165 lines
4.2 KiB
C
165 lines
4.2 KiB
C
/*
|
|
* Copyright (C) 2009 Matt Fleming
|
|
*
|
|
* Based, in part, on kernel/time/clocksource.c.
|
|
*
|
|
* This file provides arbitration code for stack unwinders.
|
|
*
|
|
* Multiple stack unwinders can be available on a system, usually with
|
|
* the most accurate unwinder being the currently active one.
|
|
*/
|
|
#include <linux/errno.h>
|
|
#include <linux/list.h>
|
|
#include <linux/spinlock.h>
|
|
#include <linux/module.h>
|
|
#include <asm/unwinder.h>
|
|
#include <asm/atomic.h>
|
|
|
|
/*
|
|
* This is the most basic stack unwinder an architecture can
|
|
* provide. For architectures without reliable frame pointers, e.g.
|
|
* RISC CPUs, it can be implemented by looking through the stack for
|
|
* addresses that lie within the kernel text section.
|
|
*
|
|
* Other CPUs, e.g. x86, can use their frame pointer register to
|
|
* construct more accurate stack traces.
|
|
*/
|
|
static struct list_head unwinder_list;
|
|
static struct unwinder stack_reader = {
|
|
.name = "stack-reader",
|
|
.dump = stack_reader_dump,
|
|
.rating = 50,
|
|
.list = {
|
|
.next = &unwinder_list,
|
|
.prev = &unwinder_list,
|
|
},
|
|
};
|
|
|
|
/*
|
|
* "curr_unwinder" points to the stack unwinder currently in use. This
|
|
* is the unwinder with the highest rating.
|
|
*
|
|
* "unwinder_list" is a linked-list of all available unwinders, sorted
|
|
* by rating.
|
|
*
|
|
* All modifications of "curr_unwinder" and "unwinder_list" must be
|
|
* performed whilst holding "unwinder_lock".
|
|
*/
|
|
static struct unwinder *curr_unwinder = &stack_reader;
|
|
|
|
static struct list_head unwinder_list = {
|
|
.next = &stack_reader.list,
|
|
.prev = &stack_reader.list,
|
|
};
|
|
|
|
static DEFINE_SPINLOCK(unwinder_lock);
|
|
|
|
/**
|
|
* select_unwinder - Select the best registered stack unwinder.
|
|
*
|
|
* Private function. Must hold unwinder_lock when called.
|
|
*
|
|
* Select the stack unwinder with the best rating. This is useful for
|
|
* setting up curr_unwinder.
|
|
*/
|
|
static struct unwinder *select_unwinder(void)
|
|
{
|
|
struct unwinder *best;
|
|
|
|
if (list_empty(&unwinder_list))
|
|
return NULL;
|
|
|
|
best = list_entry(unwinder_list.next, struct unwinder, list);
|
|
if (best == curr_unwinder)
|
|
return NULL;
|
|
|
|
return best;
|
|
}
|
|
|
|
/*
|
|
* Enqueue the stack unwinder sorted by rating.
|
|
*/
|
|
static int unwinder_enqueue(struct unwinder *ops)
|
|
{
|
|
struct list_head *tmp, *entry = &unwinder_list;
|
|
|
|
list_for_each(tmp, &unwinder_list) {
|
|
struct unwinder *o;
|
|
|
|
o = list_entry(tmp, struct unwinder, list);
|
|
if (o == ops)
|
|
return -EBUSY;
|
|
/* Keep track of the place, where to insert */
|
|
if (o->rating >= ops->rating)
|
|
entry = tmp;
|
|
}
|
|
list_add(&ops->list, entry);
|
|
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* unwinder_register - Used to install new stack unwinder
|
|
* @u: unwinder to be registered
|
|
*
|
|
* Install the new stack unwinder on the unwinder list, which is sorted
|
|
* by rating.
|
|
*
|
|
* Returns -EBUSY if registration fails, zero otherwise.
|
|
*/
|
|
int unwinder_register(struct unwinder *u)
|
|
{
|
|
unsigned long flags;
|
|
int ret;
|
|
|
|
spin_lock_irqsave(&unwinder_lock, flags);
|
|
ret = unwinder_enqueue(u);
|
|
if (!ret)
|
|
curr_unwinder = select_unwinder();
|
|
spin_unlock_irqrestore(&unwinder_lock, flags);
|
|
|
|
return ret;
|
|
}
|
|
|
|
int unwinder_faulted = 0;
|
|
|
|
/*
|
|
* Unwind the call stack and pass information to the stacktrace_ops
|
|
* functions. Also handle the case where we need to switch to a new
|
|
* stack dumper because the current one faulted unexpectedly.
|
|
*/
|
|
void unwind_stack(struct task_struct *task, struct pt_regs *regs,
|
|
unsigned long *sp, const struct stacktrace_ops *ops,
|
|
void *data)
|
|
{
|
|
unsigned long flags;
|
|
|
|
/*
|
|
* The problem with unwinders with high ratings is that they are
|
|
* inherently more complicated than the simple ones with lower
|
|
* ratings. We are therefore more likely to fault in the
|
|
* complicated ones, e.g. hitting BUG()s. If we fault in the
|
|
* code for the current stack unwinder we try to downgrade to
|
|
* one with a lower rating.
|
|
*
|
|
* Hopefully this will give us a semi-reliable stacktrace so we
|
|
* can diagnose why curr_unwinder->dump() faulted.
|
|
*/
|
|
if (unwinder_faulted) {
|
|
spin_lock_irqsave(&unwinder_lock, flags);
|
|
|
|
/* Make sure no one beat us to changing the unwinder */
|
|
if (unwinder_faulted && !list_is_singular(&unwinder_list)) {
|
|
list_del(&curr_unwinder->list);
|
|
curr_unwinder = select_unwinder();
|
|
|
|
unwinder_faulted = 0;
|
|
}
|
|
|
|
spin_unlock_irqrestore(&unwinder_lock, flags);
|
|
}
|
|
|
|
curr_unwinder->dump(task, regs, sp, ops, data);
|
|
}
|
|
EXPORT_SYMBOL_GPL(unwind_stack);
|