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process.c

/*
 * Copyright (C) 2002- 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
 * Licensed under the GPL
 */

#include <stdlib.h>
#include <unistd.h>
#include <sched.h>
#include <errno.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/ptrace.h>
#include <sys/wait.h>
#include <asm/unistd.h>
#include "as-layout.h"
#include "chan_user.h"
#include "kern_constants.h"
#include "mem.h"
#include "os.h"
#include "process.h"
#include "proc_mm.h"
#include "ptrace_user.h"
#include "registers.h"
#include "skas.h"
#include "skas_ptrace.h"
#include "user.h"
#include "sysdep/stub.h"

int is_skas_winch(int pid, int fd, void *data)
{
      if (pid != getpgrp())
            return 0;

      register_winch_irq(-1, fd, -1, data, 0);
      return 1;
}

static int ptrace_dump_regs(int pid)
{
        unsigned long regs[MAX_REG_NR];
        int i;

        if (ptrace(PTRACE_GETREGS, pid, 0, regs) < 0)
                return -errno;

      printk(UM_KERN_ERR "Stub registers -\n");
      for (i = 0; i < ARRAY_SIZE(regs); i++)
            printk(UM_KERN_ERR "\t%d - %lx\n", i, regs[i]);

        return 0;
}

/*
 * Signals that are OK to receive in the stub - we'll just continue it.
 * SIGWINCH will happen when UML is inside a detached screen.
 */
#define STUB_SIG_MASK ((1 << SIGVTALRM) | (1 << SIGWINCH))

/* Signals that the stub will finish with - anything else is an error */
#define STUB_DONE_MASK ((1 << SIGUSR1) | (1 << SIGTRAP))

void wait_stub_done(int pid)
{
      int n, status, err;

      while (1) {
            CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED | __WALL));
            if ((n < 0) || !WIFSTOPPED(status))
                  goto bad_wait;

            if (((1 << WSTOPSIG(status)) & STUB_SIG_MASK) == 0)
                  break;

            err = ptrace(PTRACE_CONT, pid, 0, 0);
            if (err)
                  panic("wait_stub_done : continue failed, errno = %d\n",
                        errno);
      }

      if (((1 << WSTOPSIG(status)) & STUB_DONE_MASK) != 0)
            return;

bad_wait:
      err = ptrace_dump_regs(pid);
      if (err)
            printk(UM_KERN_ERR "Failed to get registers from stub, "
                   "errno = %d\n", -err);
      panic("wait_stub_done : failed to wait for SIGUSR1/SIGTRAP, pid = %d, "
            "n = %d, errno = %d, status = 0x%x\n", pid, n, errno, status);
}

extern unsigned long current_stub_stack(void);

void get_skas_faultinfo(int pid, struct faultinfo * fi)
{
      int err;

      if (ptrace_faultinfo) {
            err = ptrace(PTRACE_FAULTINFO, pid, 0, fi);
            if (err)
                  panic("get_skas_faultinfo - PTRACE_FAULTINFO failed, "
                        "errno = %d\n", errno);

            /* Special handling for i386, which has different structs */
            if (sizeof(struct ptrace_faultinfo) < sizeof(struct faultinfo))
                  memset((char *)fi + sizeof(struct ptrace_faultinfo), 0,
                         sizeof(struct faultinfo) -
                         sizeof(struct ptrace_faultinfo));
      }
      else {
            err = ptrace(PTRACE_CONT, pid, 0, SIGSEGV);
            if (err)
                  panic("Failed to continue stub, pid = %d, errno = %d\n",
                        pid, errno);
            wait_stub_done(pid);

            /*
             * faultinfo is prepared by the stub-segv-handler at start of
             * the stub stack page. We just have to copy it.
             */
            memcpy(fi, (void *)current_stub_stack(), sizeof(*fi));
      }
}

static void handle_segv(int pid, struct uml_pt_regs * regs)
{
      get_skas_faultinfo(pid, &regs->faultinfo);
      segv(regs->faultinfo, 0, 1, NULL);
}

/*
 * To use the same value of using_sysemu as the caller, ask it that value
 * (in local_using_sysemu
 */
static void handle_trap(int pid, struct uml_pt_regs *regs,
                  int local_using_sysemu)
{
      int err, status;

