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Bindmount files instead of hardlinking or copying to chroot

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16591eb3cc (diff-19f999107b609d37cfb22c58e7f0bc1cf76edf1180e238dd6389e03cc279b604) (2013) added support for files to doBind

This is work towards allowing users to change the location of chrootRootDir, to, for example, a tmpfs.

inspired by trofi on matrix

> It looks like build sandbox created by nix-daemon runs on the same filesystem, as /nix/store including things like /tmp which makes all small temporary files hit the disk. Is it intentional? If it is is there an easy way to redirect chroot's root to be tmpfs?

dirsInChroot -> pathsInChroot
This commit is contained in:
Artturin 2023-09-11 00:19:21 +03:00
parent b99fdcf8db
commit 5649229394
2 changed files with 23 additions and 45 deletions
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64
src/libstore/build/local-derivation-goal.cc
View file

@ -581,7 +581,7 @@ void LocalDerivationGoal::startBuilder()
/* Allow a user-configurable set of directories from the /* Allow a user-configurable set of directories from the
host file system. */ host file system. */
dirsInChroot.clear(); pathsInChroot.clear();
for (auto i : settings.sandboxPaths.get()) { for (auto i : settings.sandboxPaths.get()) {
if (i.empty()) continue; if (i.empty()) continue;
@ -592,19 +592,19 @@ void LocalDerivationGoal::startBuilder()
} }
size_t p = i.find('='); size_t p = i.find('=');
if (p == std::string::npos) if (p == std::string::npos)
dirsInChroot[i] = {i, optional}; pathsInChroot[i] = {i, optional};
else else
dirsInChroot[i.substr(0, p)] = {i.substr(p + 1), optional}; pathsInChroot[i.substr(0, p)] = {i.substr(p + 1), optional};
} }
if (hasPrefix(worker.store.storeDir, tmpDirInSandbox)) if (hasPrefix(worker.store.storeDir, tmpDirInSandbox))
{ {
throw Error("`sandbox-build-dir` must not contain the storeDir"); throw Error("`sandbox-build-dir` must not contain the storeDir");
} }
dirsInChroot[tmpDirInSandbox] = tmpDir; pathsInChroot[tmpDirInSandbox] = tmpDir;
/* Add the closure of store paths to the chroot. */ /* Add the closure of store paths to the chroot. */
StorePathSet closure; StorePathSet closure;
for (auto & i : dirsInChroot) for (auto & i : pathsInChroot)
try { try {
if (worker.store.isInStore(i.second.source)) if (worker.store.isInStore(i.second.source))
worker.store.computeFSClosure(worker.store.toStorePath(i.second.source).first, closure); worker.store.computeFSClosure(worker.store.toStorePath(i.second.source).first, closure);
@ -615,7 +615,7 @@ void LocalDerivationGoal::startBuilder()
} }
for (auto & i : closure) { for (auto & i : closure) {
auto p = worker.store.printStorePath(i); auto p = worker.store.printStorePath(i);
dirsInChroot.insert_or_assign(p, p); pathsInChroot.insert_or_assign(p, p);
} }
PathSet allowedPaths = settings.allowedImpureHostPrefixes; PathSet allowedPaths = settings.allowedImpureHostPrefixes;
@ -643,7 +643,7 @@ void LocalDerivationGoal::startBuilder()
/* Allow files in __impureHostDeps to be missing; e.g. /* Allow files in __impureHostDeps to be missing; e.g.
macOS 11+ has no /usr/lib/libSystem*.dylib */ macOS 11+ has no /usr/lib/libSystem*.dylib */
dirsInChroot[i] = {i, true}; pathsInChroot[i] = {i, true};
} }
#if __linux__ #if __linux__
@ -711,15 +711,12 @@ void LocalDerivationGoal::startBuilder()
for (auto & i : inputPaths) { for (auto & i : inputPaths) {
auto p = worker.store.printStorePath(i); auto p = worker.store.printStorePath(i);
Path r = worker.store.toRealPath(p); Path r = worker.store.toRealPath(p);
