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signal.c

/*
 * Copyright (C) 2004 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
 * Licensed under the GPL
 */

#include "linux/ptrace.h"
#include "asm/unistd.h"
#include "asm/uaccess.h"
#include "asm/ucontext.h"
#include "frame_kern.h"
#include "skas.h"

void copy_sc(struct uml_pt_regs *regs, void *from)
{
      struct sigcontext *sc = from;

      REGS_GS(regs->gp) = sc->gs;
      REGS_FS(regs->gp) = sc->fs;
      REGS_ES(regs->gp) = sc->es;
      REGS_DS(regs->gp) = sc->ds;
      REGS_EDI(regs->gp) = sc->edi;
      REGS_ESI(regs->gp) = sc->esi;
      REGS_EBP(regs->gp) = sc->ebp;
      REGS_SP(regs->gp) = sc->esp;
      REGS_EBX(regs->gp) = sc->ebx;
      REGS_EDX(regs->gp) = sc->edx;
      REGS_ECX(regs->gp) = sc->ecx;
      REGS_EAX(regs->gp) = sc->eax;
      REGS_IP(regs->gp) = sc->eip;
      REGS_CS(regs->gp) = sc->cs;
      REGS_EFLAGS(regs->gp) = sc->eflags;
      REGS_SS(regs->gp) = sc->ss;
}

/*
 * FPU tag word conversions.
 */

static inline unsigned short twd_i387_to_fxsr(unsigned short twd)
{
      unsigned int tmp; /* to avoid 16 bit prefixes in the code */

      /* Transform each pair of bits into 01 (valid) or 00 (empty) */
      tmp = ~twd;
      tmp = (tmp | (tmp>>1)) & 0x5555; /* 0V0V0V0V0V0V0V0V */
      /* and move the valid bits to the lower byte. */
      tmp = (tmp | (tmp >> 1)) & 0x3333; /* 00VV00VV00VV00VV */
      tmp = (tmp | (tmp >> 2)) & 0x0f0f; /* 0000VVVV0000VVVV */
      tmp = (tmp | (tmp >> 4)) & 0x00ff; /* 00000000VVVVVVVV */
      return tmp;
}

static inline unsigned long twd_fxsr_to_i387(struct user_fxsr_struct *fxsave)
{
      struct _fpxreg *st = NULL;
      unsigned long twd = (unsigned long) fxsave->twd;
      unsigned long tag;
      unsigned long ret = 0xffff0000;
      int i;

#define FPREG_ADDR(f, n)      ((char *)&(f)->st_space + (n) * 16);

      for (i = 0; i < 8; i++) {
            if (twd & 0x1) {
                  st = (struct _fpxreg *) FPREG_ADDR(fxsave, i);

                  switch (st->exponent & 0x7fff) {
                  case 0x7fff:
                        tag = 2;          /* Special */
                        break;
                  case 0x0000:
                        if ( !st->significand[0] &&
                             !st->significand[1] &&
                             !st->significand[2] &&
                             !st->significand[3] ) {
                              tag = 1;    /* Zero */
                        } else {
                              tag = 2;    /* Special */
                        }
                        break;
                  default:
                        if (st->significand[3] & 0x8000) {
                              tag = 0;    /* Valid */
                        } else {
                              tag = 2;    /* Special */
                        }
                        break;
                  }
            } else {
                  tag = 3;                /* Empty */
            }
            ret |= (tag << (2 * i));
            twd = twd >> 1;
      }
      return ret;
}

static int convert_fxsr_to_user(struct _fpstate __user *buf,
                        struct user_fxsr_struct *fxsave)
{
      unsigned long env[7];
      struct _fpreg __user *to;
      struct _fpxreg *from;
      int i;

      env[0] = (unsigned long)fxsave->cwd | 0xffff0000ul;
      env[1] = (unsigned long)fxsave->swd | 0xffff0000ul;
      env[2] = twd_fxsr_to_i387(fxsave);
      env[3] = fxsave->fip;
      env[4] = fxsave->fcs | ((unsigned long)fxsave->fop << 16);
      env[5] = fxsave->foo;
      env[6] = fxsave->fos;

      if (__copy_to_user(buf, env, 7 * sizeof(unsigned long)))
            return 1;

      to = &buf->_st[0];
      from = (struct _fpxreg *) &fxsave->st_space[0];
      for (i = 0; i < 8; i++, to++, from++) {
            unsigned long __user *t = (unsigned long __user *)to;
            unsigned long *f = (unsigned long *)from;

            if (__put_user(*f, t) ||
                        __put_user(*(f + 1), t + 1) ||
                        __put_user(from->exponent, &to->exponent))
                  return 1;
      }
      return 0;
}

