arch/score/kernel/ptrace.c - maze/linux - Git at Google

 /*
  * arch/score/kernel/ptrace.c
  *
  * Score Processor version.
  *
  * Copyright (C) 2009 Sunplus Core Technology Co., Ltd.
  *  Chen Liqin <liqin.chen@sunplusct.com>
  *  Lennox Wu <lennox.wu@sunplusct.com>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
  * (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, see the file COPYING, or write
  * to the Free Software Foundation, Inc.,
  * 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  */

 #include <linux/kernel.h>
 #include <linux/ptrace.h>

 #include <asm/uaccess.h>

 static int is_16bitinsn(unsigned long insn)
 {
 	if ((insn & INSN32_MASK) == INSN32_MASK)
 		return 0;
 	else
 		return 1;
 }

 int
 read_tsk_long(struct task_struct *child,
 		unsigned long addr, unsigned long *res)
 {
 	int copied;

 	copied = access_process_vm(child, addr, res, sizeof(*res), 0);

 	return copied != sizeof(*res) ? -EIO : 0;
 }

 int
 read_tsk_short(struct task_struct *child,
 		unsigned long addr, unsigned short *res)
 {
 	int copied;

 	copied = access_process_vm(child, addr, res, sizeof(*res), 0);

 	return copied != sizeof(*res) ? -EIO : 0;
 }

 static int
 write_tsk_short(struct task_struct *child,
 		unsigned long addr, unsigned short val)
 {
 	int copied;

 	copied = access_process_vm(child, addr, &val, sizeof(val), 1);

 	return copied != sizeof(val) ? -EIO : 0;
 }

 static int
 write_tsk_long(struct task_struct *child,
 		unsigned long addr, unsigned long val)
 {
 	int copied;

 	copied = access_process_vm(child, addr, &val, sizeof(val), 1);

 	return copied != sizeof(val) ? -EIO : 0;
 }

 void set_single_step(struct task_struct *child)
 {
 	/* far_epc is the target of branch */
 	unsigned int epc, far_epc = 0;
 	unsigned long epc_insn, far_epc_insn;
 	int ninsn_type;			/* next insn type 0=16b, 1=32b */
 	unsigned int tmp, tmp2;
 	struct pt_regs *regs = task_pt_regs(child);
 	child->thread.single_step = 1;
 	child->thread.ss_nextcnt = 1;
 	epc = regs->cp0_epc;

 	read_tsk_long(child, epc, &epc_insn);

 	if (is_16bitinsn(epc_insn)) {
 		if ((epc_insn & J16M) == J16) {
 			tmp = epc_insn & 0xFFE;
 			epc = (epc & 0xFFFFF000) | tmp;
 		} else if ((epc_insn & B16M) == B16) {
 			child->thread.ss_nextcnt = 2;
 			tmp = (epc_insn & 0xFF) << 1;
 			tmp = tmp << 23;
 			tmp = (unsigned int)((int) tmp >> 23);
 			far_epc = epc + tmp;
 			epc += 2;
 		} else if ((epc_insn & BR16M) == BR16) {
 			child->thread.ss_nextcnt = 2;
 			tmp = (epc_insn >> 4) & 0xF;
 			far_epc = regs->regs[tmp];
 			epc += 2;
 		} else
 			epc += 2;
 	} else {
 		if ((epc_insn & J32M) == J32) {
 			tmp = epc_insn & 0x03FFFFFE;
 			tmp2 = tmp & 0x7FFF;
 			tmp = (((tmp >> 16) & 0x3FF) << 15) | tmp2;
 			epc = (epc & 0xFFC00000) | tmp;
 		} else if ((epc_insn & B32M) == B32) {
 			child->thread.ss_nextcnt = 2;
 			tmp = epc_insn & 0x03FFFFFE;	/* discard LK bit */
 			tmp2 = tmp & 0x3FF;
 			tmp = (((tmp >> 16) & 0x3FF) << 10) | tmp2; /* 20bit */
 			tmp = tmp << 12;
 			tmp = (unsigned int)((int) tmp >> 12);
 			far_epc = epc + tmp;
 			epc += 4;
 		} else if ((epc_insn & BR32M) == BR32) {
 			child->thread.ss_nextcnt = 2;
 			tmp = (epc_insn >> 16) & 0x1F;
 			far_epc = regs->regs[tmp];
 			epc += 4;
 		} else
 			epc += 4;
 	}

