/* ptrace.c */
/* By Ross Biro 1/23/92 */
/*
* Pentium III FXSR, SSE support
* Gareth Hughes <gareth@valinux.com>, May 2000
*/
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/smp_lock.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 <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>
/*
* 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 0x00044dd5
/* set's the trap flag. */
#define TRAP_FLAG 0x100
/*
* Offset of eflags on child stack..
*/
#define EFL_OFFSET ((EFL-2)*4-sizeof(struct pt_regs))
static inline struct pt_regs *get_child_regs(struct task_struct *task)
{
void *stack_top = (void *)task->thread.esp0;
return stack_top - 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 int get_stack_long(struct task_struct *task, int offset)
{
unsigned char *stack;
stack = (unsigned char *)task->thread.esp0;
stack += offset;
return (*((int *)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 int put_stack_long(struct task_struct *task, int offset,
unsigned long data)
{
unsigned char * stack;
stack = (unsigned char *) task->thread.esp0;
stack += offset;
*(unsigned long *) stack = data;
return 0;
}
static int putreg(struct task_struct *child,
unsigned long regno, unsigned long value)
{
switch (regno >> 2) {
case FS:
if (value && (value & 3) != 3)
return -EIO;
child->thread.fs = value;
return 0;
case GS:
if (value && (value & 3) != 3)
return -EIO;
child->thread.gs = value;
return 0;
case DS:
case ES:
if (value && (value & 3) != 3)
return -EIO;
value &= 0xffff;
break;
case SS:
case CS:
if ((value & 3) != 3)
return -EIO;
value &= 0xffff;
break;
case EFL:
value &= FLAG_MASK;
value |= get_stack_long(child, EFL_OFFSET) & ~FLAG_MASK;
break;
}
if (regno > GS*4)
regno -= 2*4;
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 retval = ~0UL;
switch (regno >> 2) {
case FS:
retval = child->thread.fs;
break;
case GS:
retval = child->thread.gs;
break;
case DS:
case ES:
case SS:
case CS:
retval = 0xffff;
/* fall through */
default:
if (regno > GS*4)
regno -= 2*4;
regno = regno - sizeof(struct pt_regs);
retval &= get_stack_long(child, regno);
}
return retval;
}
#define LDT_SEGMENT 4
static unsigned long convert_eip_to_linear(struct task_struct *child, struct pt_regs *regs)
{
unsigned long addr, seg;
addr = regs->eip;
seg = regs->xcs & 0xffff;
if (regs->eflags & VM_MASK) {
addr = (addr & 0xffff) + (seg << 4);
return addr;
}
/*
* 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;
down(&child->mm->context.sem);
desc = child->mm->context.ldt + (seg & ~7);
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 inline int is_at_popf(struct task_struct *child, struct pt_regs *regs)
{
int i, copied;
unsigned char opcode[16];
unsigned long addr = convert_eip_to_linear(child, regs);
copied = access_process_vm(child, addr, opcode, sizeof(opcode), 0);
for (i = 0; i < copied; i++) {
switch (opcode[i]) {
/* popf */
case 0x9d:
return 1;
/* 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 0xf0: case 0xf2: case 0xf3:
continue;
/*
* 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 = get_child_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_at_popf(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 = get_child_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);
}
/*
* Perform get_thread_area on behalf of the traced child.
*/
static int
ptrace_get_thread_area(struct task_struct *child,
int idx, struct user_desc __user *user_desc)
{
struct user_desc info;
struct desc_struct *desc;
/*
* Get the current Thread-Local Storage area:
*/
#define GET_BASE(desc) ( \
(((desc)->a >> 16) & 0x0000ffff) | \
(((desc)->b << 16) & 0x00ff0000) | \
( (desc)->b & 0xff000000) )
#define GET_LIMIT(desc) ( \
((desc)->a & 0x0ffff) | \
((desc)->b & 0xf0000) )
#define GET_32BIT(desc) (((desc)->b >> 22) & 1)
#define GET_CONTENTS(desc) (((desc)->b >> 10) & 3)
#define GET_WRITABLE(desc) (((desc)->b >> 9) & 1)
#define GET_LIMIT_PAGES(desc) (((desc)->b >> 23) & 1)
#define GET_PRESENT(desc) (((desc)->b >> 15) & 1)
#define GET_USEABLE(desc) (((desc)->b >> 20) & 1)
if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
return -EINVAL;
desc = child->thread.tls_array + idx - GDT_ENTRY_TLS_MIN;
info.entry_number = idx;
info.base_addr = GET_BASE(desc);
info.limit = GET_LIMIT(desc);
info.seg_32bit = GET_32BIT(desc);
info.contents = GET_CONTENTS(desc);
info.read_exec_only = !GET_WRITABLE(desc);
info.limit_in_pages = GET_LIMIT_PAGES(desc);
info.seg_not_present = !GET_PRESENT(desc);
info.useable = GET_USEABLE(desc);
if (copy_to_user(user_desc, &info, sizeof(info)))
return -EFAULT;
return 0;
}
/*
* Perform set_thread_area on behalf of the traced child.
