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signal_64.c

/*
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *  Copyright (C) 2000, 2001, 2002 Andi Kleen SuSE Labs
 *
 *  1997-11-28  Modified for POSIX.1b signals by Richard Henderson
 *  2000-06-20  Pentium III FXSR, SSE support by Gareth Hughes
 *  2000-2002   x86-64 support by Andi Kleen
 */

#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/kernel.h>
#include <linux/signal.h>
#include <linux/errno.h>
#include <linux/wait.h>
#include <linux/ptrace.h>
#include <linux/unistd.h>
#include <linux/stddef.h>
#include <linux/personality.h>
#include <linux/compiler.h>
#include <asm/ucontext.h>
#include <asm/uaccess.h>
#include <asm/i387.h>
#include <asm/proto.h>
#include <asm/ia32_unistd.h>
#include <asm/mce.h>

/* #define DEBUG_SIG 1 */

#define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))

int ia32_setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
               sigset_t *set, struct pt_regs * regs); 
int ia32_setup_frame(int sig, struct k_sigaction *ka,
            sigset_t *set, struct pt_regs * regs); 

asmlinkage long
sys_sigaltstack(const stack_t __user *uss, stack_t __user *uoss,
            struct pt_regs *regs)
{
      return do_sigaltstack(uss, uoss, regs->rsp);
}


/*
 * Do a signal return; undo the signal stack.
 */

struct rt_sigframe
{
      char __user *pretcode;
      struct ucontext uc;
      struct siginfo info;
};

static int
restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc, unsigned long *prax)
{
      unsigned int err = 0;

      /* Always make any pending restarted system calls return -EINTR */
      current_thread_info()->restart_block.fn = do_no_restart_syscall;

#define COPY(x)         err |= __get_user(regs->x, &sc->x)

      COPY(rdi); COPY(rsi); COPY(rbp); COPY(rsp); COPY(rbx);
      COPY(rdx); COPY(rcx); COPY(rip);
      COPY(r8);
      COPY(r9);
      COPY(r10);
      COPY(r11);
      COPY(r12);
      COPY(r13);
      COPY(r14);
      COPY(r15);

      /* Kernel saves and restores only the CS segment register on signals,
       * which is the bare minimum needed to allow mixed 32/64-bit code.
       * App's signal handler can save/restore other segments if needed. */
      {
            unsigned cs;
            err |= __get_user(cs, &sc->cs);
            regs->cs = cs | 3;      /* Force into user mode */
      }

      {
            unsigned int tmpflags;
            err |= __get_user(tmpflags, &sc->eflags);
            regs->eflags = (regs->eflags & ~0x40DD5) | (tmpflags & 0x40DD5);
            regs->orig_rax = -1;          /* disable syscall checks */
      }

      {
            struct _fpstate __user * buf;
            err |= __get_user(buf, &sc->fpstate);

            if (buf) {
                  if (!access_ok(VERIFY_READ, buf, sizeof(*buf)))
                        goto badframe;
                  err |= restore_i387(buf);
            } else {
                  struct task_struct *me = current;
                  if (used_math()) {
                        clear_fpu(me);
                        clear_used_math();
                  }
            }
      }

      err |= __get_user(*prax, &sc->rax);
      return err;

badframe:
      return 1;
}

asmlinkage long sys_rt_sigreturn(struct pt_regs *regs)
{
      struct rt_sigframe __user *frame;
      sigset_t set;
      unsigned long eax;

      frame = (struct rt_sigframe __user *)(regs->rsp - 8);
      if (!access_ok(VERIFY_READ, frame, sizeof(*frame))) {
            goto badframe;
      } 
      if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set))) { 
            goto badframe;
      } 

      sigdelsetmask(&set, ~_BLOCKABLE);
      spin_lock_irq(&current->sighand->siglock);
      current->blocked = set;
      recalc_sigpending();
      spin_unlock_irq(&current->sighand->siglock);
      
      if (restore_sigcontext(regs, &frame->uc.uc_mcontext, &eax))
            goto badframe;

