diff options
Diffstat (limited to 'src/libstore')
| -rw-r--r-- | src/libstore/build.cc | 89 |
1 files changed, 59 insertions, 30 deletions
diff --git a/src/libstore/build.cc b/src/libstore/build.cc index 08f44b392b00..d65e56482d77 100644 --- a/src/libstore/build.cc +++ b/src/libstore/build.cc @@ -1586,6 +1586,13 @@ void chmod_(const Path & path, mode_t mode) } +int childEntry(void * arg) +{ + ((DerivationGoal *) arg)->runChild(); + return 1; +} + + void DerivationGoal::startBuilder() { startNest(nest, lvlInfo, format( @@ -1902,11 +1909,58 @@ void DerivationGoal::startBuilder() builderOut.create(); /* Fork a child to build the package. */ - ProcessOptions options; - options.allowVfork = !buildUser.enabled(); - pid = startProcess([&]() { - runChild(); - }, options); + if (useChroot) { + /* Set up private namespaces for the build: + + - The PID namespace causes the build to start as PID 1. + Processes outside of the chroot are not visible to those + on the inside, but processes inside the chroot are + visible from the outside (though with different PIDs). + + - The private mount namespace ensures that all the bind + mounts we do will only show up in this process and its + children, and will disappear automatically when we're + done. + + - The private network namespace ensures that the builder + cannot talk to the outside world (or vice versa). It + only has a private loopback interface. + + - The IPC namespace prevents the builder from communicating + with outside processes using SysV IPC mechanisms (shared + memory, message queues, semaphores). It also ensures + that all IPC objects are destroyed when the builder + exits. + + - The UTS namespace ensures that builders see a hostname of + localhost rather than the actual hostname. + + We use a helper process to do the clone() to work around + clone() being broken in multi-threaded programs due to + at-fork handlers not being run. Note that we use + CLONE_PARENT to ensure that the real builder is parented to + us. + */ + Pid helper = startProcess([&]() { + char stack[32 * 1024]; + pid_t child = clone(childEntry, stack + sizeof(stack) - 8, + CLONE_NEWPID | CLONE_NEWNS | CLONE_NEWNET | CLONE_NEWIPC | CLONE_NEWUTS | CLONE_PARENT | SIGCHLD, this); + if (child == -1) throw SysError("cloning builder process"); + writeFull(builderOut.writeSide, int2String(child) + "\n"); + _exit(0); + }); + if (helper.wait(true) != 0) + throw Error("unable to start build process"); + pid_t tmp; + if (!string2Int<pid_t>(readLine(builderOut.readSide), tmp)) abort(); + pid = tmp; + } else { + ProcessOptions options; + options.allowVfork = !buildUser.enabled(); + pid = startProcess([&]() { + runChild(); + }, options); + } /* parent */ pid.setSeparatePG(true); @@ -1922,7 +1976,6 @@ void DerivationGoal::startBuilder() printMsg(lvlError, format("@ build-started %1% - %2% %3%") % drvPath % drv.platform % logFile); } - } @@ -1938,30 +1991,6 @@ void DerivationGoal::runChild() #if CHROOT_ENABLED if (useChroot) { - /* Set up private namespaces for the build: - - - The private mount namespace ensures that all the bind - mounts we do will only show up in this process and - its children, and will disappear automatically when - we're done. - - - The private network namespace ensures that the - builder cannot talk to the outside world (or vice - versa). It only has a private loopback interface. - - - The IPC namespace prevents the builder from - communicating with outside processes using SysV IPC - mechanisms (shared memory, message queues, - semaphores). It also ensures that all IPC objects - are destroyed when the builder exits. - - - The UTS namespace ensures that builders see a - hostname of localhost rather than the actual - hostname. - */ - if (unshare(CLONE_NEWNS | CLONE_NEWNET | CLONE_NEWIPC | CLONE_NEWUTS) == -1) - throw SysError("setting up private namespaces"); - /* Initialise the loopback interface. */ AutoCloseFD fd(socket(PF_INET, SOCK_DGRAM, IPPROTO_IP)); if (fd == -1) throw SysError("cannot open IP socket"); |