arch/x86/kernel/ptrace_64.c - arm/linux-arm64-legacy - Git at Google

 /* By Ross Biro 1/23/92 */
 /*
  * Pentium III FXSR, SSE support
  *	Gareth Hughes <gareth@valinux.com>, May 2000
  *
  * x86-64 port 2000-2002 Andi Kleen
  */

 #include <linux/kernel.h>
 #include <linux/sched.h>
 #include <linux/mm.h>
 #include <linux/smp.h>
 #include <linux/errno.h>
 #include <linux/ptrace.h>
 #include <linux/user.h>
 #include <linux/security.h>
 #include <linux/audit.h>
 #include <linux/seccomp.h>
 #include <linux/signal.h>

 #include <asm/uaccess.h>
 #include <asm/pgtable.h>
 #include <asm/system.h>
 #include <asm/processor.h>
 #include <asm/i387.h>
 #include <asm/debugreg.h>
 #include <asm/ldt.h>
 #include <asm/desc.h>
 #include <asm/proto.h>
 #include <asm/ia32.h>

 /*
  * 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].
  * Prohibits changing ID(21), VIP(20), VIF(19), VM(17), IOPL(12-13), IF(9).
  * Also masks reserved bits (63-22, 15, 5, 3, 1).
  */
 #define FLAG_MASK 0x54dd5UL

 /* set's the trap flag. */
 #define TRAP_FLAG 0x100UL

 /*
  * eflags and offset of eflags on child stack..
  */
 #define EFLAGS offsetof(struct pt_regs, eflags)
 #define EFL_OFFSET ((int)(EFLAGS-sizeof(struct pt_regs)))

 /*
  * this routine will get a word off of the processes privileged stack.
  * the offset is how far from the base addr as stored in the TSS.
  * this routine assumes that all the privileged stacks are in our
  * data space.
  */
 static inline unsigned long get_stack_long(struct task_struct *task, int offset)
 {
 	unsigned char *stack;

 	stack = (unsigned char *)task->thread.rsp0;
 	stack += offset;
 	return (*((unsigned long *)stack));
 }

 /*
  * this routine will put a word on the processes privileged stack.
  * the offset is how far from the base addr as stored in the TSS.
  * this routine assumes that all the privileged stacks are in our
  * data space.
  */
 static inline long put_stack_long(struct task_struct *task, int offset,
 	unsigned long data)
 {
 	unsigned char * stack;

 	stack = (unsigned char *) task->thread.rsp0;
 	stack += offset;
 	*(unsigned long *) stack = data;
 	return 0;
 }

 #define LDT_SEGMENT 4

 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 & LDT_SEGMENT) {
 		u32 *desc;
 		unsigned long base;

 		seg &= ~7UL;

 		down(&child->mm->context.sem);
 		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;
 		}
 		up(&child->mm->context.sem);
 	}

 	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 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;
 }

 static void set_singlestep(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 & TRAP_FLAG)
 		return;

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

 	/*
 	 * ..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;
 }

 static void clear_singlestep(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 &= ~TRAP_FLAG;
 		child->ptrace &= ~PT_DTRACE;
 	}
 }

 /*
  * Called by kernel/ptrace.c when detaching..
  *
  * Make sure the single step bit is not set.
  */
 void ptrace_disable(struct task_struct *child)
 {
 	clear_singlestep(child);
 }

 static int putreg(struct task_struct *child,
 	unsigned long regno, unsigned long value)
 {
 	unsigned long tmp;

