480 lines
12 KiB
C
480 lines
12 KiB
C
/* ptrace.c */
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/* By Ross Biro 1/23/92 */
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/* edited by Linus Torvalds */
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#include <linux/head.h>
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#include <linux/kernel.h>
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#include <linux/sched.h>
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#include <linux/mm.h>
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#include <linux/errno.h>
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#include <linux/ptrace.h>
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#include <linux/user.h>
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#include <asm/segment.h>
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#include <asm/system.h>
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#include <linux/debugreg.h>
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/*
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* does not yet catch signals sent when the child dies.
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* in exit.c or in signal.c.
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*/
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/* determines which flags the user has access to. */
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/* 1 = access 0 = no access */
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#define FLAG_MASK 0x00044dd5
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/* set's the trap flag. */
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#define TRAP_FLAG 0x100
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/*
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* this is the number to subtract from the top of the stack. To find
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* the local frame.
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*/
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#define MAGICNUMBER 68
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/* change a pid into a task struct. */
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static inline struct task_struct * get_task(int pid)
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{
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int i;
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for (i = 1; i < NR_TASKS; i++) {
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if (task[i] != NULL && (task[i]->pid == pid))
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return task[i];
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}
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return NULL;
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}
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/*
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* this routine will get a word off of the processes priviledged stack.
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* the offset is how far from the base addr as stored in the TSS.
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* this routine assumes that all the priviledged stacks are in our
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* data space.
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*/
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static inline int get_stack_long(struct task_struct *task, int offset)
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{
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unsigned char *stack;
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stack = (unsigned char *)task->tss.esp0;
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stack += offset;
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return (*((int *)stack));
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}
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/*
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* this routine will put a word on the processes priviledged stack.
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* the offset is how far from the base addr as stored in the TSS.
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* this routine assumes that all the priviledged stacks are in our
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* data space.
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*/
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static inline int put_stack_long(struct task_struct *task, int offset,
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unsigned long data)
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{
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unsigned char * stack;
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stack = (unsigned char *) task->tss.esp0;
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stack += offset;
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*(unsigned long *) stack = data;
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return 0;
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}
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/*
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* This routine gets a long from any process space by following the page
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* tables. NOTE! You should check that the long isn't on a page boundary,
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* and that it is in the task area before calling this: this routine does
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* no checking.
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*
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* NOTE2! This uses "tsk->tss.cr3" even though we know it's currently always
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* zero. This routine shouldn't have to change when we make a better mm.
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*/
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static unsigned long get_long(struct task_struct * tsk,
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unsigned long addr)
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{
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unsigned long page;
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repeat:
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page = *PAGE_DIR_OFFSET(tsk->tss.cr3,addr);
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if (page & PAGE_PRESENT) {
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page &= PAGE_MASK;
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page += PAGE_PTR(addr);
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page = *((unsigned long *) page);
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}
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if (!(page & PAGE_PRESENT)) {
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do_no_page(0,addr,tsk,0);
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goto repeat;
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}
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/* this is a hack for non-kernel-mapped video buffers and similar */
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if (page >= high_memory)
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return 0;
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page &= PAGE_MASK;
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page += addr & ~PAGE_MASK;
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return *(unsigned long *) page;
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}
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/*
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* This routine puts a long into any process space by following the page
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* tables. NOTE! You should check that the long isn't on a page boundary,
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* and that it is in the task area before calling this: this routine does
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* no checking.
