[linux-2.6-block.git] / arch / x86 / kernel / step.c

/*
 * x86 single-step support code, common to 32-bit and 64-bit.
 */
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/ptrace.h>

unsigned long convert_rip_to_linear(struct task_struct *child, struct pt_regs *regs)
{
	unsigned long addr, seg;

	addr = regs->rip;
	seg = regs->cs & 0xffff;

	/*
	 * We'll assume that the code segments in the GDT
	 * are all zero-based. That is largely true: the
	 * TLS segments are used for data, and the PNPBIOS
	 * and APM bios ones we just ignore here.
	 */
	if ((seg & SEGMENT_TI_MASK) == SEGMENT_LDT) {
		u32 *desc;
		unsigned long base;

		seg &= ~7UL;

		mutex_lock(&child->mm->context.lock);
		if (unlikely((seg >> 3) >= child->mm->context.size))
			addr = -1L; /* bogus selector, access would fault */
		else {
			desc = child->mm->context.ldt + seg;
			base = ((desc[0] >> 16) |
				((desc[1] & 0xff) << 16) |
				(desc[1] & 0xff000000));

			/* 16-bit code segment? */
			if (!((desc[1] >> 22) & 1))
				addr &= 0xffff;
			addr += base;
		}
		mutex_unlock(&child->mm->context.lock);
	}

	return addr;
}

static int is_setting_trap_flag(struct task_struct *child, struct pt_regs *regs)
{
	int i, copied;
	unsigned char opcode[15];
	unsigned long addr = convert_rip_to_linear(child, regs);

	copied = access_process_vm(child, addr, opcode, sizeof(opcode), 0);
	for (i = 0; i < copied; i++) {
		switch (opcode[i]) {
		/* popf and iret */
		case 0x9d: case 0xcf:
			return 1;

			/* CHECKME: 64 65 */

		/* opcode and address size prefixes */
		case 0x66: case 0x67:
			continue;
		/* irrelevant prefixes (segment overrides and repeats) */
		case 0x26: case 0x2e:
		case 0x36: case 0x3e:
		case 0x64: case 0x65:
		case 0xf0: case 0xf2: case 0xf3:
			continue;

		case 0x40 ... 0x4f:
			if (regs->cs != __USER_CS)
				/* 32-bit mode: register increment */
				return 0;
			/* 64-bit mode: REX prefix */
			continue;

			/* CHECKME: f2, f3 */

		/*
		 * pushf: NOTE! We should probably not let
		 * the user see the TF bit being set. But
		 * it's more pain than it's worth to avoid
		 * it, and a debugger could emulate this
		 * all in user space if it _really_ cares.
		 */
		case 0x9c:
		default:
			return 0;
		}
	}
	return 0;
}

void user_enable_single_step(struct task_struct *child)
{
	struct pt_regs *regs = task_pt_regs(child);

	/*
	 * Always set TIF_SINGLESTEP - this guarantees that
	 * we single-step system calls etc..  This will also
	 * cause us to set TF when returning to user mode.
	 */
	set_tsk_thread_flag(child, TIF_SINGLESTEP);

	/*
	 * If TF was already set, don't do anything else
	 */
	if (regs->eflags & X86_EFLAGS_TF)
		return;

	/* Set TF on the kernel stack.. */
	regs->eflags |= X86_EFLAGS_TF;

	/*
	 * ..but if TF is changed by the instruction we will trace,
	 * don't mark it as being "us" that set it, so that we
	 * won't clear it by hand later.
	 */
	if (is_setting_trap_flag(child, regs))
		return;

	child->ptrace |= PT_DTRACE;
}

void user_disable_single_step(struct task_struct *child)
{
	/* Always clear TIF_SINGLESTEP... */
	clear_tsk_thread_flag(child, TIF_SINGLESTEP);

