shmcat Code

/*
 * shmcat: Dump System V Shared Memory Objects
 * (C) 2012 by Stefan Gast (sgdev@arcor.de)
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, write to the Free Software
 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * shmdumper.c: Implementation of the shared memory dumper
 */

#include "config.h"
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <limits.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <unistd.h>

#ifdef HAVE_INTTYPES_H
#include <inttypes.h>
#endif
#ifdef HAVE_STDINT_H
#include <stdint.h>
#endif

#include "shmdumper.h"
#include "translate.h"


static ShmcatStatus dumpShm(int id, int byKey, const char *param, const char *programName)
{
	struct shmid_ds infoBuffer;
	const char *shm;
	const char *shmpos;
	const char *shmend;
	int bytesWritten;

	/* Put the segment into our address space. We do this even before
	 * we query its size, to make sure the segment does not disappear
	 * (i.e. get deleted) between getting the size and attaching it. */
	shm = shmat(id, NULL, SHM_RDONLY);
	if(shm == (const char *)-1)
	{
		if(byKey)
			fprintf(stderr, _("%s: Cannot attach the shared memory segment with the key \"%s\": %s\n"),
					programName, param, strerror(errno));
		else
			fprintf(stderr, _("%s: Cannot attach the shared memory segment with the id \"%s\": %s\n"),
					programName, param, strerror(errno));
		return SHMCAT_ERROR;
	}

	/* Now we need to know how big our segment is. */
	if(shmctl(id, IPC_STAT, &infoBuffer) == -1)
	{
		shmdt(shm);

		if(byKey)
			fprintf(stderr, _("%s: Cannot determine the size of the shared memory segment with the key \"%s\": %s\n"),
					programName, param, strerror(errno));
		else
			fprintf(stderr, _("%s: Cannot determine the size of the shared memory segment with the id \"%s\": %s\n"),
					programName, param, strerror(errno));
		return SHMCAT_ERROR;
	}

	/* Set position and end pointer. */
	shmpos = shm;
	shmend = shm + infoBuffer.shm_segsz;

	/* If we have a huge shared memory segment, we have to be
	 * careful with the size we pass to write. Otherwise the ssize_t
	 * might overflow. So we do the huge chunks first with
	 * this special loop. */
	while((uintptr_t)shmend-(uintptr_t)shmpos > (uintptr_t)SSIZE_MAX)
	{
		bytesWritten = write(STDOUT_FILENO, shmpos, SSIZE_MAX);
		if(bytesWritten <= 0)
		{
			shmdt(shm);
			fprintf(stderr, _("%s: Error writing to standard output: %s\n"),
					programName, strerror(errno));
			return SHMCAT_PANIC;
		}
		else
			shmpos += bytesWritten;
	}

	/* Now dump the rest. */
	while(shmpos != shmend)
	{
		bytesWritten = write(STDOUT_FILENO, shmpos, shmend-shmpos);
		if(bytesWritten <= 0)
		{
			shmdt(shm);
			fprintf(stderr, _("%s: Error writing to standard output: %s\n"),
					programName, strerror(errno));
			return SHMCAT_PANIC;
		}
		else
			shmpos += bytesWritten;
	}

	shmdt(shm);
	return SHMCAT_OK;
}


ShmcatStatus dumpShmKey(const char *keystr, const char *programName)
{
	char *numEnd;
	unsigned long long key;
	int id;

	key = strtoull(keystr, &numEnd, 0);
	if(*numEnd != '\0')
	{
		fprintf(stderr, _("%s: Invalid shared memory key: %s\n"),
				programName, keystr);
		return SHMCAT_ERROR;
	}
	if(key == (unsigned long long)IPC_PRIVATE)
	{
		fprintf(stderr, _("%s: \"%s\" is the key for private shared memory segments! Try passing the segment by ID instead.\n"),
				programName, keystr);
		return SHMCAT_ERROR;
	}
	if((unsigned long long)(key_t)key != key)	/* simple overflow detection */
	{
		fprintf(stderr, _("%s: Invalid shared memory key: %s\n"),
				programName, keystr);
		return SHMCAT_ERROR;
	}

	id = shmget((key_t)key, 0, 0);
	if(id == -1)
	{
		fprintf(stderr, _("%s: Cannot open a shared memory segment with the key \"%s\": %s\n"),
				programName, keystr, strerror(errno));
		return SHMCAT_ERROR;
	}

	return dumpShm(id, 1, keystr, programName);
}


ShmcatStatus dumpShmId(const char *idstr, const char *programName)
{
	char *numEnd;
	unsigned long id;

	id = strtoul(idstr, &numEnd, 0);
	if(*numEnd != '\0' || id > (unsigned long)(INT_MAX))
	{
		fprintf(stderr, _("%s: Invalid shared memory id: %s\n"),
				programName, idstr);
		return SHMCAT_ERROR;
	}

	return dumpShm((int)id, 0, idstr, programName);
}