static int collect_syscall(struct task_struct *target, struct syscall_info *info)
{
struct pt_regs *regs;
if (!try_get_task_stack(target)) {
/* Task has no stack, so the task isn't in a syscall. */
memset(info, 0, sizeof(*info));
info->data.nr = -1;
return 0;
}
regs = task_pt_regs(target);
if (unlikely(!regs)) {
put_task_stack(target);
return -EAGAIN;
}
info->sp = user_stack_pointer(regs);
info->data.instruction_pointer = instruction_pointer(regs);
info->data.nr = syscall_get_nr(target, regs);
if (info->data.nr != -1L)
syscall_get_arguments(target, regs,
(unsigned long *)&info->data.args[0]);
put_task_stack(target);
return 0;
}
void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
{
if (!try_get_task_stack(tsk))
return;
__save_stack_trace(trace, tsk, NULL, true);
put_task_stack(tsk);
}
/*
* Called from fs/proc with a reference on @p to find the function
* which called into schedule(). This needs to be done carefully
* because the task might wake up and we might look at a stack
* changing under us.
*/
unsigned long get_wchan(struct task_struct *p)
{
unsigned long start, bottom, top, sp, fp, ip, ret = 0;
int count = 0;
if (!p || p == current || p->state == TASK_RUNNING)
return 0;
if (!try_get_task_stack(p))
return 0;
start = (unsigned long)task_stack_page(p);
if (!start)
goto out;
/*
* Layout of the stack page:
*
* ----------- topmax = start + THREAD_SIZE - sizeof(unsigned long)
* PADDING
* ----------- top = topmax - TOP_OF_KERNEL_STACK_PADDING
* stack
* ----------- bottom = start
*
* The tasks stack pointer points at the location where the
* framepointer is stored. The data on the stack is:
* ... IP FP ... IP FP
*
* We need to read FP and IP, so we need to adjust the upper
* bound by another unsigned long.
*/
top = start + THREAD_SIZE - TOP_OF_KERNEL_STACK_PADDING;
top -= 2 * sizeof(unsigned long);
bottom = start;
sp = READ_ONCE(p->thread.sp);
if (sp < bottom || sp > top)
goto out;
fp = READ_ONCE_NOCHECK(((struct inactive_task_frame *)sp)->bp);
do {
if (fp < bottom || fp > top)
goto out;
ip = READ_ONCE_NOCHECK(*(unsigned long *)(fp + sizeof(unsigned long)));
if (!in_sched_functions(ip)) {
ret = ip;
goto out;
}
fp = READ_ONCE_NOCHECK(*(unsigned long *)fp);
} while (count++ < 16 && p->state != TASK_RUNNING);
out:
put_task_stack(p);
return ret;
}
/*
* This function returns an error if it detects any unreliable features of the
* stack. Otherwise it guarantees that the stack trace is reliable.
*
* If the task is not 'current', the caller *must* ensure the task is inactive.
*/
int save_stack_trace_tsk_reliable(struct task_struct *tsk,
struct stack_trace *trace)
{
int ret;
if (!try_get_task_stack(tsk))
return -EINVAL;
ret = __save_stack_trace_reliable(trace, tsk);
put_task_stack(tsk);
return ret;
}
void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
{
struct stackframe frame;
int skip;
pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
if (!tsk)
tsk = current;
if (!try_get_task_stack(tsk))
return;
if (tsk == current) {
frame.fp = (unsigned long)__builtin_frame_address(0);
frame.pc = (unsigned long)dump_backtrace;
} else {
/*
* task blocked in __switch_to
*/
frame.fp = thread_saved_fp(tsk);
frame.pc = thread_saved_pc(tsk);
}
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
frame.graph = 0;
#endif
skip = !!regs;
printk("Call trace:\n");
do {
/* skip until specified stack frame */
if (!skip) {
dump_backtrace_entry(frame.pc);
} else if (frame.fp == regs->regs[29]) {
skip = 0;
/*
* Mostly, this is the case where this function is
* called in panic/abort. As exception handler's
* stack frame does not contain the corresponding pc
* at which an exception has taken place, use regs->pc
* instead.
*/
dump_backtrace_entry(regs->pc);
}
} while (!unwind_frame(tsk, &frame));
put_task_stack(tsk);
}
/**
* stack_trace_save_tsk_reliable - Save task stack with verification
* @tsk: Pointer to the task to examine
* @store: Pointer to storage array
* @size: Size of the storage array
*
* Return: An error if it detects any unreliable features of the
* stack. Otherwise it guarantees that the stack trace is
* reliable and returns the number of entries stored.
*
* If the task is not 'current', the caller *must* ensure the task is inactive.