 	if (child->thread.ss_nextcnt == 1) {
 		read_tsk_long(child, epc, &epc_insn);

 		if (is_16bitinsn(epc_insn)) {
 			write_tsk_short(child, epc, SINGLESTEP16_INSN);
 			ninsn_type = 0;
 		} else {
 			write_tsk_long(child, epc, SINGLESTEP32_INSN);
 			ninsn_type = 1;
 		}

 		if (ninsn_type == 0) {  /* 16bits */
 			child->thread.insn1_type = 0;
 			child->thread.addr1 = epc;
 			 /* the insn may have 32bit data */
 			child->thread.insn1 = (short)epc_insn;
 		} else {
 			child->thread.insn1_type = 1;
 			child->thread.addr1 = epc;
 			child->thread.insn1 = epc_insn;
 		}
 	} else {
 		/* branch! have two target child->thread.ss_nextcnt=2 */
 		read_tsk_long(child, epc, &epc_insn);
 		read_tsk_long(child, far_epc, &far_epc_insn);
 		if (is_16bitinsn(epc_insn)) {
 			write_tsk_short(child, epc, SINGLESTEP16_INSN);
 			ninsn_type = 0;
 		} else {
 			write_tsk_long(child, epc, SINGLESTEP32_INSN);
 			ninsn_type = 1;
 		}

 		if (ninsn_type == 0) {  /* 16bits */
 			child->thread.insn1_type = 0;
 			child->thread.addr1 = epc;
 			 /* the insn may have 32bit data */
 			child->thread.insn1 = (short)epc_insn;
 		} else {
 			child->thread.insn1_type = 1;
 			child->thread.addr1 = epc;
 			child->thread.insn1 = epc_insn;
 		}

 		if (is_16bitinsn(far_epc_insn)) {
 			write_tsk_short(child, far_epc, SINGLESTEP16_INSN);
 			ninsn_type = 0;
 		} else {
 			write_tsk_long(child, far_epc, SINGLESTEP32_INSN);
 			ninsn_type = 1;
 		}

 		if (ninsn_type == 0) {  /* 16bits */
 			child->thread.insn2_type = 0;
 			child->thread.addr2 = far_epc;
 			 /* the insn may have 32bit data */
 			child->thread.insn2 = (short)far_epc_insn;
 		} else {
 			child->thread.insn2_type = 1;
 			child->thread.addr2 = far_epc;
 			child->thread.insn2 = far_epc_insn;
 		}
 	}
 }

 void clear_single_step(struct task_struct *child)
 {
 	if (child->thread.insn1_type == 0)
 		write_tsk_short(child, child->thread.addr1,
 				child->thread.insn1);

 	if (child->thread.insn1_type == 1)
 		write_tsk_long(child, child->thread.addr1,
 				child->thread.insn1);

 	if (child->thread.ss_nextcnt == 2) {	/* branch */
 		if (child->thread.insn1_type == 0)
 			write_tsk_short(child, child->thread.addr1,
 					child->thread.insn1);
 		if (child->thread.insn1_type == 1)
 			write_tsk_long(child, child->thread.addr1,
 					child->thread.insn1);
 		if (child->thread.insn2_type == 0)
 			write_tsk_short(child, child->thread.addr2,
 					child->thread.insn2);
 		if (child->thread.insn2_type == 1)
 			write_tsk_long(child, child->thread.addr2,
 					child->thread.insn2);
 	}

 	child->thread.single_step = 0;
 	child->thread.ss_nextcnt = 0;
 }


 void ptrace_disable(struct task_struct *child) {}

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

 	if (request == PTRACE_TRACEME) {
 		/* are we already being traced? */
 		if (current->ptrace & PT_PTRACED)
 			return -EPERM;

