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gc: Find roots using libproc on Darwin

Browse source 
Previously, the garbage collector found runtime roots on Darwin by
shelling out to `lsof -n -w -F n` then parsing the result.
However, this requires an lsof binary and can be extremely slow.

The official Apple lsof returns in a reasonable amount of time,
about 250ms in my tests, but the lsof packaged in nixpkgs is quite slow,
taking about 40 seconds to run the command.

Using libproc directly is about the same speed as Apple lsof,
and allows us to reënable several tests that were disabled on Darwin.

Change-Id: Ifa0adda7984e13c15535693baba835aae79a3577
This commit is contained in:
Artemis Tosini 2024-03-29 20:29:44 -04:00 committed by Artemis Tosini
parent 5420b3afd6
commit c03de0df62
12 changed files with 341 additions and 34 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
src/libstore/local.mk
View file

@ -7,6 +7,8 @@ libstore_DIR := $(d)
libstore_SOURCES := $(wildcard $(d)/*.cc $(d)/builtins/*.cc $(d)/build/*.cc)
ifdef HOST_LINUX
libstore_SOURCES += $(d)/platform/linux.cc
else ifdef HOST_DARWIN
libstore_SOURCES += $(d)/platform/darwin.cc
else
libstore_SOURCES += $(d)/platform/fallback.cc
endif

3
src/libstore/meson.build
View file

@ -162,6 +162,9 @@ libstore_headers = files(
if host_machine.system() == 'linux'
libstore_sources += files('platform/linux.cc')
libstore_headers += files('platform/linux.hh')
elif host_machine.system() == 'darwin'
libstore_sources += files('platform/darwin.cc')
libstore_headers += files('platform/darwin.hh')
else
libstore_sources += files('platform/fallback.cc')
libstore_headers += files('platform/fallback.hh')

4
src/libstore/platform.cc
View file

@ -2,6 +2,8 @@
#if __linux__
#include "platform/linux.hh"
#elif __APPLE__
#include "platform/darwin.hh"
#else
#include "platform/fallback.hh"
#endif
@ -11,6 +13,8 @@ std::shared_ptr<LocalStore> LocalStore::makeLocalStore(const Params & params)
{
#if __linux__
return std::shared_ptr<LocalStore>(new LinuxLocalStore(params));
#elif __APPLE__
return std::shared_ptr<LocalStore>(new DarwinLocalStore(params));
#else
return std::shared_ptr<LocalStore>(new FallbackLocalStore(params));
#endif