*/
int stack_trace_save_tsk_reliable(struct task_struct *tsk, unsigned long *store,
unsigned int size)
{
stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
struct stacktrace_cookie c = {
.store = store,
.size = size,
};
int ret;
/*
* If the task doesn't have a stack (e.g., a zombie), the stack is
* "reliably" empty.
*/
if (!try_get_task_stack(tsk))
return 0;
ret = arch_stack_walk_reliable(consume_entry, &c, tsk);
put_task_stack(tsk);
return ret;
}
/**
* stack_trace_save - Save a stack trace into a storage array
* @store: Pointer to storage array
* @size: Size of the storage array
* @skipnr: Number of entries to skip at the start of the stack trace
*
* Return: Number of trace entries stored.
*/
unsigned int stack_trace_save(unsigned long *store, unsigned int size,
unsigned int skipnr)
{
stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
struct stacktrace_cookie c = {
.store = store,
.size = size,
.skip = skipnr + 1,
};
arch_stack_walk(consume_entry, &c, current, NULL);
return c.len;
}
EXPORT_SYMBOL_GPL(stack_trace_save);
/**
* stack_trace_save_tsk - Save a task stack trace into a storage array
* @task: The task to examine
* @store: Pointer to storage array
* @size: Size of the storage array
* @skipnr: Number of entries to skip at the start of the stack trace
*
* Return: Number of trace entries stored.
*/
unsigned int stack_trace_save_tsk(struct task_struct *tsk, unsigned long *store,
unsigned int size, unsigned int skipnr)
{
stack_trace_consume_fn consume_entry = stack_trace_consume_entry_nosched;
struct stacktrace_cookie c = {
.store = store,
.size = size,
.skip = skipnr + 1,
};
if (!try_get_task_stack(tsk))
return 0;
arch_stack_walk(consume_entry, &c, tsk, NULL);
put_task_stack(tsk);
return c.len;
}
/**
* stack_trace_save_regs - Save a stack trace based on pt_regs into a storage array
* @regs: Pointer to pt_regs to examine
* @store: Pointer to storage array
* @size: Size of the storage array
* @skipnr: Number of entries to skip at the start of the stack trace
*
* Return: Number of trace entries stored.
*/
unsigned int stack_trace_save_regs(struct pt_regs *regs, unsigned long *store,
unsigned int size, unsigned int skipnr)
{
stack_trace_consume_fn consume_entry = stack_trace_consume_entry;
struct stacktrace_cookie c = {
.store = store,
.size = size,
.skip = skipnr,
};
arch_stack_walk(consume_entry, &c, current, regs);
return c.len;
}
void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
{
struct stackframe frame;
unsigned long irq_stack_ptr;
int skip;
pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
if (!tsk)
tsk = current;
if (!try_get_task_stack(tsk))
return;
/*
* Switching between stacks is valid when tracing current and in
* non-preemptible context.
*/
if (tsk == current && !preemptible())
irq_stack_ptr = IRQ_STACK_PTR(smp_processor_id());
else
irq_stack_ptr = 0;
if (tsk == current) {
frame.fp = (unsigned long)__builtin_frame_address(0);
frame.sp = current_stack_pointer;
frame.pc = (unsigned long)dump_backtrace;
} else {
/*
* task blocked in __switch_to
*/
frame.fp = thread_saved_fp(tsk);
frame.sp = thread_saved_sp(tsk);
frame.pc = thread_saved_pc(tsk);
}
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
frame.graph = tsk->curr_ret_stack;
#endif
skip = !!regs;
printk("Call trace:\n");
while (1) {
unsigned long where = frame.pc;
unsigned long stack;
int ret;
/* skip until specified stack frame */
if (!skip) {
dump_backtrace_entry(where);
} else if (frame.fp == regs->regs[29]) {
skip = 0;
/*
* Mostly, this is the case where this function is
* called in panic/abort. As exception handler's
* stack frame does not contain the corresponding pc
* at which an exception has taken place, use regs->pc
* instead.
*/
dump_backtrace_entry(regs->pc);
}
ret = unwind_frame(tsk, &frame);
if (ret < 0)
break;
stack = frame.sp;
if (in_exception_text(where)) {
/*
* If we switched to the irq_stack before calling this
* exception handler, then the pt_regs will be on the
* task stack. The easiest way to tell is if the large
* pt_regs would overlap with the end of the irq_stack.
*/
if (stack < irq_stack_ptr &&
(stack + sizeof(struct pt_regs)) > irq_stack_ptr)
stack = IRQ_STACK_TO_TASK_STACK(irq_stack_ptr);
dump_mem("", "Exception stack", stack,
stack + sizeof(struct pt_regs));
}
}
put_task_stack(tsk);
}