 		/* set the ptrace bit in the process flags. */
 		current->ptrace |= PT_PTRACED;
 		return 0;
 	}

 	ret = -ESRCH;
 	if (!child)
 		return ret;

 	ret = -EPERM;

 	if (request == PTRACE_ATTACH) {
 		ret = ptrace_attach(child);
 		return ret;
 	}

 	ret = ptrace_check_attach(child, request == PTRACE_KILL);
 	if (ret < 0)
 		return ret;

 	switch (request) {
 	case PTRACE_PEEKTEXT: /* read word at location addr. */
 	case PTRACE_PEEKDATA: {
 		unsigned long tmp;
 		int copied;

 		copied = access_process_vm(child, addr, &tmp, sizeof(tmp), 0);
 		ret = -EIO;
 		if (copied != sizeof(tmp))
 			break;

 		ret = put_user(tmp, (unsigned long *) data);
 		return ret;
 	}

 	/* Read the word at location addr in the USER area.  */
 	case PTRACE_PEEKUSR: {
 		struct pt_regs *regs;
 		unsigned long tmp;

 		regs = task_pt_regs(child);

 		tmp = 0;  /* Default return value. */
 		switch (addr) {
 		case 0 ... 31:
 			tmp = regs->regs[addr];
 			break;
 		case PC:
 			tmp = regs->cp0_epc;
 			break;
 		case ECR:
 			tmp = regs->cp0_ecr;
 			break;
 		case EMA:
 			tmp = regs->cp0_ema;
 			break;
 		case CEH:
 			tmp = regs->ceh;
 			break;
 		case CEL:
 			tmp = regs->cel;
 			break;
 		case CONDITION:
 			tmp = regs->cp0_condition;
 			break;
 		case PSR:
 			tmp = regs->cp0_psr;
 			break;
 		case COUNTER:
 			tmp = regs->sr0;
 			break;
 		case LDCR:
 			tmp = regs->sr1;
 			break;
 		case STCR:
 			tmp = regs->sr2;
 			break;
 		default:
 			tmp = 0;
 			return -EIO;
 		}

 		ret = put_user(tmp, (unsigned long *) data);
 		return ret;
 	}

 	case PTRACE_POKETEXT: /* write the word at location addr. */
 	case PTRACE_POKEDATA:
 		ret = 0;
 		if (access_process_vm(child, addr, &data, sizeof(data), 1)
 			== sizeof(data))
 			break;
 		ret = -EIO;
 		return ret;

 	case PTRACE_POKEUSR: {
 		struct pt_regs *regs;
 		ret = 0;
 		regs = task_pt_regs(child);

 		switch (addr) {
 		case 0 ... 31:
 			regs->regs[addr] = data;
 			break;
 		case PC:
 			regs->cp0_epc = data;
 			break;
 		case CEH:
 			regs->ceh = data;
 			break;
 		case CEL:
 			regs->cel = data;
 			break;
 		case CONDITION:
 			regs->cp0_condition = data;
 			break;
 		case PSR:
 		case COUNTER:
 		case STCR:
 		case LDCR:
 			break; /* user can't write the reg */
 		default:
 			/* The rest are not allowed. */
 			ret = -EIO;
 			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);

 		child->exit_code = data;
 		wake_up_process(child);
 		ret = 0;
 		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->state == EXIT_ZOMBIE)	/* already dead. */
 			break;
 		child->exit_code = SIGKILL;
 		clear_single_step(child);
 		wake_up_process(child);
 		break;

 	case PTRACE_SINGLESTEP: {		/* set the trap flag. */
 		ret = -EIO;
 		if ((unsigned long) data > _NSIG)
 			break;
 		clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
 		set_single_step(child);
 		child->exit_code = data;
 		/* give it a chance to run. */
 		wake_up_process(child);
 		ret = 0;
 		break;
 	}

 	case PTRACE_DETACH: /* detach a process that was attached. */
 		ret = ptrace_detach(child, data);
 		break;

 	case PTRACE_SETOPTIONS:
 		if (data & PTRACE_O_TRACESYSGOOD)
 			child->ptrace |= PT_TRACESYSGOOD;
 		else
 			child->ptrace &= ~PT_TRACESYSGOOD;
 		ret = 0;
 		break;

 	default:
 		ret = -EIO;
 		break;
 	}

 	return ret;
 }

 /*
  * Notification of system call entry/exit
  * - triggered by current->work.syscall_trace
  */
 asmlinkage void do_syscall_trace(struct pt_regs *regs, int entryexit)
 {
 	if (!(current->ptrace & PT_PTRACED))
 		return;

 	if (!test_thread_flag(TIF_SYSCALL_TRACE))
 		return;