223
src/libstore/platform/darwin.cc Normal file
View file

@ -0,0 +1,223 @@
#include "gc-store.hh"
#include "signals.hh"
#include "platform/darwin.hh"
#include "regex.hh"
#include <sys/proc_info.h>
#include <sys/sysctl.h>
#include <libproc.h>
#include <regex>
namespace nix {
void DarwinLocalStore::findPlatformRoots(UncheckedRoots & unchecked)
{
auto storePathRegex = regex::storePathRegex(storeDir);
std::vector<int> pids;
int pidBufSize = 1;
while (pidBufSize > pids.size() * sizeof(int)) {
// Reserve some extra size so we don't fail too much
pids.resize((pidBufSize + pidBufSize / 8) / sizeof(int));
pidBufSize = proc_listpids(PROC_ALL_PIDS, 0, pids.data(), pids.size() * sizeof(int));
if (pidBufSize <= 0) {
throw SysError("Listing PIDs");
}
}
pids.resize(pidBufSize / sizeof(int));
for (auto pid : pids) {
// It doesn't make sense to ask about the kernel
if (pid == 0) {
continue;
}
try {
// Process cwd/root directory
struct proc_vnodepathinfo vnodeInfo;
if (proc_pidinfo(pid, PROC_PIDVNODEPATHINFO, 0, &vnodeInfo, sizeof(vnodeInfo)) <= 0) {
throw SysError("Getting pid %1% working directory", pid);
}
unchecked[std::string(vnodeInfo.pvi_cdir.vip_path)].emplace(fmt("{libproc/%d/cwd}", pid)
);
unchecked[std::string(vnodeInfo.pvi_rdir.vip_path)].emplace(
fmt("{libproc/%d/rootdir}", pid)
);
// File descriptors
std::vector<struct proc_fdinfo> fds;
int fdBufSize = 1;
while (fdBufSize > fds.size() * sizeof(struct proc_fdinfo)) {
// Reserve some extra size so we don't fail too much
fds.resize((fdBufSize + fdBufSize / 8) / sizeof(struct proc_fdinfo));
fdBufSize = proc_pidinfo(
pid, PROC_PIDLISTFDS, 0, fds.data(), fds.size() * sizeof(struct proc_fdinfo)
);
if (fdBufSize <= 0) {
throw SysError("Listing pid %1% file descriptors", pid);
}
}
fds.resize(fdBufSize / sizeof(struct proc_fdinfo));
for (auto fd : fds) {
// By definition, only a vnode is on the filesystem
if (fd.proc_fdtype != PROX_FDTYPE_VNODE) {
continue;
}
struct vnode_fdinfowithpath fdInfo;
if (proc_pidfdinfo(
pid, fd.proc_fd, PROC_PIDFDVNODEPATHINFO, &fdInfo, sizeof(fdInfo)
)
<= 0)
{
// They probably just closed this fd, no need to cancel looking at ranges and
// arguments
if (errno == EBADF) {
continue;
}
throw SysError("Getting pid %1% fd %2% path", pid, fd.proc_fd);
}
unchecked[std::string(fdInfo.pvip.vip_path)].emplace(
fmt("{libproc/%d/fd/%d}", pid, fd.proc_fd)
);
}
// Regions (e.g. mmapped files, executables, shared libraries)
uint64_t nextAddr = 0;
while (true) {
// Seriously, what are you doing XNU?
// There's 3 flavors of PROC_PIDREGIONPATHINFO:
// * PROC_PIDREGIONPATHINFO includes all regions
// * PROC_PIDREGIONPATHINFO2 includes regions backed by a vnode
// * PROC_PIDREGIONPATHINFO3 includes regions backed by a vnode on a specified
// filesystem Only PROC_PIDREGIONPATHINFO is documented. Unfortunately, using it
// would make finding gcroots take about 100x as long and tests would fail from
// timeout. According to the Frida source code, PROC_PIDREGIONPATHINFO2 has been
// available since XNU 2782.1.97 in OS X 10.10
//
// 22 means PROC_PIDREGIONPATHINFO2
struct proc_regionwithpathinfo regionInfo;
if (proc_pidinfo(pid, 22, nextAddr, &regionInfo, sizeof(regionInfo)) <= 0) {
// PROC_PIDREGIONPATHINFO signals we're done with an error,
// so we're expected to hit this once per process
if (errno == ESRCH || errno == EINVAL) {
break;
}
throw SysError("Getting pid %1% region path", pid);
}
unchecked[std::string(regionInfo.prp_vip.vip_path)].emplace(
fmt("{libproc/%d/region}", pid)
);
nextAddr = regionInfo.prp_prinfo.pri_address + regionInfo.prp_prinfo.pri_size;
}
// Arguments and environment variables
// We can't read environment variables of binaries with entitlements unless
// nix has the `com.apple.private.read-environment-variables` entitlement or SIP is off
// We can read arguments for all applications though.
// Yes, it's a sysctl, the proc_info and sysctl APIs are mostly similar,
// but both have exclusive capabilities
int sysctlName[3] = {CTL_KERN, KERN_PROCARGS2, pid};
size_t argsSize = 0;
if (sysctl(sysctlName, 3, nullptr, &argsSize, nullptr, 0) < 0) {
throw SysError("Reading pid %1% arguments", pid);
}
std::vector<char> args(argsSize);
if (sysctl(sysctlName, 3, args.data(), &argsSize, nullptr, 0) < 0) {
throw SysError("Reading pid %1% arguments", pid);
}
if (argsSize < args.size()) {
args.resize(argsSize);
}
// We have these perfectly nice arguments, but have to ignore them because
// otherwise we'd see arguments to nix-store commands and
// `nix-store --delete /nix/store/whatever` would always fail
// First 4 bytes are an int of argc.
if (args.size() < sizeof(int)) {
continue;
}
auto argc = reinterpret_cast<int *>(args.data())[0];
auto argsIter = args.begin();
std::advance(argsIter, sizeof(int));
// Executable then argc args, each separated by some number of null bytes
for (int i = 0; argsIter != args.end() && i < argc + 1; i++) {
argsIter = std::find(argsIter, args.end(), '\0');
argsIter = std::find_if(argsIter, args.end(), [](char ch) { return ch != '\0'; });
}
if (argsIter != args.end()) {
auto env_end = std::sregex_iterator{};
for (auto i = std::sregex_iterator{argsIter, args.end(), storePathRegex};
i != env_end;
++i)
{
unchecked[i->str()].emplace(fmt("{libproc/%d/environ}", pid));
}
};
// Per-thread working directories
struct proc_taskallinfo taskAllInfo;
if (proc_pidinfo(pid, PROC_PIDTASKALLINFO, 0, &taskAllInfo, sizeof(taskAllInfo)) <= 0) {
throw SysError("Reading pid %1% tasks", pid);
}
// If the process doesn't have the per-thread cwd flag then we already have the
// process-wide cwd from PROC_PIDVNODEPATHINFO
if (taskAllInfo.pbsd.pbi_flags & PROC_FLAG_THCWD) {
std::vector<uint64_t> tids(taskAllInfo.ptinfo.pti_threadnum);
int tidBufSize = proc_pidinfo(
pid, PROC_PIDLISTTHREADS, 0, tids.data(), tids.size() * sizeof(uint64_t)
);
if (tidBufSize <= 0) {
throw SysError("Listing pid %1% threads", pid);
}
for (auto tid : tids) {
struct proc_threadwithpathinfo threadPathInfo;
if (proc_pidinfo(
pid,
PROC_PIDTHREADPATHINFO,
tid,
&threadPathInfo,
sizeof(threadPathInfo)
)
<= 0)
{
throw SysError("Reading pid %1% thread %2% cwd", pid, tid);
}
unchecked[std::string(threadPathInfo.pvip.vip_path)].emplace(
fmt("{libproc/%d/thread/%d/cwd}", pid, tid)
);
}
}
} catch (SysError & e) {
// ENOENT/ESRCH: Process no longer exists (proc_info)
// EINVAL: Process no longer exists (sysctl)
// EACCESS/EPERM: We don't have permission to read this field (proc_info)
// EIO: Kernel failed to read from target process memory during KERN_PROCARGS2 (sysctl)
if (errno == ENOENT || errno == ESRCH || errno == EINVAL || errno == EACCES
|| errno == EPERM || errno == EIO)
{
continue;
}
throw;
}
}
}
}

