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/*
* linux/kernel/ptrace.c
*
* (C) Copyright 1999 Linus Torvalds
*
* Common interfaces for "ptrace()" which we do not want
* to continually duplicate across every architecture.
*/
#include <linux/capability.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/highmem.h>
#include <linux/pagemap.h>
#include <linux/smp_lock.h>
#include <linux/ptrace.h>
#include <linux/security.h>
#include <linux/signal.h>
#include <linux/audit.h>
#include <asm/pgtable.h>
#include <asm/uaccess.h>
/*
* ptrace a task: make the debugger its new parent and
* move it to the ptrace list.
*
* Must be called with the tasklist lock write-held.
*/
void __ptrace_link(struct task_struct *child, struct task_struct *new_parent)
{
BUG_ON(!list_empty(&child->ptrace_list));
if (child->parent == new_parent)
return;
list_add(&child->ptrace_list, &child->parent->ptrace_children);
remove_parent(child);
child->parent = new_parent;
add_parent(child);
}
/*
* Turn a tracing stop into a normal stop now, since with no tracer there
* would be no way to wake it up with SIGCONT or SIGKILL. If there was a
* signal sent that would resume the child, but didn't because it was in
* TASK_TRACED, resume it now.
* Requires that irqs be disabled.
*/
void ptrace_untrace(struct task_struct *child)
{
spin_lock(&child->sighand->siglock);
if (child->state == TASK_TRACED) {
if (child->signal->flags & SIGNAL_STOP_STOPPED) {
child->state = TASK_STOPPED;
} else {
signal_wake_up(child, 1);
}
}
spin_unlock(&child->sighand->siglock);
}
/*
* unptrace a task: move it back to its original parent and
* remove it from the ptrace list.
*
* Must be called with the tasklist lock write-held.
*/
void __ptrace_unlink(struct task_struct *child)
{
BUG_ON(!child->ptrace);
child->ptrace = 0;
if (!list_empty(&child->ptrace_list)) {
list_del_init(&child->ptrace_list);
remove_parent(child);
child->parent = child->real_parent;
add_parent(child);
}
if (child->state == TASK_TRACED)
ptrace_untrace(child);
}
/*
* Check that we have indeed attached to the thing..
*/
int ptrace_check_attach(struct task_struct *child, int kill)
{
int ret = -ESRCH;
/*
* We take the read lock around doing both checks to close a
* possible race where someone else was tracing our child and
* detached between these two checks. After this locked check,
* we are sure that this is our traced child and that can only
* be changed by us so it's not changing right after this.
*/
read_lock(&tasklist_lock);
if ((child->ptrace & PT_PTRACED) && child->parent == current &&
(!(child->ptrace & PT_ATTACHED) || child->real_parent != current)
&& child->signal != NULL) {
ret = 0;
spin_lock_irq(&child->sighand->siglock);
if (child->state == TASK_STOPPED) {
child->state = TASK_TRACED;
} else if (child->state != TASK_TRACED && !kill) {
ret = -ESRCH;
}
spin_unlock_irq(&child->sighand->siglock);
}
read_unlock(&tasklist_lock);
if (!ret && !kill) {
wait_task_inactive(child);
}
/* All systems go.. */
return ret;
}
static int may_attach(struct task_struct *task)
{
/* May we inspect the given task?
* This check is used both for attaching with ptrace
* and for allowing access to sensitive information in /proc.
*
* ptrace_attach denies several cases that /proc allows
* because setting up the necessary parent/child relationship
* or halting the specified task is impossible.
*/
int dumpable = 0;
/* Don't let security modules deny introspection */
if (task == current)
return 0;
if (((current->uid != task->euid) ||
(current->uid != task->suid) ||
(current->uid != task->uid) ||
(current->gid != task->egid) ||
(current->gid != task->sgid) ||
(current->gid != task->gid)) && !capable(CAP_SYS_PTRACE))
return -EPERM;
smp_rmb();
if (task->mm)
dumpable = get_dumpable(task->mm);
if (!dumpable && !capable(CAP_SYS_PTRACE))
return -EPERM;
return security_ptrace(current, task);
}
int ptrace_may_attach(struct task_struct *task)
{
int err;
task_lock(task);
err = may_attach(task);
task_unlock(task);
return !err;
}
int ptrace_attach(struct task_struct *task)
{
int retval;
unsigned long flags;
audit_ptrace(task);
retval = -EPERM;
if (task->pid <= 1)
goto out;
if (task->tgid == current->tgid)
goto out;
repeat:
/*
* Nasty, nasty.
*
* We want to hold both the task-lock and the
* tasklist_lock for writing at the same time.
* But that's against the rules (tasklist_lock
* is taken for reading by interrupts on other
* cpu's that may have task_lock).
*/
task_lock(task);
if (!write_trylock_irqsave(&tasklist_lock, flags)) {
task_unlock(task);
do {
cpu_relax();
} while (!write_can_lock(&tasklist_lock));
goto repeat;
}
if (!task->mm)
goto bad;
/* the same process cannot be attached many times */
if (task->ptrace & PT_PTRACED)
goto bad;
retval = may_attach(task);
if (retval)
goto bad;
/* Go */
task->ptrace |= PT_PTRACED | ((task->real_parent != current)
? PT_ATTACHED : 0);
if (capable(CAP_SYS_PTRACE))
task->ptrace |= PT_PTRACE_CAP;
__ptrace_link(task, current);
force_sig_specific(SIGSTOP, task);
bad:
write_unlock_irqrestore(&tasklist_lock, flags);
task_unlock(task);
out:
return retval;
}
static inline void __ptrace_detach(struct task_struct *child, unsigned int data)
{
child->exit_code = data;
/* .. re-parent .. */
__ptrace_unlink(child);
/* .. and wake it up. */
if (child->exit_state != EXIT_ZOMBIE)
wake_up_process(child);
}
int ptrace_detach(struct task_struct *child, unsigned int data)
{
if (!valid_signal(data))
return -EIO;
/* Architecture-specific hardware disable .. */
ptrace_disable(child);
clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
write_lock_irq(&tasklist_lock);
/* protect against de_thread()->release_task() */
if (child->ptrace)
__ptrace_detach(child, data);
write_unlock_irq(&tasklist_lock);
return 0;
}
int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)
{
int copied = 0;
while (len > 0) {
char buf[128];
int this_len, retval;
this_len = (len > sizeof(buf)) ? sizeof(buf) : len;
retval = access_process_vm(tsk, src, buf, this_len, 0);
if (!retval) {
if (copied)
break;
return -EIO;
}
if (copy_to_user(dst, buf, retval))
return -EFAULT;
copied += retval;
src += retval;
dst += retval;
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