static int convert_fxsr_from_user(struct user_fxsr_struct *fxsave,
                          struct _fpstate __user *buf)
{
      unsigned long env[7];
      struct _fpxreg *to;
      struct _fpreg __user *from;
      int i;

      if (copy_from_user( env, buf, 7 * sizeof(long)))
            return 1;

      fxsave->cwd = (unsigned short)(env[0] & 0xffff);
      fxsave->swd = (unsigned short)(env[1] & 0xffff);
      fxsave->twd = twd_i387_to_fxsr((unsigned short)(env[2] & 0xffff));
      fxsave->fip = env[3];
      fxsave->fop = (unsigned short)((env[4] & 0xffff0000ul) >> 16);
      fxsave->fcs = (env[4] & 0xffff);
      fxsave->foo = env[5];
      fxsave->fos = env[6];

      to = (struct _fpxreg *) &fxsave->st_space[0];
      from = &buf->_st[0];
      for (i = 0; i < 8; i++, to++, from++) {
            unsigned long *t = (unsigned long *)to;
            unsigned long __user *f = (unsigned long __user *)from;

            if (__get_user(*t, f) ||
                __get_user(*(t + 1), f + 1) ||
                __get_user(to->exponent, &from->exponent))
                  return 1;
      }
      return 0;
}

extern int have_fpx_regs;

static int copy_sc_from_user(struct pt_regs *regs,
                       struct sigcontext __user *from)
{
      struct sigcontext sc;
      int err;

      err = copy_from_user(&sc, from, sizeof(sc));
      if (err)
            return err;

      copy_sc(&regs->regs, &sc);
      if (have_fpx_regs) {
            struct user_fxsr_struct fpx;

            err = copy_from_user(&fpx, &sc.fpstate->_fxsr_env[0],
                             sizeof(struct user_fxsr_struct));
            if (err)
                  return 1;

            err = convert_fxsr_from_user(&fpx, sc.fpstate);
            if (err)
                  return 1;

            err = restore_fpx_registers(userspace_pid[current_thread->cpu],
                                  (unsigned long *) &fpx);
            if (err < 0) {
                  printk(KERN_ERR "copy_sc_from_user - "
                         "restore_fpx_registers failed, errno = %d\n",
                         -err);
                  return 1;
            }
      }
      else {
            struct user_i387_struct fp;

            err = copy_from_user(&fp, sc.fpstate,
                             sizeof(struct user_i387_struct));
            if (err)
                  return 1;

            err = restore_fp_registers(userspace_pid[current_thread->cpu],
                                 (unsigned long *) &fp);
            if (err < 0) {
                  printk(KERN_ERR "copy_sc_from_user - "
                         "restore_fp_registers failed, errno = %d\n",
                         -err);
                  return 1;
            }
      }

      return 0;
}

static int copy_sc_to_user(struct sigcontext __user *to,
                     struct _fpstate __user *to_fp, struct pt_regs *regs,
                     unsigned long sp)
{
      struct sigcontext sc;
      struct faultinfo * fi = &current->thread.arch.faultinfo;
      int err;

      sc.gs = REGS_GS(regs->regs.gp);
      sc.fs = REGS_FS(regs->regs.gp);
      sc.es = REGS_ES(regs->regs.gp);
      sc.ds = REGS_DS(regs->regs.gp);
      sc.edi = REGS_EDI(regs->regs.gp);
      sc.esi = REGS_ESI(regs->regs.gp);
      sc.ebp = REGS_EBP(regs->regs.gp);
      sc.esp = sp;
      sc.ebx = REGS_EBX(regs->regs.gp);
      sc.edx = REGS_EDX(regs->regs.gp);
      sc.ecx = REGS_ECX(regs->regs.gp);
      sc.eax = REGS_EAX(regs->regs.gp);
      sc.eip = REGS_IP(regs->regs.gp);
      sc.cs = REGS_CS(regs->regs.gp);
      sc.eflags = REGS_EFLAGS(regs->regs.gp);
      sc.esp_at_signal = regs->regs.gp[UESP];
      sc.ss = regs->regs.gp[SS];
      sc.cr2 = fi->cr2;
      sc.err = fi->error_code;
      sc.trapno = fi->trap_no;

      to_fp = (to_fp ? to_fp : (struct _fpstate __user *) (to + 1));
      sc.fpstate = to_fp;

      if (have_fpx_regs) {
            struct user_fxsr_struct fpx;