 	/* The 0x80 provides a way for the tracing parent to distinguish
 	   between a syscall stop and SIGTRAP delivery. */
 	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;
 	}
 }
	/*
	* arch/score/kernel/ptrace.c
	*
	* Score Processor version.
	*
	* Copyright (C) 2009 Sunplus Core Technology Co., Ltd.
	* Chen Liqin <liqin.chen@sunplusct.com>
	* Lennox Wu <lennox.wu@sunplusct.com>
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation; either version 2 of the License, or
	* (at your option) any later version.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program; if not, see the file COPYING, or write
	* to the Free Software Foundation, Inc.,
	* 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
	*/

	#include <linux/kernel.h>
	#include <linux/ptrace.h>

	#include <asm/uaccess.h>

	static int is_16bitinsn(unsigned long insn)
	{
	if ((insn & INSN32_MASK) == INSN32_MASK)
	return 0;
	else
	return 1;
	}

	int
	read_tsk_long(struct task_struct *child,
	unsigned long addr, unsigned long *res)
	{
	int copied;

	copied = access_process_vm(child, addr, res, sizeof(*res), 0);

	return copied != sizeof(*res) ? -EIO : 0;
	}

	int
	read_tsk_short(struct task_struct *child,
	unsigned long addr, unsigned short *res)
	{
	int copied;

	copied = access_process_vm(child, addr, res, sizeof(*res), 0);

	return copied != sizeof(*res) ? -EIO : 0;
	}

	static int
	write_tsk_short(struct task_struct *child,
	unsigned long addr, unsigned short val)
	{
	int copied;

	copied = access_process_vm(child, addr, &val, sizeof(val), 1);

	return copied != sizeof(val) ? -EIO : 0;
	}

	static int
	write_tsk_long(struct task_struct *child,
	unsigned long addr, unsigned long val)
	{
	int copied;

	copied = access_process_vm(child, addr, &val, sizeof(val), 1);

	return copied != sizeof(val) ? -EIO : 0;
	}

	void set_single_step(struct task_struct *child)
	{
	/* far_epc is the target of branch */
	unsigned int epc, far_epc = 0;
	unsigned long epc_insn, far_epc_insn;
	int ninsn_type; /* next insn type 0=16b, 1=32b */
	unsigned int tmp, tmp2;
	struct pt_regs *regs = task_pt_regs(child);
	child->thread.single_step = 1;
	child->thread.ss_nextcnt = 1;
	epc = regs->cp0_epc;

	read_tsk_long(child, epc, &epc_insn);

	if (is_16bitinsn(epc_insn)) {
	if ((epc_insn & J16M) == J16) {
	tmp = epc_insn & 0xFFE;
	epc = (epc & 0xFFFFF000) \| tmp;
	} else if ((epc_insn & B16M) == B16) {
	child->thread.ss_nextcnt = 2;
	tmp = (epc_insn & 0xFF) << 1;
	tmp = tmp << 23;
	tmp = (unsigned int)((int) tmp >> 23);
	far_epc = epc + tmp;
	epc += 2;
	} else if ((epc_insn & BR16M) == BR16) {
	child->thread.ss_nextcnt = 2;
	tmp = (epc_insn >> 4) & 0xF;
	far_epc = regs->regs[tmp];
	epc += 2;
	} else
	epc += 2;
	} else {
	if ((epc_insn & J32M) == J32) {
	tmp = epc_insn & 0x03FFFFFE;
	tmp2 = tmp & 0x7FFF;
	tmp = (((tmp >> 16) & 0x3FF) << 15) \| tmp2;
	epc = (epc & 0xFFC00000) \| tmp;
	} else if ((epc_insn & B32M) == B32) {
	child->thread.ss_nextcnt = 2;
	tmp = epc_insn & 0x03FFFFFE; /* discard LK bit */
	tmp2 = tmp & 0x3FF;
	tmp = (((tmp >> 16) & 0x3FF) << 10) \| tmp2; /* 20bit */
	tmp = tmp << 12;
	tmp = (unsigned int)((int) tmp >> 12);
	far_epc = epc + tmp;
	epc += 4;
	} else if ((epc_insn & BR32M) == BR32) {
	child->thread.ss_nextcnt = 2;
	tmp = (epc_insn >> 16) & 0x1F;
	far_epc = regs->regs[tmp];
	epc += 4;
	} else
	epc += 4;
	}