      /* Mark this as a syscall */
      UPT_SYSCALL_NR(regs) = PT_SYSCALL_NR(regs->gp);

      if (!local_using_sysemu)
      {
            err = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_NR_OFFSET,
                       __NR_getpid);
            if (err < 0)
                  panic("handle_trap - nullifying syscall failed, "
                        "errno = %d\n", errno);

            err = ptrace(PTRACE_SYSCALL, pid, 0, 0);
            if (err < 0)
                  panic("handle_trap - continuing to end of syscall "
                        "failed, errno = %d\n", errno);

            CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED | __WALL));
            if ((err < 0) || !WIFSTOPPED(status) ||
               (WSTOPSIG(status) != SIGTRAP + 0x80)) {
                        err = ptrace_dump_regs(pid);
                        if (err)
                                printk(UM_KERN_ERR "Failed to get registers "
                               "from process, errno = %d\n", -err);
                  panic("handle_trap - failed to wait at end of syscall, "
                        "errno = %d, status = %d\n", errno, status);
                }
      }

      handle_syscall(regs);
}

extern int __syscall_stub_start;

static int userspace_tramp(void *stack)
{
      void *addr;
      int err;

      ptrace(PTRACE_TRACEME, 0, 0, 0);

      signal(SIGTERM, SIG_DFL);
      err = set_interval();
      if (err)
            panic("userspace_tramp - setting timer failed, errno = %d\n",
                  err);

      if (!proc_mm) {
            /*
             * This has a pte, but it can't be mapped in with the usual
             * tlb_flush mechanism because this is part of that mechanism
             */
            int fd;
            unsigned long long offset;
            fd = phys_mapping(to_phys(&__syscall_stub_start), &offset);
            addr = mmap64((void *) STUB_CODE, UM_KERN_PAGE_SIZE,
                        PROT_EXEC, MAP_FIXED | MAP_PRIVATE, fd, offset);
            if (addr == MAP_FAILED) {
                  printk(UM_KERN_ERR "mapping mmap stub at 0x%lx failed, "
                         "errno = %d\n", STUB_CODE, errno);
                  exit(1);
            }

            if (stack != NULL) {
                  fd = phys_mapping(to_phys(stack), &offset);
                  addr = mmap((void *) STUB_DATA,
                            UM_KERN_PAGE_SIZE, PROT_READ | PROT_WRITE,
                            MAP_FIXED | MAP_SHARED, fd, offset);
                  if (addr == MAP_FAILED) {
                        printk(UM_KERN_ERR "mapping segfault stack "
                               "at 0x%lx failed, errno = %d\n",
                               STUB_DATA, errno);
                        exit(1);
                  }
            }
      }
      if (!ptrace_faultinfo && (stack != NULL)) {
            struct sigaction sa;

            unsigned long v = STUB_CODE +
                          (unsigned long) stub_segv_handler -
                          (unsigned long) &__syscall_stub_start;

            set_sigstack((void *) STUB_DATA, UM_KERN_PAGE_SIZE);
            sigemptyset(&sa.sa_mask);
            sigaddset(&sa.sa_mask, SIGIO);
            sigaddset(&sa.sa_mask, SIGWINCH);
            sigaddset(&sa.sa_mask, SIGVTALRM);
            sigaddset(&sa.sa_mask, SIGUSR1);
            sa.sa_flags = SA_ONSTACK;
            sa.sa_handler = (void *) v;
            sa.sa_restorer = NULL;
            if (sigaction(SIGSEGV, &sa, NULL) < 0)
                  panic("userspace_tramp - setting SIGSEGV handler "
                        "failed - errno = %d\n", errno);
      }

      kill(os_getpid(), SIGSTOP);
      return 0;
}

/* Each element set once, and only accessed by a single processor anyway */
#undef NR_CPUS
#define NR_CPUS 1
int userspace_pid[NR_CPUS];

int start_userspace(unsigned long stub_stack)
{
      void *stack;
      unsigned long sp;
      int pid, status, n, flags;

      stack = mmap(NULL, UM_KERN_PAGE_SIZE,
                 PROT_READ | PROT_WRITE | PROT_EXEC,
                 MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
      if (stack == MAP_FAILED)
            panic("start_userspace : mmap failed, errno = %d", errno);
      sp = (unsigned long) stack + UM_KERN_PAGE_SIZE - sizeof(void *);