            err = save_fpx_registers(userspace_pid[current_thread->cpu],
                               (unsigned long *) &fpx);
            if (err < 0){
                  printk(KERN_ERR "copy_sc_to_user - save_fpx_registers "
                         "failed, errno = %d\n", err);
                  return 1;
            }

            err = convert_fxsr_to_user(to_fp, &fpx);
            if (err)
                  return 1;

            err |= __put_user(fpx.swd, &to_fp->status);
            err |= __put_user(X86_FXSR_MAGIC, &to_fp->magic);
            if (err)
                  return 1;

            if (copy_to_user(&to_fp->_fxsr_env[0], &fpx,
                         sizeof(struct user_fxsr_struct)))
                  return 1;
      }
      else {
            struct user_i387_struct fp;

            err = save_fp_registers(userspace_pid[current_thread->cpu],
                              (unsigned long *) &fp);
            if (copy_to_user(to_fp, &fp, sizeof(struct user_i387_struct)))
                  return 1;
      }

      return copy_to_user(to, &sc, sizeof(sc));
}

static int copy_ucontext_to_user(struct ucontext __user *uc,
                         struct _fpstate __user *fp, sigset_t *set,
                         unsigned long sp)
{
      int err = 0;

      err |= put_user(current->sas_ss_sp, &uc->uc_stack.ss_sp);
      err |= put_user(sas_ss_flags(sp), &uc->uc_stack.ss_flags);
      err |= put_user(current->sas_ss_size, &uc->uc_stack.ss_size);
      err |= copy_sc_to_user(&uc->uc_mcontext, fp, &current->thread.regs, sp);
      err |= copy_to_user(&uc->uc_sigmask, set, sizeof(*set));
      return err;
}

struct sigframe
{
      char __user *pretcode;
      int sig;
      struct sigcontext sc;
      struct _fpstate fpstate;
      unsigned long extramask[_NSIG_WORDS-1];
      char retcode[8];
};

struct rt_sigframe
{
      char __user *pretcode;
      int sig;
      struct siginfo __user *pinfo;
      void __user *puc;
      struct siginfo info;
      struct ucontext uc;
      struct _fpstate fpstate;
      char retcode[8];
};

int setup_signal_stack_sc(unsigned long stack_top, int sig,
                    struct k_sigaction *ka, struct pt_regs *regs,
                    sigset_t *mask)
{
      struct sigframe __user *frame;
      void __user *restorer;
      unsigned long save_sp = PT_REGS_SP(regs);
      int err = 0;

      /* This is the same calculation as i386 - ((sp + 4) & 15) == 0 */
      stack_top = ((stack_top + 4) & -16UL) - 4;
      frame = (struct sigframe __user *) stack_top - 1;
      if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
            return 1;

      restorer = frame->retcode;
      if (ka->sa.sa_flags & SA_RESTORER)
            restorer = ka->sa.sa_restorer;

      /* Update SP now because the page fault handler refuses to extend
       * the stack if the faulting address is too far below the current
       * SP, which frame now certainly is.  If there's an error, the original
       * value is restored on the way out.
       * When writing the sigcontext to the stack, we have to write the
       * original value, so that's passed to copy_sc_to_user, which does
       * the right thing with it.
       */
      PT_REGS_SP(regs) = (unsigned long) frame;

      err |= __put_user(restorer, &frame->pretcode);
      err |= __put_user(sig, &frame->sig);
      err |= copy_sc_to_user(&frame->sc, NULL, regs, save_sp);
      err |= __put_user(mask->sig[0], &frame->sc.oldmask);
      if (_NSIG_WORDS > 1)
            err |= __copy_to_user(&frame->extramask, &mask->sig[1],
                              sizeof(frame->extramask));

      /*
       * This is popl %eax ; movl $,%eax ; int $0x80
       *
       * WE DO NOT USE IT ANY MORE! It's only left here for historical
       * reasons and because gdb uses it as a signature to notice
       * signal handler stack frames.
       */
      err |= __put_user(0xb858, (short __user *)(frame->retcode+0));
      err |= __put_user(__NR_sigreturn, (int __user *)(frame->retcode+2));
      err |= __put_user(0x80cd, (short __user *)(frame->retcode+6));

      if (err)
            goto err;

