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8a3b1e25cd
Also includes a few other changes for safety, e.g. making the child exit via QuitGS rather than exit() or _exit(). The vfork_and_run() routine is based on code from my port of hush.
129 lines
4.0 KiB
C
129 lines
4.0 KiB
C
/*
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* Copyright (c) 2014, 2016 Stephen Heumann
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <unistd.h>
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#include <stdlib.h>
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#include <string.h>
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#ifdef __GNO__
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#include <gno/gno.h>
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#endif
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/* Like vfork, but calls fn(arg) in the child instead of returning.
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* This is designed to match the semantics of GNO's fork2 call.
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*/
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#ifndef __GNO__
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pid_t vfork_and_run(void (*fn)(void*) /*NORETURN*/, void *arg) {
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/* Use fork rather than vfork because vfork is problematic on OS X. */
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pid_t pid = fork();
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if (pid == 0) {
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fn(arg);
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}
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return pid;
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}
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#else
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# include <signal.h>
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# include <gno/kvm.h>
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# include <orca.h>
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/* Turn off all ORCA/C stack repair code to avoid corruption. */
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# ifdef __ORCAC__
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# pragma optimize 72
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# endif
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# pragma databank 1
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void fork_thunk(void (*fn)(void*) /*NORETURN*/, void *arg, long sigmask) {
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sigsetmask(sigmask);
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fn(arg);
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}
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# pragma databank 0
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const char *forked_child_name = "telnetd pty slave proc";
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#define CHILD_STACKSIZE 1024
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pid_t vfork_and_run(void (*fn)(void*) /*NORETURN*/, void *arg) {
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/* GNO's fork2 call will return immediately and allow the parent and
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* child processes to execute concurrently using the same memory
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* space. To prevent them stomping on each other, we want to get
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* behavior like a traditional vfork() implementation, where the
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* parent blocks until the child terminates or execs.
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*
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* Our approach is to check the process tables to make sure the
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* child has actually finished or exec'd. If not, we loop and try again.
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* We can't just rely on the fact that the child signaled us, because
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* it may still be running in libc's implementation of exec*.
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*/
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long oldmask;
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pid_t pid;
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kvmt *kvm_context;
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struct pentry *proc_entry;
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int done = 0;
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/* Isolate child process's environment from parent */
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if (environPush() != 0)
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return -1;
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/* Block all signals for now */
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oldmask = sigblock(-1);
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pid = fork2(fork_thunk, CHILD_STACKSIZE, 0, forked_child_name,
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(sizeof(fn) + sizeof(arg) + sizeof(oldmask) + 1) / 2,
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fn, arg, oldmask);
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if (pid < 0)
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goto ret;
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while (!done) {
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/* Wait for ~100 ms. If procsend worked, the child could send a
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* message with it to end the waiting earlier, but this isn't
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* possible in GNO 2.0.6 because procsend is broken. This isn't
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* too big an issue, since 100ms isn't very long to wait anyhow. */
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procrecvtim(1);
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/* Check if the child is really dead or forked by inspecting
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* the kernel's process entry for it. */
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kvm_context = kvm_open();
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if (kvm_context == NULL)
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break;
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proc_entry = kvmgetproc(kvm_context, pid);
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if (proc_entry == NULL
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|| (proc_entry->args != NULL
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&& strcmp(forked_child_name, proc_entry->args + 8) != 0))
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done = 1;
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kvm_close(kvm_context);
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}
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ret:
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sigsetmask(oldmask);
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environPop();
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return pid;
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}
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#endif
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