#ifdef DEBUG_SIG
      printk("%d sigreturn rip:%lx rsp:%lx frame:%p rax:%lx\n",current->pid,regs->rip,regs->rsp,frame,eax);
#endif

      if (do_sigaltstack(&frame->uc.uc_stack, NULL, regs->rsp) == -EFAULT)
            goto badframe;

      return eax;

badframe:
      signal_fault(regs,frame,"sigreturn");
      return 0;
}     

/*
 * Set up a signal frame.
 */

static inline int
setup_sigcontext(struct sigcontext __user *sc, struct pt_regs *regs, unsigned long mask, struct task_struct *me)
{
      int err = 0;

      err |= __put_user(regs->cs, &sc->cs);
      err |= __put_user(0, &sc->gs);
      err |= __put_user(0, &sc->fs);

      err |= __put_user(regs->rdi, &sc->rdi);
      err |= __put_user(regs->rsi, &sc->rsi);
      err |= __put_user(regs->rbp, &sc->rbp);
      err |= __put_user(regs->rsp, &sc->rsp);
      err |= __put_user(regs->rbx, &sc->rbx);
      err |= __put_user(regs->rdx, &sc->rdx);
      err |= __put_user(regs->rcx, &sc->rcx);
      err |= __put_user(regs->rax, &sc->rax);
      err |= __put_user(regs->r8, &sc->r8);
      err |= __put_user(regs->r9, &sc->r9);
      err |= __put_user(regs->r10, &sc->r10);
      err |= __put_user(regs->r11, &sc->r11);
      err |= __put_user(regs->r12, &sc->r12);
      err |= __put_user(regs->r13, &sc->r13);
      err |= __put_user(regs->r14, &sc->r14);
      err |= __put_user(regs->r15, &sc->r15);
      err |= __put_user(me->thread.trap_no, &sc->trapno);
      err |= __put_user(me->thread.error_code, &sc->err);
      err |= __put_user(regs->rip, &sc->rip);
      err |= __put_user(regs->eflags, &sc->eflags);
      err |= __put_user(mask, &sc->oldmask);
      err |= __put_user(me->thread.cr2, &sc->cr2);

      return err;
}

/*
 * Determine which stack to use..
 */

static void __user *
get_stack(struct k_sigaction *ka, struct pt_regs *regs, unsigned long size)
{
      unsigned long rsp;

      /* Default to using normal stack - redzone*/
      rsp = regs->rsp - 128;

      /* This is the X/Open sanctioned signal stack switching.  */
      if (ka->sa.sa_flags & SA_ONSTACK) {
            if (sas_ss_flags(rsp) == 0)
                  rsp = current->sas_ss_sp + current->sas_ss_size;
      }

      return (void __user *)round_down(rsp - size, 16); 
}

static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info,
                     sigset_t *set, struct pt_regs * regs)
{
      struct rt_sigframe __user *frame;
      struct _fpstate __user *fp = NULL; 
      int err = 0;
      struct task_struct *me = current;

      if (used_math()) {
            fp = get_stack(ka, regs, sizeof(struct _fpstate)); 
            frame = (void __user *)round_down(
                  (unsigned long)fp - sizeof(struct rt_sigframe), 16) - 8;

            if (!access_ok(VERIFY_WRITE, fp, sizeof(struct _fpstate)))
                  goto give_sigsegv;

            if (save_i387(fp) < 0) 
                  err |= -1; 
      } else
            frame = get_stack(ka, regs, sizeof(struct rt_sigframe)) - 8;

      if (!access_ok(VERIFY_WRITE, frame, sizeof(*frame)))
            goto give_sigsegv;

      if (ka->sa.sa_flags & SA_SIGINFO) { 
            err |= copy_siginfo_to_user(&frame->info, info);
            if (err)
                  goto give_sigsegv;
      }
            
      /* Create the ucontext.  */
      err |= __put_user(0, &frame->uc.uc_flags);
      err |= __put_user(0, &frame->uc.uc_link);
      err |= __put_user(me->sas_ss_sp, &frame->uc.uc_stack.ss_sp);
      err |= __put_user(sas_ss_flags(regs->rsp),
                    &frame->uc.uc_stack.ss_flags);
      err |= __put_user(me->sas_ss_size, &frame->uc.uc_stack.ss_size);
      err |= setup_sigcontext(&frame->uc.uc_mcontext, regs, set->sig[0], me);
      err |= __put_user(fp, &frame->uc.uc_mcontext.fpstate);
      if (sizeof(*set) == 16) { 
            __put_user(set->sig[0], &frame->uc.uc_sigmask.sig[0]);
            __put_user(set->sig[1], &frame->uc.uc_sigmask.sig[1]); 
      } else
            err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));