if (S_ISDIR(lstat(r).st_mode)) pathsInChroot.insert_or_assign(p, r);
dirsInChroot.insert_or_assign(p, r);
else
linkOrCopy(r, chrootRootDir + p);
} }
/* If we're repairing, checking or rebuilding part of a /* If we're repairing, checking or rebuilding part of a
multiple-outputs derivation, it's possible that we're multiple-outputs derivation, it's possible that we're
rebuilding a path that is in settings.dirsInChroot rebuilding a path that is in settings.sandbox-paths
(typically the dependencies of /bin/sh). Throw them (typically the dependencies of /bin/sh). Throw them
out. */ out. */
for (auto & i : drv->outputsAndOptPaths(worker.store)) { for (auto & i : drv->outputsAndOptPaths(worker.store)) {
@ -729,7 +726,7 @@ void LocalDerivationGoal::startBuilder()
is already in the sandbox, so we don't need to worry about is already in the sandbox, so we don't need to worry about
removing it. */ removing it. */
if (i.second.second) if (i.second.second)
dirsInChroot.erase(worker.store.printStorePath(*i.second.second)); pathsInChroot.erase(worker.store.printStorePath(*i.second.second));
} }
if (cgroup) { if (cgroup) {
@ -787,9 +784,9 @@ void LocalDerivationGoal::startBuilder()
} else { } else {
auto p = line.find('='); auto p = line.find('=');
if (p == std::string::npos) if (p == std::string::npos)
dirsInChroot[line] = line; pathsInChroot[line] = line;
else else
dirsInChroot[line.substr(0, p)] = line.substr(p + 1); pathsInChroot[line.substr(0, p)] = line.substr(p + 1);
} }
} }
} }
@ -1779,7 +1776,7 @@ void LocalDerivationGoal::runChild()
/* Set up a nearly empty /dev, unless the user asked to /* Set up a nearly empty /dev, unless the user asked to
bind-mount the host /dev. */ bind-mount the host /dev. */
Strings ss; Strings ss;
if (dirsInChroot.find("/dev") == dirsInChroot.end()) { if (pathsInChroot.find("/dev") == pathsInChroot.end()) {
createDirs(chrootRootDir + "/dev/shm"); createDirs(chrootRootDir + "/dev/shm");
createDirs(chrootRootDir + "/dev/pts"); createDirs(chrootRootDir + "/dev/pts");
ss.push_back("/dev/full"); ss.push_back("/dev/full");
@ -1814,34 +1811,15 @@ void LocalDerivationGoal::runChild()
ss.push_back(path); ss.push_back(path);
if (settings.caFile != "") if (settings.caFile != "")
dirsInChroot.try_emplace("/etc/ssl/certs/ca-certificates.crt", settings.caFile, true); pathsInChroot.try_emplace("/etc/ssl/certs/ca-certificates.crt", settings.caFile, true);
} }
for (auto & i : ss) dirsInChroot.emplace(i, i); for (auto & i : ss) pathsInChroot.emplace(i, i);
/* Bind-mount all the directories from the "host" /* Bind-mount all the directories from the "host"
filesystem that we want in the chroot filesystem that we want in the chroot
environment. */ environment. */
auto doBind = [&](const Path & source, const Path & target, bool optional = false) { for (auto & i : pathsInChroot) {
debug("bind mounting '%1%' to '%2%'", source, target);
struct stat st;
if (stat(source.c_str(), &st) == -1) {
if (optional && errno == ENOENT)
return;
else
throw SysError("getting attributes of path '%1%'", source);
}
if (S_ISDIR(st.st_mode))
createDirs(target);
else {
createDirs(dirOf(target));
writeFile(target, "");
}
if (mount(source.c_str(), target.c_str(), "", MS_BIND | MS_REC, 0) == -1)
throw SysError("bind mount from '%1%' to '%2%' failed", source, target);
};
for (auto & i : dirsInChroot) {
if (i.second.source == "/proc") continue; // backwards compatibility if (i.second.source == "/proc") continue; // backwards compatibility
#if HAVE_EMBEDDED_SANDBOX_SHELL #if HAVE_EMBEDDED_SANDBOX_SHELL
@ -1882,7 +1860,7 @@ void LocalDerivationGoal::runChild()