	/* But touch TF only if it was set by us.. */
	if (child->ptrace & PT_DTRACE) {
		struct pt_regs *regs = task_pt_regs(child);
		regs->eflags &= ~X86_EFLAGS_TF;
		child->ptrace &= ~PT_DTRACE;
	}
}
Commit	Line	Data
fa1e03ea RM	1	/*
	2	* x86 single-step support code, common to 32-bit and 64-bit.
	3	*/
	4	#include <linux/sched.h>
	5	#include <linux/mm.h>
	6	#include <linux/ptrace.h>
	7
fa1e03ea RM	8	unsigned long convert_rip_to_linear(struct task_struct child, struct pt_regs regs)
	9	{
	10	unsigned long addr, seg;
	11
	12	addr = regs->rip;
	13	seg = regs->cs & 0xffff;
	14
	15	/*
	16	* We'll assume that the code segments in the GDT
	17	* are all zero-based. That is largely true: the
	18	* TLS segments are used for data, and the PNPBIOS
	19	* and APM bios ones we just ignore here.
	20	*/
3f80c1ad	21	if ((seg & SEGMENT_TI_MASK) == SEGMENT_LDT) {
fa1e03ea RM	22	u32 *desc;
	23	unsigned long base;
	24
	25	seg &= ~7UL;
	26
	27	mutex_lock(&child->mm->context.lock);
	28	if (unlikely((seg >> 3) >= child->mm->context.size))
	29	addr = -1L; /* bogus selector, access would fault */
	30	else {
	31	desc = child->mm->context.ldt + seg;
	32	base = ((desc[0] >> 16) \|
	33	((desc[1] & 0xff) << 16) \|
	34	(desc[1] & 0xff000000));
	35
	36	/* 16-bit code segment? */
	37	if (!((desc[1] >> 22) & 1))
	38	addr &= 0xffff;
	39	addr += base;
	40	}
	41	mutex_unlock(&child->mm->context.lock);
	42	}
	43
	44	return addr;
	45	}
	46
	47	static int is_setting_trap_flag(struct task_struct child, struct pt_regs regs)
	48	{
	49	int i, copied;
	50	unsigned char opcode[15];
	51	unsigned long addr = convert_rip_to_linear(child, regs);
	52
	53	copied = access_process_vm(child, addr, opcode, sizeof(opcode), 0);
	54	for (i = 0; i < copied; i++) {
	55	switch (opcode[i]) {
	56	/* popf and iret */
	57	case 0x9d: case 0xcf:
	58	return 1;
	59
	60	/* CHECKME: 64 65 */
	61
	62	/* opcode and address size prefixes */
	63	case 0x66: case 0x67:
	64	continue;
	65	/* irrelevant prefixes (segment overrides and repeats) */
	66	case 0x26: case 0x2e:
	67	case 0x36: case 0x3e:
	68	case 0x64: case 0x65:
5f76cb1f	69	case 0xf0: case 0xf2: case 0xf3:
fa1e03ea RM	70	continue;
	71
	72	case 0x40 ... 0x4f:
	73	if (regs->cs != __USER_CS)
	74	/* 32-bit mode: register increment */
	75	return 0;
	76	/* 64-bit mode: REX prefix */
	77	continue;
	78
	79	/* CHECKME: f2, f3 */
	80
	81	/*
	82	* pushf: NOTE! We should probably not let
	83	* the user see the TF bit being set. But
	84	* it's more pain than it's worth to avoid
	85	* it, and a debugger could emulate this
	86	* all in user space if it _really_ cares.
	87	*/
	88	case 0x9c:
	89	default:
	90	return 0;
	91	}
	92	}
	93	return 0;
	94	}
	95
	96	void user_enable_single_step(struct task_struct *child)
	97	{
	98	struct pt_regs *regs = task_pt_regs(child);
	99
	100	/*
	101	* Always set TIF_SINGLESTEP - this guarantees that
	102	* we single-step system calls etc.. This will also
	103	* cause us to set TF when returning to user mode.
	104	*/
	105	set_tsk_thread_flag(child, TIF_SINGLESTEP);
	106
	107	/*
	108	* If TF was already set, don't do anything else
	109	*/
	110	if (regs->eflags & X86_EFLAGS_TF)
	111	return;
	112
	113	/* Set TF on the kernel stack.. */
	114	regs->eflags \|= X86_EFLAGS_TF;
	115
	116	/*
	117	* ..but if TF is changed by the instruction we will trace,
	118	* don't mark it as being "us" that set it, so that we
	119	* won't clear it by hand later.
	120	*/
	121	if (is_setting_trap_flag(child, regs))
	122	return;
	123
	124	child->ptrace \|= PT_DTRACE;
	125	}
	126
	127	void user_disable_single_step(struct task_struct *child)
	128	{
	129	/* Always clear TIF_SINGLESTEP... */
	130	clear_tsk_thread_flag(child, TIF_SINGLESTEP);
	131
	132	/* But touch TF only if it was set by us.. */
	133	if (child->ptrace & PT_DTRACE) {
134	struct pt_regs *regs = task_pt_regs(child);
135	regs->eflags &= ~X86_EFLAGS_TF;
136	child->ptrace &= ~PT_DTRACE;
137	}
138	}