 	switch (regno) {
 		case offsetof(struct user_regs_struct,fs):
 			if (value && (value & 3) != 3)
 				return -EIO;
 			child->thread.fsindex = value & 0xffff;
 			return 0;
 		case offsetof(struct user_regs_struct,gs):
 			if (value && (value & 3) != 3)
 				return -EIO;
 			child->thread.gsindex = value & 0xffff;
 			return 0;
 		case offsetof(struct user_regs_struct,ds):
 			if (value && (value & 3) != 3)
 				return -EIO;
 			child->thread.ds = value & 0xffff;
 			return 0;
 		case offsetof(struct user_regs_struct,es):
 			if (value && (value & 3) != 3)
 				return -EIO;
 			child->thread.es = value & 0xffff;
 			return 0;
 		case offsetof(struct user_regs_struct,ss):
 			if ((value & 3) != 3)
 				return -EIO;
 			value &= 0xffff;
 			return 0;
 		case offsetof(struct user_regs_struct,fs_base):
 			if (value >= TASK_SIZE_OF(child))
 				return -EIO;
 			child->thread.fs = value;
 			return 0;
 		case offsetof(struct user_regs_struct,gs_base):
 			if (value >= TASK_SIZE_OF(child))
 				return -EIO;
 			child->thread.gs = value;
 			return 0;
 		case offsetof(struct user_regs_struct, eflags):
 			value &= FLAG_MASK;
 			tmp = get_stack_long(child, EFL_OFFSET);
 			tmp &= ~FLAG_MASK;
 			value |= tmp;
 			break;
 		case offsetof(struct user_regs_struct,cs):
 			if ((value & 3) != 3)
 				return -EIO;
 			value &= 0xffff;
 			break;
 	}
 	put_stack_long(child, regno - sizeof(struct pt_regs), value);
 	return 0;
 }

 static unsigned long getreg(struct task_struct *child, unsigned long regno)
 {
 	unsigned long val;
 	switch (regno) {
 		case offsetof(struct user_regs_struct, fs):
 			return child->thread.fsindex;
 		case offsetof(struct user_regs_struct, gs):
 			return child->thread.gsindex;
 		case offsetof(struct user_regs_struct, ds):
 			return child->thread.ds;
 		case offsetof(struct user_regs_struct, es):
 			return child->thread.es;
 		case offsetof(struct user_regs_struct, fs_base):
 			return child->thread.fs;
 		case offsetof(struct user_regs_struct, gs_base):
 			return child->thread.gs;
 		default:
 			regno = regno - sizeof(struct pt_regs);
 			val = get_stack_long(child, regno);
 			if (test_tsk_thread_flag(child, TIF_IA32))
 				val &= 0xffffffff;
 			return val;
 	}

 }

 long arch_ptrace(struct task_struct *child, long request, long addr, long data)
 {
 	long i, ret;
 	unsigned ui;

 	switch (request) {
 	/* when I and D space are separate, these will need to be fixed. */
 	case PTRACE_PEEKTEXT: /* read word at location addr. */
 	case PTRACE_PEEKDATA:
 		ret = generic_ptrace_peekdata(child, addr, data);
 		break;

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

 		ret = -EIO;
 		if ((addr & 7) ||
 		    addr > sizeof(struct user) - 7)
 			break;

 		switch (addr) {
 		case 0 ... sizeof(struct user_regs_struct) - sizeof(long):
 			tmp = getreg(child, addr);
 			break;
 		case offsetof(struct user, u_debugreg[0]):
 			tmp = child->thread.debugreg0;
 			break;
 		case offsetof(struct user, u_debugreg[1]):
 			tmp = child->thread.debugreg1;
 			break;
 		case offsetof(struct user, u_debugreg[2]):
 			tmp = child->thread.debugreg2;
 			break;
 		case offsetof(struct user, u_debugreg[3]):
 			tmp = child->thread.debugreg3;
 			break;
 		case offsetof(struct user, u_debugreg[6]):
 			tmp = child->thread.debugreg6;
 			break;
 		case offsetof(struct user, u_debugreg[7]):
 			tmp = child->thread.debugreg7;
 			break;
 		default:
 			tmp = 0;
 			break;
 		}
 		ret = put_user(tmp,(unsigned long __user *) data);
 		break;
 	}