if /dev/ptx/ptmx exists). */ if /dev/ptx/ptmx exists). */
if (pathExists("/dev/pts/ptmx") && if (pathExists("/dev/pts/ptmx") &&
!pathExists(chrootRootDir + "/dev/ptmx") !pathExists(chrootRootDir + "/dev/ptmx")
&& !dirsInChroot.count("/dev/pts")) && !pathsInChroot.count("/dev/pts"))
{ {
if (mount("none", (chrootRootDir + "/dev/pts").c_str(), "devpts", 0, "newinstance,mode=0620") == 0) if (mount("none", (chrootRootDir + "/dev/pts").c_str(), "devpts", 0, "newinstance,mode=0620") == 0)
{ {
@ -2017,7 +1995,7 @@ void LocalDerivationGoal::runChild()
/* We build the ancestry before adding all inputPaths to the store because we know they'll /* We build the ancestry before adding all inputPaths to the store because we know they'll
all have the same parents (the store), and there might be lots of inputs. This isn't all have the same parents (the store), and there might be lots of inputs. This isn't
particularly efficient... I doubt it'll be a bottleneck in practice */ particularly efficient... I doubt it'll be a bottleneck in practice */
for (auto & i : dirsInChroot) { for (auto & i : pathsInChroot) {
Path cur = i.first; Path cur = i.first;
while (cur.compare("/") != 0) { while (cur.compare("/") != 0) {
cur = dirOf(cur); cur = dirOf(cur);
@ -2025,7 +2003,7 @@ void LocalDerivationGoal::runChild()
} }
} }
/* And we want the store in there regardless of how empty dirsInChroot. We include the innermost /* And we want the store in there regardless of how empty pathsInChroot. We include the innermost
path component this time, since it's typically /nix/store and we care about that. */ path component this time, since it's typically /nix/store and we care about that. */
Path cur = worker.store.storeDir; Path cur = worker.store.storeDir;
while (cur.compare("/") != 0) { while (cur.compare("/") != 0) {
@ -2036,7 +2014,7 @@ void LocalDerivationGoal::runChild()
/* Add all our input paths to the chroot */ /* Add all our input paths to the chroot */
for (auto & i : inputPaths) { for (auto & i : inputPaths) {
auto p = worker.store.printStorePath(i); auto p = worker.store.printStorePath(i);
dirsInChroot[p] = p; pathsInChroot[p] = p;
} }
/* Violations will go to the syslog if you set this. Unfortunately the destination does not appear to be configurable */ /* Violations will go to the syslog if you set this. Unfortunately the destination does not appear to be configurable */
@ -2067,7 +2045,7 @@ void LocalDerivationGoal::runChild()
without file-write* allowed, access() incorrectly returns EPERM without file-write* allowed, access() incorrectly returns EPERM
*/ */
sandboxProfile += "(allow file-read* file-write* process-exec\n"; sandboxProfile += "(allow file-read* file-write* process-exec\n";
for (auto & i : dirsInChroot) { for (auto & i : pathsInChroot) {
if (i.first != i.second.source) if (i.first != i.second.source)
throw Error( throw Error(
"can't map '%1%' to '%2%': mismatched impure paths not supported on Darwin", "can't map '%1%' to '%2%': mismatched impure paths not supported on Darwin",

4
src/libstore/build/local-derivation-goal.hh
View file

@ -86,8 +86,8 @@ struct LocalDerivationGoal : public DerivationGoal
: source(source), optional(optional) : source(source), optional(optional)
{ } { }
}; };
typedef map<Path, ChrootPath> DirsInChroot; // maps target path to source path typedef map<Path, ChrootPath> PathsInChroot; // maps target path to source path
DirsInChroot dirsInChroot; PathsInChroot pathsInChroot;
typedef map<std::string, std::string> Environment; typedef map<std::string, std::string> Environment;
Environment env; Environment env;