*/
static int
ptrace_set_thread_area(struct task_struct *child,
int idx, struct user_desc __user *user_desc)
{
struct user_desc info;
struct desc_struct *desc;
if (copy_from_user(&info, user_desc, sizeof(info)))
return -EFAULT;
if (idx < GDT_ENTRY_TLS_MIN || idx > GDT_ENTRY_TLS_MAX)
return -EINVAL;
desc = child->thread.tls_array + idx - GDT_ENTRY_TLS_MIN;
if (LDT_empty(&info)) {
desc->a = 0;
desc->b = 0;
} else {
desc->a = LDT_entry_a(&info);
desc->b = LDT_entry_b(&info);
}
return 0;
}
asmlinkage int sys_ptrace(long request, long pid, long addr, long data)
{
struct task_struct *child;
struct user * dummy = NULL;
int i, ret;
unsigned long __user *datap = (unsigned long __user *)data;
lock_kernel();
ret = -EPERM;
if (request == PTRACE_TRACEME) {
/* are we already being traced? */
if (current->ptrace & PT_PTRACED)
goto out;
ret = security_ptrace(current->parent, current);
if (ret)
goto out;
/* set the ptrace bit in the process flags. */
current->ptrace |= PT_PTRACED;
ret = 0;
goto out;
}
ret = -ESRCH;
read_lock(&tasklist_lock);
child = find_task_by_pid(pid);
if (child)
get_task_struct(child);
read_unlock(&tasklist_lock);
if (!child)
goto out;
ret = -EPERM;
if (pid == 1) /* you may not mess with init */
goto out_tsk;
if (request == PTRACE_ATTACH) {
ret = ptrace_attach(child);
goto out_tsk;
}
ret = ptrace_check_attach(child, request == PTRACE_KILL);
if (ret < 0)
goto out_tsk;
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: {
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, datap);
break;
}
/* read the word at location addr in the USER area. */
case PTRACE_PEEKUSR: {
unsigned long tmp;
ret = -EIO;
if ((addr & 3) || addr < 0 ||
addr > sizeof(struct user) - 3)
break;
tmp = 0; /* Default return condition */
if(addr < FRAME_SIZE*sizeof(long))
tmp = getreg(child, addr);
if(addr >= (long) &dummy->u_debugreg[0] &&
addr <= (long) &dummy->u_debugreg[7]){
addr -= (long) &dummy->u_debugreg[0];
addr = addr >> 2;
tmp = child->thread.debugreg[addr];
}
ret = put_user(tmp, datap);
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 = 0;
if (access_process_vm(child, addr, &data, sizeof(data), 1) == sizeof(data))
break;
ret = -EIO;
break;
case PTRACE_POKEUSR: /* write the word at location addr in the USER area */
ret = -EIO;
if ((addr & 3) || addr < 0 ||
addr > sizeof(struct user) - 3)
break;
if (addr < FRAME_SIZE*sizeof(long)) {
ret = putreg(child, addr, data);
break;
}
/* We need to be very careful here. We implicitly
want to modify a portion of the task_struct, and we
have to be selective about what portions we allow someone
to modify. */
ret = -EIO;
if(addr >= (long) &dummy->u_debugreg[0] &&
addr <= (long) &dummy->u_debugreg[7]){
if(addr == (long) &dummy->u_debugreg[4]) break;
if(addr == (long) &dummy->u_debugreg[5]) break;
if(addr < (long) &dummy->u_debugreg[4] &&
((unsigned long) data) >= TASK_SIZE-3) break;
/* Sanity-check data. Take one half-byte at once with
* check = (val >> (16 + 4*i)) & 0xf. It contains the
* R/Wi and LENi bits; bits 0 and 1 are R/Wi, and bits
* 2 and 3 are LENi. Given a list of invalid values,
* we do mask |= 1 << invalid_value, so that
* (mask >> check) & 1 is a correct test for invalid
* values.
*
* R/Wi contains the type of the breakpoint /
* watchpoint, LENi contains the length of the watched
* data in the watchpoint case.
*
* The invalid values are:
* - LENi == 0x10 (undefined), so mask |= 0x0f00.
* - R/Wi == 0x10 (break on I/O reads or writes), so
* mask |= 0x4444.
* - R/Wi == 0x00 && LENi != 0x00, so we have mask |=
* 0x1110.
*
* Finally, mask = 0x0f00 | 0x4444 | 0x1110 == 0x5f54.
*
* See the Intel Manual "System Programming Guide",
* 15.2.4
*
* Note that LENi == 0x10 is defined on x86_64 in long
* mode (i.e. even for 32-bit userspace software, but
* 64-bit kernel), so the x86_64 mask value is 0x5454.
