[PATCH] i386: 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>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/i386/kernel/entry.S

@@ -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"
 

arch/i386/kernel/process.c

@@ -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);
 }
 
 /*

arch/i386/kernel/traps.c

@@ -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>
@@ -170,14 +171,43 @@ static inline unsigned long print_context_stack(struct thread_info *tinfo,
 	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) : );
@@ -198,13 +228,13 @@ static void show_trace_log_lvl(struct task_struct *task,
 	}
 }
 
-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;
@@ -225,13 +255,13 @@ static void show_stack_log_lvl(struct task_struct *task, unsigned long *esp,
 		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, "");
 }
 
 /*
@@ -241,7 +271,7 @@ void dump_stack(void)
 {
 	unsigned long stack;
 
-	show_trace(current, &stack);
+	show_trace(current, NULL, &stack);
 }
 
 EXPORT_SYMBOL(dump_stack);
@@ -285,7 +315,7 @@ 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: ");
 

arch/i386/kernel/vmlinux.lds.S

@@ -71,6 +71,15 @@ 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)

include/asm-i386/processor.h

@@ -555,7 +555,7 @@ extern void prepare_to_copy(struct task_struct *tsk);
 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);
 

include/asm-i386/unwind.h

+#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 */

lib/Kconfig.debug

@@ -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.