Add PATH variable.

libc/execvpe.cpp

@@ -1,6 +1,6 @@
 /*******************************************************************************
 
-    Copyright(C) Jonas 'Sortie' Termansen 2011, 2012.
+    Copyright(C) Jonas 'Sortie' Termansen 2011, 2012, 2013.
 
     This file is part of the Sortix C Library.
 
@@ -22,31 +22,79 @@
 
 *******************************************************************************/
 
+#include <errno.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
 
-#if defined(PLATFORM_X86)
-	#define CPUTYPE_STR "i486-sortix"
-#elif defined(PLATFORM_X64)
-	#define CPUTYPE_STR "x86_64-sortix"
-#else
-	#error No cputype environmental variable provided here.
-#endif
+// TODO: Move this to some generic environment interface!
+static const char* LookupEnvironment(const char* name, char* const* envp)
+{
+	size_t equalpos = strcspn(name, "=");
+	if ( name[equalpos] == '=' )
+		return NULL;
+	size_t namelen = equalpos;
+	for ( size_t i = 0; envp[i]; i++ )
+	{
+		if ( strncmp(name, envp[i], namelen) )
+			continue;
+		if ( envp[i][namelen] != '=' )
+			continue;
+		return envp[i] + namelen + 1;
+	}
+	return NULL;
+}
 
-// Note that the only PATH variable in Sortix is the one used here.
+// TODO: Provide an interface that allows user-space to find out which command
+// would have been executed (according to PATH) had execvpe been called now.
+// This is of value to programs such as which(1), instead of repeating much of
+// this logic there.
 extern "C" int execvpe(const char* filename, char* const* argv,
                        char* const* envp)
 {
-	if ( strchr(filename, '/') )
+	const char* path = LookupEnvironment("PATH", envp);
+	// TODO: Should there be a default PATH value?
+	if ( strchr(filename, '/') || !path )
 		return execve(filename, argv, envp);
-	size_t filenamelen = strlen(filename);
-	const char* PATH = "/" CPUTYPE_STR "/bin";
-	size_t pathlen = strlen(PATH);
-	char* pathname = (char*) malloc(filenamelen + 1 + pathlen + 1);
-	if ( !pathname ) { return -1; }
-	stpcpy(stpcpy(stpcpy(pathname, PATH), "/"), filename);
-	int result = execve(pathname, argv, envp);
-	free(pathname);
-	return result;
+
+	// Search each directory in the PATH variable for a suitable file.
+	size_t filename_len = strlen(filename);
+	while ( *path )
+	{
+		size_t len = strcspn(path, ":");
+		if ( !len )
+		{
+			// Sortix doesn't support that the empty string means current
+			// directory. While it does inductively make sense, the common
+			// kernel interfaces such as openat doesn't accept it and software
+			// often just prefix their directories and a colon to PATH without
+			// regard to whether it's already empty. S
+			path++;
+			continue;
+		}
+
+		// Determine the full path to the file if it is in the directory.
+		size_t fullpath_len = len + 1 + filename_len + 1;
+		char* fullpath = (char*) malloc(fullpath_len * sizeof(char));
+		if ( !fullpath )
+			return -1;
+		stpcpy(stpcpy(stpncpy(fullpath, path, len), "/"), filename);
+		if ( (path += len + 1)[0] == ':' )
+			path++;
+
+		execve(fullpath, argv, envp);
+		free(fullpath);
+
+		// TODO: There may be some security concerns here as to whether to
+		// continue or abort execution. For instance, if a directory in the
+		// start of the PATH has permissions set up too restrictively, then
+		// it would never look in the later directories (and you can't execute
+		// anything without absolute paths). And other situations.
+		if ( errno == EACCES )
+			return -1;
+		if ( errno == ENOENT )
+			continue;
+
+	}
+	return -1;
 }

utils/init.cpp

@@ -79,6 +79,15 @@ int main(int /*argc*/, char* /*argv*/[])
 	// we are running.
 	setenv("objtype", getenv("cputype"), 0);
 
+	// Set up the PATH variable.
+	const char* prefix = "/";
+	const char* cputype = getenv("cputype");
+	const char* suffix = "/bin";
+	char* path = new char[strlen(prefix) + strlen(cputype) + strlen(suffix) + 1];
+	stpcpy(stpcpy(stpcpy(path, prefix), cputype), suffix);
+	setenv("PATH", path, 0);
+	delete[] path;
+
 	// Make sure that we have a /tmp directory.
 	mkdir("/tmp", 01777);