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121 lines
3.6 KiB
C
121 lines
3.6 KiB
C
//===- SystemUtils.h - Utilities to do low-level system stuff --*- C++ -*--===//
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//
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// This file contains functions used to do a variety of low-level, often
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// system-specific, tasks.
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//
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//===----------------------------------------------------------------------===//
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#include "SysUtils.h"
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#include "Config/dlfcn.h"
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#include "Config/fcntl.h"
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#include "Config/unistd.h"
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#include "Config/sys/stat.h"
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#include "Config/sys/types.h"
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#include "Config/sys/wait.h"
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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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/*
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* isExecutable - This function returns true if given struct stat describes the
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* file as being executable.
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*/
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unsigned isExecutable(const struct stat *buf) {
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if (!(buf->st_mode & S_IFREG))
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return 0; // Not a regular file?
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if (buf->st_uid == getuid()) // Owner of file?
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return buf->st_mode & S_IXUSR;
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else if (buf->st_gid == getgid()) // In group of file?
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return buf->st_mode & S_IXGRP;
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else // Unrelated to file?
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return buf->st_mode & S_IXOTH;
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}
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/*
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* isExecutableFile - This function returns true if the filename specified
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* exists and is executable.
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*/
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unsigned isExecutableFile(const char *ExeFileName) {
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struct stat buf;
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if (stat(ExeFileName, &buf))
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return 0; // Must not be executable!
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return isExecutable(&buf);
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}
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/*
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* FindExecutable - Find a named executable in the directories listed in $PATH.
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* If the executable cannot be found, returns NULL.
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*/
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char *FindExecutable(const char *ExeName) {
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/* Try to find the executable in the path */
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const char *PathStr = getenv("PATH");
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if (PathStr == 0) return 0;
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/* Now we have a colon separated list of directories to search, try them. */
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unsigned PathLen = strlen(PathStr);
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while (PathLen) {
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/* Find the next colon */
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const char *Colon = strchr(PathStr, ':');
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/* Check to see if this first directory contains the executable... */
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unsigned DirLen = Colon ? (unsigned)(Colon-PathStr) : strlen(PathStr);
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char *FilePath = alloca(sizeof(char) * (DirLen+1+strlen(ExeName)+1));
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unsigned i, e;
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for (i = 0; i != DirLen; ++i)
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FilePath[i] = PathStr[i];
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FilePath[i] = '/';
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for (i = 0, e = strlen(ExeName); i != e; ++i)
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FilePath[DirLen + 1 + i] = ExeName[i];
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FilePath[DirLen + 1 + i] = '\0';
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if (isExecutableFile(FilePath))
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return strdup(FilePath); /* Found the executable! */
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/* If Colon is NULL, there are no more colon separators and no more dirs */
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if (!Colon) break;
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/* Nope, it wasn't in this directory, check the next range! */
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PathLen -= DirLen;
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PathStr = Colon;
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while (*PathStr == ':') { /* Advance past colons */
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PathStr++;
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PathLen--;
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}
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/* Advance past the colon */
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++Colon;
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}
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/* If we fell out, we ran out of directories to search, return failure. */
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return NULL;
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}
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/*
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* The type of the execve() function is long and boring, but required.
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*/
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typedef int(*execveTy)(const char*, char *const[], char *const[]);
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/*
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* This method finds the real `execve' call in the C library and executes the
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* given program.
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*/
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int executeProgram(const char *filename, char *const argv[], char *const envp[])
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{
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/*
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* Find a pointer to the *real* execve() function starting the search in the
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* next library and forward, to avoid finding the one defined in this file.
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*/
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char *error;
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execveTy execvePtr = (execveTy) dlsym(RTLD_NEXT, "execve");
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if ((error = dlerror()) != NULL) {
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fprintf(stderr, "%s\n", error);
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return -1;
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}
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/* Really execute the program */
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return execvePtr(filename, argv, envp);
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}
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