      PT_REGS_SP(regs) = (unsigned long) frame;
      PT_REGS_IP(regs) = (unsigned long) ka->sa.sa_handler;
      PT_REGS_EAX(regs) = (unsigned long) sig;
      PT_REGS_EDX(regs) = (unsigned long) 0;
      PT_REGS_ECX(regs) = (unsigned long) 0;

      if ((current->ptrace & PT_DTRACE) && (current->ptrace & PT_PTRACED))
            ptrace_notify(SIGTRAP);
      return 0;

err:
      PT_REGS_SP(regs) = save_sp;
      return err;
}

int setup_signal_stack_si(unsigned long stack_top, int sig,
                    struct k_sigaction *ka, struct pt_regs *regs,
                    siginfo_t *info, sigset_t *mask)
{
      struct rt_sigframe __user *frame;
      void __user *restorer;
      unsigned long save_sp = PT_REGS_SP(regs);
      int err = 0;

      stack_top &= -8UL;
      frame = (struct rt_sigframe __user *) stack_top - 1;
      if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
            return 1;

      restorer = frame->retcode;
      if (ka->sa.sa_flags & SA_RESTORER)
            restorer = ka->sa.sa_restorer;

      /* See comment above about why this is here */
      PT_REGS_SP(regs) = (unsigned long) frame;

      err |= __put_user(restorer, &frame->pretcode);
      err |= __put_user(sig, &frame->sig);
      err |= __put_user(&frame->info, &frame->pinfo);
      err |= __put_user(&frame->uc, &frame->puc);
      err |= copy_siginfo_to_user(&frame->info, info);
      err |= copy_ucontext_to_user(&frame->uc, &frame->fpstate, mask,
                             save_sp);

      /*
       * This is movl $,%eax ; int $0x80
       *
       * WE DO NOT USE IT ANY MORE! It's only left here for historical
       * reasons and because gdb uses it as a signature to notice
       * signal handler stack frames.
       */
      err |= __put_user(0xb8, (char __user *)(frame->retcode+0));
      err |= __put_user(__NR_rt_sigreturn, (int __user *)(frame->retcode+1));
      err |= __put_user(0x80cd, (short __user *)(frame->retcode+5));

      if (err)
            goto err;

      PT_REGS_IP(regs) = (unsigned long) ka->sa.sa_handler;
      PT_REGS_EAX(regs) = (unsigned long) sig;
      PT_REGS_EDX(regs) = (unsigned long) &frame->info;
      PT_REGS_ECX(regs) = (unsigned long) &frame->uc;

      if ((current->ptrace & PT_DTRACE) && (current->ptrace & PT_PTRACED))
            ptrace_notify(SIGTRAP);
      return 0;

err:
      PT_REGS_SP(regs) = save_sp;
      return err;
}

long sys_sigreturn(struct pt_regs regs)
{
      unsigned long sp = PT_REGS_SP(&current->thread.regs);
      struct sigframe __user *frame = (struct sigframe __user *)(sp - 8);
      sigset_t set;
      struct sigcontext __user *sc = &frame->sc;
      unsigned long __user *oldmask = &sc->oldmask;
      unsigned long __user *extramask = frame->extramask;
      int sig_size = (_NSIG_WORDS - 1) * sizeof(unsigned long);

      if (copy_from_user(&set.sig[0], oldmask, sizeof(set.sig[0])) ||
          copy_from_user(&set.sig[1], extramask, sig_size))
            goto segfault;

      sigdelsetmask(&set, ~_BLOCKABLE);

      spin_lock_irq(&current->sighand->siglock);
      current->blocked = set;
      recalc_sigpending();
      spin_unlock_irq(&current->sighand->siglock);

      if (copy_sc_from_user(&current->thread.regs, sc))
            goto segfault;

      /* Avoid ERESTART handling */
      PT_REGS_SYSCALL_NR(&current->thread.regs) = -1;
      return PT_REGS_SYSCALL_RET(&current->thread.regs);

 segfault:
      force_sig(SIGSEGV, current);
      return 0;
}

long sys_rt_sigreturn(struct pt_regs regs)
{
      unsigned long sp = PT_REGS_SP(&current->thread.regs);
      struct rt_sigframe __user *frame =
            (struct rt_sigframe __user *) (sp - 4);
      sigset_t set;
      struct ucontext __user *uc = &frame->uc;
      int sig_size = _NSIG_WORDS * sizeof(unsigned long);

      if (copy_from_user(&set, &uc->uc_sigmask, sig_size))
            goto segfault;

      sigdelsetmask(&set, ~_BLOCKABLE);

      spin_lock_irq(&current->sighand->siglock);
      current->blocked = set;
      recalc_sigpending();
      spin_unlock_irq(&current->sighand->siglock);

      if (copy_sc_from_user(&current->thread.regs, &uc->uc_mcontext))
            goto segfault;

      /* Avoid ERESTART handling */
      PT_REGS_SYSCALL_NR(&current->thread.regs) = -1;
      return PT_REGS_SYSCALL_RET(&current->thread.regs);

 segfault:
      force_sig(SIGSEGV, current);
      return 0;
}

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