main.c

Go to the documentation of this file.

/*
 * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
 * Licensed under the GPL
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <signal.h>
#include <string.h>
#include <sys/resource.h>
#include <as-layout.h>
#include <init.h>
#include <kern_util.h>
#include <os.h>
#include <um_malloc.h>

#define PGD_BOUND (4 * 1024 * 1024)
#define STACKSIZE (8 * 1024 * 1024)
#define THREAD_NAME_LEN (256)

long elf_aux_hwcap;

static void set_stklim(void)
{
    struct rlimit lim;

    if (getrlimit(RLIMIT_STACK, &lim) < 0) {
        perror("getrlimit");
        exit(1);
    }
    if ((lim.rlim_cur == RLIM_INFINITY) || (lim.rlim_cur > STACKSIZE)) {
        lim.rlim_cur = STACKSIZE;
        if (setrlimit(RLIMIT_STACK, &lim) < 0) {
            perror("setrlimit");
            exit(1);
        }
    }
}

static __init void do_uml_initcalls(void)
{
    initcall_t *call;

    call = &__uml_initcall_start;
    while (call < &__uml_initcall_end) {
        (*call)();
        call++;
    }
}

static void last_ditch_exit(int sig)
{
    uml_cleanup();
    exit(1);
}

static void install_fatal_handler(int sig)
{
    struct sigaction action;

    /* All signals are enabled in this handler ... */
    sigemptyset(&action.sa_mask);

    /*
     * ... including the signal being handled, plus we want the
     * handler reset to the default behavior, so that if an exit
     * handler is hanging for some reason, the UML will just die
     * after this signal is sent a second time.
     */
    action.sa_flags = SA_RESETHAND | SA_NODEFER;
    action.sa_restorer = NULL;
    action.sa_handler = last_ditch_exit;
    if (sigaction(sig, &action, NULL) < 0) {
        printf("failed to install handler for signal %d - errno = %d\n",
               sig, errno);
        exit(1);
    }
}

#define UML_LIB_PATH    ":" OS_LIB_PATH "/uml"

static void setup_env_path(void)
{
    char *new_path = NULL;
    char *old_path = NULL;
    int path_len = 0;

    old_path = getenv("PATH");
    /*
     * if no PATH variable is set or it has an empty value
     * just use the default + /usr/lib/uml
     */
    if (!old_path || (path_len = strlen(old_path)) == 0) {
        if (putenv("PATH=:/bin:/usr/bin/" UML_LIB_PATH))
            perror("couldn't putenv");
        return;
    }

    /* append /usr/lib/uml to the existing path */
    path_len += strlen("PATH=" UML_LIB_PATH) + 1;
    new_path = malloc(path_len);
    if (!new_path) {
        perror("couldn't malloc to set a new PATH");
        return;
    }
    snprintf(new_path, path_len, "PATH=%s" UML_LIB_PATH, old_path);
    if (putenv(new_path)) {
        perror("couldn't putenv to set a new PATH");
        free(new_path);
    }
}

extern void scan_elf_aux( char **envp);

int __init main(int argc, char **argv, char **envp)
{
    char **new_argv;
    int ret, i, err;

    set_stklim();

    setup_env_path();

    new_argv = malloc((argc + 1) * sizeof(char *));
    if (new_argv == NULL) {
        perror("Mallocing argv");
        exit(1);
    }
    for (i = 0; i < argc; i++) {
        new_argv[i] = strdup(argv[i]);
        if (new_argv[i] == NULL) {
            perror("Mallocing an arg");
            exit(1);
        }
    }
    new_argv[argc] = NULL;

    /*
     * Allow these signals to bring down a UML if all other
     * methods of control fail.
     */
    install_fatal_handler(SIGINT);
    install_fatal_handler(SIGTERM);

#ifdef CONFIG_ARCH_REUSE_HOST_VSYSCALL_AREA
    scan_elf_aux(envp);
#endif

    do_uml_initcalls();
    ret = linux_main(argc, argv);

    /*
     * Disable SIGPROF - I have no idea why libc doesn't do this or turn
     * off the profiling time, but UML dies with a SIGPROF just before
     * exiting when profiling is active.
     */
    change_sig(SIGPROF, 0);

    /*
     * This signal stuff used to be in the reboot case.  However,
     * sometimes a SIGVTALRM can come in when we're halting (reproducably
     * when writing out gcov information, presumably because that takes
     * some time) and cause a segfault.
     */

    /* stop timers and set SIGVTALRM to be ignored */
    disable_timer();

    /* disable SIGIO for the fds and set SIGIO to be ignored */
    err = deactivate_all_fds();
    if (err)
        printf("deactivate_all_fds failed, errno = %d\n", -err);

    /*
     * Let any pending signals fire now.  This ensures
     * that they won't be delivered after the exec, when
     * they are definitely not expected.
     */
    unblock_signals();

    /* Reboot */
    if (ret) {
        printf("\n");
        execvp(new_argv[0], new_argv);
        perror("Failed to exec kernel");
        ret = 1;
    }
    printf("\n");
    return uml_exitcode;
}

extern void *__real_malloc(int);

void *__wrap_malloc(int size)
{
    void *ret;

    if (!kmalloc_ok)
        return __real_malloc(size);
    else if (size <= UM_KERN_PAGE_SIZE)
        /* finding contiguous pages can be hard*/
        ret = uml_kmalloc(size, UM_GFP_KERNEL);
    else ret = vmalloc(size);

    /*
     * glibc people insist that if malloc fails, errno should be
     * set by malloc as well. So we do.
     */
    if (ret == NULL)
        errno = ENOMEM;

    return ret;
}

void *__wrap_calloc(int n, int size)
{
    void *ptr = __wrap_malloc(n * size);

    if (ptr == NULL)
        return NULL;
    memset(ptr, 0, n * size);
    return ptr;
}

extern void __real_free(void *);

extern unsigned long high_physmem;

void __wrap_free(void *ptr)
{
    unsigned long addr = (unsigned long) ptr;

    /*
     * We need to know how the allocation happened, so it can be correctly
     * freed.  This is done by seeing what region of memory the pointer is
     * in -
     *  physical memory - kmalloc/kfree
     *  kernel virtual memory - vmalloc/vfree
     *  anywhere else - malloc/free
     * If kmalloc is not yet possible, then either high_physmem and/or
     * end_vm are still 0 (as at startup), in which case we call free, or
     * we have set them, but anyway addr has not been allocated from those
     * areas. So, in both cases __real_free is called.
     *
     * CAN_KMALLOC is checked because it would be bad to free a buffer
     * with kmalloc/vmalloc after they have been turned off during
     * shutdown.
     * XXX: However, we sometimes shutdown CAN_KMALLOC temporarily, so
     * there is a possibility for memory leaks.
     */

    if ((addr >= uml_physmem) && (addr < high_physmem)) {
        if (kmalloc_ok)
            kfree(ptr);
    }
    else if ((addr >= start_vm) && (addr < end_vm)) {
        if (kmalloc_ok)
            vfree(ptr);
    }
    else __real_free(ptr);
}