process.c

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/*
 * 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/wait.h>
#include <asm/unistd.h>
#include <as-layout.h>
#include <init.h>
#include <kern_util.h>
#include <mem.h>
#include <os.h>
#include <proc_mm.h>
#include <ptrace_user.h>
#include <registers.h>
#include <skas.h>
#include <skas_ptrace.h>
#include <sysdep/stub.h>

int is_skas_winch(int pid, int fd, void *data)
{
    return pid == getpgrp();
}

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 << 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) {
            printk(UM_KERN_ERR "wait_stub_done : continue failed, "
                   "errno = %d\n", errno);
            fatal_sigsegv();
        }
    }

    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);
    printk(UM_KERN_ERR "wait_stub_done : failed to wait for SIGTRAP, "
           "pid = %d, n = %d, errno = %d, status = 0x%x\n", pid, n, errno,
           status);
    fatal_sigsegv();
}

extern unsigned long current_stub_stack(void);

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

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

        /* 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 {
        unsigned long fpregs[FP_SIZE];

        err = get_fp_registers(pid, fpregs);
        if (err < 0) {
            printk(UM_KERN_ERR "save_fp_registers returned %d\n",
                   err);
            fatal_sigsegv();
        }
        err = ptrace(PTRACE_CONT, pid, 0, SIGSEGV);
        if (err) {
            printk(UM_KERN_ERR "Failed to continue stub, pid = %d, "
                   "errno = %d\n", pid, errno);
            fatal_sigsegv();
        }
        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));

        err = put_fp_registers(pid, fpregs);
        if (err < 0) {
            printk(UM_KERN_ERR "put_fp_registers returned %d\n",
                   err);
            fatal_sigsegv();
        }
    }
}

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;

    if ((UPT_IP(regs) >= STUB_START) && (UPT_IP(regs) < STUB_END))
        fatal_sigsegv();

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

    if (!local_using_sysemu)
    {
        err = ptrace(PTRACE_POKEUSER, pid, PT_SYSCALL_NR_OFFSET,
                 __NR_getpid);
        if (err < 0) {
            printk(UM_KERN_ERR "handle_trap - nullifying syscall "
                   "failed, errno = %d\n", errno);
            fatal_sigsegv();
        }

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

        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);
            printk(UM_KERN_ERR "handle_trap - failed to wait at "
                   "end of syscall, errno = %d, status = %d\n",
                   errno, status);
            fatal_sigsegv();
        }
    }

    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);
    signal(SIGWINCH, SIG_IGN);
    err = set_interval();
    if (err) {
        printk(UM_KERN_ERR "userspace_tramp - setting timer failed, "
               "errno = %d\n", err);
        exit(1);
    }

    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);
        sa.sa_flags = SA_ONSTACK | SA_NODEFER | SA_SIGINFO;
        sa.sa_sigaction = (void *) v;
        sa.sa_restorer = NULL;
        if (sigaction(SIGSEGV, &sa, NULL) < 0) {
            printk(UM_KERN_ERR "userspace_tramp - setting SIGSEGV "
                   "handler failed - errno = %d\n", errno);
            exit(1);
        }
    }

    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, err;

    stack = mmap(NULL, UM_KERN_PAGE_SIZE,
             PROT_READ | PROT_WRITE | PROT_EXEC,
             MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
    if (stack == MAP_FAILED) {
        err = -errno;
        printk(UM_KERN_ERR "start_userspace : mmap failed, "
               "errno = %d\n", errno);
        return err;
    }

    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) {
        err = -errno;
        printk(UM_KERN_ERR "start_userspace : clone failed, "
               "errno = %d\n", errno);
        return err;
    }

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

    if (!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP)) {
        err = -EINVAL;
        printk(UM_KERN_ERR "start_userspace : expected SIGSTOP, got "
               "status = %d\n", status);
        goto out_kill;
    }

    if (ptrace(PTRACE_OLDSETOPTIONS, pid, NULL,
           (void *) PTRACE_O_TRACESYSGOOD) < 0) {
        err = -errno;
        printk(UM_KERN_ERR "start_userspace : PTRACE_OLDSETOPTIONS "
               "failed, errno = %d\n", errno);
        goto out_kill;
    }

    if (munmap(stack, UM_KERN_PAGE_SIZE) < 0) {
        err = -errno;
        printk(UM_KERN_ERR "start_userspace : munmap failed, "
               "errno = %d\n", errno);
        goto out_kill;
    }

    return pid;

 out_kill:
    os_kill_ptraced_process(pid, 1);
    return err;
}

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;
    siginfo_t si;

    /* Handle any immediate reschedules or signals */
    interrupt_end();

    if (getitimer(ITIMER_VIRTUAL, &timer))
        printk(UM_KERN_ERR "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) {
        /*
         * This can legitimately fail if the process loads a
         * bogus value into a segment register.  It will
         * segfault and PTRACE_GETREGS will read that value
         * out of the process.  However, PTRACE_SETREGS will
         * fail.  In this case, there is nothing to do but
         * just kill the process.
         */
        if (ptrace(PTRACE_SETREGS, pid, 0, regs->gp))
            fatal_sigsegv();

        if (put_fp_registers(pid, regs->fp))
            fatal_sigsegv();