      flags = CLONE_FILES;
      if (proc_mm)
            flags |= CLONE_VM;
      else
            flags |= SIGCHLD;

      pid = clone(userspace_tramp, (void *) sp, flags, (void *) stub_stack);
      if (pid < 0)
            panic("start_userspace : clone failed, errno = %d", errno);

      do {
            CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED | __WALL));
            if (n < 0)
                  panic("start_userspace : wait failed, errno = %d",
                        errno);
      } while (WIFSTOPPED(status) && (WSTOPSIG(status) == SIGVTALRM));

      if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP))
            panic("start_userspace : expected SIGSTOP, got status = %d",
                  status);

      if (ptrace(PTRACE_OLDSETOPTIONS, pid, NULL,
               (void *) PTRACE_O_TRACESYSGOOD) < 0)
            panic("start_userspace : PTRACE_OLDSETOPTIONS failed, "
                  "errno = %d\n", errno);

      if (munmap(stack, UM_KERN_PAGE_SIZE) < 0)
            panic("start_userspace : munmap failed, errno = %d\n", errno);

      return pid;
}

void userspace(struct uml_pt_regs *regs)
{
      struct itimerval timer;
      unsigned long long nsecs, now;
      int err, status, op, pid = userspace_pid[0];
      /* To prevent races if using_sysemu changes under us.*/
      int local_using_sysemu;

      if (getitimer(ITIMER_VIRTUAL, &timer))
            printk("Failed to get itimer, errno = %d\n", errno);
      nsecs = timer.it_value.tv_sec * UM_NSEC_PER_SEC +
            timer.it_value.tv_usec * UM_NSEC_PER_USEC;
      nsecs += os_nsecs();

      while (1) {
            restore_registers(pid, regs);

            /* Now we set local_using_sysemu to be used for one loop */
            local_using_sysemu = get_using_sysemu();

            op = SELECT_PTRACE_OPERATION(local_using_sysemu,
                                   singlestepping(NULL));

            err = ptrace(op, pid, 0, 0);
            if (err)
                  panic("userspace - could not resume userspace process, "
                        "pid=%d, ptrace operation = %d, errno = %d\n",
                        pid, op, errno);

            CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED | __WALL));
            if (err < 0)
                  panic("userspace - waitpid failed, errno = %d\n",
                        errno);

            regs->is_user = 1;
            save_registers(pid, regs);
            UPT_SYSCALL_NR(regs) = -1; /* Assume: It's not a syscall */

            if (WIFSTOPPED(status)) {
                  int sig = WSTOPSIG(status);
                  switch(sig) {
                  case SIGSEGV:
                        if (PTRACE_FULL_FAULTINFO ||
                            !ptrace_faultinfo) {
                              get_skas_faultinfo(pid,
                                             &regs->faultinfo);
                              (*sig_info[SIGSEGV])(SIGSEGV, regs);
                        }
                        else handle_segv(pid, regs);
                        break;
                  case SIGTRAP + 0x80:
                          handle_trap(pid, regs, local_using_sysemu);
                        break;
                  case SIGTRAP:
                        relay_signal(SIGTRAP, regs);
                        break;
                  case SIGVTALRM:
                        now = os_nsecs();
                        if(now < nsecs)
                              break;
                        block_signals();
                        (*sig_info[sig])(sig, regs);
                        unblock_signals();
                        nsecs = timer.it_value.tv_sec *
                              UM_NSEC_PER_SEC +
                              timer.it_value.tv_usec *
                              UM_NSEC_PER_USEC;
                        nsecs += os_nsecs();
                        break;
                  case SIGIO:
                  case SIGILL:
                  case SIGBUS:
                  case SIGFPE:
                  case SIGWINCH:
                        block_signals();
                        (*sig_info[sig])(sig, regs);
                        unblock_signals();
                        break;
                  default:
                          printk(UM_KERN_ERR "userspace - child stopped "
                               "with signal %d\n", sig);
                  }
                  pid = userspace_pid[0];
                  interrupt_end();