 	/* when I and D space are separate, this will have to be fixed. */
 	case PTRACE_POKETEXT: /* write the word at location addr. */
 	case PTRACE_POKEDATA:
 		ret = generic_ptrace_pokedata(child, addr, data);
 		break;

 	case PTRACE_POKEUSR: /* write the word at location addr in the USER area */
 	{
 		int dsize = test_tsk_thread_flag(child, TIF_IA32) ? 3 : 7;
 		ret = -EIO;
 		if ((addr & 7) ||
 		    addr > sizeof(struct user) - 7)
 			break;

 		switch (addr) {
 		case 0 ... sizeof(struct user_regs_struct) - sizeof(long):
 			ret = putreg(child, addr, data);
 			break;
 		/* Disallows to set a breakpoint into the vsyscall */
 		case offsetof(struct user, u_debugreg[0]):
 			if (data >= TASK_SIZE_OF(child) - dsize) break;
 			child->thread.debugreg0 = data;
 			ret = 0;
 			break;
 		case offsetof(struct user, u_debugreg[1]):
 			if (data >= TASK_SIZE_OF(child) - dsize) break;
 			child->thread.debugreg1 = data;
 			ret = 0;
 			break;
 		case offsetof(struct user, u_debugreg[2]):
 			if (data >= TASK_SIZE_OF(child) - dsize) break;
 			child->thread.debugreg2 = data;
 			ret = 0;
 			break;
 		case offsetof(struct user, u_debugreg[3]):
 			if (data >= TASK_SIZE_OF(child) - dsize) break;
 			child->thread.debugreg3 = data;
 			ret = 0;
 			break;
 		case offsetof(struct user, u_debugreg[6]):
 				  if (data >> 32)
 				break;
 			child->thread.debugreg6 = data;
 			ret = 0;
 			break;
 		case offsetof(struct user, u_debugreg[7]):
 			/* See arch/i386/kernel/ptrace.c for an explanation of
 			 * this awkward check.*/
 			data &= ~DR_CONTROL_RESERVED;
 			for(i=0; i<4; i++)
 				if ((0x5554 >> ((data >> (16 + 4*i)) & 0xf)) & 1)
 					break;
 			if (i == 4) {
 			  child->thread.debugreg7 = data;
 			  if (data)
 			  	set_tsk_thread_flag(child, TIF_DEBUG);
 			  else
 			  	clear_tsk_thread_flag(child, TIF_DEBUG);
 			  ret = 0;
 		  	}
 		  break;
 		}
 		break;
 	}
 	case PTRACE_SYSCALL: /* continue and stop at next (return from) syscall */
 	case PTRACE_CONT:    /* restart after signal. */

 		ret = -EIO;
 		if (!valid_signal(data))
 			break;
 		if (request == PTRACE_SYSCALL)
 			set_tsk_thread_flag(child,TIF_SYSCALL_TRACE);
 		else
 			clear_tsk_thread_flag(child,TIF_SYSCALL_TRACE);
 		clear_tsk_thread_flag(child, TIF_SINGLESTEP);
 		child->exit_code = data;
 		/* make sure the single step bit is not set. */
 		clear_singlestep(child);
 		wake_up_process(child);
 		ret = 0;
 		break;

 #ifdef CONFIG_IA32_EMULATION
 		/* This makes only sense with 32bit programs. Allow a
 		   64bit debugger to fully examine them too. Better
 		   don't use it against 64bit processes, use
 		   PTRACE_ARCH_PRCTL instead. */
 	case PTRACE_SET_THREAD_AREA: {
 		struct user_desc __user *p;
 		int old;
 		p = (struct user_desc __user *)data;
 		get_user(old,  &p->entry_number);
 		put_user(addr, &p->entry_number);
 		ret = do_set_thread_area(&child->thread, p);
 		put_user(old,  &p->entry_number);
 		break;
 	case PTRACE_GET_THREAD_AREA:
 		p = (struct user_desc __user *)data;
 		get_user(old,  &p->entry_number);
 		put_user(addr, &p->entry_number);
 		ret = do_get_thread_area(&child->thread, p);
 		put_user(old,  &p->entry_number);
 		break;
 	}
 #endif
 		/* 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;

