arch/x86/kernel/ptrace.c

/* By Ross Biro 1/23/92 */
/*
 * Pentium III FXSR, SSE support
 *	Gareth Hughes <gareth@valinux.com>, May 2000
 */

#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/ptrace.h>
#include <linux/regset.h>
#include <linux/tracehook.h>
#include <linux/user.h>
#include <linux/elf.h>
#include <linux/security.h>
#include <linux/audit.h>
#include <linux/seccomp.h>
#include <linux/signal.h>
#include <linux/perf_event.h>
#include <linux/hw_breakpoint.h>
#include <linux/rcupdate.h>

#include <asm/uaccess.h>
#include <asm/pgtable.h>
#include <asm/processor.h>
#include <asm/i387.h>
#include <asm/fpu-internal.h>
#include <asm/debugreg.h>
#include <asm/ldt.h>
#include <asm/desc.h>
#include <asm/prctl.h>
#include <asm/proto.h>
#include <asm/hw_breakpoint.h>
#include <asm/traps.h>

#include "tls.h"

#define CREATE_TRACE_POINTS
#include <trace/events/syscalls.h>

enum x86_regset {
	REGSET_GENERAL,
	REGSET_FP,
	REGSET_XFP,
	REGSET_IOPERM64 = REGSET_XFP,
	REGSET_XSTATE,
	REGSET_TLS,
	REGSET_IOPERM32,
};

struct pt_regs_offset {
	const char *name;
	int offset;
};

#define REG_OFFSET_NAME(r) {.name = #r, .offset = offsetof(struct pt_regs, r)}
#define REG_OFFSET_END {.name = NULL, .offset = 0}

static const struct pt_regs_offset regoffset_table[] = {
#ifdef CONFIG_X86_64
	REG_OFFSET_NAME(r15),
	REG_OFFSET_NAME(r14),
	REG_OFFSET_NAME(r13),
	REG_OFFSET_NAME(r12),
	REG_OFFSET_NAME(r11),
	REG_OFFSET_NAME(r10),
	REG_OFFSET_NAME(r9),
	REG_OFFSET_NAME(r8),
#endif
	REG_OFFSET_NAME(bx),
	REG_OFFSET_NAME(cx),
	REG_OFFSET_NAME(dx),
	REG_OFFSET_NAME(si),
	REG_OFFSET_NAME(di),
	REG_OFFSET_NAME(bp),
	REG_OFFSET_NAME(ax),
#ifdef CONFIG_X86_32
	REG_OFFSET_NAME(ds),
	REG_OFFSET_NAME(es),
	REG_OFFSET_NAME(fs),
	REG_OFFSET_NAME(gs),
#endif
	REG_OFFSET_NAME(orig_ax),
	REG_OFFSET_NAME(ip),
	REG_OFFSET_NAME(cs),
	REG_OFFSET_NAME(flags),
	REG_OFFSET_NAME(sp),
	REG_OFFSET_NAME(ss),
	REG_OFFSET_END,
};

/**
 * regs_query_register_offset() - query register offset from its name
 * @name:	the name of a register
 *
 * regs_query_register_offset() returns the offset of a register in struct
 * pt_regs from its name. If the name is invalid, this returns -EINVAL;
 */
int regs_query_register_offset(const char *name)
{
	const struct pt_regs_offset *roff;
	for (roff = regoffset_table; roff->name != NULL; roff++)
		if (!strcmp(roff->name, name))
			return roff->offset;
	return -EINVAL;
}

/**
 * regs_query_register_name() - query register name from its offset
 * @offset:	the offset of a register in struct pt_regs.
 *
 * regs_query_register_name() returns the name of a register from its
 * offset in struct pt_regs. If the @offset is invalid, this returns NULL;
 */
const char *regs_query_register_name(unsigned int offset)
{
	const struct pt_regs_offset *roff;
	for (roff = regoffset_table; roff->name != NULL; roff++)
		if (roff->offset == offset)
			return roff->name;
	return NULL;
}

static const int arg_offs_table[] = {
#ifdef CONFIG_X86_32
	[0] = offsetof(struct pt_regs, ax),
	[1] = offsetof(struct pt_regs, dx),
	[2] = offsetof(struct pt_regs, cx)
#else /* CONFIG_X86_64 */
	[0] = offsetof(struct pt_regs, di),
	[1] = offsetof(struct pt_regs, si),
	[2] = offsetof(struct pt_regs, dx),
	[3] = offsetof(struct pt_regs, cx),
	[4] = offsetof(struct pt_regs, r8),
	[5] = offsetof(struct pt_regs, r9)
#endif
};

/*
 * does not yet catch signals sent when the child dies.
 * in exit.c or in signal.c.
 */

/*
 * Determines which flags the user has access to [1 = access, 0 = no access].
 */
#define FLAG_MASK_32		((unsigned long)			\
				 (X86_EFLAGS_CF | X86_EFLAGS_PF |	\
				  X86_EFLAGS_AF | X86_EFLAGS_ZF |	\
				  X86_EFLAGS_SF | X86_EFLAGS_TF |	\
				  X86_EFLAGS_DF | X86_EFLAGS_OF |	\
				  X86_EFLAGS_RF | X86_EFLAGS_AC))

/*
 * Determines whether a value may be installed in a segment register.
 */
static inline bool invalid_selector(u16 value)
{
	return unlikely(value != 0 && (value & SEGMENT_RPL_MASK) != USER_RPL);
}