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*
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* Now keeps R/W state of page so that a text page stays readonly
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* even if a debugger scribbles breakpoints into it. -M.U-
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*/
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static void put_long(struct task_struct * tsk, unsigned long addr,
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unsigned long data)
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{
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unsigned long page, pte = 0;
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int readonly = 0;
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repeat:
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page = *PAGE_DIR_OFFSET(tsk->tss.cr3,addr);
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if (page & PAGE_PRESENT) {
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page &= PAGE_MASK;
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page += PAGE_PTR(addr);
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pte = page;
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page = *((unsigned long *) page);
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}
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if (!(page & PAGE_PRESENT)) {
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do_no_page(0 /* PAGE_RW */ ,addr,tsk,0);
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goto repeat;
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}
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if (!(page & PAGE_RW)) {
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if(!(page & PAGE_COW))
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readonly = 1;
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do_wp_page(PAGE_RW | PAGE_PRESENT,addr,tsk,0);
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goto repeat;
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}
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/* this is a hack for non-kernel-mapped video buffers and similar */
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if (page >= high_memory)
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return;
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/* we're bypassing pagetables, so we have to set the dirty bit ourselves */
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*(unsigned long *) pte |= (PAGE_DIRTY|PAGE_COW);
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page &= PAGE_MASK;
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page += addr & ~PAGE_MASK;
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*(unsigned long *) page = data;
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if(readonly) {
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*(unsigned long *) pte &=~ (PAGE_RW|PAGE_COW);
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invalidate();
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}
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}
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/*
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* This routine checks the page boundaries, and that the offset is
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* within the task area. It then calls get_long() to read a long.
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*/
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static int read_long(struct task_struct * tsk, unsigned long addr,
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unsigned long * result)
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{
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unsigned long low,high;
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if (addr > TASK_SIZE-sizeof(long))
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return -EIO;
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if ((addr & ~PAGE_MASK) > PAGE_SIZE-sizeof(long)) {
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low = get_long(tsk,addr & ~(sizeof(long)-1));
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high = get_long(tsk,(addr+sizeof(long)) & ~(sizeof(long)-1));
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switch (addr & (sizeof(long)-1)) {
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case 1:
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low >>= 8;
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low |= high << 24;
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break;
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case 2:
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low >>= 16;
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low |= high << 16;
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break;
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case 3:
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low >>= 24;
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low |= high << 8;
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break;
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}
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*result = low;
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} else
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*result = get_long(tsk,addr);
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return 0;
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}
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/*
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* This routine checks the page boundaries, and that the offset is
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* within the task area. It then calls put_long() to write a long.
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*/
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static int write_long(struct task_struct * tsk, unsigned long addr,
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unsigned long data)
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{
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unsigned long low,high;
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if (addr > TASK_SIZE-sizeof(long))
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return -EIO;
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if ((addr & ~PAGE_MASK) > PAGE_SIZE-sizeof(long)) {
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low = get_long(tsk,addr & ~(sizeof(long)-1));
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high = get_long(tsk,(addr+sizeof(long)) & ~(sizeof(long)-1));
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switch (addr & (sizeof(long)-1)) {
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case 0: /* shouldn't happen, but safety first */
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low = data;
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break;
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case 1:
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low &= 0x000000ff;
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low |= data << 8;
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high &= ~0xff;
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high |= data >> 24;
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break;
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case 2:
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low &= 0x0000ffff;
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low |= data << 16;
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high &= ~0xffff;
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high |= data >> 16;
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break;
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case 3:
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low &= 0x00ffffff;
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low |= data << 24;
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high &= ~0xffffff;
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high |= data >> 8;
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break;
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}
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put_long(tsk,addr & ~(sizeof(long)-1),low);
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put_long(tsk,(addr+sizeof(long)) & ~(sizeof(long)-1),high);
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} else
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put_long(tsk,addr,data);
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return 0;
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}
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asmlinkage int sys_ptrace(long request, long pid, long addr, long data)
