linux/arch/x86/kernel/dumpstack_32.c
Steven Rostedt 7ee991fbc6 ftrace: print real return in dumpstack for function graph
Impact: better dumpstack output

I noticed in my crash dumps and even in the stack tracer that a
lot of functions listed in the stack trace are simply
return_to_handler which is ftrace graphs way to insert its own
call into the return of a function.

But we lose out where the actually function was called from.

This patch adds in hooks to the dumpstack mechanism that detects
this and finds the real function to print. Both are printed to
let the user know that a hook is still in place.

This does give a funny side effect in the stack tracer output:

        Depth   Size      Location    (80 entries)
        -----   ----      --------
  0)     4144      48   save_stack_trace+0x2f/0x4d
  1)     4096     128   ftrace_call+0x5/0x2b
  2)     3968      16   mempool_alloc_slab+0x16/0x18
  3)     3952     384   return_to_handler+0x0/0x73
  4)     3568    -240   stack_trace_call+0x11d/0x209
  5)     3808     144   return_to_handler+0x0/0x73
  6)     3664    -128   mempool_alloc+0x4d/0xfe
  7)     3792     128   return_to_handler+0x0/0x73
  8)     3664     -32   scsi_sg_alloc+0x48/0x4a [scsi_mod]

As you can see, the real functions are now negative. This is due
to them not being found inside the stack.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2008-12-03 08:56:25 +01:00

155 lines
3.2 KiB
C

/*
* Copyright (C) 1991, 1992 Linus Torvalds
* Copyright (C) 2000, 2001, 2002 Andi Kleen, SuSE Labs
*/
#include <linux/kallsyms.h>
#include <linux/kprobes.h>
#include <linux/uaccess.h>
#include <linux/utsname.h>
#include <linux/hardirq.h>
#include <linux/kdebug.h>
#include <linux/module.h>
#include <linux/ptrace.h>
#include <linux/kexec.h>
#include <linux/bug.h>
#include <linux/nmi.h>
#include <linux/sysfs.h>
#include <asm/stacktrace.h>
#include "dumpstack.h"
void dump_trace(struct task_struct *task, struct pt_regs *regs,
unsigned long *stack, unsigned long bp,
const struct stacktrace_ops *ops, void *data)
{
int graph = 0;
if (!task)
task = current;
if (!stack) {
unsigned long dummy;
stack = &dummy;
if (task && task != current)
stack = (unsigned long *)task->thread.sp;
}
#ifdef CONFIG_FRAME_POINTER
if (!bp) {
if (task == current) {
/* Grab bp right from our regs */
get_bp(bp);
} else {
/* bp is the last reg pushed by switch_to */
bp = *(unsigned long *) task->thread.sp;
}
}
#endif
for (;;) {
struct thread_info *context;
context = (struct thread_info *)
((unsigned long)stack & (~(THREAD_SIZE - 1)));
bp = print_context_stack(context, stack, bp, ops,
data, NULL, &graph);
stack = (unsigned long *)context->previous_esp;
if (!stack)
break;
if (ops->stack(data, "IRQ") < 0)
break;
touch_nmi_watchdog();
}
}
EXPORT_SYMBOL(dump_trace);
void
show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs,
unsigned long *sp, unsigned long bp, char *log_lvl)
{
unsigned long *stack;
int i;
if (sp == NULL) {
if (task)
sp = (unsigned long *)task->thread.sp;
else
sp = (unsigned long *)&sp;
}
stack = sp;
for (i = 0; i < kstack_depth_to_print; i++) {
if (kstack_end(stack))
break;
if (i && ((i % STACKSLOTS_PER_LINE) == 0))
printk("\n%s", log_lvl);
printk(" %08lx", *stack++);
touch_nmi_watchdog();
}
printk("\n");
show_trace_log_lvl(task, regs, sp, bp, log_lvl);
}
void show_registers(struct pt_regs *regs)
{
int i;
print_modules();
__show_regs(regs, 0);
printk(KERN_EMERG "Process %.*s (pid: %d, ti=%p task=%p task.ti=%p)\n",
TASK_COMM_LEN, current->comm, task_pid_nr(current),
current_thread_info(), current, task_thread_info(current));
/*
* When in-kernel, we also print out the stack and code at the
* time of the fault..
*/
if (!user_mode_vm(regs)) {
unsigned int code_prologue = code_bytes * 43 / 64;
unsigned int code_len = code_bytes;
unsigned char c;
u8 *ip;
printk(KERN_EMERG "Stack:\n");
show_stack_log_lvl(NULL, regs, &regs->sp,
0, KERN_EMERG);
printk(KERN_EMERG "Code: ");
ip = (u8 *)regs->ip - code_prologue;
if (ip < (u8 *)PAGE_OFFSET || probe_kernel_address(ip, c)) {
/* try starting at IP */
ip = (u8 *)regs->ip;
code_len = code_len - code_prologue + 1;
}
for (i = 0; i < code_len; i++, ip++) {
if (ip < (u8 *)PAGE_OFFSET ||
probe_kernel_address(ip, c)) {
printk(" Bad EIP value.");
break;
}
if (ip == (u8 *)regs->ip)
printk("<%02x> ", c);
else
printk("%02x ", c);
}
}
printk("\n");
}
int is_valid_bugaddr(unsigned long ip)
{
unsigned short ud2;
if (ip < PAGE_OFFSET)
return 0;
if (probe_kernel_address((unsigned short *)ip, ud2))
return 0;
return ud2 == 0x0b0f;
}