#ifdef CONFIG_X86_32

#define FLAG_MASK		FLAG_MASK_32

/*
 * X86_32 CPUs don't save ss and esp if the CPU is already in kernel mode
 * when it traps.  The previous stack will be directly underneath the saved
 * registers, and 'sp/ss' won't even have been saved. Thus the '&regs->sp'.
 *
 * Now, if the stack is empty, '&regs->sp' is out of range. In this
 * case we try to take the previous stack. To always return a non-null
 * stack pointer we fall back to regs as stack if no previous stack
 * exists.
 *
 * This is valid only for kernel mode traps.
 */
unsigned long kernel_stack_pointer(struct pt_regs *regs)
{
	unsigned long context = (unsigned long)regs & ~(THREAD_SIZE - 1);
	unsigned long sp = (unsigned long)&regs->sp;
	struct thread_info *tinfo;

	if (context == (sp & ~(THREAD_SIZE - 1)))
		return sp;

	tinfo = (struct thread_info *)context;
	if (tinfo->previous_esp)
		return tinfo->previous_esp;

	return (unsigned long)regs;
}

static unsigned long *pt_regs_access(struct pt_regs *regs, unsigned long regno)
{
	BUILD_BUG_ON(offsetof(struct pt_regs, bx) != 0);
	return &regs->bx + (regno >> 2);
}

static u16 get_segment_reg(struct task_struct *task, unsigned long offset)
{
	/*
	 * Returning the value truncates it to 16 bits.
	 */
	unsigned int retval;
	if (offset != offsetof(struct user_regs_struct, gs))
		retval = *pt_regs_access(task_pt_regs(task), offset);
	else {
		if (task == current)
			retval = get_user_gs(task_pt_regs(task));
		else
			retval = task_user_gs(task);
	}
	return retval;
}

static int set_segment_reg(struct task_struct *task,
			   unsigned long offset, u16 value)
{
	/*
	 * The value argument was already truncated to 16 bits.
	 */
	if (invalid_selector(value))
		return -EIO;

	/*
	 * For %cs and %ss we cannot permit a null selector.
	 * We can permit a bogus selector as long as it has USER_RPL.
	 * Null selectors are fine for other segment registers, but
	 * we will never get back to user mode with invalid %cs or %ss
	 * and will take the trap in iret instead.  Much code relies
	 * on user_mode() to distinguish a user trap frame (which can
	 * safely use invalid selectors) from a kernel trap frame.
	 */
	switch (offset) {
	case offsetof(struct user_regs_struct, cs):
	case offsetof(struct user_regs_struct, ss):
		if (unlikely(value == 0))
			return -EIO;

	default:
		*pt_regs_access(task_pt_regs(task), offset) = value;
		break;

	case offsetof(struct user_regs_struct, gs):
		if (task == current)
			set_user_gs(task_pt_regs(task), value);
		else
			task_user_gs(task) = value;
	}

	return 0;
}

#else  /* CONFIG_X86_64 */

#define FLAG_MASK		(FLAG_MASK_32 | X86_EFLAGS_NT)

static unsigned long *pt_regs_access(struct pt_regs *regs, unsigned long offset)
{
	BUILD_BUG_ON(offsetof(struct pt_regs, r15) != 0);
	return &regs->r15 + (offset / sizeof(regs->r15));
}

static u16 get_segment_reg(struct task_struct *task, unsigned long offset)
{
	/*
	 * Returning the value truncates it to 16 bits.
	 */
	unsigned int seg;

	switch (offset) {
	case offsetof(struct user_regs_struct, fs):
		if (task == current) {
			/* Older gas can't assemble movq %?s,%r?? */
			asm("movl %%fs,%0" : "=r" (seg));
			return seg;
		}
		return task->thread.fsindex;
	case offsetof(struct user_regs_struct, gs):
		if (task == current) {
			asm("movl %%gs,%0" : "=r" (seg));
			return seg;
		}
		return task->thread.gsindex;
	case offsetof(struct user_regs_struct, ds):
		if (task == current) {
			asm("movl %%ds,%0" : "=r" (seg));
			return seg;
		}
		return task->thread.ds;
	case offsetof(struct user_regs_struct, es):
		if (task == current) {
			asm("movl %%es,%0" : "=r" (seg));
			return seg;
		}
		return task->thread.es;

	case offsetof(struct user_regs_struct, cs):
	case offsetof(struct user_regs_struct, ss):
		break;
	}
	return *pt_regs_access(task_pt_regs(task), offset);
}

static int set_segment_reg(struct task_struct *task,
			   unsigned long offset, u16 value)
{
	/*
	 * The value argument was already truncated to 16 bits.
	 */
	if (invalid_selector(value))
		return -EIO;

	switch (offset) {
	case offsetof(struct user_regs_struct,fs):
		/*
		 * If this is setting fs as for normal 64-bit use but
		 * setting fs_base has implicitly changed it, leave it.
		 */
		if ((value == FS_TLS_SEL && task->thread.fsindex == 0 &&
		     task->thread.fs != 0) ||
		    (value == 0 && task->thread.fsindex == FS_TLS_SEL &&
		     task->thread.fs == 0))
			break;
		task->thread.fsindex = value;
		if (task == current)
			loadsegment(fs, task->thread.fsindex);
		break;
	case offsetof(struct user_regs_struct,gs):
		/*
		 * If this is setting gs as for normal 64-bit use but
		 * setting gs_base has implicitly changed it, leave it.
		 */
		if ((value == GS_TLS_SEL && task->thread.gsindex == 0 &&
		     task->thread.gs != 0) ||
		    (value == 0 && task->thread.gsindex == GS_TLS_SEL &&
		     task->thread.gs == 0))
			break;
		task->thread.gsindex = value;
		if (task == current)
			load_gs_index(task->thread.gsindex);
		break;
	case offsetof(struct user_regs_struct,ds):
		task->thread.ds = value;
		if (task == current)
			loadsegment(ds, task->thread.ds);
		break;
	case offsetof(struct user_regs_struct,es):
		task->thread.es = value;
		if (task == current)
			loadsegment(es, task->thread.es);
		break;

		/*
		 * Can't actually change these in 64-bit mode.
		 */
	case offsetof(struct user_regs_struct,cs):
		if (unlikely(value == 0))
			return -EIO;
#ifdef CONFIG_IA32_EMULATION
		if (test_tsk_thread_flag(task, TIF_IA32))
			task_pt_regs(task)->cs = value;
#endif
		break;
	case offsetof(struct user_regs_struct,ss):
		if (unlikely(value == 0))
			return -EIO;
#ifdef CONFIG_IA32_EMULATION
		if (test_tsk_thread_flag(task, TIF_IA32))
			task_pt_regs(task)->ss = value;
#endif
		break;
	}

	return 0;
}

#endif	/* CONFIG_X86_32 */

static unsigned long get_flags(struct task_struct *task)
{
	unsigned long retval = task_pt_regs(task)->flags;

