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/* -*- linux-c -*-
*
* ctl.c - staprun control channel
*
* This file is part of systemtap, and is free software. You can
* redistribute it and/or modify it under the terms of the GNU General
* Public License (GPL); either version 2, or (at your option) any
* later version.
*
* Copyright (C) 2012-2018 Red Hat Inc.
*/
#include "staprun.h"
#define CTL_CHANNEL_NAME ".cmd"
#ifndef HAVE_OPENAT
#error "need openat"
#endif
// This function does multiple things:
//
// 1) if needed, open the running module's directory (the one that
// contains .ctl), stash fd in relay_basedir_fd; this will be
// passed to stapio children via -F$fd for privilege passing
//
// 2) (re)open the running module's .ctl file, stash fd in the
// control_channel global; this will be used all over the place.
//
// Return 0 on success.
//
// See also PR14245, PR26665, RHBZ1902696 = PR23512
//
int init_ctl_channel(const char *name, int verb)
{
(void) verb;
// Already got them both?
if (control_channel >= 0 && relay_basedir_fd >= 0)
return 0;
// Need relay_basedir_fd .... ok try /sys/kernel/debug/systemtap/
if (relay_basedir_fd < 0) {
char buf[PATH_MAX] = "";
struct statfs st;
if (sprintf_chk(buf, "/sys/kernel/debug/systemtap/%s", name))
return -EINVAL;
if (statfs("/sys/kernel/debug", &st) == 0 && (int)st.f_type == (int)DEBUGFS_MAGIC)
relay_basedir_fd = open (buf, O_DIRECTORY | O_RDONLY);
}
// Still need relay_basedir_fd ... ok try /proc/systemtap/
if (relay_basedir_fd < 0) {
char buf[PATH_MAX] = "";
if (sprintf_chk(buf, "/proc/systemtap/%s", name))
return -EINVAL;
relay_basedir_fd = open (buf, O_DIRECTORY | O_RDONLY);
}
// Got relay_basedir_fd, need .ctl
if (relay_basedir_fd >= 0) {
// verify that the ctl file is accessible to our real uid/gid
if (faccessat(relay_basedir_fd, CTL_CHANNEL_NAME, R_OK|W_OK, 0) != 0)
return -EPERM;
control_channel = openat_cloexec(relay_basedir_fd,
CTL_CHANNEL_NAME, O_RDWR, 0);
}
// Fell through
if (relay_basedir_fd < 0 || control_channel < 0) {
err(_("Cannot attach to module %s control channel; not running?\n"),
name);
return -EINVAL;
}
return 0;
}
void close_ctl_channel(void)
{
if (control_channel >= 0) {
dbug(2, "Closed ctl fd %d\n", control_channel);
close(control_channel);
control_channel = -1;
}
}
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