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{
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struct task_struct *child;
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struct user * dummy;
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int i;
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dummy = NULL;
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if (request == PTRACE_TRACEME) {
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/* are we already being traced? */
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if (current->flags & PF_PTRACED)
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return -EPERM;
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/* set the ptrace bit in the proccess flags. */
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current->flags |= PF_PTRACED;
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return 0;
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}
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if (pid == 1) /* you may not mess with init */
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return -EPERM;
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if (!(child = get_task(pid)))
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return -ESRCH;
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if (request == PTRACE_ATTACH) {
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if (child == current)
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return -EPERM;
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if ((!child->dumpable || (current->uid != child->euid) ||
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(current->gid != child->egid)) && !suser())
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return -EPERM;
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/* the same process cannot be attached many times */
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if (child->flags & PF_PTRACED)
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return -EPERM;
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child->flags |= PF_PTRACED;
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if (child->p_pptr != current) {
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REMOVE_LINKS(child);
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child->p_pptr = current;
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SET_LINKS(child);
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}
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send_sig(SIGSTOP, child, 1);
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return 0;
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}
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if (!(child->flags & PF_PTRACED))
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return -ESRCH;
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if (child->state != TASK_STOPPED) {
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if (request != PTRACE_KILL)
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return -ESRCH;
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}
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if (child->p_pptr != current)
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return -ESRCH;
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switch (request) {
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/* when I and D space are seperate, these will need to be fixed. */
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case PTRACE_PEEKTEXT: /* read word at location addr. */
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case PTRACE_PEEKDATA: {
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unsigned long tmp;
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int res;
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res = read_long(child, addr, &tmp);
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if (res < 0)
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return res;
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res = verify_area(VERIFY_WRITE, (void *) data, sizeof(long));
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if (!res)
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put_fs_long(tmp,(unsigned long *) data);
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return res;
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}
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/* read the word at location addr in the USER area. */
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case PTRACE_PEEKUSR: {
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unsigned long tmp;
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int res;
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if ((addr & 3) || addr < 0 ||
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addr > sizeof(struct user) - 3)
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return -EIO;
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res = verify_area(VERIFY_WRITE, (void *) data, sizeof(long));
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if (res)
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return res;
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tmp = 0; /* Default return condition */
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if(addr < 17*sizeof(long)) {
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addr = addr >> 2; /* temporary hack. */
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tmp = get_stack_long(child, sizeof(long)*addr - MAGICNUMBER);
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if (addr == DS || addr == ES ||
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addr == FS || addr == GS ||
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addr == CS || addr == SS)
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tmp &= 0xffff;
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};
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if(addr >= (long) &dummy->u_debugreg[0] &&
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addr <= (long) &dummy->u_debugreg[7]){
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addr -= (long) &dummy->u_debugreg[0];
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addr = addr >> 2;
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tmp = child->debugreg[addr];
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};
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put_fs_long(tmp,(unsigned long *) data);
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return 0;
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}
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/* when I and D space are seperate, this will have to be fixed. */
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case PTRACE_POKETEXT: /* write the word at location addr. */
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case PTRACE_POKEDATA:
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return write_long(child,addr,data);
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case PTRACE_POKEUSR: /* write the word at location addr in the USER area */
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if ((addr & 3) || addr < 0 ||
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addr > sizeof(struct user) - 3)
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return -EIO;
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addr = addr >> 2; /* temproary hack. */
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if (addr == ORIG_EAX)
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return -EIO;
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if (addr == DS || addr == ES ||
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addr == FS || addr == GS ||
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addr == CS || addr == SS) {
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data &= 0xffff;
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if (data && (data & 3) != 3)
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return -EIO;
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}
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if (addr == EFL) { /* flags. */
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data &= FLAG_MASK;
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data |= get_stack_long(child, EFL*sizeof(long)-MAGICNUMBER) & ~FLAG_MASK;
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}
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/* Do not allow the user to set the debug register for kernel
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address space */
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if(addr < 17){
