path: root/pym/portage_exec.py

# portage.py -- core Portage functionality
# Copyright 1998-2004 Gentoo Foundation
# Distributed under the terms of the GNU General Public License v2
# $Header: /local/data/ulm/cvs/history/var/cvsroot/gentoo-src/portage/pym/portage_exec.py,v 1.21 2005/02/26 06:41:48 ferringb Exp $
cvs_id_string="$Id: portage_exec.py,v 1.21 2005/02/26 06:41:48 ferringb Exp $"[5:-2]

import os,types,string,sys
import signal
import portage_data
import portage_util
import portage_const

selinux_capable = False
sandbox_capable = os.path.exists(portage_const.SANDBOX_BINARY)
userpriv_capable = (os.getuid() == 0)
fakeroot_capable = False


try:
	import resource
	max_fd_limit=resource.getrlimit(RLIMIT_NOFILE)
except SystemExit, e:
	raise
except:
	# hokay, no resource module.
	max_fd_limit=256

# pids this process knows of.
spawned_pids = []

def cleanup(pids,block_exceptions=True):
	"""function to go through and reap the list of pids passed to it"""
	global spawned_pids
	if type(pids) == int:
		pids = [pids]
	for x in pids:
		try:
			os.kill(x,signal.SIGTERM)
			if os.waitpid(x,os.WNOHANG)[1] == 0:
				# feisty bugger, still alive.
				os.kill(x,signal.SIGKILL)
				os.waitpid(x,0)

		except OSError, oe:
			if block_exceptions:
				pass
			if oe.errno not in (10,3):
				raise oe
		except SystemExit:
			raise
		except Exception:
			if block_exceptions:
				pass
		try:			spawned_pids.remove(x)
		except IndexError:	pass

from portage_const import BASH_BINARY,SANDBOX_BINARY,SANDBOX_PIDS_FILE

def spawn_bash(mycommand,env={},debug=False,opt_name=None,**keywords):
	"""spawn mycommand as an arguement to bash"""
	args=[BASH_BINARY]
	if not opt_name:
		opt_name=mycommand.split()[0]
	if not env.has_key("BASH_ENV"):
		env["BASH_ENV"] = "/etc/spork/is/not/valid/profile.env"
	if debug:
		args.append("-x")
	args.append("-c")
	args.append(mycommand)
	return spawn(args,env=env,opt_name=opt_name,**keywords)

def spawn_sandbox(mycommand,uid=None,opt_name=None,**keywords):
	"""spawn mycommand as an arguement to the sandbox binary.
	basically, LD_PRELOAD="libsandbox.so" mycommand"""
	args=[SANDBOX_BINARY]
	if not opt_name:
		opt_name=mycommand.split()[0]
	args.append(mycommand)
	if not uid:
		uid=os.getuid()
	try:
		os.chown(SANDBOX_PIDS_FILE,uid,portage_data.portage_gid)
		os.chmod(SANDBOX_PIDS_FILE,0664)
	except SystemExit, e:
		raise
	except:
		pass
	return spawn(args,uid=uid,opt_name=opt_name,**keywords)

def find_binary(myc):
	"""look through the environmental path for an executable file named whatever myc is"""
	# this sucks. badly.
	p=os.getenv("PATH")
	if p == None:
		return None
	for x in p.split(":"):
		#if it exists, and is executable
		if os.path.exists("%s/%s" % (x,myc)) and os.stat("%s/%s" % (x,myc))[0] & 0x0248:
			return "%s/%s" % (x,myc)
	return None


def spawn_func(func,args=[],kwargs={},exit_func=None,**keywords):
	"""spawn a python function in a fork
	func: python function
	args: positional args to positionally expand for the function
	kwargs: optional args to expand for the function call
	exit_func: optional function for parsing the return of func, and 
	returning the desired exit code
	note exit_func should handle applicable exceptions.  Unhandled exemptions are caught,
	and the process exits with a code of 1."""
	if exit_func:
		return spawn((func,args,kwargs,exit_func), func_call=True,**keywords)
	return spawn((func,args,kwargs), func_call=True,**keywords)

# base spawn function
def spawn(mycommand,env={},raw_exit_code=False,opt_name=None,fd_pipes=None,returnpid=False,\
	uid=None,gid=None,groups=None,umask=None,logfile=None,path_lookup=True, selinux_context=None,
	raise_signals=False, func_call=False):
	"""base fork/execve function.
	mycommand is the desired command- if you need a command to execute in a bash/sandbox/fakeroot
	environment, use the appropriate spawn call.  This is a straight fork/exec code path.
	Can either have a tuple, or a string passed in.  If uid/gid/groups/umask specified, it changes
	the forked process to said value.  If path_lookup is on, a non-absolute command will be converted
	to an absolute command, otherwise it returns None.