* See the AMD manual no. 24593 (AMD64 System
* Programming)*/
if(addr == (long) &dummy->u_debugreg[7]) {
data &= ~DR_CONTROL_RESERVED;
for(i=0; i<4; i++)
if ((0x5f54 >> ((data >> (16 + 4*i)) & 0xf)) & 1)
goto out_tsk;
}
addr -= (long) &dummy->u_debugreg;
addr = addr >> 2;
child->thread.debugreg[addr] = data;
ret = 0;
}
break;
case PTRACE_SYSCALL: /* continue and stop at next (return from) syscall */
case PTRACE_CONT: /* restart after signal. */
ret = -EIO;
if ((unsigned long) data > _NSIG)
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;
/* make sure the single step bit is not set. */
clear_singlestep(child);
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->exit_state == EXIT_ZOMBIE) /* already dead */
break;
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 ((unsigned long) data > _NSIG)
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_DETACH:
/* detach a process that was attached. */
ret = ptrace_detach(child, data);
break;
case PTRACE_GETREGS: { /* Get all gp regs from the child. */
if (!access_ok(VERIFY_WRITE, datap, FRAME_SIZE*sizeof(long))) {
ret = -EIO;
break;
}
for ( i = 0; i < FRAME_SIZE*sizeof(long); i += sizeof(long) ) {
__put_user(getreg(child, i), datap);
datap++;
}
ret = 0;
break;
}
case PTRACE_SETREGS: { /* Set all gp regs in the child. */
unsigned long tmp;
if (!access_ok(VERIFY_READ, datap, FRAME_SIZE*sizeof(long))) {
ret = -EIO;
break;
}
for ( i = 0; i < FRAME_SIZE*sizeof(long); i += sizeof(long) ) {
__get_user(tmp, datap);
putreg(child, i, tmp);
datap++;
}
ret = 0;
break;
}
case PTRACE_GETFPREGS: { /* Get the child FPU state. */
if (!access_ok(VERIFY_WRITE, datap,
sizeof(struct user_i387_struct))) {
ret = -EIO;
break;
}
ret = 0;
if (!tsk_used_math(child))
init_fpu(child);
get_fpregs((struct user_i387_struct __user *)data, child);
break;
}
case PTRACE_SETFPREGS: { /* Set the child FPU state. */
if (!access_ok(VERIFY_READ, datap,
sizeof(struct user_i387_struct))) {
ret = -EIO;
break;
}
set_stopped_child_used_math(child);
set_fpregs(child, (struct user_i387_struct __user *)data);
ret = 0;
break;
}
case PTRACE_GETFPXREGS: { /* Get the child extended FPU state. */
if (!access_ok(VERIFY_WRITE, datap,
sizeof(struct user_fxsr_struct))) {
ret = -EIO;
break;
}
if (!tsk_used_math(child))
init_fpu(child);
ret = get_fpxregs((struct user_fxsr_struct __user *)data, child);
break;
}
case PTRACE_SETFPXREGS: { /* Set the child extended FPU state. */
if (!access_ok(VERIFY_READ, datap,
sizeof(struct user_fxsr_struct))) {
ret = -EIO;
break;
}
set_stopped_child_used_math(child);
ret = set_fpxregs(child, (struct user_fxsr_struct __user *)data);
break;
}
case PTRACE_GET_THREAD_AREA:
ret = ptrace_get_thread_area(child, addr,
(struct user_desc __user *) data);
break;
case PTRACE_SET_THREAD_AREA:
ret = ptrace_set_thread_area(child, addr,
(struct user_desc __user *) data);
break;
default:
ret = ptrace_request(child, request, addr, data);
break;
}
out_tsk:
put_task_struct(child);
out:
unlock_kernel();
return ret;
}
void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs, int error_code)
{
struct siginfo info;
tsk->thread.trap_no = 1;
tsk->thread.error_code = error_code;
memset(&info, 0, sizeof(info));
info.si_signo = SIGTRAP;
info.si_code = TRAP_BRKPT;
/* User-mode eip? */
info.si_addr = user_mode(regs) ? (void __user *) regs->eip : NULL;
/* Send us the fakey SIGTRAP */
force_sig_info(SIGTRAP, &info, tsk);
}
/* notification of system call entry/exit
* - triggered by current->work.syscall_trace
*/
__attribute__((regparm(3)))
void do_syscall_trace(struct pt_regs *regs, int entryexit)
{
/* do the secure computing check first */
secure_computing(regs->orig_eax);
if (unlikely(current->audit_context)) {
if (!entryexit)
audit_syscall_entry(current, regs->orig_eax,
regs->ebx, regs->ecx,
regs->edx, regs->esi);
else
audit_syscall_exit(current, regs->eax);
}
if (!(current->ptrace & PT_PTRACED))
return;
/* Fake a debug trap */
if (test_thread_flag(TIF_SINGLESTEP))
send_sigtrap(current, regs, 0);
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;
}
}