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if (put_stack_long(child, sizeof(long)*addr-MAGICNUMBER, data))
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return -EIO;
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return 0;
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};
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/* We need to be very careful here. We implicitly
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want to modify a portion of the task_struct, and we
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have to be selective about what portions we allow someone
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to modify. */
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addr = addr << 2; /* Convert back again */
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if(addr >= (long) &dummy->u_debugreg[0] &&
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addr <= (long) &dummy->u_debugreg[7]){
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if(addr == (long) &dummy->u_debugreg[4]) return -EIO;
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if(addr == (long) &dummy->u_debugreg[5]) return -EIO;
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if(addr < (long) &dummy->u_debugreg[4] &&
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((unsigned long) data) >= 0xbffffffd) return -EIO;
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if(addr == (long) &dummy->u_debugreg[7]) {
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data &= ~DR_CONTROL_RESERVED;
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for(i=0; i<4; i++)
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if ((0x5f54 >> ((data >> (16 + 4*i)) & 0xf)) & 1)
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return -EIO;
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};
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addr -= (long) &dummy->u_debugreg;
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addr = addr >> 2;
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child->debugreg[addr] = data;
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return 0;
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};
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return -EIO;
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case PTRACE_SYSCALL: /* continue and stop at next (return from) syscall */
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case PTRACE_CONT: { /* restart after signal. */
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long tmp;
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if ((unsigned long) data > NSIG)
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return -EIO;
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if (request == PTRACE_SYSCALL)
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child->flags |= PF_TRACESYS;
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else
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child->flags &= ~PF_TRACESYS;
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child->exit_code = data;
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child->state = TASK_RUNNING;
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/* make sure the single step bit is not set. */
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tmp = get_stack_long(child, sizeof(long)*EFL-MAGICNUMBER) & ~TRAP_FLAG;
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put_stack_long(child, sizeof(long)*EFL-MAGICNUMBER,tmp);
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return 0;
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}
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/*
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* make the child exit. Best I can do is send it a sigkill.
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* perhaps it should be put in the status that it want's to
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* exit.
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*/
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case PTRACE_KILL: {
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long tmp;
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child->state = TASK_RUNNING;
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child->exit_code = SIGKILL;
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/* make sure the single step bit is not set. */
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tmp = get_stack_long(child, sizeof(long)*EFL-MAGICNUMBER) & ~TRAP_FLAG;
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put_stack_long(child, sizeof(long)*EFL-MAGICNUMBER,tmp);
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return 0;
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}
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case PTRACE_SINGLESTEP: { /* set the trap flag. */
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long tmp;
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if ((unsigned long) data > NSIG)
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return -EIO;
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child->flags &= ~PF_TRACESYS;
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tmp = get_stack_long(child, sizeof(long)*EFL-MAGICNUMBER) | TRAP_FLAG;
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put_stack_long(child, sizeof(long)*EFL-MAGICNUMBER,tmp);
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child->state = TASK_RUNNING;
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child->exit_code = data;
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/* give it a chance to run. */
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return 0;
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}
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case PTRACE_DETACH: { /* detach a process that was attached. */
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long tmp;
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if ((unsigned long) data > NSIG)
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return -EIO;
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child->flags &= ~(PF_PTRACED|PF_TRACESYS);
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child->state = TASK_RUNNING;
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child->exit_code = data;
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REMOVE_LINKS(child);
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child->p_pptr = child->p_opptr;
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SET_LINKS(child);
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/* make sure the single step bit is not set. */
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tmp = get_stack_long(child, sizeof(long)*EFL-MAGICNUMBER) & ~TRAP_FLAG;
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put_stack_long(child, sizeof(long)*EFL-MAGICNUMBER,tmp);
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return 0;
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}
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default:
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return -EIO;
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}
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}
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asmlinkage void syscall_trace(void)
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{
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if ((current->flags & (PF_PTRACED|PF_TRACESYS))
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!= (PF_PTRACED|PF_TRACESYS))
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return;
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current->exit_code = SIGTRAP;
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current->state = TASK_STOPPED;
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notify_parent(current);
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schedule();
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/*
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* this isn't the same as continuing with a signal, but it will do
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* for normal use. strace only continues with a signal if the
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* stopping signal is not SIGTRAP. -brl
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*/
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if (current->exit_code)
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current->signal |= (1 << (current->exit_code - 1));
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current->exit_code = 0;
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}
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