	selinux_context is the desired context, dependant on selinux being available.
	opt_name controls the name the processor goes by.
	fd_pipes controls which file descriptor numbers are left open in the forked process- it's a dict of
	current fd's raw fd #, desired #.

	func_call is a boolean for specifying to execute a python function- use spawn_func instead.
	raise_signals is questionable.  Basically throw an exception if signal'd.  No exception is thrown
	if raw_input is on.

	logfile overloads the specified fd's to write to a tee process which logs to logfile
	returnpid returns the relevant pids (a list, including the logging process if logfile is on).
	
	non-returnpid calls to spawn will block till the process has exited, returning the exitcode/signal
	raw_exit_code controls whether the actual waitpid result is returned, or intrepretted."""
	myc=''
	if not func_call:
		if type(mycommand)==types.StringType:
			mycommand=mycommand.split()
		myc = mycommand[0]
		if not os.access(myc, os.X_OK):
			if not path_lookup:
				return None
			myc = find_binary(myc)
			if myc == None:
				return None
	mypid=[]
	if logfile:
		pr,pw=os.pipe()
		mypid.extend(spawn(('tee','-i','-a',logfile),returnpid=True,fd_pipes={0:pr,1:1,2:2}))
		retval=os.waitpid(mypid[-1],os.WNOHANG)[1]
		if retval != 0:
			# he's dead jim.
			if raw_exit_code:
				return retval
			return process_exit_code(retval)

		if fd_pipes == None:
			fd_pipes={}
			fd_pipes[0] = 0
		fd_pipes[1]=pw
		fd_pipes[2]=pw
		
	if not opt_name:
		opt_name = mycommand[0]
	myargs=[opt_name]
	myargs.extend(mycommand[1:])
	global spawned_pids
	mypid.append(os.fork())
	if mypid[-1] != 0:
		#log the bugger.
		spawned_pids.extend(mypid)

	if mypid[-1] == 0:
		if func_call:
			spawned_pids = []

		# this may look ugly, but basically it moves file descriptors around to ensure no
		# handles that are needed are accidentally closed during the final dup2 calls.
		trg_fd=[]
		if type(fd_pipes)==types.DictType:
			src_fd=[]
			k=fd_pipes.keys()
			k.sort()

			#build list of which fds will be where, and where they are at currently
			for x in k:
				trg_fd.append(x)
				src_fd.append(fd_pipes[x])

			# run through said list dup'ing descriptors so that they won't be waxed
			# by other dup calls.
			for x in range(0,len(trg_fd)):
				if trg_fd[x] == src_fd[x]:
					continue
				if trg_fd[x] in src_fd[x+1:]:
					new=os.dup2(trg_fd[x],max(src_fd) + 1)
					os.close(trg_fd[x])
					try:
						while True: 
							src_fd[s.index(trg_fd[x])]=new
					except SystemExit, e:
						raise
					except:
						pass

			# transfer the fds to their final pre-exec position.
			for x in range(0,len(trg_fd)):
				if trg_fd[x] != src_fd[x]:
					os.dup2(src_fd[x], trg_fd[x])
		else:
			trg_fd=[0,1,2]
	
		# wax all open descriptors that weren't requested be left open.
		for x in range(0,max_fd_limit):
			if x not in trg_fd:
				try: 
					os.close(x)
				except SystemExit, e:
					raise
				except:
					pass

		# note this order must be preserved- can't change gid/groups if you change uid first.
		if selinux_capable and selinux_context:
			import selinux
			selinux.setexec(selinux_context)
		if gid:
			os.setgid(gid)
		if groups:
			os.setgroups(groups)
		if uid:
			os.setuid(uid)
		if umask:
			os.umask(umask)

		try:
			#print "execing", myc, myargs
			if func_call:
				# either use a passed in func for interpretting the results, or return if no exception.
				# note the passed in list, and dict are expanded.
				if len(mycommand) == 4:
					os._exit(mycommand[3](mycommand[0](*mycommand[1],**mycommand[2])))
				try:
					mycommand[0](*mycommand[1],**mycommand[2])
				except Exception,e:
					print "caught exception",e," in forked func",mycommand[0]
				sys.exit(0)

			os.execve(myc,myargs,env)
		except SystemExit, e:
			raise
		except Exception, e:
			if not func_call:
				raise str(e)+":\n   "+myc+" "+string.join(myargs)
			print "func call failed"