 /*
  * make the child exit.  Best I can do is send it a sigkill.
  * perhaps it should be put in the status that it wants to
  * exit.
  */
 	case PTRACE_KILL:
 		ret = 0;
 		if (child->exit_state == EXIT_ZOMBIE)	/* already dead */
 			break;
 		clear_tsk_thread_flag(child, TIF_SINGLESTEP);
 		child->exit_code = SIGKILL;
 		/* make sure the single step bit is not set. */
 		clear_singlestep(child);
 		wake_up_process(child);
 		break;

 	case PTRACE_SINGLESTEP:    /* set the trap flag. */
 		ret = -EIO;
 		if (!valid_signal(data))
 			break;
 		clear_tsk_thread_flag(child,TIF_SYSCALL_TRACE);
 		set_singlestep(child);
 		child->exit_code = data;
 		/* give it a chance to run. */
 		wake_up_process(child);
 		ret = 0;
 		break;

 	case PTRACE_GETREGS: { /* Get all gp regs from the child. */
 	  	if (!access_ok(VERIFY_WRITE, (unsigned __user *)data,
 			       sizeof(struct user_regs_struct))) {
 			ret = -EIO;
 			break;
 		}
 		ret = 0;
 		for (ui = 0; ui < sizeof(struct user_regs_struct); ui += sizeof(long)) {
 			ret |= __put_user(getreg(child, ui),(unsigned long __user *) data);
 			data += sizeof(long);
 		}
 		break;
 	}

 	case PTRACE_SETREGS: { /* Set all gp regs in the child. */
 		unsigned long tmp;
 	  	if (!access_ok(VERIFY_READ, (unsigned __user *)data,
 			       sizeof(struct user_regs_struct))) {
 			ret = -EIO;
 			break;
 		}
 		ret = 0;
 		for (ui = 0; ui < sizeof(struct user_regs_struct); ui += sizeof(long)) {
 			ret = __get_user(tmp, (unsigned long __user *) data);
 			if (ret)
 				break;
 			ret = putreg(child, ui, tmp);
 			if (ret)
 				break;
 			data += sizeof(long);
 		}
 		break;
 	}

 	case PTRACE_GETFPREGS: { /* Get the child extended FPU state. */
 		if (!access_ok(VERIFY_WRITE, (unsigned __user *)data,
 			       sizeof(struct user_i387_struct))) {
 			ret = -EIO;
 			break;
 		}
 		ret = get_fpregs((struct user_i387_struct __user *)data, child);
 		break;
 	}

 	case PTRACE_SETFPREGS: { /* Set the child extended FPU state. */
 		if (!access_ok(VERIFY_READ, (unsigned __user *)data,
 			       sizeof(struct user_i387_struct))) {
 			ret = -EIO;
 			break;
 		}
 		set_stopped_child_used_math(child);
 		ret = set_fpregs(child, (struct user_i387_struct __user *)data);
 		break;
 	}

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

 static void syscall_trace(struct pt_regs *regs)
 {

 #if 0
 	printk("trace %s rip %lx rsp %lx rax %d origrax %d caller %lx tiflags %x ptrace %x\n",
 	       current->comm,
 	       regs->rip, regs->rsp, regs->rax, regs->orig_rax, __builtin_return_address(0),
 	       current_thread_info()->flags, current->ptrace);
 #endif

 	ptrace_notify(SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD)
 				? 0x80 : 0));
 	/*
 	 * this isn't the same as continuing with a signal, but it will do
 	 * for normal use.  strace only continues with a signal if the
 	 * stopping signal is not SIGTRAP.  -brl
 	 */
 	if (current->exit_code) {
 		send_sig(current->exit_code, current, 1);
 		current->exit_code = 0;
 	}
 }

 asmlinkage void syscall_trace_enter(struct pt_regs *regs)
 {
 	/* do the secure computing check first */
 	secure_computing(regs->orig_rax);

 	if (test_thread_flag(TIF_SYSCALL_TRACE)
 	    && (current->ptrace & PT_PTRACED))
 		syscall_trace(regs);

 	if (unlikely(current->audit_context)) {
 		if (test_thread_flag(TIF_IA32)) {
 			audit_syscall_entry(AUDIT_ARCH_I386,
 					    regs->orig_rax,
 					    regs->rbx, regs->rcx,
 					    regs->rdx, regs->rsi);
 		} else {
 			audit_syscall_entry(AUDIT_ARCH_X86_64,
 					    regs->orig_rax,
 					    regs->rdi, regs->rsi,
 					    regs->rdx, regs->r10);
 		}
 	}
 }