      /* Set up to return from userspace.  If provided, use a stub
         already in userspace.  */
      /* x86-64 should always use SA_RESTORER. */
      if (ka->sa.sa_flags & SA_RESTORER) {
            err |= __put_user(ka->sa.sa_restorer, &frame->pretcode);
      } else {
            /* could use a vstub here */
            goto give_sigsegv; 
      }

      if (err)
            goto give_sigsegv;

#ifdef DEBUG_SIG
      printk("%d old rip %lx old rsp %lx old rax %lx\n", current->pid,regs->rip,regs->rsp,regs->rax);
#endif

      /* Set up registers for signal handler */
      regs->rdi = sig;
      /* In case the signal handler was declared without prototypes */ 
      regs->rax = 0;    

      /* This also works for non SA_SIGINFO handlers because they expect the
         next argument after the signal number on the stack. */
      regs->rsi = (unsigned long)&frame->info; 
      regs->rdx = (unsigned long)&frame->uc; 
      regs->rip = (unsigned long) ka->sa.sa_handler;

      regs->rsp = (unsigned long)frame;

      /* Set up the CS register to run signal handlers in 64-bit mode,
         even if the handler happens to be interrupting 32-bit code. */
      regs->cs = __USER_CS;

      /* This, by contrast, has nothing to do with segment registers -
         see include/asm-x86_64/uaccess.h for details. */
      set_fs(USER_DS);

      regs->eflags &= ~TF_MASK;
      if (test_thread_flag(TIF_SINGLESTEP))
            ptrace_notify(SIGTRAP);
#ifdef DEBUG_SIG
      printk("SIG deliver (%s:%d): sp=%p pc=%lx ra=%p\n",
            current->comm, current->pid, frame, regs->rip, frame->pretcode);
#endif

      return 0;

give_sigsegv:
      force_sigsegv(sig, current);
      return -EFAULT;
}

/*
 * OK, we're invoking a handler
 */   

static int
handle_signal(unsigned long sig, siginfo_t *info, struct k_sigaction *ka,
            sigset_t *oldset, struct pt_regs *regs)
{
      int ret;

#ifdef DEBUG_SIG
      printk("handle_signal pid:%d sig:%lu rip:%lx rsp:%lx regs=%p\n",
            current->pid, sig,
            regs->rip, regs->rsp, regs);
#endif

      /* Are we from a system call? */
      if ((long)regs->orig_rax >= 0) {
            /* If so, check system call restarting.. */
            switch (regs->rax) {
                    case -ERESTART_RESTARTBLOCK:
                  case -ERESTARTNOHAND:
                        regs->rax = -EINTR;
                        break;

                  case -ERESTARTSYS:
                        if (!(ka->sa.sa_flags & SA_RESTART)) {
                              regs->rax = -EINTR;
                              break;
                        }
                        /* fallthrough */
                  case -ERESTARTNOINTR:
                        regs->rax = regs->orig_rax;
                        regs->rip -= 2;
                        break;
            }
      }

      /*
       * If TF is set due to a debugger (PT_DTRACE), clear the TF
       * flag so that register information in the sigcontext is
       * correct.
       */
      if (unlikely(regs->eflags & TF_MASK)) {
            if (likely(current->ptrace & PT_DTRACE)) {
                  current->ptrace &= ~PT_DTRACE;
                  regs->eflags &= ~TF_MASK;
            }
      }

