/*
 * Copyright (C) 2015 Thomas Meyer (thomas@m3y3r.de)
 * 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 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) {
                os_warn("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();

        setsid();

        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

        change_sig(SIGPIPE, 0);
        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 timer signal 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 timer signal to be ignored */
        os_timer_disable();

        /* disable SIGIO for the fds and set SIGIO to be ignored */
        err = deactivate_all_fds();
        if (err)
                os_warn("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();

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