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filesystem: add flag to open files in a RAM

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On Linux, it uses memfd_create syscall that can be found on Linux 3.17 and
higher. By default memfds are executable, so we set MFD_NOEXEC_SEAL flag to
prevent execution at creation time.
This commit is contained in:
Alibek Omarov 2024-12-19 04:18:19 +03:00
parent 93c5853356
commit 3d60770b84
2 changed files with 50 additions and 15 deletions
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58
filesystem/filesystem.c
View file

@ -16,6 +16,8 @@ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
*/
#define _GNU_SOURCE 1
#include "build.h"
#include <fcntl.h>
#include <sys/types.h>
@ -32,6 +34,9 @@ GNU General Public License for more details.
#endif
#include <stdio.h>
#include <stdarg.h>
#if HAVE_MEMFD_CREATE
#include <sys/mman.h>
#endif
#include "port.h"
#include "defaults.h"
#include "const.h"
@ -1666,9 +1671,10 @@ Internal function used to create a file_t and open the relevant non-packed file
*/
file_t *FS_SysOpen( const char *filepath, const char *mode )
{
file_t *file;
int mod, opt;
uint ind;
file_t *file;
int mod, opt, fd = -1;
qboolean memfile = false;
uint ind;
// Parse the mode string
switch( mode[0] )
@ -1708,30 +1714,52 @@ file_t *FS_SysOpen( const char *filepath, const char *mode )
}
}
file = (file_t *)Mem_Calloc( fs_mempool, sizeof( *file ));
file->filetime = FS_SysFileTime( filepath );
file->ungetc = EOF;
// the 'm' flag let's user to create temporary file in memory
// through so-called "anonymous files"
if( Q_strchr( mode, 'm' ))
{
#if HAVE_MEMFD_CREATE
#ifndef MFD_NOEXEC_SEAL
#define MFD_NOEXEC_SEAL 8U
#endif
fd = memfd_create( filepath, MFD_CLOEXEC | MFD_NOEXEC_SEAL );
// through fcntl() and MFD_ALLOW_SEALING we could enforce
// read-write flags but we don't really care about them yet
if( fd < 0 )
Con_Printf( S_ERROR "%s: can't create anonymous file %s: %s", __func__, filepath, strerror( errno ));
else memfile = true;
#endif
// if it's unsupported, we can open it on disk
}
if( fd < 0 )
{
#if XASH_WIN32
file->handle = _wopen( FS_PathToWideChar( filepath ), mod | opt, 0666 );
fd = _wopen( FS_PathToWideChar( filepath ), mod | opt, 0666 );
#else
file->handle = open( filepath, mod|opt, 0666 );
fd = open( filepath, mod|opt, 0666 );
#endif
}
#if !XASH_WIN32
if( file->handle < 0 )
FS_BackupFileName( file, filepath, mod|opt );
#endif
if( file->handle < 0 )
if( fd < 0 )
{
if( errno != ENOENT )
Con_Printf( S_ERROR "%s: can't open file %s: %s\n", __func__, filepath, strerror( errno ));
Mem_Free( file );
return NULL;
}
file = (file_t *)Mem_Calloc( fs_mempool, sizeof( *file ));
file->filetime = memfile ? 0 : FS_SysFileTime( filepath );
file->ungetc = EOF;
file->handle = fd;
#if !XASH_WIN32
if( !memfile )
FS_BackupFileName( file, filepath, mod|opt );
#endif
file->searchpath = NULL;
file->real_length = lseek( file->handle, 0, SEEK_END );

7
filesystem/wscript
View file

@ -1,5 +1,9 @@
#!/usr/bin/env python
MEMFD_CREATE_TEST = '''#define _GNU_SOURCE
#include <sys/mman.h>
int main(int argc, char **argv) { return memfd_create(argv[0], 0); }'''
def options(opt):
pass
@ -11,6 +15,9 @@ def configure(conf):
elif conf.env.cxxshlib_PATTERN.startswith('lib'): # remove lib prefix for other systems than Android
conf.env.cxxshlib_PATTERN = conf.env.cxxshlib_PATTERN[3:]
if conf.check_cc(fragment=MEMFD_CREATE_TEST, msg='Checking for memfd_create', mandatory=False):
conf.define('HAVE_MEMFD_CREATE', 1)
def build(bld):
bld(name = 'filesystem_includes', export_includes = '.')