 asmlinkage void syscall_trace_leave(struct pt_regs *regs)
 {
 	if (unlikely(current->audit_context))
 		audit_syscall_exit(AUDITSC_RESULT(regs->rax), regs->rax);

 	if ((test_thread_flag(TIF_SYSCALL_TRACE)
 	     || test_thread_flag(TIF_SINGLESTEP))
 	    && (current->ptrace & PT_PTRACED))
 		syscall_trace(regs);
 }
	/* By Ross Biro 1/23/92 */
	/*
	* Pentium III FXSR, SSE support
	* Gareth Hughes <gareth@valinux.com>, May 2000
	*
	* x86-64 port 2000-2002 Andi Kleen
	*/

	#include <linux/kernel.h>
	#include <linux/sched.h>
	#include <linux/mm.h>
	#include <linux/smp.h>
	#include <linux/errno.h>
	#include <linux/ptrace.h>
	#include <linux/user.h>
	#include <linux/security.h>
	#include <linux/audit.h>
	#include <linux/seccomp.h>
	#include <linux/signal.h>

	#include <asm/uaccess.h>
	#include <asm/pgtable.h>
	#include <asm/system.h>
	#include <asm/processor.h>
	#include <asm/i387.h>
	#include <asm/debugreg.h>
	#include <asm/ldt.h>
	#include <asm/desc.h>
	#include <asm/proto.h>
	#include <asm/ia32.h>

	/*
	* 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].
	* Prohibits changing ID(21), VIP(20), VIF(19), VM(17), IOPL(12-13), IF(9).
	* Also masks reserved bits (63-22, 15, 5, 3, 1).
	*/
	#define FLAG_MASK 0x54dd5UL

	/* set's the trap flag. */
	#define TRAP_FLAG 0x100UL

	/*
	* eflags and offset of eflags on child stack..
	*/
	#define EFLAGS offsetof(struct pt_regs, eflags)
	#define EFL_OFFSET ((int)(EFLAGS-sizeof(struct pt_regs)))

	/*
	* this routine will get a word off of the processes privileged stack.
	* the offset is how far from the base addr as stored in the TSS.
	* this routine assumes that all the privileged stacks are in our
	* data space.
	*/
	static inline unsigned long get_stack_long(struct task_struct *task, int offset)
	{
	unsigned char *stack;

	stack = (unsigned char *)task->thread.rsp0;
	stack += offset;
	return (((unsigned long )stack));
	}

	/*
	* this routine will put a word on the processes privileged stack.
	* the offset is how far from the base addr as stored in the TSS.
	* this routine assumes that all the privileged stacks are in our
	* data space.
	*/
	static inline long put_stack_long(struct task_struct *task, int offset,
	unsigned long data)
	{
	unsigned char * stack;

	stack = (unsigned char *) task->thread.rsp0;
	stack += offset;
	(unsigned long ) stack = data;
	return 0;
	}

	#define LDT_SEGMENT 4

	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 & LDT_SEGMENT) {
	u32 *desc;
	unsigned long base;

	seg &= ~7UL;

	down(&child->mm->context.sem);
	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;
	}
	up(&child->mm->context.sem);
	}

	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 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;
	}

	static void set_singlestep(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 & TRAP_FLAG)
	return;

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

	/*
	* ..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;
	}

	static void clear_singlestep(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 &= ~TRAP_FLAG;
	child->ptrace &= ~PT_DTRACE;
	}
	}

	/*
	* Called by kernel/ptrace.c when detaching..
	*
	* Make sure the single step bit is not set.
	*/
	void ptrace_disable(struct task_struct *child)
	{
	clear_singlestep(child);
	}

	static int putreg(struct task_struct *child,
	unsigned long regno, unsigned long value)
	{
	unsigned long tmp;

