util.c

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/*
 * 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 <termios.h>
#include <wait.h>
#include <sys/mman.h>
#include <sys/utsname.h>
#include <os.h>

void stack_protections(unsigned long address)
{
    if (mprotect((void *) address, UM_THREAD_SIZE,
            PROT_READ | PROT_WRITE | PROT_EXEC) < 0)
        panic("protecting stack failed, errno = %d", errno);
}

int raw(int fd)
{
    struct termios tt;
    int err;

    CATCH_EINTR(err = tcgetattr(fd, &tt));
    if (err < 0)
        return -errno;

    cfmakeraw(&tt);

    CATCH_EINTR(err = tcsetattr(fd, TCSADRAIN, &tt));
    if (err < 0)
        return -errno;

    /*
     * XXX tcsetattr could have applied only some changes
     * (and cfmakeraw() is a set of changes)
     */
    return 0;
}

void setup_machinename(char *machine_out)
{
    struct utsname host;

    uname(&host);
#ifdef UML_CONFIG_UML_X86
# ifndef UML_CONFIG_64BIT
    if (!strcmp(host.machine, "x86_64")) {
        strcpy(machine_out, "i686");
        return;
    }
# else
    if (!strcmp(host.machine, "i686")) {
        strcpy(machine_out, "x86_64");
        return;
    }
# endif
#endif
    strcpy(machine_out, host.machine);
}

void setup_hostinfo(char *buf, int len)
{
    struct utsname host;

    uname(&host);
    snprintf(buf, len, "%s %s %s %s %s", host.sysname, host.nodename,
         host.release, host.version, host.machine);
}

/*
 * We cannot use glibc's abort(). It makes use of tgkill() which
 * has no effect within UML's kernel threads.
 * After that glibc would execute an invalid instruction to kill
 * the calling process and UML crashes with SIGSEGV.
 */
static inline void __attribute__ ((noreturn)) uml_abort(void)
{
    sigset_t sig;

    fflush(NULL);

    if (!sigemptyset(&sig) && !sigaddset(&sig, SIGABRT))
        sigprocmask(SIG_UNBLOCK, &sig, 0);

    for (;;)
        if (kill(getpid(), SIGABRT) < 0)
            exit(127);
}

void os_dump_core(void)
{
    int pid;

    signal(SIGSEGV, SIG_DFL);

    /*
     * We are about to SIGTERM this entire process group to ensure that
     * nothing is around to run after the kernel exits.  The
     * kernel wants to abort, not die through SIGTERM, so we
     * ignore it here.
     */

    signal(SIGTERM, SIG_IGN);
    kill(0, SIGTERM);
    /*
     * Most of the other processes associated with this UML are
     * likely sTopped, so give them a SIGCONT so they see the
     * SIGTERM.
     */
    kill(0, SIGCONT);

    /*
     * Now, having sent signals to everyone but us, make sure they
     * die by ptrace.  Processes can survive what's been done to
     * them so far - the mechanism I understand is receiving a
     * SIGSEGV and segfaulting immediately upon return.  There is
     * always a SIGSEGV pending, and (I'm guessing) signals are
     * processed in numeric order so the SIGTERM (signal 15 vs
     * SIGSEGV being signal 11) is never handled.
     *
     * Run a waitpid loop until we get some kind of error.
     * Hopefully, it's ECHILD, but there's not a lot we can do if
     * it's something else.  Tell os_kill_ptraced_process not to
     * wait for the child to report its death because there's
     * nothing reasonable to do if that fails.
     */

    while ((pid = waitpid(-1, NULL, WNOHANG | __WALL)) > 0)
        os_kill_ptraced_process(pid, 0);

    uml_abort();
}

void um_early_printk(const char *s, unsigned int n)
{
    printf("%.*s", n, s);
}