	/*
	 * If the debugger set TF, hide it from the readout.
	 */
	if (test_tsk_thread_flag(task, TIF_FORCED_TF))
		retval &= ~X86_EFLAGS_TF;

	return retval;
}

static int set_flags(struct task_struct *task, unsigned long value)
{
	struct pt_regs *regs = task_pt_regs(task);

	/*
	 * If the user value contains TF, mark that
	 * it was not "us" (the debugger) that set it.
	 * If not, make sure it stays set if we had.
	 */
	if (value & X86_EFLAGS_TF)
		clear_tsk_thread_flag(task, TIF_FORCED_TF);
	else if (test_tsk_thread_flag(task, TIF_FORCED_TF))
		value |= X86_EFLAGS_TF;

	regs->flags = (regs->flags & ~FLAG_MASK) | (value & FLAG_MASK);

	return 0;
}

static int putreg(struct task_struct *child,
		  unsigned long offset, unsigned long value)
{
	switch (offset) {
	case offsetof(struct user_regs_struct, cs):
	case offsetof(struct user_regs_struct, ds):
	case offsetof(struct user_regs_struct, es):
	case offsetof(struct user_regs_struct, fs):
	case offsetof(struct user_regs_struct, gs):
	case offsetof(struct user_regs_struct, ss):
		return set_segment_reg(child, offset, value);

	case offsetof(struct user_regs_struct, flags):
		return set_flags(child, value);

#ifdef CONFIG_X86_64
	case offsetof(struct user_regs_struct,fs_base):
		if (value >= TASK_SIZE_OF(child))
			return -EIO;
		/*
		 * When changing the segment base, use do_arch_prctl
		 * to set either thread.fs or thread.fsindex and the
		 * corresponding GDT slot.
		 */
		if (child->thread.fs != value)
			return do_arch_prctl(child, ARCH_SET_FS, value);
		return 0;
	case offsetof(struct user_regs_struct,gs_base):
		/*
		 * Exactly the same here as the %fs handling above.
		 */
		if (value >= TASK_SIZE_OF(child))
			return -EIO;
		if (child->thread.gs != value)
			return do_arch_prctl(child, ARCH_SET_GS, value);
		return 0;
#endif
	}

	*pt_regs_access(task_pt_regs(child), offset) = value;
	return 0;
}

static unsigned long getreg(struct task_struct *task, unsigned long offset)
{
	switch (offset) {
	case offsetof(struct user_regs_struct, cs):
	case offsetof(struct user_regs_struct, ds):
	case offsetof(struct user_regs_struct, es):
	case offsetof(struct user_regs_struct, fs):
	case offsetof(struct user_regs_struct, gs):
	case offsetof(struct user_regs_struct, ss):
		return get_segment_reg(task, offset);

	case offsetof(struct user_regs_struct, flags):
		return get_flags(task);

#ifdef CONFIG_X86_64
	case offsetof(struct user_regs_struct, fs_base): {
		/*
		 * do_arch_prctl may have used a GDT slot instead of
		 * the MSR.  To userland, it appears the same either
		 * way, except the %fs segment selector might not be 0.
		 */
		unsigned int seg = task->thread.fsindex;
		if (task->thread.fs != 0)
			return task->thread.fs;
		if (task == current)
			asm("movl %%fs,%0" : "=r" (seg));
		if (seg != FS_TLS_SEL)
			return 0;
		return get_desc_base(&task->thread.tls_array[FS_TLS]);
	}
	case offsetof(struct user_regs_struct, gs_base): {
		/*
		 * Exactly the same here as the %fs handling above.
		 */
		unsigned int seg = task->thread.gsindex;
		if (task->thread.gs != 0)
			return task->thread.gs;
		if (task == current)
			asm("movl %%gs,%0" : "=r" (seg));
		if (seg != GS_TLS_SEL)
			return 0;
		return get_desc_base(&task->thread.tls_array[GS_TLS]);
	}
#endif
	}

	return *pt_regs_access(task_pt_regs(task), offset);
}

static int genregs_get(struct task_struct *target,
		       const struct user_regset *regset,
		       unsigned int pos, unsigned int count,
		       void *kbuf, void __user *ubuf)
{
	if (kbuf) {
		unsigned long *k = kbuf;
		while (count >= sizeof(*k)) {
			*k++ = getreg(target, pos);
			count -= sizeof(*k);
			pos += sizeof(*k);
		}
	} else {
		unsigned long __user *u = ubuf;
		while (count >= sizeof(*u)) {
			if (__put_user(getreg(target, pos), u++))
				return -EFAULT;
			count -= sizeof(*u);
			pos += sizeof(*u);
		}
	}

	return 0;
}

static int genregs_set(struct task_struct *target,
		       const struct user_regset *regset,
		       unsigned int pos, unsigned int count,
		       const void *kbuf, const void __user *ubuf)
{
	int ret = 0;
	if (kbuf) {
		const unsigned long *k = kbuf;
		while (count >= sizeof(*k) && !ret) {
			ret = putreg(target, pos, *k++);
			count -= sizeof(*k);
			pos += sizeof(*k);
		}
	} else {
		const unsigned long  __user *u = ubuf;
		while (count >= sizeof(*u) && !ret) {
			unsigned long word;
			ret = __get_user(word, u++);
			if (ret)
				break;
			ret = putreg(target, pos, word);
			count -= sizeof(*u);
			pos += sizeof(*u);
		}
	}
	return ret;
}

static void ptrace_triggered(struct perf_event *bp,
			     struct perf_sample_data *data,
			     struct pt_regs *regs)
{
	int i;
	struct thread_struct *thread = &(current->thread);

