[deliverable/linux.git] / arch / i386 / oprofile / backtrace.c

/**
 * @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>
#include <asm/uaccess.h>

struct frame_head {
	struct frame_head * ebp;
	unsigned long ret;
} __attribute__((packed));

static struct frame_head *
dump_backtrace(struct frame_head * head)
{
	struct frame_head bufhead[2];

	/* Also check accessibility of one struct frame_head beyond */
	if (!access_ok(VERIFY_READ, head, sizeof(bufhead)))
		return NULL;
	if (__copy_from_user_inatomic(bufhead, head, sizeof(bufhead)))
		return NULL;

	oprofile_add_trace(bufhead[0].ret);

	/* frame pointers should strictly progress back up the stack
	 * (towards higher addresses) */
	if (head >= bufhead[0].ebp)
		return NULL;

	return bufhead[0].ebp;
}

/*
 * |             | /\ Higher addresses
 * |             |
 * --------------- stack base (address of current_thread_info)
 * | thread info |
 * .             .
 * |    stack    |
 * --------------- saved regs->ebp value if valid (frame_head address)
 * .             .
 * --------------- saved regs->rsp value if x86_64
 * |             |
 * --------------- struct pt_regs * stored on stack if 32-bit
 * |             |
 * .             .
 * |             |
 * --------------- %esp
 * |             |
 * |             | \/ Lower addresses
 *
 * Thus, regs (or regs->rsp for x86_64) <-> stack base restricts the
 * valid(ish) ebp values. Note: (1) for x86_64, NMI and several other
 * exceptions use special stacks, maintained by the interrupt stack table
 * (IST). These stacks are set up in trap_init() in
 * arch/x86_64/kernel/traps.c. Thus, for x86_64, regs now does not point
 * to the kernel stack; instead, it points to some location on the NMI
 * stack. On the other hand, regs->rsp is the stack pointer saved when the
 * NMI occurred. (2) For 32-bit, regs->esp is not valid because the
 * processor does not save %esp on the kernel stack when interrupts occur
 * in the kernel mode.
 */
#ifdef CONFIG_FRAME_POINTER
static int valid_kernel_stack(struct frame_head * head, struct pt_regs * regs)
{
	unsigned long headaddr = (unsigned long)head;
#ifdef CONFIG_X86_64
	unsigned long stack = (unsigned long)regs->rsp;
#else
	unsigned long stack = (unsigned long)regs;
#endif
	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_vm(regs)) {
		while (depth-- && valid_kernel_stack(head, regs))
			head = dump_backtrace(head);
		return;
	}

	while (depth-- && head)
		head = dump_backtrace(head);
}
Commit	Line	Data
1da177e4 LT	1	/**
	2	* @file backtrace.c
	3	*
	4	* @remark Copyright 2002 OProfile authors
	5	* @remark Read the file COPYING
	6	*
	7	* @author John Levon
	8	* @author David Smith
	9	*/
	10
	11	#include <linux/oprofile.h>
	12	#include <linux/sched.h>
	13	#include <linux/mm.h>
	14	#include <asm/ptrace.h>
c34d1b4d	15	#include <asm/uaccess.h>
1da177e4 LT	16
	17	struct frame_head {
	18	struct frame_head * ebp;
	19	unsigned long ret;
	20	} __attribute__((packed));
	21
	22	static struct frame_head *
	23	dump_backtrace(struct frame_head * head)
	24	{
c34d1b4d	25	struct frame_head bufhead[2];
1da177e4	26
c34d1b4d HD	27	/* Also check accessibility of one struct frame_head beyond */
	28	if (!access_ok(VERIFY_READ, head, sizeof(bufhead)))
	29	return NULL;
	30	if (__copy_from_user_inatomic(bufhead, head, sizeof(bufhead)))
1da177e4 LT	31	return NULL;
1da177e4 LT	32
c34d1b4d	33	oprofile_add_trace(bufhead[0].ret);
1da177e4	34
c34d1b4d HD	35	/* frame pointers should strictly progress back up the stack
	36	* (towards higher addresses) */
	37	if (head >= bufhead[0].ebp)
	38	return NULL;
1da177e4	39
c34d1b4d	40	return bufhead[0].ebp;
1da177e4 LT	41	}
	42
	43	/*
	44	* \| \| /\ Higher addresses
	45	* \| \|
	46	* --------------- stack base (address of current_thread_info)
	47	* \| thread info \|
	48	* . .
	49	* \| stack \|
	50	* --------------- saved regs->ebp value if valid (frame_head address)
	51	* . .
23332c2e TL	52	* --------------- saved regs->rsp value if x86_64
	53	* \| \|
	54	* --------------- struct pt_regs * stored on stack if 32-bit
1da177e4 LT	55	* \| \|
	56	* . .
	57	* \| \|
	58	* --------------- %esp
	59	* \| \|
	60	* \| \| \/ Lower addresses
	61	*
23332c2e TL	62	* Thus, regs (or regs->rsp for x86_64) <-> stack base restricts the
	63	* valid(ish) ebp values. Note: (1) for x86_64, NMI and several other
	64	* exceptions use special stacks, maintained by the interrupt stack table
	65	* (IST). These stacks are set up in trap_init() in
	66	* arch/x86_64/kernel/traps.c. Thus, for x86_64, regs now does not point
	67	* to the kernel stack; instead, it points to some location on the NMI
	68	* stack. On the other hand, regs->rsp is the stack pointer saved when the
	69	* NMI occurred. (2) For 32-bit, regs->esp is not valid because the
	70	* processor does not save %esp on the kernel stack when interrupts occur
	71	* in the kernel mode.
1da177e4 LT	72	*/
	73	#ifdef CONFIG_FRAME_POINTER
	74	static int valid_kernel_stack(struct frame_head * head, struct pt_regs * regs)
	75	{
	76	unsigned long headaddr = (unsigned long)head;
23332c2e TL	77	#ifdef CONFIG_X86_64
	78	unsigned long stack = (unsigned long)regs->rsp;
	79	#else
1da177e4	80	unsigned long stack = (unsigned long)regs;
23332c2e	81	#endif
1da177e4 LT	82	unsigned long stack_base = (stack & ~(THREAD_SIZE - 1)) + THREAD_SIZE;
	83
	84	return headaddr > stack && headaddr < stack_base;
	85	}
	86	#else
	87	/* without fp, it's just junk */
	88	static int valid_kernel_stack(struct frame_head * head, struct pt_regs * regs)
	89	{
	90	return 0;
	91	}
	92	#endif
	93
	94
	95	void
	96	x86_backtrace(struct pt_regs * const regs, unsigned int depth)
	97	{
	98	struct frame_head *head;
	99
	100	#ifdef CONFIG_X86_64
	101	head = (struct frame_head *)regs->rbp;
	102	#else
	103	head = (struct frame_head *)regs->ebp;
	104	#endif
	105
fa1e1bdf	106	if (!user_mode_vm(regs)) {
1da177e4 LT	107	while (depth-- && valid_kernel_stack(head, regs))
	108	head = dump_backtrace(head);
	109	return;
	110	}
	111
c34d1b4d	112	while (depth-- && head)
1da177e4	113	head = dump_backtrace(head);
1da177e4	114	}