	if (child->thread.ss_nextcnt == 1) {
	read_tsk_long(child, epc, &epc_insn);

	if (is_16bitinsn(epc_insn)) {
	write_tsk_short(child, epc, SINGLESTEP16_INSN);
	ninsn_type = 0;
	} else {
	write_tsk_long(child, epc, SINGLESTEP32_INSN);
	ninsn_type = 1;
	}

	if (ninsn_type == 0) { /* 16bits */
	child->thread.insn1_type = 0;
	child->thread.addr1 = epc;
	/* the insn may have 32bit data */
	child->thread.insn1 = (short)epc_insn;
	} else {
	child->thread.insn1_type = 1;
	child->thread.addr1 = epc;
	child->thread.insn1 = epc_insn;
	}
	} else {
	/* branch! have two target child->thread.ss_nextcnt=2 */
	read_tsk_long(child, epc, &epc_insn);
	read_tsk_long(child, far_epc, &far_epc_insn);
	if (is_16bitinsn(epc_insn)) {
	write_tsk_short(child, epc, SINGLESTEP16_INSN);
	ninsn_type = 0;
	} else {
	write_tsk_long(child, epc, SINGLESTEP32_INSN);
	ninsn_type = 1;
	}

	if (ninsn_type == 0) { /* 16bits */
	child->thread.insn1_type = 0;
	child->thread.addr1 = epc;
	/* the insn may have 32bit data */
	child->thread.insn1 = (short)epc_insn;
	} else {
	child->thread.insn1_type = 1;
	child->thread.addr1 = epc;
	child->thread.insn1 = epc_insn;
	}

	if (is_16bitinsn(far_epc_insn)) {
	write_tsk_short(child, far_epc, SINGLESTEP16_INSN);
	ninsn_type = 0;
	} else {
	write_tsk_long(child, far_epc, SINGLESTEP32_INSN);
	ninsn_type = 1;
	}

	if (ninsn_type == 0) { /* 16bits */
	child->thread.insn2_type = 0;
	child->thread.addr2 = far_epc;
	/* the insn may have 32bit data */
	child->thread.insn2 = (short)far_epc_insn;
	} else {
	child->thread.insn2_type = 1;
	child->thread.addr2 = far_epc;
	child->thread.insn2 = far_epc_insn;
	}
	}
	}

	void clear_single_step(struct task_struct *child)
	{
	if (child->thread.insn1_type == 0)
	write_tsk_short(child, child->thread.addr1,
	child->thread.insn1);

	if (child->thread.insn1_type == 1)
	write_tsk_long(child, child->thread.addr1,
	child->thread.insn1);

	if (child->thread.ss_nextcnt == 2) { /* branch */
	if (child->thread.insn1_type == 0)
	write_tsk_short(child, child->thread.addr1,
	child->thread.insn1);
	if (child->thread.insn1_type == 1)
	write_tsk_long(child, child->thread.addr1,
	child->thread.insn1);
	if (child->thread.insn2_type == 0)
	write_tsk_short(child, child->thread.addr2,
	child->thread.insn2);
	if (child->thread.insn2_type == 1)
	write_tsk_long(child, child->thread.addr2,
	child->thread.insn2);
	}

	child->thread.single_step = 0;
	child->thread.ss_nextcnt = 0;
	}


	void ptrace_disable(struct task_struct *child) {}

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

	if (request == PTRACE_TRACEME) {
	/* are we already being traced? */
	if (current->ptrace & PT_PTRACED)
	return -EPERM;

