# Copyright (C) 2016-2021 all contributors
# License: AGPL-3.0+
#
# This allows vfork to be used for spawning subprocesses if
# ~/.cache/public-inbox/inline-c is writable or if PERL_INLINE_DIRECTORY
# is explicitly defined in the environment (and writable).
# Under Linux, vfork can make a big difference in spawning performance
# as process size increases (fork still needs to mark pages for CoW use).
# Currently, we only use this for code intended for long running
# daemons (inside the PSGI code (-httpd) and -nntpd). The short-lived
# scripts (-mda, -index, -learn, -init) either use IPC::run or standard
# Perl routines.
#
# There'll probably be more OS-level C stuff here, down the line.
# We don't want too many DSOs: https://udrepper.livejournal.com/8790.html
package PublicInbox::Spawn;
use strict;
use parent qw(Exporter);
use Symbol qw(gensym);
use PublicInbox::ProcessPipe;
our @EXPORT_OK = qw(which spawn popen_rd run_die nodatacow_dir);
our @RLIMITS = qw(RLIMIT_CPU RLIMIT_CORE RLIMIT_DATA);
my $all_libc = <<'ALL_LIBC'; # all *nix systems we support
#include
#include
#include
#include
#include
#include
#include
#include
/* some platforms need alloca.h, but some don't */
#if defined(__GNUC__) && !defined(alloca)
# define alloca(sz) __builtin_alloca(sz)
#endif
#include
#include
/*
* From the av_len apidoc:
* Note that, unlike what the name implies, it returns
* the highest index in the array, so to get the size of
* the array you need to use "av_len(av) + 1".
* This is unlike "sv_len", which returns what you would expect.
*/
#define AV2C_COPY(dst, src) do { \
I32 i; \
I32 top_index = av_len(src); \
I32 real_len = top_index + 1; \
I32 capa = real_len + 1; \
dst = alloca(capa * sizeof(char *)); \
for (i = 0; i < real_len; i++) { \
SV **sv = av_fetch(src, i, 0); \
dst[i] = SvPV_nolen(*sv); \
} \
dst[real_len] = 0; \
} while (0)
/* needs to be safe inside a vfork'ed process */
static void exit_err(const char *fn, volatile int *cerrnum)
{
*cerrnum = errno;
write(2, fn, strlen(fn));
_exit(1);
}
/*
* unstable internal API. It'll be updated depending on
* whatever we'll need in the future.
* Be sure to update PublicInbox::SpawnPP if this changes
*/
int pi_fork_exec(SV *redirref, SV *file, SV *cmdref, SV *envref, SV *rlimref,
const char *cd, int pgid)
{
AV *redir = (AV *)SvRV(redirref);
AV *cmd = (AV *)SvRV(cmdref);
AV *env = (AV *)SvRV(envref);
AV *rlim = (AV *)SvRV(rlimref);
const char *filename = SvPV_nolen(file);
pid_t pid;
char **argv, **envp;
sigset_t set, old;
int ret, perrnum;
volatile int cerrnum = 0; /* shared due to vfork */
int chld_is_member;
I32 max_fd = av_len(redir);
AV2C_COPY(argv, cmd);
AV2C_COPY(envp, env);
if (sigfillset(&set)) return -1;
if (sigprocmask(SIG_SETMASK, &set, &old)) return -1;
chld_is_member = sigismember(&old, SIGCHLD);
if (chld_is_member < 0) return -1;
if (chld_is_member > 0)
sigdelset(&old, SIGCHLD);
pid = vfork();
if (pid == 0) {
int sig;
I32 i, child_fd, max_rlim;
for (child_fd = 0; child_fd <= max_fd; child_fd++) {
SV **parent = av_fetch(redir, child_fd, 0);
int parent_fd = SvIV(*parent);
if (parent_fd == child_fd)
continue;
if (dup2(parent_fd, child_fd) < 0)
