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ptrace_32.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/errno.h>
#include <linux/ptrace.h>
#include <linux/user.h>
#include <linux/security.h>
#include <linux/audit.h>
#include <linux/seccomp.h>
#include <linux/signal.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].
 * Prohibits changing ID(21), VIP(20), VIF(19), VM(17), NT(14), IOPL(12-13), IF(9).
 * Also masks reserved bits (31-22, 15, 5, 3, 1).
 */
#define FLAG_MASK 0x00050dd5

/* set's the trap flag. */
#define TRAP_FLAG 0x100

/*
 * Offset of eflags on child stack..
 */
#define EFL_OFFSET offsetof(struct pt_regs, eflags)

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 bytes into the pt_regs structure on the stack.
 * 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 - sizeof(struct pt_regs);
      stack += offset;
      return (*((int *)stack));
}

/*
 * This routine will put a word on the processes privileged stack.
 * the offset is bytes into the pt_regs structure on the stack.
 * 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 - sizeof(struct pt_regs);
      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 GS:
                  if (value && (value & 3) != 3)
                        return -EIO;
                  child->thread.gs = value;
                  return 0;
            case DS:
            case ES:
            case FS:
                  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 > FS*4)
            regno -= 1*4;
      put_stack_long(child, regno, value);
      return 0;
}

static unsigned long getreg(struct task_struct *child,
      unsigned long regno)
{
      unsigned long retval = ~0UL;

      switch (regno >> 2) {
            case GS:
                  retval = child->thread.gs;
                  break;
            case DS:
            case ES:
            case FS:
            case SS:
            case CS:
                  retval = 0xffff;
                  /* fall through */
            default:
                  if (regno > FS*4)
                        regno -= 1*4;
                  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;

            seg &= ~7UL;

            mutex_lock(&child->mm->context.lock);
            if (unlikely((seg >> 3) >= child->mm->context.size))
                  addr = -1L; /* bogus selector, access would fault */
            else {
                  desc = child->mm->context.ldt + seg;
                  base = ((desc[0] >> 16) |
                        ((desc[1] & 0xff) << 16) |
                        (desc[1] & 0xff000000));

                  /* 16-bit code segment? */
                  if (!((desc[1] >> 22) & 1))
                        addr &= 0xffff;
                  addr += base;
            }
            mutex_unlock(&child->mm->context.lock);
      }
      return addr;
}

static inline int is_setting_trap_flag(struct task_struct *child, struct pt_regs *regs)
{
      int i, copied;
      unsigned char opcode[15];
      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 and iret */
            case 0x9d: case 0xcf:
                  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_setting_trap_flag(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);
      clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
}

/*
 * 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;
}

long arch_ptrace(struct task_struct *child, long request, long addr, long data)
{
      struct user * dummy = NULL;
      int i, ret;
      unsigned long __user *datap = (unsigned long __user *)data;

      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:
            ret = generic_ptrace_peekdata(child, addr, data);
            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 = generic_ptrace_pokedata(child, addr, data);
            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;
                          if (data)
                                set_tsk_thread_flag(child, TIF_DEBUG);
                          else
                                clear_tsk_thread_flag(child, TIF_DEBUG);
                    }
                    addr -= (long) &dummy->u_debugreg;
                    addr = addr >> 2;
                    child->thread.debugreg[addr] = data;
                    ret = 0;
              }
              break;

      case PTRACE_SYSEMU: /* continue and stop at next syscall, which will not be executed */
      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_SYSEMU) {
                  set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
                  clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
            } else if (request == PTRACE_SYSCALL) {
                  set_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
                  clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
            } else {
                  clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
                  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_SYSEMU_SINGLESTEP: /* Same as SYSEMU, but singlestep if not syscall */
      case PTRACE_SINGLESTEP: /* set the trap flag. */
            ret = -EIO;
            if (!valid_signal(data))
                  break;

            if (request == PTRACE_SYSEMU_SINGLESTEP)
                  set_tsk_thread_flag(child, TIF_SYSCALL_EMU);
            else
                  clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);

            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_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:
      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_vm(regs) ? (void __user *) regs->eip : NULL;

      /* Send us the fake SIGTRAP */
      force_sig_info(SIGTRAP, &info, tsk);
}

/* notification of system call entry/exit
 * - triggered by current->work.syscall_trace
 */
__attribute__((regparm(3)))
int do_syscall_trace(struct pt_regs *regs, int entryexit)
{
      int is_sysemu = test_thread_flag(TIF_SYSCALL_EMU);
      /*
       * With TIF_SYSCALL_EMU set we want to ignore TIF_SINGLESTEP for syscall
       * interception
       */
      int is_singlestep = !is_sysemu && test_thread_flag(TIF_SINGLESTEP);
      int ret = 0;

      /* do the secure computing check first */
      if (!entryexit)
            secure_computing(regs->orig_eax);

      if (unlikely(current->audit_context)) {
            if (entryexit)
                  audit_syscall_exit(AUDITSC_RESULT(regs->eax),
                                    regs->eax);
            /* Debug traps, when using PTRACE_SINGLESTEP, must be sent only
             * on the syscall exit path. Normally, when TIF_SYSCALL_AUDIT is
             * not used, entry.S will call us only on syscall exit, not
             * entry; so when TIF_SYSCALL_AUDIT is used we must avoid
             * calling send_sigtrap() on syscall entry.
             *
             * Note that when PTRACE_SYSEMU_SINGLESTEP is used,
             * is_singlestep is false, despite his name, so we will still do
             * the correct thing.
             */
            else if (is_singlestep)
                  goto out;
      }

      if (!(current->ptrace & PT_PTRACED))
            goto out;

      /* If a process stops on the 1st tracepoint with SYSCALL_TRACE
       * and then is resumed with SYSEMU_SINGLESTEP, it will come in
       * here. We have to check this and return */
      if (is_sysemu && entryexit)
            return 0;

      /* Fake a debug trap */
      if (is_singlestep)
            send_sigtrap(current, regs, 0);

      if (!test_thread_flag(TIF_SYSCALL_TRACE) && !is_sysemu)
            goto out;

      /* the 0x80 provides a way for the tracing parent to distinguish
         between a syscall stop and SIGTRAP delivery */
      /* Note that the debugger could change the result of test_thread_flag!*/
      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;
      }
      ret = is_sysemu;
out:
      if (unlikely(current->audit_context) && !entryexit)
            audit_syscall_entry(AUDIT_ARCH_I386, regs->orig_eax,
                            regs->ebx, regs->ecx, regs->edx, regs->esi);
      if (ret == 0)
            return 0;

      regs->orig_eax = -1; /* force skip of syscall restarting */
      if (unlikely(current->audit_context))
            audit_syscall_exit(AUDITSC_RESULT(regs->eax), regs->eax);
      return 1;
}

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