                  /* Avoid -ERESTARTSYS handling in host */
                  if (PT_SYSCALL_NR_OFFSET != PT_SYSCALL_RET_OFFSET)
                        PT_SYSCALL_NR(regs->gp) = -1;
            }
      }
}

static unsigned long thread_regs[MAX_REG_NR];

static int __init init_thread_regs(void)
{
      get_safe_registers(thread_regs);
      /* Set parent's instruction pointer to start of clone-stub */
      thread_regs[REGS_IP_INDEX] = STUB_CODE +
                        (unsigned long) stub_clone_handler -
                        (unsigned long) &__syscall_stub_start;
      thread_regs[REGS_SP_INDEX] = STUB_DATA + UM_KERN_PAGE_SIZE -
            sizeof(void *);
#ifdef __SIGNAL_FRAMESIZE
      thread_regs[REGS_SP_INDEX] -= __SIGNAL_FRAMESIZE;
#endif
      return 0;
}

__initcall(init_thread_regs);

int copy_context_skas0(unsigned long new_stack, int pid)
{
      struct timeval tv = { .tv_sec = 0, .tv_usec = UM_USEC_PER_SEC / UM_HZ };
      int err;
      unsigned long current_stack = current_stub_stack();
      struct stub_data *data = (struct stub_data *) current_stack;
      struct stub_data *child_data = (struct stub_data *) new_stack;
      unsigned long long new_offset;
      int new_fd = phys_mapping(to_phys((void *)new_stack), &new_offset);

      /*
       * prepare offset and fd of child's stack as argument for parent's
       * and child's mmap2 calls
       */
      *data = ((struct stub_data) { .offset     = MMAP_OFFSET(new_offset),
                              .fd   = new_fd,
                              .timer    = ((struct itimerval)
                                         { .it_value = tv,
                                         .it_interval = tv }) });

      err = ptrace_setregs(pid, thread_regs);
      if (err < 0)
            panic("copy_context_skas0 : PTRACE_SETREGS failed, "
                  "pid = %d, errno = %d\n", pid, -err);

      /* set a well known return code for detection of child write failure */
      child_data->err = 12345678;

      /*
       * Wait, until parent has finished its work: read child's pid from
       * parent's stack, and check, if bad result.
       */
      err = ptrace(PTRACE_CONT, pid, 0, 0);
      if (err)
            panic("Failed to continue new process, pid = %d, "
                  "errno = %d\n", pid, errno);
      wait_stub_done(pid);

      pid = data->err;
      if (pid < 0)
            panic("copy_context_skas0 - stub-parent reports error %d\n",
                  -pid);

      /*
       * Wait, until child has finished too: read child's result from
       * child's stack and check it.
       */
      wait_stub_done(pid);
      if (child_data->err != STUB_DATA)
            panic("copy_context_skas0 - stub-child reports error %ld\n",
                  child_data->err);

      if (ptrace(PTRACE_OLDSETOPTIONS, pid, NULL,
               (void *)PTRACE_O_TRACESYSGOOD) < 0)
            panic("copy_context_skas0 : PTRACE_OLDSETOPTIONS failed, "
                  "errno = %d\n", errno);

      return pid;
}

/*
 * This is used only, if stub pages are needed, while proc_mm is
 * available. Opening /proc/mm creates a new mm_context, which lacks
 * the stub-pages. Thus, we map them using /proc/mm-fd
 */
void map_stub_pages(int fd, unsigned long code,
                unsigned long data, unsigned long stack)
{
      struct proc_mm_op mmop;
      int n;
      unsigned long long code_offset;
      int code_fd = phys_mapping(to_phys((void *) &__syscall_stub_start),
                           &code_offset);

      mmop = ((struct proc_mm_op) { .op        = MM_MMAP,
                              .u         =
                              { .mmap    =
                              { .addr    = code,
                                .len     = UM_KERN_PAGE_SIZE,
                                .prot    = PROT_EXEC,
                                .flags   = MAP_FIXED | MAP_PRIVATE,
                                .fd      = code_fd,
                                .offset  = code_offset
      } } });
      CATCH_EINTR(n = write(fd, &mmop, sizeof(mmop)));
      if (n != sizeof(mmop)) {
            n = errno;
            printk(UM_KERN_ERR "mmap args - addr = 0x%lx, fd = %d, "
                   "offset = %llx\n", code, code_fd,
                   (unsigned long long) code_offset);
            panic("map_stub_pages : /proc/mm map for code failed, "
                  "err = %d\n", n);
      }

