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/* -*- c++ -*- */
/*
* Copyright 2003,2013 Free Software Foundation, Inc.
*
* This file is part of GNU Radio
*
* SPDX-License-Identifier: GPL-3.0-or-later
*
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include "vmcircbuf_sysv_shm.h"
#include <assert.h>
#include <fcntl.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdexcept>
#ifdef HAVE_SYS_IPC_H
#include <sys/ipc.h>
#endif
#ifdef HAVE_SYS_SHM_H
#include <sys/shm.h>
#endif
#include "pagesize.h"
#include <errno.h>
#include <stdio.h>
#define MAX_SYSV_SHM_ATTEMPTS 3
namespace gr {
vmcircbuf_sysv_shm::vmcircbuf_sysv_shm(int size) : gr::vmcircbuf(size)
{
#if !defined(HAVE_SYS_SHM_H)
GR_LOG_ERROR(d_logger, "sysv shared memory is not available");
throw std::runtime_error("gr::vmcircbuf_sysv_shm");
#else
gr::thread::scoped_lock guard(s_vm_mutex);
int pagesize = gr::pagesize();
if (size <= 0 || (size % pagesize) != 0) {
GR_LOG_ERROR(d_logger, boost::format("invalid size = %d") % size);
throw std::runtime_error("gr::vmcircbuf_sysv_shm");
}
// Attempt to allocate buffers (handle bad_alloc errors)
int attempts_remain(MAX_SYSV_SHM_ATTEMPTS);
while (attempts_remain-- > 0) {
int shmid_guard = -1;
int shmid1 = -1;
int shmid2 = -1;
// We use this as a guard page. We'll map it read-only on both ends of the
// buffer. Ideally we'd map it no access, but I don't think that's possible with
// SysV
if ((shmid_guard = shmget(IPC_PRIVATE, pagesize, IPC_CREAT | 0400)) == -1) {
GR_LOG_ERROR(d_logger, boost::format("shmget (0): %s") % strerror(errno));
continue;
}
if ((shmid2 = shmget(IPC_PRIVATE, 2 * size + 2 * pagesize, IPC_CREAT | 0700)) ==
-1) {
GR_LOG_ERROR(d_logger, boost::format("shmget (1): %s") % strerror(errno));
shmctl(shmid_guard, IPC_RMID, 0);
continue;
}
if ((shmid1 = shmget(IPC_PRIVATE, size, IPC_CREAT | 0700)) == -1) {
GR_LOG_ERROR(d_logger, boost::format("shmget (2): %s") % strerror(errno));
shmctl(shmid_guard, IPC_RMID, 0);
shmctl(shmid2, IPC_RMID, 0);
continue;
}
void* first_copy = shmat(shmid2, 0, 0);
if (first_copy == (void*)-1) {
GR_LOG_ERROR(d_logger, boost::format("shmat (1): %s") % strerror(errno));
shmctl(shmid_guard, IPC_RMID, 0);
shmctl(shmid2, IPC_RMID, 0);
shmctl(shmid1, IPC_RMID, 0);
continue;
}
shmctl(shmid2, IPC_RMID, 0);
// There may be a race between our detach and attach.
//
// If the system allocates all shared memory segments at the same
// virtual addresses in all processes and if the system allocates
// some other segment to first_copy or first_copoy + size between
// our detach and attach, the attaches below could fail [I've never
// seen it fail for this reason].
shmdt(first_copy);
// first read-only guard page
if (shmat(shmid_guard, first_copy, SHM_RDONLY) == (void*)-1) {
GR_LOG_ERROR(d_logger, boost::format("shmat (2): %s") % strerror(errno));
shmctl(shmid_guard, IPC_RMID, 0);
shmctl(shmid1, IPC_RMID, 0);
continue;
}
// first copy
if (shmat(shmid1, (char*)first_copy + pagesize, 0) == (void*)-1) {
GR_LOG_ERROR(d_logger, boost::format("shmat (3): %s") % strerror(errno));
shmctl(shmid_guard, IPC_RMID, 0);
shmctl(shmid1, IPC_RMID, 0);
shmdt(first_copy);
continue;
}
// second copy
if (shmat(shmid1, (char*)first_copy + pagesize + size, 0) == (void*)-1) {
GR_LOG_ERROR(d_logger, boost::format("shmat (4): %s") % strerror(errno));
shmctl(shmid_guard, IPC_RMID, 0);
shmctl(shmid1, IPC_RMID, 0);
shmdt((char*)first_copy + pagesize);
continue;
}
// second read-only guard page
if (shmat(shmid_guard, (char*)first_copy + pagesize + 2 * size, SHM_RDONLY) ==
(void*)-1) {
GR_LOG_ERROR(d_logger, boost::format("shmat (5): %s") % strerror(errno));
shmctl(shmid_guard, IPC_RMID, 0);
shmctl(shmid1, IPC_RMID, 0);
shmdt(first_copy);
shmdt((char*)first_copy + pagesize);
shmdt((char*)first_copy + pagesize + size);
continue;
}
shmctl(shmid1, IPC_RMID, 0);
shmctl(shmid_guard, IPC_RMID, 0);
// Now remember the important stuff
d_base = (char*)first_copy + pagesize;
d_size = size;
break;
}
if (attempts_remain < 0) {
throw std::runtime_error("gr::vmcircbuf_sysv_shm");
}
#endif
}
vmcircbuf_sysv_shm::~vmcircbuf_sysv_shm()
{
#if defined(HAVE_SYS_SHM_H)
gr::thread::scoped_lock guard(s_vm_mutex);
if (shmdt(d_base - gr::pagesize()) == -1 || shmdt(d_base) == -1 ||
shmdt(d_base + d_size) == -1 || shmdt(d_base + 2 * d_size) == -1) {
GR_LOG_ERROR(d_logger, boost::format("shmdt (2): %s") % strerror(errno));
}
#endif
}
// ----------------------------------------------------------------
// The factory interface
// ----------------------------------------------------------------
gr::vmcircbuf_factory* vmcircbuf_sysv_shm_factory::s_the_factory = 0;
gr::vmcircbuf_factory* vmcircbuf_sysv_shm_factory::singleton()
{
if (s_the_factory)
return s_the_factory;
s_the_factory = new gr::vmcircbuf_sysv_shm_factory();
return s_the_factory;
}
int vmcircbuf_sysv_shm_factory::granularity() { return gr::pagesize(); }
gr::vmcircbuf* vmcircbuf_sysv_shm_factory::make(int size)
{
try {
return new vmcircbuf_sysv_shm(size);
} catch (...) {
return 0;
}
}
} /* namespace gr */
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