	switch (regno) {
	case offsetof(struct user_regs_struct,fs):
	if (value && (value & 3) != 3)
	return -EIO;
	child->thread.fsindex = value & 0xffff;
	return 0;
	case offsetof(struct user_regs_struct,gs):
	if (value && (value & 3) != 3)
	return -EIO;
	child->thread.gsindex = value & 0xffff;
	return 0;
	case offsetof(struct user_regs_struct,ds):
	if (value && (value & 3) != 3)
	return -EIO;
	child->thread.ds = value & 0xffff;
	return 0;
	case offsetof(struct user_regs_struct,es):
	if (value && (value & 3) != 3)
	return -EIO;
	child->thread.es = value & 0xffff;
	return 0;
	case offsetof(struct user_regs_struct,ss):
	if ((value & 3) != 3)
	return -EIO;
	value &= 0xffff;
	return 0;
	case offsetof(struct user_regs_struct,fs_base):
	if (value >= TASK_SIZE_OF(child))
	return -EIO;
	child->thread.fs = value;
	return 0;
	case offsetof(struct user_regs_struct,gs_base):
	if (value >= TASK_SIZE_OF(child))
	return -EIO;
	child->thread.gs = value;
	return 0;
	case offsetof(struct user_regs_struct, eflags):
	value &= FLAG_MASK;
	tmp = get_stack_long(child, EFL_OFFSET);
	tmp &= ~FLAG_MASK;
	value \|= tmp;
	break;
	case offsetof(struct user_regs_struct,cs):
	if ((value & 3) != 3)
	return -EIO;
	value &= 0xffff;
	break;
	}
	put_stack_long(child, regno - sizeof(struct pt_regs), value);
	return 0;
	}

	static unsigned long getreg(struct task_struct *child, unsigned long regno)
	{
	unsigned long val;
	switch (regno) {
	case offsetof(struct user_regs_struct, fs):
	return child->thread.fsindex;
	case offsetof(struct user_regs_struct, gs):
	return child->thread.gsindex;
	case offsetof(struct user_regs_struct, ds):
	return child->thread.ds;
	case offsetof(struct user_regs_struct, es):
	return child->thread.es;
	case offsetof(struct user_regs_struct, fs_base):
	return child->thread.fs;
	case offsetof(struct user_regs_struct, gs_base):
	return child->thread.gs;
	default:
	regno = regno - sizeof(struct pt_regs);
	val = get_stack_long(child, regno);
	if (test_tsk_thread_flag(child, TIF_IA32))
	val &= 0xffffffff;
	return val;
	}

	}

	long arch_ptrace(struct task_struct *child, long request, long addr, long data)
	{
	long i, ret;
	unsigned ui;

	switch (request) {
	/* when I and D space are separate, these will need to be fixed. */
	case PTRACE_PEEKTEXT: /* read word at location addr. */
	case PTRACE_PEEKDATA:
	ret = generic_ptrace_peekdata(child, addr, data);
	break;

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

	ret = -EIO;
	if ((addr & 7) \|\|
	addr > sizeof(struct user) - 7)
	break;

	switch (addr) {
	case 0 ... sizeof(struct user_regs_struct) - sizeof(long):
	tmp = getreg(child, addr);
	break;
	case offsetof(struct user, u_debugreg[0]):
	tmp = child->thread.debugreg0;
	break;
	case offsetof(struct user, u_debugreg[1]):
	tmp = child->thread.debugreg1;
	break;
	case offsetof(struct user, u_debugreg[2]):
	tmp = child->thread.debugreg2;
	break;
	case offsetof(struct user, u_debugreg[3]):
	tmp = child->thread.debugreg3;
	break;
	case offsetof(struct user, u_debugreg[6]):
	tmp = child->thread.debugreg6;
	break;
	case offsetof(struct user, u_debugreg[7]):
	tmp = child->thread.debugreg7;
	break;
	default:
	tmp = 0;
	break;
	}
	ret = put_user(tmp,(unsigned long __user *) data);
	break;
	}