        /* 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));

        if (ptrace(op, pid, 0, 0)) {
            printk(UM_KERN_ERR "userspace - ptrace continue "
                   "failed, op = %d, errno = %d\n", op, errno);
            fatal_sigsegv();
        }

        CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED | __WALL));
        if (err < 0) {
            printk(UM_KERN_ERR "userspace - wait failed, "
                   "errno = %d\n", errno);
            fatal_sigsegv();
        }

        regs->is_user = 1;
        if (ptrace(PTRACE_GETREGS, pid, 0, regs->gp)) {
            printk(UM_KERN_ERR "userspace - PTRACE_GETREGS failed, "
                   "errno = %d\n", errno);
            fatal_sigsegv();
        }

        if (get_fp_registers(pid, regs->fp)) {
            printk(UM_KERN_ERR "userspace -  get_fp_registers failed, "
                   "errno = %d\n", errno);
            fatal_sigsegv();
        }

        UPT_SYSCALL_NR(regs) = -1; /* Assume: It's not a syscall */

        if (WIFSTOPPED(status)) {
            int sig = WSTOPSIG(status);

            ptrace(PTRACE_GETSIGINFO, pid, 0, &si);

            switch (sig) {
            case SIGSEGV:
                if (PTRACE_FULL_FAULTINFO ||
                    !ptrace_faultinfo) {
                    get_skas_faultinfo(pid,
                               &regs->faultinfo);
                    (*sig_info[SIGSEGV])(SIGSEGV, &si,
                                 regs);
                }
                else handle_segv(pid, regs);
                break;
            case SIGTRAP + 0x80:
                    handle_trap(pid, regs, local_using_sysemu);
                break;
            case SIGTRAP:
                relay_signal(SIGTRAP, &si, regs);
                break;
            case SIGVTALRM:
                now = os_nsecs();
                if (now < nsecs)
                    break;
                block_signals();
                (*sig_info[sig])(sig, &si, 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, &si, regs);
                unblock_signals();
                break;
            default:
                printk(UM_KERN_ERR "userspace - child stopped "
                       "with signal %d\n", sig);
                fatal_sigsegv();
            }
            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 unsigned long thread_fp_regs[FP_SIZE];

static int __init init_thread_regs(void)
{
    get_safe_registers(thread_regs, thread_fp_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) {
        err = -errno;
        printk(UM_KERN_ERR "copy_context_skas0 : PTRACE_SETREGS "
               "failed, pid = %d, errno = %d\n", pid, -err);
        return err;
    }

    err = put_fp_registers(pid, thread_fp_regs);
    if (err < 0) {
        printk(UM_KERN_ERR "copy_context_skas0 : put_fp_registers "
               "failed, pid = %d, err = %d\n", pid, err);
        return 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) {
        err = -errno;
        printk(UM_KERN_ERR "Failed to continue new process, pid = %d, "
               "errno = %d\n", pid, errno);
        return err;
    }

    wait_stub_done(pid);

    pid = data->err;
    if (pid < 0) {
        printk(UM_KERN_ERR "copy_context_skas0 - stub-parent reports "
               "error %d\n", -pid);
        return 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) {
        printk(UM_KERN_ERR "copy_context_skas0 - stub-child reports "
               "error %ld\n", child_data->err);
        err = child_data->err;
        goto out_kill;
    }

    if (ptrace(PTRACE_OLDSETOPTIONS, pid, NULL,
           (void *)PTRACE_O_TRACESYSGOOD) < 0) {
        err = -errno;
        printk(UM_KERN_ERR "copy_context_skas0 : PTRACE_OLDSETOPTIONS "
               "failed, errno = %d\n", errno);
        goto out_kill;
    }

    return pid;

 out_kill:
    os_kill_ptraced_process(pid, 1);
    return err;
}

/*
 * 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
 */
int 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);
        printk(UM_KERN_ERR "map_stub_pages : /proc/mm map for code "
               "failed, err = %d\n", n);
        return -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)) {
            n = errno;
            printk(UM_KERN_ERR "map_stub_pages : /proc/mm map for "
                   "data failed, err = %d\n", n);
            return -n;
        }
    }

    return 0;
}

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);

    /*
     * 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:
        printk(UM_KERN_ERR "Bad sigsetjmp return in "
               "start_idle_thread - %d\n", n);
        fatal_sigsegv();
    }
    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) {
            printk(UM_KERN_ERR "__switch_mm - PTRACE_SWITCH_MM "
                   "failed, errno = %d\n", errno);
            fatal_sigsegv();
        }
    }
    else userspace_pid[0] = mm_idp->u.pid;
}