exit_err("dup2", &cerrnum);
}
if (pgid >= 0 && setpgid(0, pgid) < 0)
exit_err("setpgid", &cerrnum);
for (sig = 1; sig < NSIG; sig++)
signal(sig, SIG_DFL); /* ignore errors on signals */
if (*cd && chdir(cd) < 0)
exit_err("chdir", &cerrnum);
max_rlim = av_len(rlim);
for (i = 0; i < max_rlim; i += 3) {
struct rlimit rl;
SV **res = av_fetch(rlim, i, 0);
SV **soft = av_fetch(rlim, i + 1, 0);
SV **hard = av_fetch(rlim, i + 2, 0);
rl.rlim_cur = SvIV(*soft);
rl.rlim_max = SvIV(*hard);
if (setrlimit(SvIV(*res), &rl) < 0)
exit_err("setrlimit", &cerrnum);
}
(void)sigprocmask(SIG_SETMASK, &old, NULL);
execve(filename, argv, envp);
exit_err("execve", &cerrnum);
}
perrnum = errno;
if (chld_is_member > 0)
sigaddset(&old, SIGCHLD);
ret = sigprocmask(SIG_SETMASK, &old, NULL);
assert(ret == 0 && "BUG calling sigprocmask to restore");
if (cerrnum) {
int err_fd = STDERR_FILENO;
if (err_fd <= max_fd) {
SV **parent = av_fetch(redir, err_fd, 0);
err_fd = SvIV(*parent);
}
if (pid > 0)
waitpid(pid, NULL, 0);
pid = -1;
/* continue message started by exit_err in child */
dprintf(err_fd, ": %s\n", strerror(cerrnum));
errno = cerrnum;
} else if (perrnum) {
errno = perrnum;
}
return (int)pid;
}
#if defined(CMSG_SPACE) && defined(CMSG_LEN)
#define SEND_FD_CAPA 10
#define SEND_FD_SPACE (SEND_FD_CAPA * sizeof(int))
union my_cmsg {
struct cmsghdr hdr;
char pad[sizeof(struct cmsghdr) + 16 + SEND_FD_SPACE];
};
SV *send_cmd4(PerlIO *s, SV *svfds, SV *data, int flags)
{
struct msghdr msg = { 0 };
union my_cmsg cmsg = { 0 };
STRLEN dlen = 0;
struct iovec iov;
ssize_t sent;
AV *fds = (AV *)SvRV(svfds);
I32 i, nfds = av_len(fds) + 1;
int *fdp;
if (SvOK(data)) {
iov.iov_base = SvPV(data, dlen);
iov.iov_len = dlen;
}
if (!dlen) { /* must be non-zero */
iov.iov_base = &msg.msg_namelen; /* whatever */
iov.iov_len = 1;
}
msg.msg_iov = &iov;
msg.msg_iovlen = 1;
if (nfds) {
if (nfds > SEND_FD_CAPA) {
fprintf(stderr, "FIXME: bump SEND_FD_CAPA=%d\n", nfds);
nfds = SEND_FD_CAPA;
}
msg.msg_control = &cmsg.hdr;
msg.msg_controllen = CMSG_SPACE(nfds * sizeof(int));
cmsg.hdr.cmsg_level = SOL_SOCKET;
cmsg.hdr.cmsg_type = SCM_RIGHTS;
cmsg.hdr.cmsg_len = CMSG_LEN(nfds * sizeof(int));
fdp = (int *)CMSG_DATA(&cmsg.hdr);
for (i = 0; i < nfds; i++) {
SV **fd = av_fetch(fds, i, 0);
*fdp++ = SvIV(*fd);
}
}
sent = sendmsg(PerlIO_fileno(s), &msg, flags);
return sent >= 0 ? newSViv(sent) : &PL_sv_undef;
}
void recv_cmd4(PerlIO *s, SV *buf, STRLEN n)
{
union my_cmsg cmsg = { 0 };
struct msghdr msg = { 0 };
struct iovec iov;
ssize_t i;
Inline_Stack_Vars;
Inline_Stack_Reset;
if (!SvOK(buf))
sv_setpvn(buf, "", 0);
iov.iov_base = SvGROW(buf, n + 1);
iov.iov_len = n;
msg.msg_iov = &iov;
msg.msg_iovlen = 1;
msg.msg_control = &cmsg.hdr;
msg.msg_controllen = CMSG_SPACE(SEND_FD_SPACE);
i = recvmsg(PerlIO_fileno(s), &msg, 0);
if (i < 0)
Inline_Stack_Push(&PL_sv_undef);
else
SvCUR_set(buf, i);
if (i > 0 && cmsg.hdr.cmsg_level == SOL_SOCKET &&
cmsg.hdr.cmsg_type == SCM_RIGHTS) {
size_t len = cmsg.hdr.cmsg_len;
int *fdp = (int *)CMSG_DATA(&cmsg.hdr);
for (i = 0; CMSG_LEN((i + 1) * sizeof(int)) <= len; i++)
Inline_Stack_Push(sv_2mortal(newSViv(*fdp++)));
}
Inline_Stack_Done;