	/*
	 * Store in the virtual DR6 register the fact that the breakpoint
	 * was hit so the thread's debugger will see it.
	 */
	for (i = 0; i < HBP_NUM; i++) {
		if (thread->ptrace_bps[i] == bp)
			break;
	}

	thread->debugreg6 |= (DR_TRAP0 << i);
}

/*
 * Walk through every ptrace breakpoints for this thread and
 * build the dr7 value on top of their attributes.
 *
 */
static unsigned long ptrace_get_dr7(struct perf_event *bp[])
{
	int i;
	int dr7 = 0;
	struct arch_hw_breakpoint *info;

	for (i = 0; i < HBP_NUM; i++) {
		if (bp[i] && !bp[i]->attr.disabled) {
			info = counter_arch_bp(bp[i]);
			dr7 |= encode_dr7(i, info->len, info->type);
		}
	}

	return dr7;
}

static int
ptrace_modify_breakpoint(struct perf_event *bp, int len, int type,
			 struct task_struct *tsk, int disabled)
{
	int err;
	int gen_len, gen_type;
	struct perf_event_attr attr;

	/*
	 * We should have at least an inactive breakpoint at this
	 * slot. It means the user is writing dr7 without having
	 * written the address register first
	 */
	if (!bp)
		return -EINVAL;

	err = arch_bp_generic_fields(len, type, &gen_len, &gen_type);
	if (err)
		return err;

	attr = bp->attr;
	attr.bp_len = gen_len;
	attr.bp_type = gen_type;
	attr.disabled = disabled;

	return modify_user_hw_breakpoint(bp, &attr);
}

/*
 * Handle ptrace writes to debug register 7.
 */
static int ptrace_write_dr7(struct task_struct *tsk, unsigned long data)
{
	struct thread_struct *thread = &(tsk->thread);
	unsigned long old_dr7;
	int i, orig_ret = 0, rc = 0;
	int enabled, second_pass = 0;
	unsigned len, type;
	struct perf_event *bp;

	if (ptrace_get_breakpoints(tsk) < 0)
		return -ESRCH;

	data &= ~DR_CONTROL_RESERVED;
	old_dr7 = ptrace_get_dr7(thread->ptrace_bps);
restore:
	/*
	 * Loop through all the hardware breakpoints, making the
	 * appropriate changes to each.
	 */
	for (i = 0; i < HBP_NUM; i++) {
		enabled = decode_dr7(data, i, &len, &type);
		bp = thread->ptrace_bps[i];

		if (!enabled) {
			if (bp) {
				/*
				 * Don't unregister the breakpoints right-away,
				 * unless all register_user_hw_breakpoint()
				 * requests have succeeded. This prevents
				 * any window of opportunity for debug
				 * register grabbing by other users.
				 */
				if (!second_pass)
					continue;

				rc = ptrace_modify_breakpoint(bp, len, type,
							      tsk, 1);
				if (rc)
					break;
			}
			continue;
		}

		rc = ptrace_modify_breakpoint(bp, len, type, tsk, 0);
		if (rc)
			break;
	}
	/*
	 * Make a second pass to free the remaining unused breakpoints
	 * or to restore the original breakpoints if an error occurred.
	 */
	if (!second_pass) {
		second_pass = 1;
		if (rc < 0) {
			orig_ret = rc;
			data = old_dr7;
		}
		goto restore;
	}

	ptrace_put_breakpoints(tsk);

	return ((orig_ret < 0) ? orig_ret : rc);
}

/*
 * Handle PTRACE_PEEKUSR calls for the debug register area.
 */
static unsigned long ptrace_get_debugreg(struct task_struct *tsk, int n)
{
	struct thread_struct *thread = &(tsk->thread);
	unsigned long val = 0;

	if (n < HBP_NUM) {
		struct perf_event *bp;

		if (ptrace_get_breakpoints(tsk) < 0)
			return -ESRCH;

		bp = thread->ptrace_bps[n];
		if (!bp)
			val = 0;
		else
			val = bp->hw.info.address;

		ptrace_put_breakpoints(tsk);
	} else if (n == 6) {
		val = thread->debugreg6;
	 } else if (n == 7) {
		val = thread->ptrace_dr7;
	}
	return val;
}

static int ptrace_set_breakpoint_addr(struct task_struct *tsk, int nr,
				      unsigned long addr)
{
	struct perf_event *bp;
	struct thread_struct *t = &tsk->thread;
	struct perf_event_attr attr;
	int err = 0;

	if (ptrace_get_breakpoints(tsk) < 0)
		return -ESRCH;

	if (!t->ptrace_bps[nr]) {
		ptrace_breakpoint_init(&attr);
		/*
		 * Put stub len and type to register (reserve) an inactive but
		 * correct bp
		 */
		attr.bp_addr = addr;
		attr.bp_len = HW_BREAKPOINT_LEN_1;
		attr.bp_type = HW_BREAKPOINT_W;
		attr.disabled = 1;

		bp = register_user_hw_breakpoint(&attr, ptrace_triggered,
						 NULL, tsk);

		/*
		 * CHECKME: the previous code returned -EIO if the addr wasn't
		 * a valid task virtual addr. The new one will return -EINVAL in
		 *  this case.
		 * -EINVAL may be what we want for in-kernel breakpoints users,
		 * but -EIO looks better for ptrace, since we refuse a register
		 * writing for the user. And anyway this is the previous
		 * behaviour.
		 */
		if (IS_ERR(bp)) {
			err = PTR_ERR(bp);
			goto put;
		}

		t->ptrace_bps[nr] = bp;
	} else {
		bp = t->ptrace_bps[nr];

		attr = bp->attr;
		attr.bp_addr = addr;
		err = modify_user_hw_breakpoint(bp, &attr);
	}

put:
	ptrace_put_breakpoints(tsk);
	return err;
}

/*
 * Handle PTRACE_POKEUSR calls for the debug register area.
 */
static int ptrace_set_debugreg(struct task_struct *tsk, int n,
			       unsigned long val)
{
	struct thread_struct *thread = &(tsk->thread);
	int rc = 0;

