[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>

4 files changed, 79 insertions, 11 deletions

diff --git a/arch/i386/kernel/entry.S b/arch/i386/kernel/entry.S
index cfc683f153b9..e802f3cac7e3 100644
--- a/arch/i386/kernel/entry.S
+++ b/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"
 
diff --git a/arch/i386/kernel/process.c b/arch/i386/kernel/process.c
index 6259afea46d1..525432e3fef7 100644
--- a/arch/i386/kernel/process.c
+++ b/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);
 }
 
 /*
diff --git a/arch/i386/kernel/traps.c b/arch/i386/kernel/traps.c
index dcc14477af1f..286584667865 100644
--- a/arch/i386/kernel/traps.c
+++ b/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: ");
 
diff --git a/arch/i386/kernel/vmlinux.lds.S b/arch/i386/kernel/vmlinux.lds.S
index 7512f39c9f25..2d4f1386e2b1 100644
--- a/arch/i386/kernel/vmlinux.lds.S
+++ b/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)