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89 lines
2.5 KiB
89 lines
2.5 KiB
4 months ago
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// Copyright 2019 The Chromium OS Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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// +build libc_exec
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package main
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// #include <errno.h>
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// #include <stdio.h>
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// #include <stdlib.h>
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// #include <string.h>
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// #include <unistd.h>
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// #include <sys/types.h>
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// #include <sys/wait.h>
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//
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// int libc_exec(const char *pathname, char *const argv[], char *const envp[]) {
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// // Since fork() brings us to one thread, we can only use async-signal-safe funcs below.
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// pid_t pid = fork();
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// if (pid == 0) {
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// execve(pathname, argv, envp);
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// fprintf(stderr, "exec failed (errno: %d)\n", errno);
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// _exit(1);
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// }
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// if (pid < 0) {
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// return errno;
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// }
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//
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// int wstatus;
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// pid_t waited = waitpid(pid, &wstatus, 0);
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// if (waited == -1) {
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// return errno;
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// }
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// exit(WEXITSTATUS(wstatus));
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//}
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import "C"
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import (
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"os/exec"
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"unsafe"
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)
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// Replacement for syscall.Execve that uses the libc.
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// This allows tools that rely on intercepting syscalls via
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// LD_PRELOAD to work properly (e.g. gentoo sandbox).
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// Note that this changes the go binary to be a dynamically linked one.
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// See crbug.com/1000863 for details.
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// To use this version of exec, please add '-tags libc_exec' when building Go binary.
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// Without the tags, libc_exec.go will not be used.
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func execCmd(env env, cmd *command) error {
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freeList := []unsafe.Pointer{}
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defer func() {
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for _, ptr := range freeList {
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C.free(ptr)
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}
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}()
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goStrToC := func(goStr string) *C.char {
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cstr := C.CString(goStr)
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freeList = append(freeList, unsafe.Pointer(cstr))
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return cstr
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}
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goSliceToC := func(goSlice []string) **C.char {
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// len(goSlice)+1 as the c array needs to be null terminated.
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cArray := C.malloc(C.size_t(len(goSlice)+1) * C.size_t(unsafe.Sizeof(uintptr(0))))
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freeList = append(freeList, cArray)
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// Convert the C array to a Go Array so we can index it.
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// Note: Storing pointers to the c heap in go pointer types is ok
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// (see https://golang.org/cmd/cgo/).
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cArrayForIndex := (*[1<<30 - 1]*C.char)(cArray)
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for i, str := range goSlice {
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cArrayForIndex[i] = goStrToC(str)
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}
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cArrayForIndex[len(goSlice)] = nil
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return (**C.char)(cArray)
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}
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execCmd := exec.Command(cmd.Path, cmd.Args...)
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mergedEnv := mergeEnvValues(env.environ(), cmd.EnvUpdates)
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if errno := C.libc_exec(goStrToC(execCmd.Path), goSliceToC(execCmd.Args), goSliceToC(mergedEnv)); errno != 0 {
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return newErrorwithSourceLocf("exec error: %d", errno)
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}
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return nil
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}
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