Linux0.96c/kernel/ptrace.c
/* ptrace.c */
/* By Ross Biro 1/23/92 */
/* edited by Linus Torvalds */
#include <linux/head.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <asm/segment.h>
#include <asm/system.h>
#include <errno.h>
#include <sys/ptrace.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 */
#define FLAG_MASK 0x00000dd9
/* set's the trap flag. */
#define TRAP_FLAG 0x100
/*
* this is the number to subtract from the top of the stack. To find
* the local frame.
*/
#define MAGICNUMBER 68
void do_no_page(unsigned long, unsigned long, struct task_struct *, unsigned long);
void write_verify(unsigned long);
/* change a pid into a task struct. */
static inline struct task_struct * get_task(int pid)
{
int i;
for (i = 0; i < NR_TASKS; i++) {
if (task[i] != NULL && (task[i]->pid == pid))
return task[i];
}
return NULL;
}
/*
* this routine will get a word off of the processes priviledged stack.
* the offset is how far from the base addr as stored in the TSS.
* this routine assumes that all the priviledged stacks are in our
* data space.
*/
static inline int get_stack_long(struct task_struct *task, int offset)
{
unsigned char *stack;
stack = (unsigned char *)task->tss.esp0;
stack += offset;
return (*((int *)stack));
}
/*
* this routine will put a word on the processes priviledged stack.
* the offset is how far from the base addr as stored in the TSS.
* this routine assumes that all the priviledged stacks are in our
* data space.
*/
static inline int put_stack_long(struct task_struct *task, int offset,
unsigned long data)
{
unsigned char * stack;
stack = (unsigned char *) task->tss.esp0;
stack += offset;
*(unsigned long *) stack = data;
return 0;
}
/*
* This routine gets a long from any process space by following the page
* tables. NOTE! You should check that the long isn't on a page boundary,
* and that it is in the task area before calling this: this routine does
* no checking.
*
* NOTE2! This uses "tsk->tss.cr3" even though we know it's currently always
* zero. This routine shouldn't have to change when we make a better mm.
*/
static unsigned long get_long(struct task_struct * tsk,
unsigned long addr)
{
unsigned long page;
addr += tsk->start_code;
repeat:
page = tsk->tss.cr3 + ((addr >> 20) & 0xffc);
page = *(unsigned long *) page;
if (page & PAGE_PRESENT) {
page &= 0xfffff000;
page += (addr >> 10) & 0xffc;
page = *((unsigned long *) page);
}
if (!(page & PAGE_PRESENT)) {
do_no_page(0,addr,tsk,0);
goto repeat;
}
page &= 0xfffff000;
page += addr & 0xfff;
return *(unsigned long *) page;
}
/*
* This routine puts a long into any process space by following the page
* tables. NOTE! You should check that the long isn't on a page boundary,
* and that it is in the task area before calling this: this routine does
* no checking.
*/
static void put_long(struct task_struct * tsk, unsigned long addr,
unsigned long data)
{
unsigned long page;
addr += tsk->start_code;
repeat:
page = tsk->tss.cr3 + ((addr >> 20) & 0xffc);
page = *(unsigned long *) page;
if (page & PAGE_PRESENT) {
page &= 0xfffff000;
page += (addr >> 10) & 0xffc;
page = *((unsigned long *) page);
}
if (!(page & PAGE_PRESENT)) {
do_no_page(0,addr,tsk,0);
goto repeat;
}
if (!(page & PAGE_RW)) {
write_verify(addr);
goto repeat;
}
page &= 0xfffff000;
page += addr & 0xfff;
*(unsigned long *) page = data;
}
/*
* This routine checks the page boundaries, and that the offset is
* within the task area. It then calls get_long() to read a long.
*/
static int read_long(struct task_struct * tsk, unsigned long addr,
unsigned long * result)
{
unsigned long low,high;
if (addr > TASK_SIZE-4)
return -EIO;
if ((addr & 0xfff) > PAGE_SIZE-4) {
low = get_long(tsk,addr & 0xfffffffc);
high = get_long(tsk,(addr+4) & 0xfffffffc);
switch (addr & 3) {
case 1:
low >>= 8;
low |= high << 24;
break;
case 2:
low >>= 16;
low |= high << 16;
break;
case 3:
low >>= 24;
low |= high << 8;
break;
}
*result = low;
} else
*result = get_long(tsk,addr);
return 0;
}
/*
* This routine checks the page boundaries, and that the offset is
* within the task area. It then calls put_long() to write a long.
