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