	/* There are no DR4 or DR5 registers */
	if (n == 4 || n == 5)
		return -EIO;

	if (n == 6) {
		thread->debugreg6 = val;
		goto ret_path;
	}
	if (n < HBP_NUM) {
		rc = ptrace_set_breakpoint_addr(tsk, n, val);
		if (rc)
			return rc;
	}
	/* All that's left is DR7 */
	if (n == 7) {
		rc = ptrace_write_dr7(tsk, val);
		if (!rc)
			thread->ptrace_dr7 = val;
	}

ret_path:
	return rc;
}

/*
 * These access the current or another (stopped) task's io permission
 * bitmap for debugging or core dump.
 */
static int ioperm_active(struct task_struct *target,
			 const struct user_regset *regset)
{
	return target->thread.io_bitmap_max / regset->size;
}

static int ioperm_get(struct task_struct *target,
		      const struct user_regset *regset,
		      unsigned int pos, unsigned int count,
		      void *kbuf, void __user *ubuf)
{
	if (!target->thread.io_bitmap_ptr)
		return -ENXIO;

	return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
				   target->thread.io_bitmap_ptr,
				   0, IO_BITMAP_BYTES);
}

/*
 * Called by kernel/ptrace.c when detaching..
 *
 * Make sure the single step bit is not set.
 */
void ptrace_disable(struct task_struct *child)
{
	user_disable_single_step(child);
#ifdef TIF_SYSCALL_EMU
	clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
#endif
}

#if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION
static const struct user_regset_view user_x86_32_view; /* Initialized below. */
#endif

long arch_ptrace(struct task_struct *child, long request,
		 unsigned long addr, unsigned long data)
{
	int ret;
	unsigned long __user *datap = (unsigned long __user *)data;

	switch (request) {
	/* read the word at location addr in the USER area. */
	case PTRACE_PEEKUSR: {
		unsigned long tmp;

		ret = -EIO;
		if ((addr & (sizeof(data) - 1)) || addr >= sizeof(struct user))
			break;

		tmp = 0;  /* Default return condition */
		if (addr < sizeof(struct user_regs_struct))
			tmp = getreg(child, addr);
		else if (addr >= offsetof(struct user, u_debugreg[0]) &&
			 addr <= offsetof(struct user, u_debugreg[7])) {
			addr -= offsetof(struct user, u_debugreg[0]);
			tmp = ptrace_get_debugreg(child, addr / sizeof(data));
		}
		ret = put_user(tmp, datap);
		break;
	}

	case PTRACE_POKEUSR: /* write the word at location addr in the USER area */
		ret = -EIO;
		if ((addr & (sizeof(data) - 1)) || addr >= sizeof(struct user))
			break;

		if (addr < sizeof(struct user_regs_struct))
			ret = putreg(child, addr, data);
		else if (addr >= offsetof(struct user, u_debugreg[0]) &&
			 addr <= offsetof(struct user, u_debugreg[7])) {
			addr -= offsetof(struct user, u_debugreg[0]);
			ret = ptrace_set_debugreg(child,
						  addr / sizeof(data), data);
		}
		break;

	case PTRACE_GETREGS:	/* Get all gp regs from the child. */
		return copy_regset_to_user(child,
					   task_user_regset_view(current),
					   REGSET_GENERAL,
					   0, sizeof(struct user_regs_struct),
					   datap);

	case PTRACE_SETREGS:	/* Set all gp regs in the child. */
		return copy_regset_from_user(child,
					     task_user_regset_view(current),
					     REGSET_GENERAL,
					     0, sizeof(struct user_regs_struct),
					     datap);

	case PTRACE_GETFPREGS:	/* Get the child FPU state. */
		return copy_regset_to_user(child,
					   task_user_regset_view(current),
					   REGSET_FP,
					   0, sizeof(struct user_i387_struct),
					   datap);

	case PTRACE_SETFPREGS:	/* Set the child FPU state. */
		return copy_regset_from_user(child,
					     task_user_regset_view(current),
					     REGSET_FP,
					     0, sizeof(struct user_i387_struct),
					     datap);

#ifdef CONFIG_X86_32
	case PTRACE_GETFPXREGS:	/* Get the child extended FPU state. */
		return copy_regset_to_user(child, &user_x86_32_view,
					   REGSET_XFP,
					   0, sizeof(struct user_fxsr_struct),
					   datap) ? -EIO : 0;

	case PTRACE_SETFPXREGS:	/* Set the child extended FPU state. */
		return copy_regset_from_user(child, &user_x86_32_view,
					     REGSET_XFP,
					     0, sizeof(struct user_fxsr_struct),
					     datap) ? -EIO : 0;
#endif

#if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION
	case PTRACE_GET_THREAD_AREA:
		if ((int) addr < 0)
			return -EIO;
		ret = do_get_thread_area(child, addr,
					(struct user_desc __user *)data);
		break;

	case PTRACE_SET_THREAD_AREA:
		if ((int) addr < 0)
			return -EIO;
		ret = do_set_thread_area(child, addr,
					(struct user_desc __user *)data, 0);
		break;
#endif

#ifdef CONFIG_X86_64
		/* normal 64bit interface to access TLS data.
		   Works just like arch_prctl, except that the arguments
		   are reversed. */
	case PTRACE_ARCH_PRCTL:
		ret = do_arch_prctl(child, data, addr);
		break;
#endif

	default:
		ret = ptrace_request(child, request, addr, data);
		break;
	}

	return ret;
}

#ifdef CONFIG_IA32_EMULATION

#include <linux/compat.h>
#include <linux/syscalls.h>
#include <asm/ia32.h>
#include <asm/user32.h>

#define R32(l,q)							\
	case offsetof(struct user32, regs.l):				\
		regs->q = value; break

#define SEG32(rs)							\
	case offsetof(struct user32, regs.rs):				\
		return set_segment_reg(child,				\
				       offsetof(struct user_regs_struct, rs), \
				       value);				\
		break

static int putreg32(struct task_struct *child, unsigned regno, u32 value)
{
	struct pt_regs *regs = task_pt_regs(child);

	switch (regno) {

	SEG32(cs);
	SEG32(ds);
	SEG32(es);
	SEG32(fs);
	SEG32(gs);
	SEG32(ss);