}
#endif /* defined(CMSG_SPACE) && defined(CMSG_LEN) */
ALL_LIBC
# btrfs on Linux is copy-on-write (COW) by default. As of Linux 5.7,
# this still leads to fragmentation for SQLite and Xapian files where
# random I/O happens, so we disable COW just for SQLite files and Xapian
# directories. Disabling COW disables checksumming, so we only do this
# for regeneratable files, and not canonical git storage (git doesn't
# checksum refs, only data under $GIT_DIR/objects).
my $set_nodatacow = $^O eq 'linux' ? <<'SET_NODATACOW' : '';
#include
#include
#include
#include
#include
#include
#include
#include
void nodatacow_fd(int fd)
{
struct statfs buf;
int val = 0;
if (fstatfs(fd, &buf) < 0) {
fprintf(stderr, "fstatfs: %s\\n", strerror(errno));
return;
}
/* only btrfs is known to have this problem, so skip for non-btrfs */
if (buf.f_type != BTRFS_SUPER_MAGIC)
return;
if (ioctl(fd, FS_IOC_GETFLAGS, &val) < 0) {
fprintf(stderr, "FS_IOC_GET_FLAGS: %s\\n", strerror(errno));
return;
}
val |= FS_NOCOW_FL;
if (ioctl(fd, FS_IOC_SETFLAGS, &val) < 0)
fprintf(stderr, "FS_IOC_SET_FLAGS: %s\\n", strerror(errno));
}
void nodatacow_dir(const char *dir)
{
DIR *dh = opendir(dir);
int fd;
if (!dh) croak("opendir(%s): %s", dir, strerror(errno));
fd = dirfd(dh);
if (fd >= 0)
nodatacow_fd(fd);
/* ENOTSUP probably won't happen under Linux... */
closedir(dh);
}
SET_NODATACOW
my $inline_dir = $ENV{PERL_INLINE_DIRECTORY} //= (
$ENV{XDG_CACHE_HOME} //
( ($ENV{HOME} // '/nonexistent').'/.cache' )
).'/public-inbox/inline-c';
$set_nodatacow = $all_libc = undef unless -d $inline_dir && -w _;
if (defined $all_libc) {
# Inline 0.64 or later has locking in multi-process env,
# but we support 0.5 on Debian wheezy
use Fcntl qw(:flock);
eval {
my $f = "$inline_dir/.public-inbox.lock";
open my $fh, '>', $f or die "failed to open $f: $!\n";
flock($fh, LOCK_EX) or die "LOCK_EX failed on $f: $!\n";
eval 'use Inline C => $all_libc.$set_nodatacow';
# . ', BUILD_NOISY => 1';
my $err = $@;
my $ndc_err;
if ($err && $set_nodatacow) { # missing Linux kernel headers
$ndc_err = $err;
undef $set_nodatacow;
eval 'use Inline C => $all_libc';
}
flock($fh, LOCK_UN) or die "LOCK_UN failed on $f: $!\n";
die $err if $err;
warn $ndc_err if $ndc_err;
};
if ($@) {
warn "Inline::C failed for vfork: $@\n";
$set_nodatacow = $all_libc = undef;
}
}
unless ($all_libc) {
require PublicInbox::SpawnPP;
*pi_fork_exec = \&PublicInbox::SpawnPP::pi_fork_exec
}
unless ($set_nodatacow) {
require PublicInbox::NDC_PP;
no warnings 'once';
*nodatacow_fd = \&PublicInbox::NDC_PP::nodatacow_fd;
*nodatacow_dir = \&PublicInbox::NDC_PP::nodatacow_dir;
}
undef $set_nodatacow;
undef $all_libc;
sub which ($) {
my ($file) = @_;
return $file if index($file, '/') >= 0;
for my $p (split(/:/, $ENV{PATH})) {
$p .= "/$file";
return $p if -x $p;
}
undef;
}
sub spawn ($;$$) {
my ($cmd, $env, $opts) = @_;
my $f = which($cmd->[0]) // die "$cmd->[0]: command not found\n";
my @env;
$opts ||= {};
my %env = (%ENV, $env ? %$env : ());
while (my ($k, $v) = each %env) {
push @env, "$k=$v" if defined($v);
}
my $redir = [];
for my $child_fd (0..2) {
my $parent_fd = $opts->{$child_fd};
if (defined($parent_fd) && $parent_fd !~ /\A[0-9]+\z/) {
my $fd = fileno($parent_fd) //
die "$parent_fd not an IO GLOB? $!";
$parent_fd = $fd;
}
$redir->[$child_fd] = $parent_fd // $child_fd;
}
my $rlim = [];
foreach my $l (@RLIMITS) {
my $v = $opts->{$l} // next;
my $r = eval "require BSD::Resource; BSD::Resource::$l();";
unless (defined $r) {
warn "$l undefined by BSD::Resource: $@\n";
next;
}
push @$rlim, $r, @$v;
}
my $cd = $opts->{'-C'} // ''; # undef => NULL mapping doesn't work?
my $pgid = $opts->{pgid} // -1;
my $pid = pi_fork_exec($redir, $f, $cmd, \@env, $rlim, $cd, $pgid);
die "fork_exec @$cmd failed: $!\n" unless $pid > 0;
$pid;
}
sub popen_rd {
my ($cmd, $env, $opt) = @_;
pipe(my ($r, $w)) or die "pipe: $!\n";
$opt ||= {};
$opt->{1} = fileno($w);
my $pid = spawn($cmd, $env, $opt);
return ($r, $pid) if wantarray;
my $ret = gensym;
tie *$ret, 'PublicInbox::ProcessPipe', $pid, $r, @$opt{qw(cb arg)};
$ret;
}
sub run_die ($;$$) {
my ($cmd, $env, $rdr) = @_;
my $pid = spawn($cmd, $env, $rdr);
waitpid($pid, 0) == $pid or die "@$cmd did not finish";
$? == 0 or die "@$cmd failed: \$?=$?\n";
}
1;