	/* set the ptrace bit in the process flags. */
	current->ptrace \|= PT_PTRACED;
	return 0;
	}

	ret = -ESRCH;
	if (!child)
	return ret;

	ret = -EPERM;

	if (request == PTRACE_ATTACH) {
	ret = ptrace_attach(child);
	return ret;
	}

	ret = ptrace_check_attach(child, request == PTRACE_KILL);
	if (ret < 0)
	return ret;

	switch (request) {
	case PTRACE_PEEKTEXT: /* read word at location addr. */
	case PTRACE_PEEKDATA: {
	unsigned long tmp;
	int copied;

	copied = access_process_vm(child, addr, &tmp, sizeof(tmp), 0);
	ret = -EIO;
	if (copied != sizeof(tmp))
	break;

	ret = put_user(tmp, (unsigned long *) data);
	return ret;
	}

	/* Read the word at location addr in the USER area. */
	case PTRACE_PEEKUSR: {
	struct pt_regs *regs;
	unsigned long tmp;

	regs = task_pt_regs(child);

	tmp = 0; /* Default return value. */
	switch (addr) {
	case 0 ... 31:
	tmp = regs->regs[addr];
	break;
	case PC:
	tmp = regs->cp0_epc;
	break;
	case ECR:
	tmp = regs->cp0_ecr;
	break;
	case EMA:
	tmp = regs->cp0_ema;
	break;
	case CEH:
	tmp = regs->ceh;
	break;
	case CEL:
	tmp = regs->cel;
	break;
	case CONDITION:
	tmp = regs->cp0_condition;
	break;
	case PSR:
	tmp = regs->cp0_psr;
	break;
	case COUNTER:
	tmp = regs->sr0;
	break;
	case LDCR:
	tmp = regs->sr1;
	break;
	case STCR:
	tmp = regs->sr2;
	break;
	default:
	tmp = 0;
	return -EIO;
	}

	ret = put_user(tmp, (unsigned long *) data);
	return ret;
	}

	case PTRACE_POKETEXT: /* write the word at location addr. */
	case PTRACE_POKEDATA:
	ret = 0;
	if (access_process_vm(child, addr, &data, sizeof(data), 1)
	== sizeof(data))
	break;
	ret = -EIO;
	return ret;

	case PTRACE_POKEUSR: {
	struct pt_regs *regs;
	ret = 0;
	regs = task_pt_regs(child);

	switch (addr) {
	case 0 ... 31:
	regs->regs[addr] = data;
	break;
	case PC:
	regs->cp0_epc = data;
	break;
	case CEH:
	regs->ceh = data;
	break;
	case CEL:
	regs->cel = data;
	break;
	case CONDITION:
	regs->cp0_condition = data;
	break;
	case PSR:
	case COUNTER:
	case STCR:
	case LDCR:
	break; /* user can't write the reg */
	default:
	/* The rest are not allowed. */
	ret = -EIO;
	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);

	child->exit_code = data;
	wake_up_process(child);
	ret = 0;
	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->state == EXIT_ZOMBIE) /* already dead. */
	break;
	child->exit_code = SIGKILL;
	clear_single_step(child);
	wake_up_process(child);
	break;

	case PTRACE_SINGLESTEP: { /* set the trap flag. */
	ret = -EIO;
	if ((unsigned long) data > _NSIG)
	break;
	clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
	set_single_step(child);
	child->exit_code = data;
	/* give it a chance to run. */
	wake_up_process(child);
	ret = 0;
	break;
	}

	case PTRACE_DETACH: /* detach a process that was attached. */
	ret = ptrace_detach(child, data);
	break;

	case PTRACE_SETOPTIONS:
	if (data & PTRACE_O_TRACESYSGOOD)
	child->ptrace \|= PT_TRACESYSGOOD;
	else
	child->ptrace &= ~PT_TRACESYSGOOD;
	ret = 0;
	break;

	default:
	ret = -EIO;
	break;
	}

	return ret;
	}

	/*
	* Notification of system call entry/exit
	* - triggered by current->work.syscall_trace
	*/
	asmlinkage void do_syscall_trace(struct pt_regs *regs, int entryexit)
	{
	if (!(current->ptrace & PT_PTRACED))
	return;

	if (!test_thread_flag(TIF_SYSCALL_TRACE))
	return;

	/* The 0x80 provides a way for the tracing parent to distinguish
	between a syscall stop and SIGTRAP delivery. */
	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;
	}
	}