	R32(ebx, bx);
	R32(ecx, cx);
	R32(edx, dx);
	R32(edi, di);
	R32(esi, si);
	R32(ebp, bp);
	R32(eax, ax);
	R32(eip, ip);
	R32(esp, sp);

	case offsetof(struct user32, regs.orig_eax):
		/*
		 * A 32-bit debugger setting orig_eax means to restore
		 * the state of the task restarting a 32-bit syscall.
		 * Make sure we interpret the -ERESTART* codes correctly
		 * in case the task is not actually still sitting at the
		 * exit from a 32-bit syscall with TS_COMPAT still set.
		 */
		regs->orig_ax = value;
		if (syscall_get_nr(child, regs) >= 0)
			task_thread_info(child)->status |= TS_COMPAT;
		break;

	case offsetof(struct user32, regs.eflags):
		return set_flags(child, value);

	case offsetof(struct user32, u_debugreg[0]) ...
		offsetof(struct user32, u_debugreg[7]):
		regno -= offsetof(struct user32, u_debugreg[0]);
		return ptrace_set_debugreg(child, regno / 4, value);

	default:
		if (regno > sizeof(struct user32) || (regno & 3))
			return -EIO;

		/*
		 * Other dummy fields in the virtual user structure
		 * are ignored
		 */
		break;
	}
	return 0;
}

#undef R32
#undef SEG32

#define R32(l,q)							\
	case offsetof(struct user32, regs.l):				\
		*val = regs->q; break

#define SEG32(rs)							\
	case offsetof(struct user32, regs.rs):				\
		*val = get_segment_reg(child,				\
				       offsetof(struct user_regs_struct, rs)); \
		break

static int getreg32(struct task_struct *child, unsigned regno, u32 *val)
{
	struct pt_regs *regs = task_pt_regs(child);

	switch (regno) {

	SEG32(ds);
	SEG32(es);
	SEG32(fs);
	SEG32(gs);

	R32(cs, cs);
	R32(ss, ss);
	R32(ebx, bx);
	R32(ecx, cx);
	R32(edx, dx);
	R32(edi, di);
	R32(esi, si);
	R32(ebp, bp);
	R32(eax, ax);
	R32(orig_eax, orig_ax);
	R32(eip, ip);
	R32(esp, sp);

	case offsetof(struct user32, regs.eflags):
		*val = get_flags(child);
		break;

	case offsetof(struct user32, u_debugreg[0]) ...
		offsetof(struct user32, u_debugreg[7]):
		regno -= offsetof(struct user32, u_debugreg[0]);
		*val = ptrace_get_debugreg(child, regno / 4);
		break;

	default:
		if (regno > sizeof(struct user32) || (regno & 3))
			return -EIO;

		/*
		 * Other dummy fields in the virtual user structure
		 * are ignored
		 */
		*val = 0;
		break;
	}
	return 0;
}

#undef R32
#undef SEG32

static int genregs32_get(struct task_struct *target,
			 const struct user_regset *regset,
			 unsigned int pos, unsigned int count,
			 void *kbuf, void __user *ubuf)
{
	if (kbuf) {
		compat_ulong_t *k = kbuf;
		while (count >= sizeof(*k)) {
			getreg32(target, pos, k++);
			count -= sizeof(*k);
			pos += sizeof(*k);
		}
	} else {
		compat_ulong_t __user *u = ubuf;
		while (count >= sizeof(*u)) {
			compat_ulong_t word;
			getreg32(target, pos, &word);
			if (__put_user(word, u++))
				return -EFAULT;
			count -= sizeof(*u);
			pos += sizeof(*u);
		}
	}

	return 0;
}

static int genregs32_set(struct task_struct *target,
			 const struct user_regset *regset,
			 unsigned int pos, unsigned int count,
			 const void *kbuf, const void __user *ubuf)
{
	int ret = 0;
	if (kbuf) {
		const compat_ulong_t *k = kbuf;
		while (count >= sizeof(*k) && !ret) {
			ret = putreg32(target, pos, *k++);
			count -= sizeof(*k);
			pos += sizeof(*k);
		}
	} else {
		const compat_ulong_t __user *u = ubuf;
		while (count >= sizeof(*u) && !ret) {
			compat_ulong_t word;
			ret = __get_user(word, u++);
			if (ret)
				break;
			ret = putreg32(target, pos, word);
			count -= sizeof(*u);
			pos += sizeof(*u);
		}
	}
	return ret;
}

#ifdef CONFIG_X86_X32_ABI
static long x32_arch_ptrace(struct task_struct *child,
			    compat_long_t request, compat_ulong_t caddr,
			    compat_ulong_t cdata)
{
	unsigned long addr = caddr;
	unsigned long data = cdata;
	void __user *datap = compat_ptr(data);
	int ret;

	switch (request) {
	/* Read 32bits at location addr in the USER area.  Only allow
	   to return the lower 32bits of segment and debug registers.  */
	case PTRACE_PEEKUSR: {
		u32 tmp;

		ret = -EIO;
		if ((addr & (sizeof(data) - 1)) || addr >= sizeof(struct user) ||
		    addr < offsetof(struct user_regs_struct, cs))
			break;

		tmp = 0;  /* Default return condition */
		if (addr < sizeof(struct user_regs_struct))
			tmp = getreg(child, addr);
		else if (addr >= offsetof(struct user, u_debugreg[0]) &&
			 addr <= offsetof(struct user, u_debugreg[7])) {
			addr -= offsetof(struct user, u_debugreg[0]);
			tmp = ptrace_get_debugreg(child, addr / sizeof(data));
		}
		ret = put_user(tmp, (__u32 __user *)datap);
		break;
	}