      if (stack) {
            unsigned long long map_offset;
            int map_fd = phys_mapping(to_phys((void *)stack), &map_offset);
            mmop = ((struct proc_mm_op)
                        { .op        = MM_MMAP,
                          .u         =
                          { .mmap    =
                            { .addr    = data,
                              .len     = UM_KERN_PAGE_SIZE,
                              .prot    = PROT_READ | PROT_WRITE,
                              .flags   = MAP_FIXED | MAP_SHARED,
                              .fd      = map_fd,
                              .offset  = map_offset
            } } });
            CATCH_EINTR(n = write(fd, &mmop, sizeof(mmop)));
            if (n != sizeof(mmop))
                  panic("map_stub_pages : /proc/mm map for data failed, "
                        "err = %d\n", errno);
      }
}

void new_thread(void *stack, jmp_buf *buf, void (*handler)(void))
{
      (*buf)[0].JB_IP = (unsigned long) handler;
      (*buf)[0].JB_SP = (unsigned long) stack + UM_THREAD_SIZE -
            sizeof(void *);
}

#define INIT_JMP_NEW_THREAD 0
#define INIT_JMP_CALLBACK 1
#define INIT_JMP_HALT 2
#define INIT_JMP_REBOOT 3

void switch_threads(jmp_buf *me, jmp_buf *you)
{
      if (UML_SETJMP(me) == 0)
            UML_LONGJMP(you, 1);
}

static jmp_buf initial_jmpbuf;

/* XXX Make these percpu */
static void (*cb_proc)(void *arg);
static void *cb_arg;
static jmp_buf *cb_back;

int start_idle_thread(void *stack, jmp_buf *switch_buf)
{
      int n;

      set_handler(SIGWINCH, (__sighandler_t) sig_handler,
                SA_ONSTACK | SA_RESTART, SIGUSR1, SIGIO, SIGVTALRM, -1);

      /*
       * Can't use UML_SETJMP or UML_LONGJMP here because they save
       * and restore signals, with the possible side-effect of
       * trying to handle any signals which came when they were
       * blocked, which can't be done on this stack.
       * Signals must be blocked when jumping back here and restored
       * after returning to the jumper.
       */
      n = setjmp(initial_jmpbuf);
      switch(n) {
      case INIT_JMP_NEW_THREAD:
            (*switch_buf)[0].JB_IP = (unsigned long) new_thread_handler;
            (*switch_buf)[0].JB_SP = (unsigned long) stack +
                  UM_THREAD_SIZE - sizeof(void *);
            break;
      case INIT_JMP_CALLBACK:
            (*cb_proc)(cb_arg);
            longjmp(*cb_back, 1);
            break;
      case INIT_JMP_HALT:
            kmalloc_ok = 0;
            return 0;
      case INIT_JMP_REBOOT:
            kmalloc_ok = 0;
            return 1;
      default:
            panic("Bad sigsetjmp return in start_idle_thread - %d\n", n);
      }
      longjmp(*switch_buf, 1);
}

void initial_thread_cb_skas(void (*proc)(void *), void *arg)
{
      jmp_buf here;

      cb_proc = proc;
      cb_arg = arg;
      cb_back = &here;

      block_signals();
      if (UML_SETJMP(&here) == 0)
            UML_LONGJMP(&initial_jmpbuf, INIT_JMP_CALLBACK);
      unblock_signals();

      cb_proc = NULL;
      cb_arg = NULL;
      cb_back = NULL;
}

void halt_skas(void)
{
      block_signals();
      UML_LONGJMP(&initial_jmpbuf, INIT_JMP_HALT);
}

void reboot_skas(void)
{
      block_signals();
      UML_LONGJMP(&initial_jmpbuf, INIT_JMP_REBOOT);
}

void __switch_mm(struct mm_id *mm_idp)
{
      int err;

      /* FIXME: need cpu pid in __switch_mm */
      if (proc_mm) {
            err = ptrace(PTRACE_SWITCH_MM, userspace_pid[0], 0,
                       mm_idp->u.mm_fd);
            if (err)
                  panic("__switch_mm - PTRACE_SWITCH_MM failed, "
                        "errno = %d\n", errno);
      }
      else userspace_pid[0] = mm_idp->u.pid;
}

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