*/
static int write_long(struct task_struct * tsk, unsigned long addr,
unsigned long data)
{
unsigned long low,high;
if (addr > TASK_SIZE-4)
return -EIO;
if ((addr & 0xfff) > PAGE_SIZE-4) {
low = get_long(tsk,addr & 0xfffffffc);
high = get_long(tsk,(addr+4) & 0xfffffffc);
switch (addr & 3) {
case 0: /* shouldn't happen, but safety first */
low = data;
break;
case 1:
low &= 0x000000ff;
low |= data << 8;
high &= 0xffffff00;
high |= data >> 24;
break;
case 2:
low &= 0x0000ffff;
low |= data << 16;
high &= 0xffff0000;
high |= data >> 16;
break;
case 3:
low &= 0x00ffffff;
low |= data << 24;
high &= 0xff000000;
high |= data >> 8;
break;
}
put_long(tsk,addr & 0xfffffffc,low);
put_long(tsk,(addr+4) & 0xfffffffc,high);
} else
put_long(tsk,addr,data);
return 0;
}
int sys_ptrace(long request, long pid, long addr, long data)
{
struct task_struct *child;
if (request == PTRACE_TRACEME) {
/* are we already being traced? */
if (current->flags & PF_PTRACED)
return -EPERM;
/* set the ptrace bit in the proccess flags. */
current->flags |= PF_PTRACED;
return 0;
}
if (!(child = get_task(pid)))
return -ESRCH;
if (request == PTRACE_ATTACH) {
long tmp;
if ((!current->dumpable || (current->uid != child->euid) ||
(current->gid != child->egid)) && !suser())
return -EPERM;
/* the same process cannot be attached many times */
if (child->flags & PF_PTRACED)
return -EPERM;
child->flags |= PF_PTRACED;
if (child->p_pptr != current) {
REMOVE_LINKS(child);
child->p_pptr = current;
SET_LINKS(child);
}
tmp = get_stack_long(child, 4*EFL-MAGICNUMBER) | TRAP_FLAG;
put_stack_long(child, 4*EFL-MAGICNUMBER,tmp);
if (child->state == TASK_INTERRUPTIBLE ||
child->state == TASK_STOPPED)
child->state = TASK_RUNNING;
child->signal = 0;
return 0;
}
if (!(child->flags & PF_PTRACED) || child->state != TASK_STOPPED)
return -ESRCH;
if (child->p_pptr != current)
return -ESRCH;
switch (request) {
/* when I and D space are seperate, these will need to be fixed. */
case PTRACE_PEEKTEXT: /* read word at location addr. */
case PTRACE_PEEKDATA: {
int tmp,res;
res = read_long(child, addr, &tmp);
if (res < 0)
return res;
verify_area((void *) data, 4);
put_fs_long(tmp,(unsigned long *) data);
return 0;
}
/* read the word at location addr in the USER area. */
case PTRACE_PEEKUSR: {
int tmp;
addr = addr >> 2; /* temporary hack. */
if (addr < 0 || addr >= 17)
return -EIO;
verify_area((void *) data, 4);
tmp = get_stack_long(child, 4*addr - MAGICNUMBER);
put_fs_long(tmp,(unsigned long *) data);
return 0;
}
/* when I and D space are seperate, this will have to be fixed. */
case PTRACE_POKETEXT: /* write the word at location addr. */
case PTRACE_POKEDATA:
return write_long(child,addr,data);
case PTRACE_POKEUSR: /* write the word at location addr in the USER area */
addr = addr >> 2; /* temproary hack. */
if (addr < 0 || addr >= 17)
return -EIO;
if (addr == ORIG_EAX)
return -EIO;
if (addr == EFL) { /* flags. */
data &= FLAG_MASK;
data |= get_stack_long(child, EFL*4-MAGICNUMBER) & ~FLAG_MASK;
}
if (put_stack_long(child, 4*addr-MAGICNUMBER, data))
return -EIO;
return 0;
case PTRACE_CONT: { /* restart after signal. */
long tmp;
child->signal = 0;
if (data > 0 && data <= NSIG)
child->signal = 1<<(data-1);
child->state = TASK_RUNNING;
/* make sure the single step bit is not set. */
tmp = get_stack_long(child, 4*EFL-MAGICNUMBER) & ~TRAP_FLAG;
put_stack_long(child, 4*EFL-MAGICNUMBER,tmp);
return 0;
}
/*
* make the child exit. Best I can do is send it a sigkill.
* perhaps it should be put in the status that it want's to
* exit.
*/
case PTRACE_KILL: {
long tmp;
child->state = TASK_RUNNING;
child->signal = 1 << (SIGKILL-1);
/* make sure the single step bit is not set. */
tmp = get_stack_long(child, 4*EFL-MAGICNUMBER) & ~TRAP_FLAG;
put_stack_long(child, 4*EFL-MAGICNUMBER,tmp);
return 0;
}
case PTRACE_SINGLESTEP: { /* set the trap flag. */
long tmp;
tmp = get_stack_long(child, 4*EFL-MAGICNUMBER) | TRAP_FLAG;
put_stack_long(child, 4*EFL-MAGICNUMBER,tmp);
child->state = TASK_RUNNING;
child->signal = 0;
if (data > 0 && data <= NSIG)
child->signal= 1<<(data-1);
/* give it a chance to run. */
return 0;
}
case PTRACE_DETACH: { /* detach a process that was attached. */
long tmp;
child->flags &= ~PF_PTRACED;
child->signal=0;
child->state = 0;
REMOVE_LINKS(child);
child->p_pptr = child->p_opptr;
SET_LINKS(child);
/* make sure the single step bit is not set. */
tmp = get_stack_long(child, 4*EFL-MAGICNUMBER) & ~TRAP_FLAG;
put_stack_long(child, 4*EFL-MAGICNUMBER,tmp);
return 0;
}
default:
return -EIO;
}
}