	/* Write the word at location addr in the USER area.  Only allow
	   to update segment and debug registers with the upper 32bits
	   zero-extended. */
	case PTRACE_POKEUSR:
		ret = -EIO;
		if ((addr & (sizeof(data) - 1)) || addr >= sizeof(struct user) ||
		    addr < offsetof(struct user_regs_struct, cs))
			break;

		if (addr < sizeof(struct user_regs_struct))
			ret = putreg(child, addr, data);
		else if (addr >= offsetof(struct user, u_debugreg[0]) &&
			 addr <= offsetof(struct user, u_debugreg[7])) {
			addr -= offsetof(struct user, u_debugreg[0]);
			ret = ptrace_set_debugreg(child,
						  addr / sizeof(data), data);
		}
		break;

	case PTRACE_GETREGS:	/* Get all gp regs from the child. */
		return copy_regset_to_user(child,
					   task_user_regset_view(current),
					   REGSET_GENERAL,
					   0, sizeof(struct user_regs_struct),
					   datap);

	case PTRACE_SETREGS:	/* Set all gp regs in the child. */
		return copy_regset_from_user(child,
					     task_user_regset_view(current),
					     REGSET_GENERAL,
					     0, sizeof(struct user_regs_struct),
					     datap);

	case PTRACE_GETFPREGS:	/* Get the child FPU state. */
		return copy_regset_to_user(child,
					   task_user_regset_view(current),
					   REGSET_FP,
					   0, sizeof(struct user_i387_struct),
					   datap);

	case PTRACE_SETFPREGS:	/* Set the child FPU state. */
		return copy_regset_from_user(child,
					     task_user_regset_view(current),
					     REGSET_FP,
					     0, sizeof(struct user_i387_struct),
					     datap);

	default:
		return compat_ptrace_request(child, request, addr, data);
	}

	return ret;
}
#endif

long compat_arch_ptrace(struct task_struct *child, compat_long_t request,
			compat_ulong_t caddr, compat_ulong_t cdata)
{
	unsigned long addr = caddr;
	unsigned long data = cdata;
	void __user *datap = compat_ptr(data);
	int ret;
	__u32 val;

#ifdef CONFIG_X86_X32_ABI
	if (!is_ia32_task())
		return x32_arch_ptrace(child, request, caddr, cdata);
#endif

	switch (request) {
	case PTRACE_PEEKUSR:
		ret = getreg32(child, addr, &val);
		if (ret == 0)
			ret = put_user(val, (__u32 __user *)datap);
		break;

	case PTRACE_POKEUSR:
		ret = putreg32(child, addr, data);
		break;

	case PTRACE_GETREGS:	/* Get all gp regs from the child. */
		return copy_regset_to_user(child, &user_x86_32_view,
					   REGSET_GENERAL,
					   0, sizeof(struct user_regs_struct32),
					   datap);

	case PTRACE_SETREGS:	/* Set all gp regs in the child. */
		return copy_regset_from_user(child, &user_x86_32_view,
					     REGSET_GENERAL, 0,
					     sizeof(struct user_regs_struct32),
					     datap);

	case PTRACE_GETFPREGS:	/* Get the child FPU state. */
		return copy_regset_to_user(child, &user_x86_32_view,
					   REGSET_FP, 0,
					   sizeof(struct user_i387_ia32_struct),
					   datap);

	case PTRACE_SETFPREGS:	/* Set the child FPU state. */
		return copy_regset_from_user(
			child, &user_x86_32_view, REGSET_FP,
			0, sizeof(struct user_i387_ia32_struct), datap);

	case PTRACE_GETFPXREGS:	/* Get the child extended FPU state. */
		return copy_regset_to_user(child, &user_x86_32_view,
					   REGSET_XFP, 0,
					   sizeof(struct user32_fxsr_struct),
					   datap);

	case PTRACE_SETFPXREGS:	/* Set the child extended FPU state. */
		return copy_regset_from_user(child, &user_x86_32_view,
					     REGSET_XFP, 0,
					     sizeof(struct user32_fxsr_struct),
					     datap);

	case PTRACE_GET_THREAD_AREA:
	case PTRACE_SET_THREAD_AREA:
		return arch_ptrace(child, request, addr, data);

	default:
		return compat_ptrace_request(child, request, addr, data);
	}

	return ret;
}

#endif	/* CONFIG_IA32_EMULATION */

#ifdef CONFIG_X86_64

static struct user_regset x86_64_regsets[] __read_mostly = {
	[REGSET_GENERAL] = {
		.core_note_type = NT_PRSTATUS,
		.n = sizeof(struct user_regs_struct) / sizeof(long),
		.size = sizeof(long), .align = sizeof(long),
		.get = genregs_get, .set = genregs_set
	},
	[REGSET_FP] = {
		.core_note_type = NT_PRFPREG,
		.n = sizeof(struct user_i387_struct) / sizeof(long),
		.size = sizeof(long), .align = sizeof(long),
		.active = xfpregs_active, .get = xfpregs_get, .set = xfpregs_set
	},
	[REGSET_XSTATE] = {
		.core_note_type = NT_X86_XSTATE,
		.size = sizeof(u64), .align = sizeof(u64),
		.active = xstateregs_active, .get = xstateregs_get,
		.set = xstateregs_set
	},
	[REGSET_IOPERM64] = {
		.core_note_type = NT_386_IOPERM,
		.n = IO_BITMAP_LONGS,
		.size = sizeof(long), .align = sizeof(long),
		.active = ioperm_active, .get = ioperm_get
	},
};

static const struct user_regset_view user_x86_64_view = {
	.name = "x86_64", .e_machine = EM_X86_64,
	.regsets = x86_64_regsets, .n = ARRAY_SIZE(x86_64_regsets)
};

#else  /* CONFIG_X86_32 */

#define user_regs_struct32	user_regs_struct
#define genregs32_get		genregs_get
#define genregs32_set		genregs_set

