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/*
* libhugetlbfs - Easy use of Linux hugepages
* Copyright (C) 2005-2006 David Gibson & Adam Litke, IBM Corporation.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public License
* as published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#define _GNU_SOURCE
#include <dlfcn.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <sys/types.h>
#include "libhugetlbfs_internal.h"
#include "hugetlbfs.h"
#include <sys/syscall.h>
#if defined(SYS_shmget) || defined(SYS_ipc)
#define HAVE_SHMGET_SYSCALL
#endif
#ifdef HAVE_SHMGET_SYSCALL
/*
* The calls to dlsym() and dlerror() in the shmget() wrapper below force
* a dependency on libdl.so. This does not work for static executables
* as the glibc dynamic library implementation does not automatically
* have static dl* function stubs linked into static executables.
*
* Work around this problem by adding a weak attribute to the declarations
* of dlsym() and dlerror(). (The declaration is otherwise the same as in
* <dlfcn.h>). This allows a static executable to be linked without -ldl.
* If &dlsym is NULL then this is a static executable and a call to the
* system shmget() may be performed without worry as there is no dynamic
* call chain.
*/
extern void *dlsym (void *__restrict __handle, __const char *__restrict __name)
__attribute__((weak)) __THROW __nonnull ((2));
extern char *dlerror (void) __attribute__((weak)) __THROW;
/* call syscall shmget through the generic syscall mechanism */
static int syscall_shmget(key_t key, size_t size, int shmflg)
{
#ifdef SYS_shmget
return syscall(SYS_shmget, key, size, shmflg);
#else
/*
* Some platforms do not have have a direct shmget syscall. Instead,
* all SysV IPC calls are funneled through the ipc() system call.
*
* ipc() is expected to only be used by libc implementors, so using
* it has not been smoothed out. There is no function declaration.
* The needed define for SHMGET is in linux/ipc.h, but that file
* also includes a conflicting definition of ipc_perm. So,
* just define the needed items here.
*
* When compiling -m32 on x86_64, the ipc glibc wrapper does not
* exist. Instead, just use SYS_ipc.
*
* The ipc system call below does not set the IPC_64 version flag
* with SHMGET because that would have required more private defines
* and the version number is not used for the SHMGET call.
*/
#define SHMGET 23
return syscall(SYS_ipc, SHMGET, key, size, shmflg, (void *)NULL, 0L);
#endif
}
#endif /* HAVE_SHMGET_SYSCALL */
int shmget(key_t key, size_t size, int shmflg)
{
static int (*real_shmget)(key_t key, size_t size, int shmflg) = NULL;
char *error;
int retval;
size_t aligned_size = size;
DEBUG("hugetlb_shmem: entering overridden shmget() call\n");
/* Get a handle to the "real" shmget system call */
if (!real_shmget) {
#ifdef HAVE_SHMGET_SYSCALL
if (&dlsym == NULL) {
/* in a static executable, call shmget directly */
real_shmget = syscall_shmget;
} else
#endif /* HAVE_SHMGET_SYSCALL */
{
real_shmget = dlsym(RTLD_NEXT, "shmget");
if ((error = dlerror()) != NULL) {
ERROR("%s", error);
return -1;
}
}
}
/* Align the size and set SHM_HUGETLB on request */
if (__hugetlb_opts.shm_enabled) {
/*
* Use /proc/meminfo because shm always uses the system
* default huge page size.
*/
long hpage_size = kernel_default_hugepage_size();
aligned_size = ALIGN(size, hpage_size);
if (size != aligned_size) {
DEBUG("hugetlb_shmem: size growth align %zd -> %zd\n",
size, aligned_size);
}
INFO("hugetlb_shmem: Adding SHM_HUGETLB flag\n");
shmflg |= SHM_HUGETLB;
} else {
DEBUG("hugetlb_shmem: shmget override not requested\n");
}
/* Call the "real" shmget. If hugepages fail, use small pages */
retval = real_shmget(key, aligned_size, shmflg);
if (retval == -1 && __hugetlb_opts.shm_enabled) {
WARNING("While overriding shmget(%zd) to add SHM_HUGETLB: %s\n",
aligned_size, strerror(errno));
shmflg &= ~SHM_HUGETLB;
retval = real_shmget(key, size, shmflg);
WARNING("Using small pages for shmget despite HUGETLB_SHM\n");
}
return retval;
}
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