101 lines
3.3 KiB
C++
101 lines
3.3 KiB
C++
/*******************************************************************************
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Copyright(C) Jonas 'Sortie' Termansen 2011, 2012, 2013.
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This file is part of the Sortix C Library.
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The Sortix C Library is free software: you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation, either version 3 of the License, or (at your
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option) any later version.
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The Sortix C Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with the Sortix C Library. If not, see <http://www.gnu.org/licenses/>.
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execvpe.cpp
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Loads a process image.
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*******************************************************************************/
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#include <errno.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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// TODO: Move this to some generic environment interface!
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static const char* LookupEnvironment(const char* name, char* const* envp)
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{
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size_t equalpos = strcspn(name, "=");
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if ( name[equalpos] == '=' )
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return NULL;
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size_t namelen = equalpos;
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for ( size_t i = 0; envp[i]; i++ )
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{
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if ( strncmp(name, envp[i], namelen) )
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continue;
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if ( envp[i][namelen] != '=' )
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continue;
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return envp[i] + namelen + 1;
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}
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return NULL;
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}
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// TODO: Provide an interface that allows user-space to find out which command
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// would have been executed (according to PATH) had execvpe been called now.
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// This is of value to programs such as which(1), instead of repeating much of
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// this logic there.
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extern "C" int execvpe(const char* filename, char* const* argv,
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char* const* envp)
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{
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const char* path = LookupEnvironment("PATH", envp);
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// TODO: Should there be a default PATH value?
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if ( strchr(filename, '/') || !path )
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return execve(filename, argv, envp);
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// Search each directory in the PATH variable for a suitable file.
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size_t filename_len = strlen(filename);
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while ( *path )
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{
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size_t len = strcspn(path, ":");
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if ( !len )
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{
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// Sortix doesn't support that the empty string means current
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// directory. While it does inductively make sense, the common
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// kernel interfaces such as openat doesn't accept it and software
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// often just prefix their directories and a colon to PATH without
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// regard to whether it's already empty. S
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path++;
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continue;
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}
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// Determine the full path to the file if it is in the directory.
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size_t fullpath_len = len + 1 + filename_len + 1;
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char* fullpath = (char*) malloc(fullpath_len * sizeof(char));
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if ( !fullpath )
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return -1;
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stpcpy(stpcpy(stpncpy(fullpath, path, len), "/"), filename);
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if ( (path += len + 1)[0] == ':' )
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path++;
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execve(fullpath, argv, envp);
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free(fullpath);
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// TODO: There may be some security concerns here as to whether to
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// continue or abort execution. For instance, if a directory in the
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// start of the PATH has permissions set up too restrictively, then
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// it would never look in the later directories (and you can't execute
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// anything without absolute paths). And other situations.
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if ( errno == EACCES )
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return -1;
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if ( errno == ENOENT )
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continue;
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}
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return -1;
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}
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