#ifdef CONFIG_IA32_EMULATION
      if (test_thread_flag(TIF_IA32)) {
            if (ka->sa.sa_flags & SA_SIGINFO)
                  ret = ia32_setup_rt_frame(sig, ka, info, oldset, regs);
            else
                  ret = ia32_setup_frame(sig, ka, oldset, regs);
      } else 
#endif
      ret = setup_rt_frame(sig, ka, info, oldset, regs);

      if (ret == 0) {
            spin_lock_irq(&current->sighand->siglock);
            sigorsets(&current->blocked,&current->blocked,&ka->sa.sa_mask);
            if (!(ka->sa.sa_flags & SA_NODEFER))
                  sigaddset(&current->blocked,sig);
            recalc_sigpending();
            spin_unlock_irq(&current->sighand->siglock);
      }

      return ret;
}

/*
 * Note that 'init' is a special process: it doesn't get signals it doesn't
 * want to handle. Thus you cannot kill init even with a SIGKILL even by
 * mistake.
 */
static void do_signal(struct pt_regs *regs)
{
      struct k_sigaction ka;
      siginfo_t info;
      int signr;
      sigset_t *oldset;

      /*
       * We want the common case to go fast, which
       * is why we may in certain cases get here from
       * kernel mode. Just return without doing anything
       * if so.
       */
      if (!user_mode(regs))
            return;

      if (test_thread_flag(TIF_RESTORE_SIGMASK))
            oldset = &current->saved_sigmask;
      else
            oldset = &current->blocked;

      signr = get_signal_to_deliver(&info, &ka, regs, NULL);
      if (signr > 0) {
            /* Re-enable any watchpoints before delivering the
             * signal to user space. The processor register will
             * have been cleared if the watchpoint triggered
             * inside the kernel.
             */
            if (current->thread.debugreg7)
                  set_debugreg(current->thread.debugreg7, 7);

            /* Whee!  Actually deliver the signal.  */
            if (handle_signal(signr, &info, &ka, oldset, regs) == 0) {
                  /* a signal was successfully delivered; the saved
                   * sigmask will have been stored in the signal frame,
                   * and will be restored by sigreturn, so we can simply
                   * clear the TIF_RESTORE_SIGMASK flag */
                  clear_thread_flag(TIF_RESTORE_SIGMASK);
            }
            return;
      }

      /* Did we come from a system call? */
      if ((long)regs->orig_rax >= 0) {
            /* Restart the system call - no handlers present */
            long res = regs->rax;
            switch (res) {
            case -ERESTARTNOHAND:
            case -ERESTARTSYS:
            case -ERESTARTNOINTR:
                  regs->rax = regs->orig_rax;
                  regs->rip -= 2;
                  break;
            case -ERESTART_RESTARTBLOCK:
                  regs->rax = test_thread_flag(TIF_IA32) ?
                              __NR_ia32_restart_syscall :
                              __NR_restart_syscall;
                  regs->rip -= 2;
                  break;
            }
      }

      /* if there's no signal to deliver, we just put the saved sigmask
         back. */
      if (test_thread_flag(TIF_RESTORE_SIGMASK)) {
            clear_thread_flag(TIF_RESTORE_SIGMASK);
            sigprocmask(SIG_SETMASK, &current->saved_sigmask, NULL);
      }
}

void
do_notify_resume(struct pt_regs *regs, void *unused, __u32 thread_info_flags)
{
#ifdef DEBUG_SIG
      printk("do_notify_resume flags:%x rip:%lx rsp:%lx caller:%p pending:%x\n",
             thread_info_flags, regs->rip, regs->rsp, __builtin_return_address(0),signal_pending(current)); 
#endif
             
      /* Pending single-step? */
      if (thread_info_flags & _TIF_SINGLESTEP) {
            regs->eflags |= TF_MASK;
            clear_thread_flag(TIF_SINGLESTEP);
      }

#ifdef CONFIG_X86_MCE
      /* notify userspace of pending MCEs */
      if (thread_info_flags & _TIF_MCE_NOTIFY)
            mce_notify_user();
#endif /* CONFIG_X86_MCE */

      /* deal with pending signal delivery */
      if (thread_info_flags & (_TIF_SIGPENDING|_TIF_RESTORE_SIGMASK))
            do_signal(regs);
}

void signal_fault(struct pt_regs *regs, void __user *frame, char *where)
{ 
      struct task_struct *me = current; 
      if (show_unhandled_signals && printk_ratelimit())
            printk("%s[%d] bad frame in %s frame:%p rip:%lx rsp:%lx orax:%lx\n",
             me->comm,me->pid,where,frame,regs->rip,regs->rsp,regs->orig_rax); 

      force_sig(SIGSEGV, me); 
} 

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