		# If the execve fails, we need to report it, and exit
		# *carefully* --- report error here
		os._exit(1)
		sys.exit(1)
		return # should never get reached

	# if we were logging, kill the pipes.
	if logfile:
		os.close(pr)
		os.close(pw)
	
	if returnpid:
		return mypid

	# loop through pids (typically one, unless logging), either waiting on their death, or waxing them
	# if the main pid (mycommand) returned badly.
	while len(mypid):
		retval=os.waitpid(mypid[-1],0)[1]
		if retval != 0:
			cleanup(mypid[0:-1],block_exceptions=False)
			# at this point we've killed all other kid pids generated via this call.
			# return now.			
			if raw_exit_code:
				return retval
			return process_exit_code(retval,throw_signals=raise_signals)
		else:
			mypid.pop(-1)
	cleanup(mypid)
	return 0

def process_exit_code(retval,throw_signals=False):
	"""process a waitpid returned exit code, returning exit code if it exit'd, or the
	signal if it died from signalling
	if throw_signals is on, it raises a SystemExit if the process was signaled.
	This is intended for usage with threads, although at the moment you can't signal individual
	threads in python, only the master thread, so it's a questionable option."""
	if (retval & 0xff)==0:
		return retval >> 8 # return exit code
	else:
		if throw_signals:
			#use systemexit, since portage is stupid about exception catching.
			raise SystemExit()
		return (retval & 0xff) << 8 # interrupted by signal

def spawn_get_output(mycommand,spawn_type=spawn,raw_exit_code=False,emulate_gso=True, \
	collect_fds=[1],fd_pipes=None,**keywords):
	"""call spawn, collecting the output to fd's specified in collect_fds list
	emulate_gso is a compatability hack to emulate commands.getstatusoutput's return, minus the 
	requirement it always be a bash call (spawn_type controls the actual spawn call), and minus the
	'lets let log only stdin and let stderr slide by'.
	
	emulate_gso was deprecated from the day it was added, so convert your code over.
	spawn_type is the passed in function to call- typically spawn_bash, spawn, spawn_sandbox, or spawn_fakeroot"""
	global selinux_capable
	pr,pw=os.pipe()

	if type(spawn_type) not in [types.FunctionType, types.MethodType]:
		s="spawn_type must be passed a function, not",type(spawn_type),spawn_type
		raise Exception,s

	if fd_pipes==None:
		fd_pipes={}
		fd_pipes[0] = 0

	for x in collect_fds:
		fd_pipes[x] = pw
	keywords["returnpid"]=True

	mypid=spawn_type(mycommand,fd_pipes=fd_pipes,**keywords)
	os.close(pw)
	if type(mypid) != types.ListType:
		os.close(pr)
		return [mypid, "%s: No such file or directory" % mycommand.split()[0]]

	fd=os.fdopen(pr,"r")
	mydata=fd.readlines()
	fd.close()
	if emulate_gso:
		mydata=string.join(mydata)
		if len(mydata) and mydata[-1] == "\n":
			mydata=mydata[:-1]
	retval=os.waitpid(mypid[0],0)[1]
	cleanup(mypid)
	if raw_exit_code:
		return [retval,mydata]
	retval=process_exit_code(retval)
	return [retval, mydata]

def spawn_fakeroot(mycommand, save_file, env={}, opt_name=None,**keywords):
	"""spawn a fakerooted process, saving/loading from save_file"""
	if opt_name == None:
		opt_name = "fakeroot %s" % mycommand
	myc=[portage_const.FAKEROOT_PATH,"-u","-b","20","-s","%s" % save_file]
	if not save_file:
		import traceback
		traceback.print_stack()
		print "save_file=",save_file
		print "this is invalid"
		sys.exit(1)

	if os.path.exists(save_file):
		myc.extend(["-i","%s" % save_file])
	myc.extend(["--"])
	mycl = mycommand.split()
	if not os.path.exists(mycl[0]):
		mycl[0] = find_binary(mycl[0])
		if mycl[0] == None:
			return None
	myc.extend(mycl)
	return spawn(myc,env=env,opt_name=opt_name,**keywords)

if os.path.exists(portage_const.FAKEROOT_PATH):
	r,s=spawn_get_output((portage_const.FAKEROOT_PATH, "--version"),emulate_gso=False,
		fd_pipes={1:1,2:2})
	if r == 0:
		if len(s) == 1 and "version 1." in s[0]:
			fakeroot_capable = True
		else:
			print "fakeroot not available, need at least version 1.0"