#endif	/* CONFIG_X86_64 */

#if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION
static struct user_regset x86_32_regsets[] __read_mostly = {
	[REGSET_GENERAL] = {
		.core_note_type = NT_PRSTATUS,
		.n = sizeof(struct user_regs_struct32) / sizeof(u32),
		.size = sizeof(u32), .align = sizeof(u32),
		.get = genregs32_get, .set = genregs32_set
	},
	[REGSET_FP] = {
		.core_note_type = NT_PRFPREG,
		.n = sizeof(struct user_i387_ia32_struct) / sizeof(u32),
		.size = sizeof(u32), .align = sizeof(u32),
		.active = fpregs_active, .get = fpregs_get, .set = fpregs_set
	},
	[REGSET_XFP] = {
		.core_note_type = NT_PRXFPREG,
		.n = sizeof(struct user32_fxsr_struct) / sizeof(u32),
		.size = sizeof(u32), .align = sizeof(u32),
		.active = xfpregs_active, .get = xfpregs_get, .set = xfpregs_set
	},
	[REGSET_XSTATE] = {
		.core_note_type = NT_X86_XSTATE,
		.size = sizeof(u64), .align = sizeof(u64),
		.active = xstateregs_active, .get = xstateregs_get,
		.set = xstateregs_set
	},
	[REGSET_TLS] = {
		.core_note_type = NT_386_TLS,
		.n = GDT_ENTRY_TLS_ENTRIES, .bias = GDT_ENTRY_TLS_MIN,
		.size = sizeof(struct user_desc),
		.align = sizeof(struct user_desc),
		.active = regset_tls_active,
		.get = regset_tls_get, .set = regset_tls_set
	},
	[REGSET_IOPERM32] = {
		.core_note_type = NT_386_IOPERM,
		.n = IO_BITMAP_BYTES / sizeof(u32),
		.size = sizeof(u32), .align = sizeof(u32),
		.active = ioperm_active, .get = ioperm_get
	},
};

static const struct user_regset_view user_x86_32_view = {
	.name = "i386", .e_machine = EM_386,
	.regsets = x86_32_regsets, .n = ARRAY_SIZE(x86_32_regsets)
};
#endif

/*
 * This represents bytes 464..511 in the memory layout exported through
 * the REGSET_XSTATE interface.
 */
u64 xstate_fx_sw_bytes[USER_XSTATE_FX_SW_WORDS];

void update_regset_xstate_info(unsigned int size, u64 xstate_mask)
{
#ifdef CONFIG_X86_64
	x86_64_regsets[REGSET_XSTATE].n = size / sizeof(u64);
#endif
#if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION
	x86_32_regsets[REGSET_XSTATE].n = size / sizeof(u64);
#endif
	xstate_fx_sw_bytes[USER_XSTATE_XCR0_WORD] = xstate_mask;
}

const struct user_regset_view *task_user_regset_view(struct task_struct *task)
{
#ifdef CONFIG_IA32_EMULATION
	if (test_tsk_thread_flag(task, TIF_IA32))
#endif
#if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION
		return &user_x86_32_view;
#endif
#ifdef CONFIG_X86_64
	return &user_x86_64_view;
#endif
}

static void fill_sigtrap_info(struct task_struct *tsk,
				struct pt_regs *regs,
				int error_code, int si_code,
				struct siginfo *info)
{
	tsk->thread.trap_nr = X86_TRAP_DB;
	tsk->thread.error_code = error_code;

	memset(info, 0, sizeof(*info));
	info->si_signo = SIGTRAP;
	info->si_code = si_code;
	info->si_addr = user_mode_vm(regs) ? (void __user *)regs->ip : NULL;
}

void user_single_step_siginfo(struct task_struct *tsk,
				struct pt_regs *regs,
				struct siginfo *info)
{
	fill_sigtrap_info(tsk, regs, 0, TRAP_BRKPT, info);
}

void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs,
					 int error_code, int si_code)
{
	struct siginfo info;

	fill_sigtrap_info(tsk, regs, error_code, si_code, &info);
	/* Send us the fake SIGTRAP */
	force_sig_info(SIGTRAP, &info, tsk);
}


#ifdef CONFIG_X86_32
# define IS_IA32	1
#elif defined CONFIG_IA32_EMULATION
# define IS_IA32	is_compat_task()
#else
# define IS_IA32	0
#endif

/*
 * We must return the syscall number to actually look up in the table.
 * This can be -1L to skip running any syscall at all.
 */
long syscall_trace_enter(struct pt_regs *regs)
{
	long ret = 0;

	rcu_user_exit();

	/*
	 * If we stepped into a sysenter/syscall insn, it trapped in
	 * kernel mode; do_debug() cleared TF and set TIF_SINGLESTEP.
	 * If user-mode had set TF itself, then it's still clear from
	 * do_debug() and we need to set it again to restore the user
	 * state.  If we entered on the slow path, TF was already set.
	 */
	if (test_thread_flag(TIF_SINGLESTEP))
		regs->flags |= X86_EFLAGS_TF;

	/* do the secure computing check first */
	if (secure_computing(regs->orig_ax)) {
		/* seccomp failures shouldn't expose any additional code. */
		ret = -1L;
		goto out;
	}

	if (unlikely(test_thread_flag(TIF_SYSCALL_EMU)))
		ret = -1L;

	if ((ret || test_thread_flag(TIF_SYSCALL_TRACE)) &&
	    tracehook_report_syscall_entry(regs))
		ret = -1L;

	if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
		trace_sys_enter(regs, regs->orig_ax);

	if (IS_IA32)
		audit_syscall_entry(AUDIT_ARCH_I386,
				    regs->orig_ax,
				    regs->bx, regs->cx,
				    regs->dx, regs->si);
#ifdef CONFIG_X86_64
	else
		audit_syscall_entry(AUDIT_ARCH_X86_64,
				    regs->orig_ax,
				    regs->di, regs->si,
				    regs->dx, regs->r10);
#endif

out:
	return ret ?: regs->orig_ax;
}

void syscall_trace_leave(struct pt_regs *regs)
{
	bool step;

	audit_syscall_exit(regs);

	if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
		trace_sys_exit(regs, regs->ax);

	/*
	 * If TIF_SYSCALL_EMU is set, we only get here because of
	 * TIF_SINGLESTEP (i.e. this is PTRACE_SYSEMU_SINGLESTEP).
	 * We already reported this syscall instruction in
	 * syscall_trace_enter().
	 */
	step = unlikely(test_thread_flag(TIF_SINGLESTEP)) &&
			!test_thread_flag(TIF_SYSCALL_EMU);
	if (step || test_thread_flag(TIF_SYSCALL_TRACE))
		tracehook_report_syscall_exit(regs, step);

	rcu_user_enter();
}