	/* when I and D space are separate, this will have to be fixed. */
	case PTRACE_POKETEXT: /* write the word at location addr. */
	case PTRACE_POKEDATA:
	ret = generic_ptrace_pokedata(child, addr, data);
	break;

	case PTRACE_POKEUSR: /* write the word at location addr in the USER area */
	{
	int dsize = test_tsk_thread_flag(child, TIF_IA32) ? 3 : 7;
	ret = -EIO;
	if ((addr & 7) \|\|
	addr > sizeof(struct user) - 7)
	break;

	switch (addr) {
	case 0 ... sizeof(struct user_regs_struct) - sizeof(long):
	ret = putreg(child, addr, data);
	break;
	/* Disallows to set a breakpoint into the vsyscall */
	case offsetof(struct user, u_debugreg[0]):
	if (data >= TASK_SIZE_OF(child) - dsize) break;
	child->thread.debugreg0 = data;
	ret = 0;
	break;
	case offsetof(struct user, u_debugreg[1]):
	if (data >= TASK_SIZE_OF(child) - dsize) break;
	child->thread.debugreg1 = data;
	ret = 0;
	break;
	case offsetof(struct user, u_debugreg[2]):
	if (data >= TASK_SIZE_OF(child) - dsize) break;
	child->thread.debugreg2 = data;
	ret = 0;
	break;
	case offsetof(struct user, u_debugreg[3]):
	if (data >= TASK_SIZE_OF(child) - dsize) break;
	child->thread.debugreg3 = data;
	ret = 0;
	break;
	case offsetof(struct user, u_debugreg[6]):
	if (data >> 32)
	break;
	child->thread.debugreg6 = data;
	ret = 0;
	break;
	case offsetof(struct user, u_debugreg[7]):
	/* See arch/i386/kernel/ptrace.c for an explanation of
	* this awkward check.*/
	data &= ~DR_CONTROL_RESERVED;
	for(i=0; i<4; i++)
	if ((0x5554 >> ((data >> (16 + 4*i)) & 0xf)) & 1)
	break;
	if (i == 4) {
	child->thread.debugreg7 = data;
	if (data)
	set_tsk_thread_flag(child, TIF_DEBUG);
	else
	clear_tsk_thread_flag(child, TIF_DEBUG);
	ret = 0;
	}
	break;
	}
	break;
	}
	case PTRACE_SYSCALL: /* continue and stop at next (return from) syscall */
	case PTRACE_CONT: /* restart after signal. */

	ret = -EIO;
	if (!valid_signal(data))
	break;
	if (request == PTRACE_SYSCALL)
	set_tsk_thread_flag(child,TIF_SYSCALL_TRACE);
	else
	clear_tsk_thread_flag(child,TIF_SYSCALL_TRACE);
	clear_tsk_thread_flag(child, TIF_SINGLESTEP);
	child->exit_code = data;
	/* make sure the single step bit is not set. */
	clear_singlestep(child);
	wake_up_process(child);
	ret = 0;
	break;

	#ifdef CONFIG_IA32_EMULATION
	/* This makes only sense with 32bit programs. Allow a
	64bit debugger to fully examine them too. Better
	don't use it against 64bit processes, use
	PTRACE_ARCH_PRCTL instead. */
	case PTRACE_SET_THREAD_AREA: {
	struct user_desc __user *p;
	int old;
	p = (struct user_desc __user *)data;
	get_user(old, &p->entry_number);
	put_user(addr, &p->entry_number);
	ret = do_set_thread_area(&child->thread, p);
	put_user(old, &p->entry_number);
	break;
	case PTRACE_GET_THREAD_AREA:
	p = (struct user_desc __user *)data;
	get_user(old, &p->entry_number);
	put_user(addr, &p->entry_number);
	ret = do_get_thread_area(&child->thread, p);
	put_user(old, &p->entry_number);
	break;
	}
	#endif
	/* 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;

	/*
	* make the child exit. Best I can do is send it a sigkill.
	* perhaps it should be put in the status that it wants to
	* exit.
	*/
	case PTRACE_KILL:
	ret = 0;
	if (child->exit_state == EXIT_ZOMBIE) /* already dead */
	break;
	clear_tsk_thread_flag(child, TIF_SINGLESTEP);
	child->exit_code = SIGKILL;
	/* make sure the single step bit is not set. */
	clear_singlestep(child);
	wake_up_process(child);
	break;

