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/**
* @file backtrace.c
*
* @remark Copyright 2002 OProfile authors
* @remark Read the file COPYING
*
* @author John Levon
* @author David Smith
*/
#include <linux/oprofile.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <asm/ptrace.h>
struct frame_head {
struct frame_head * ebp;
unsigned long ret;
} __attribute__((packed));
static struct frame_head *
dump_backtrace(struct frame_head * head)
{
oprofile_add_trace(head->ret);
/* frame pointers should strictly progress back up the stack
* (towards higher addresses) */
if (head >= head->ebp)
return NULL;
return head->ebp;
}
/* check that the page(s) containing the frame head are present */
static int pages_present(struct frame_head * head)
{
struct mm_struct * mm = current->mm;
/* FIXME: only necessary once per page */
if (!check_user_page_readable(mm, (unsigned long)head))
return 0;
return check_user_page_readable(mm, (unsigned long)(head + 1));
}
/*
* | | /\ Higher addresses
* | |
* --------------- stack base (address of current_thread_info)
* | thread info |
* . .
* | stack |
* --------------- saved regs->ebp value if valid (frame_head address)
* . .
* --------------- struct pt_regs stored on stack (struct pt_regs *)
* | |
* . .
* | |
* --------------- %esp
* | |
* | | \/ Lower addresses
*
* Thus, &pt_regs <-> stack base restricts the valid(ish) ebp values
*/
#ifdef CONFIG_FRAME_POINTER
static int valid_kernel_stack(struct frame_head * head, struct pt_regs * regs)
{
unsigned long headaddr = (unsigned long)head;
unsigned long stack = (unsigned long)regs;
unsigned long stack_base = (stack & ~(THREAD_SIZE - 1)) + THREAD_SIZE;
return headaddr > stack && headaddr < stack_base;
}
#else
/* without fp, it's just junk */
static int valid_kernel_stack(struct frame_head * head, struct pt_regs * regs)
{
return 0;
}
#endif
void
x86_backtrace(struct pt_regs * const regs, unsigned int depth)
{
struct frame_head *head;
#ifdef CONFIG_X86_64
head = (struct frame_head *)regs->rbp;
#else
head = (struct frame_head *)regs->ebp;
#endif
if (!user_mode(regs)) {
while (depth-- && valid_kernel_stack(head, regs))
head = dump_backtrace(head);
return;
}
#ifdef CONFIG_SMP
if (!spin_trylock(¤t->mm->page_table_lock))
return;
#endif
while (depth-- && head && pages_present(head))
head = dump_backtrace(head);
#ifdef CONFIG_SMP
spin_unlock(¤t->mm->page_table_lock);
#endif
}
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