace_log_lvl(task, regs, esp, log_lvl);
}

void show_stack(struct task_struct *task, unsigned long *esp)
{
printk(" ");
- show_stack_log_lvl(task, esp, "");
+ show_stack_log_lvl(task, NULL, esp, "");
}

/*
@@ -235,7 +265,7 @@ void dump_stack(void)
{
unsigned long stack;

- show_trace(current, &stack);
+ show_trace(current, NULL, &stack);
}

EXPORT_SYMBOL(dump_stack);
@@ -278,7 +308,7 @@ void show_registers(struct pt_regs *regs
u8 __user *eip;

printk("\n" KERN_EMERG "Stack: ");
- show_stack_log_lvl(NULL, (unsigned long *)esp, KERN_EMERG);
+ show_stack_log_lvl(NULL, regs, (unsigned long *)esp, KERN_EMERG);

printk(KERN_EMERG "Code: ");

Index: unwind-2.6.17-rc5/arch/i386/kernel/vmlinux.lds.S
===================================================================
--- unwind-2.6.17-rc5.orig/arch/i386/kernel/vmlinux.lds.S 2006-05-26 09:01:15.000000000 +0200
+++ unwind-2.6.17-rc5/arch/i386/kernel/vmlinux.lds.S 2006-05-30 09:35:00.000000000 +0200
@@ -64,6 +64,15 @@ SECTIONS
.data.read_mostly : AT(ADDR(.data.read_mostly) - LOAD_OFFSET) { *(.data.read_mostly) }
_edata = .; /* End of data section */

+#ifdef CONFIG_STACK_UNWIND
+ . = ALIGN(4);
+ .eh_frame : AT(ADDR(.eh_frame) - LOAD_OFFSET) {
+ __start_unwind = .;
+ *(.eh_frame)
+ __end_unwind = .;
+ }
+#endif
+
. = ALIGN(THREAD_SIZE); /* init_task */
.data.init_task : AT(ADDR(.data.init_task) - LOAD_OFFSET) {
*(.data.init_task)
Index: unwind-2.6.17-rc5/include/asm-i386/processor.h
===================================================================
--- unwind-2.6.17-rc5.orig/include/asm-i386/processor.h 2006-05-26 09:02:08.000000000 +0200
+++ unwind-2.6.17-rc5/include/asm-i386/processor.h 2006-05-30 09:35:00.000000000 +0200
@@ -555,7 +555,7 @@ extern void prepare_to_copy(struct task_
extern int kernel_thread(int (*fn)(void *), void * arg, unsigned long flags);

extern unsigned long thread_saved_pc(struct task_struct *tsk);
-void show_trace(struct task_struct *task, unsigned long *stack);
+void show_trace(struct task_struct *task, struct pt_regs *regs, unsigned long *stack);

unsigned long get_wchan(struct task_struct *p);

Index: unwind-2.6.17-rc5/include/asm-i386/unwind.h
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ unwind-2.6.17-rc5/include/asm-i386/unwind.h 2006-05-30 09:35:00.000000000 +0200
@@ -0,0 +1,98 @@
+#ifndef _ASM_I386_UNWIND_H
+#define _ASM_I386_UNWIND_H
+
+/*
+ * Copyright (C) 2002-2006 Novell, Inc.
+ * Jan Beulich <jbeulich@novell.com>
+ * This code is released under version 2 of the GNU GPL.
+ */
+
+#ifdef CONFIG_STACK_UNWIND
+
+#include <linux/sched.h>
+#include <asm/fixmap.h>
+#include <asm/ptrace.h>
+#include <asm/uaccess.h>
+
+struct unwind_frame_info
+{
+ struct pt_regs regs;
+ struct task_struct *task;
+};
+
+#define UNW_PC(frame) (frame)->regs.eip
+#define UNW_SP(frame) (frame)->regs.esp
+#ifdef CONFIG_FRAME_POINTER
+#define UNW_FP(frame) (frame)->regs.ebp
+#define FRAME_RETADDR_OFFSET 4
+#define FRAME_LINK_OFFSET 0
+#define STACK_BOTTOM(tsk) STACK_LIMIT((tsk)->thread.esp0)
+#define STACK_TOP(tsk) ((tsk)->thread.esp0)
+#endif
+#define STACK_LIMIT(ptr) (((ptr) - 1) & ~(THREAD_SIZE - 1))
+
+#define UNW_REGISTER_INFO \
+ PTREGS_INFO(eax), \
+ PTREGS_INFO(ecx), \
+ PTREGS_INFO(edx), \
+ PTREGS_INFO(ebx), \
+ PTREGS_INFO(esp), \
+ PTREGS_INFO(ebp), \
+ PTREGS_INFO(esi), \
+ PTREGS_INFO(edi), \
+ PTREGS_INFO(eip)
+
+static inline void arch_unw_init_frame_info(struct unwind_frame_info *info,
+ /*const*/ struct pt_regs *regs)
+{
+ if (user_mode_vm(regs))
+ info->regs = *regs;
+ else {
+ memcpy(&info->regs, regs, offsetof(struct pt_regs, esp));
+ info->regs.esp = (unsigned long)&regs->esp;
+ info->regs.xss = __KERNEL_DS;
+ }
+}
+
+static inline void arch_unw_init_blocked(struct unwind_frame_info *info)
+{
+ memset(&info->regs, 0, sizeof(info->regs));
+ info->regs.eip = info->task->thread.eip;
+ info->regs.xcs = __KERNEL_CS;
+ __get_user(info->regs.ebp, (long *)info->task->thread.esp);
+ info->regs.esp = info->task->thread.esp;
+ info->regs.xss = __KERNEL_DS;
+ info->regs.xds = __USER_DS;
+ info->regs.xes = __USER_DS;
+}
+
+extern asmlinkage void arch_unwind_init_running(struct unwind_frame_info *,
+ asmlinkage void (*callback)(struct unwind_frame_info *,
+ void *arg),
+ void *arg);
+
+static inline int arch_unw_user_mode(const struct unwind_frame_info *info)
+{
+#if 0 /* This can only work when selector register and EFLAGS saves/restores
+ are properly annotated (and tracked in UNW_REGISTER_INFO). */
+ return user_mode_vm(&info->regs);
+#else
+ return info->regs.eip < PAGE_OFFSET
+ || (info->regs.eip >= __fix_to_virt(FIX_VSYSCALL)
+ && info->regs.eip < __fix_to_virt(FIX_VSYSCALL) + PAGE_SIZE)
+ || info->regs.esp < PAGE_OFFSET;
+#endif
+}
+
+#else
+
+#define UNW_PC(frame) ((void)(frame), 0)
+
+static inline int arch_unw_user_mode(const void *info)
+{
+ return 0;
+}
+
+#endif
+
+#endif /* _ASM_I386_UNWIND_H */
Index: unwind-2.6.17-rc5/lib/Kconfig.debug
===================================================================
--- unwind-2.6.17-rc5.orig/lib/Kconfig.debug 2006-05-30 09:34:53.000000000 +0200
+++ unwind-2.6.17-rc5/lib/Kconfig.debug 2006-05-30 09:35:00.000000000 +0200
@@ -199,7 +199,7 @@ config UNWIND_INFO
config STACK_UNWIND
bool "Stack unwind support"
depends on UNWIND_INFO
- depends on X86_64
+ depends on X86
help
This enables more precise stack traces, omitting all unrelated
occurrences of pointers into kernel code from the dump.

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