	case PTRACE_SINGLESTEP: /* set the trap flag. */
	ret = -EIO;
	if (!valid_signal(data))
	break;
	clear_tsk_thread_flag(child,TIF_SYSCALL_TRACE);
	set_singlestep(child);
	child->exit_code = data;
	/* give it a chance to run. */
	wake_up_process(child);
	ret = 0;
	break;

	case PTRACE_GETREGS: { /* Get all gp regs from the child. */
	if (!access_ok(VERIFY_WRITE, (unsigned __user *)data,
	sizeof(struct user_regs_struct))) {
	ret = -EIO;
	break;
	}
	ret = 0;
	for (ui = 0; ui < sizeof(struct user_regs_struct); ui += sizeof(long)) {
	ret \|= __put_user(getreg(child, ui),(unsigned long __user *) data);
	data += sizeof(long);
	}
	break;
	}

	case PTRACE_SETREGS: { /* Set all gp regs in the child. */
	unsigned long tmp;
	if (!access_ok(VERIFY_READ, (unsigned __user *)data,
	sizeof(struct user_regs_struct))) {
	ret = -EIO;
	break;
	}
	ret = 0;
	for (ui = 0; ui < sizeof(struct user_regs_struct); ui += sizeof(long)) {
	ret = __get_user(tmp, (unsigned long __user *) data);
	if (ret)
	break;
	ret = putreg(child, ui, tmp);
	if (ret)
	break;
	data += sizeof(long);
	}
	break;
	}

	case PTRACE_GETFPREGS: { /* Get the child extended FPU state. */
	if (!access_ok(VERIFY_WRITE, (unsigned __user *)data,
	sizeof(struct user_i387_struct))) {
	ret = -EIO;
	break;
	}
	ret = get_fpregs((struct user_i387_struct __user *)data, child);
	break;
	}

	case PTRACE_SETFPREGS: { /* Set the child extended FPU state. */
	if (!access_ok(VERIFY_READ, (unsigned __user *)data,
	sizeof(struct user_i387_struct))) {
	ret = -EIO;
	break;
	}
	set_stopped_child_used_math(child);
	ret = set_fpregs(child, (struct user_i387_struct __user *)data);
	break;
	}

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

	static void syscall_trace(struct pt_regs *regs)
	{

	#if 0
	printk("trace %s rip %lx rsp %lx rax %d origrax %d caller %lx tiflags %x ptrace %x\n",
	current->comm,
	regs->rip, regs->rsp, regs->rax, regs->orig_rax, __builtin_return_address(0),
	current_thread_info()->flags, current->ptrace);
	#endif

	ptrace_notify(SIGTRAP \| ((current->ptrace & PT_TRACESYSGOOD)
	? 0x80 : 0));
	/*
	* this isn't the same as continuing with a signal, but it will do
	* for normal use. strace only continues with a signal if the
	* stopping signal is not SIGTRAP. -brl
	*/
	if (current->exit_code) {
	send_sig(current->exit_code, current, 1);
	current->exit_code = 0;
	}
	}

	asmlinkage void syscall_trace_enter(struct pt_regs *regs)
	{
	/* do the secure computing check first */
	secure_computing(regs->orig_rax);

	if (test_thread_flag(TIF_SYSCALL_TRACE)
	&& (current->ptrace & PT_PTRACED))
	syscall_trace(regs);

	if (unlikely(current->audit_context)) {
	if (test_thread_flag(TIF_IA32)) {
	audit_syscall_entry(AUDIT_ARCH_I386,
	regs->orig_rax,
	regs->rbx, regs->rcx,
	regs->rdx, regs->rsi);
	} else {
	audit_syscall_entry(AUDIT_ARCH_X86_64,
	regs->orig_rax,
	regs->rdi, regs->rsi,
	regs->rdx, regs->r10);
	}
	}
	}

	asmlinkage void syscall_trace_leave(struct pt_regs *regs)
	{
	if (unlikely(current->audit_context))
	audit_syscall_exit(AUDITSC_RESULT(regs->rax), regs->rax);

	if ((test_thread_flag(TIF_SYSCALL_TRACE)
	\|\| test_thread_flag(TIF_SINGLESTEP))
	&& (current->ptrace & PT_PTRACED))
	syscall_trace(regs);
	}