35
src/libstore/platform/darwin.hh Normal file
View file

@ -0,0 +1,35 @@
#pragma once
///@file
#include "gc-store.hh"
#include "local-store.hh"
namespace nix {
/**
* Darwin-specific implementation of LocalStore
*/
class DarwinLocalStore : public LocalStore
{
public:
DarwinLocalStore(const Params & params)
: StoreConfig(params)
, LocalFSStoreConfig(params)
, LocalStoreConfig(params)
, Store(params)
, LocalFSStore(params)
, LocalStore(params)
{
}
DarwinLocalStore(const std::string scheme, std::string path, const Params & params)
: DarwinLocalStore(params)
{
throw UnimplementedError("DarwinLocalStore");
}
private:
void findPlatformRoots(UncheckedRoots & unchecked) override;
};
}

10
src/libstore/platform/linux.cc
View file

@ -1,6 +1,7 @@
#include "gc-store.hh"
#include "signals.hh"
#include "platform/linux.hh"
#include "regex.hh"
#include <regex>
@ -26,12 +27,6 @@ static void readProcLink(const std::string & file, UncheckedRoots & roots)
}
}
static std::string quoteRegexChars(const std::string & raw)
{
static auto specialRegex = std::regex(R"([.^$\\*+?()\[\]{}|])");
return std::regex_replace(raw, specialRegex, R"(\$&)");
}
static void readFileRoots(const char * path, UncheckedRoots & roots)
{
try {
@ -50,8 +45,7 @@ void LinuxLocalStore::findPlatformRoots(UncheckedRoots & unchecked)
struct dirent * ent;
auto digitsRegex = std::regex(R"(^\d+$)");
auto mapRegex = std::regex(R"(^\s*\S+\s+\S+\s+\S+\s+\S+\s+\S+\s+(/\S+)\s*$)");
auto storePathRegex =
std::regex(quoteRegexChars(storeDir) + R"(/[0-9a-z]+[0-9a-zA-Z\+\-\._\?=]*)");
auto storePathRegex = regex::storePathRegex(storeDir);
while (errno = 0, ent = readdir(procDir.get())) {
checkInterrupt();
if (std::regex_match(ent->d_name, digitsRegex)) {

2
src/libutil/meson.build
View file

@ -22,6 +22,7 @@ libutil_sources = files(
'position.cc',
'print-elided.cc',
'references.cc',
'regex.cc',
'serialise.cc',
'shlex.cc',
'signals.cc',
@ -77,6 +78,7 @@ libutil_headers = files(
'ref.hh',
'references.hh',
'regex-combinators.hh',
'regex.hh',
'repair-flag.hh',
'serialise.hh',
'shlex.hh',

16
src/libutil/regex.cc Normal file
View file

@ -0,0 +1,16 @@
#include <string>
#include <regex>
namespace nix::regex {
std::string quoteRegexChars(const std::string & raw)
{
static auto specialRegex = std::regex(R"([.^$\\*+?()\[\]{}|])");
return std::regex_replace(raw, specialRegex, R"(\$&)");
}
std::regex storePathRegex(const std::string & storeDir)
{
return std::regex(quoteRegexChars(storeDir) + R"(/[0-9a-z]+[0-9a-zA-Z\+\-\._\?=]*)");
}
}

11
src/libutil/regex.hh Normal file
View file

@ -0,0 +1,11 @@
#pragma once
///@file
#include <string>
#include <regex>
namespace nix::regex {
std::string quoteRegexChars(const std::string & raw);
std::regex storePathRegex(const std::string & storeDir);
}

1
tests/functional/common/vars-and-functions.sh.in
View file

@ -24,7 +24,6 @@ if [[ -n $NIX_STORE ]]; then
export _NIX_TEST_NO_SANDBOX=1
fi
export _NIX_IN_TEST=$TEST_ROOT/shared
export _NIX_TEST_NO_LSOF=1
export NIX_REMOTE=${NIX_REMOTE_-}
unset NIX_PATH
export TEST_HOME=$TEST_ROOT/test-home

36
tests/functional/gc-runtime.nix
View file

@ -1,17 +1,29 @@
with import ./config.nix;
mkDerivation {
name = "gc-runtime";
builder =
# Test inline source file definitions.
builtins.toFile "builder.sh" ''
mkdir $out
{
environ = mkDerivation {
name = "gc-runtime-environ";
buildCommand = "mkdir $out; echo environ > $out/environ";
};
cat > $out/program <<EOF
#! ${shell}
sleep 10000
EOF
open = mkDerivation {
name = "gc-runtime-open";
buildCommand = "mkdir $out; echo open > $out/open";
};
chmod +x $out/program
'';
program = mkDerivation {
name = "gc-runtime-program";
builder =
# Test inline source file definitions.
builtins.toFile "builder.sh" ''
mkdir $out
cat > $out/program <<EOF
#! ${shell}
sleep 10000 < \$1
EOF
chmod +x $out/program
'';
};
}

32
tests/functional/gc-runtime.sh
View file

@ -1,38 +1,44 @@
source common.sh
case $system in
*linux*)
;;
*)
skipTest "Not running Linux";
esac
set -m # enable job control, needed for kill
profiles="$NIX_STATE_DIR"/profiles
rm -rf $profiles
nix-env -p $profiles/test -f ./gc-runtime.nix -i gc-runtime
nix-env -p $profiles/test -f ./gc-runtime.nix -i gc-runtime-{program,environ,open}
outPath=$(nix-env -p $profiles/test -q --no-name --out-path gc-runtime)
echo $outPath
programPath=$(nix-env -p $profiles/test -q --no-name --out-path gc-runtime-program)
environPath=$(nix-env -p $profiles/test -q --no-name --out-path gc-runtime-environ)
openPath=$(nix-env -p $profiles/test -q --no-name --out-path gc-runtime-open)
echo $programPath $environPath $openPath
echo "backgrounding program..."
$profiles/test/program &
export environPath
$profiles/test/program $openPath/open &
sleep 2 # hack - wait for the program to get started
child=$!
echo PID=$child
nix-env -p $profiles/test -e gc-runtime
nix-env -p $profiles/test -e gc-runtime-{program,environ,open}
nix-env -p $profiles/test --delete-generations old
nix-store --gc
kill -- -$child
if ! test -e $outPath; then
if ! test -e $programPath; then
echo "running program was garbage collected!"
exit 1
fi
if ! test -e $environPath; then
echo "file in environment variable was garbage collected!"
exit 1
fi
if ! test -e $openPath; then
echo "opened file was garbage collected!"
exit 1
fi
exit 0