posix.h File Reference

#include <stdint.h>
#include <stdlib.h>
#include <stddef.h>
#include <stdio.h>
#include <sys/types.h>

Go to the source code of this file.

Macros
#define	PROT_READ   1
	POSIX mmap()/munmap() support for TARFS.
#define	PROT_WRITE   2
#define	PROT_EXEC   4
#define	MAP_FILE   0
#define	MAP_SHARED   1
#define	MAP_PRIVATE   2
#define	MAP_FIXED   4
#define	MAP_ANONYMOUS   8
#define	MAP_ANON   8
#define	MAP_FAILED   ((void *)(-1))

Functions
void *	mmap (void *addr, size_t length, int prot, int flags, int fd, off_t offset)
	Map a file into the process address space.
int	munmap (void *addr, size_t length)
	Remove a previously created memory mapping.

Macro Definition Documentation

MAP_ANON

#define MAP_ANON   8

Definition at line 38 of file posix.h.

MAP_ANONYMOUS

#define MAP_ANONYMOUS   8

Unsupported, use malloc() instead

Definition at line 37 of file posix.h.

Referenced by tarf_mmap().

MAP_FAILED

#define MAP_FAILED   ((void *)(-1))

Definition at line 41 of file posix.h.

Referenced by mmap(), and tarf_mmap().

MAP_FILE

#define MAP_FILE   0

Default flag is MAP_FILE, we do not support MAP_ANON, we always expect MAP_FILE

Definition at line 32 of file posix.h.

MAP_FIXED

#define MAP_FIXED   4

Ignored, no legit use for this flag :)

Definition at line 36 of file posix.h.

Referenced by tarf_mmap().

MAP_PRIVATE

#define MAP_PRIVATE   2

Supported

Definition at line 34 of file posix.h.

MAP_SHARED

#define MAP_SHARED   1

Supported

Definition at line 33 of file posix.h.

PROT_EXEC

#define PROT_EXEC   4

Ignored

Definition at line 30 of file posix.h.

Referenced by tarf_mmap().

PROT_READ

#define PROT_READ   1

POSIX mmap()/munmap() support for TARFS.

Default memory protection flag.

Definition at line 28 of file posix.h.

PROT_WRITE

#define PROT_WRITE   2

Ignored, if used together with PROT_READ. Alone causes mmap() error (RO filesystem!)

Definition at line 29 of file posix.h.

Referenced by tarf_mmap().

Function Documentation

mmap()

void * mmap	(	void *	addr,
		size_t	length,
		int	prot,
		int	flags,
		int	fd,
		off_t	offset )

Map a file into the process address space.

Subset of POSIX functions.

Typical usage:

int fd = open(...);
void *ptr = mmap(NULL, length, PROT_READ, flags, fd, offset);
close(fd);
 
// use ptr

The mapping remains valid after the file descriptor has been closed.

Since TARFS is a read-only filesystem, this implementation does not support the PROT_WRITE protection flag. MAP_ANONYMOUS is also not supported: mmap() is intended exclusively for mapping files.

There is no limit on the number of active mappings. Every file in TARFS may be mapped simultaneously, provided the underlying flash memory can hold it. Mappings do not consume any runtime resources. In contrast, each open file occupies one file descriptor until it is closed.

Parameters

addr	Must be NULL. Fixed-address mappings are not supported.
length	Number of bytes to map.
prot	Memory protection flags. Only PROT_READ is supported.
flags	Mapping flags. Use MAP_SHARED or MAP_PRIVATE. On a read-only filesystem both behave identically.
fd	Open file descriptor to map.
offset	File offset where the mapping begins.

Returns

Pointer to the mapped file data, or MAP_FAILED on error.

Map a file into the process address space.

Mimic POSIX mmap().

< Convert global fd number to local fd number. arg=&int

Definition at line 54 of file posix.c.

References ioctl_req::fd, FIOGETFD, ioctl_req::fs_idx, MAP_FAILED, and tarf_mmap().

munmap()

int munmap	(	void *	addr,
		size_t	length )

Remove a previously created memory mapping.

POSIX munmap().

Since mappings themselves do not allocate runtime resources, failing to call munmap() does not lead to resource leaks. However, an active mapping keeps the filesystem mounted, preventing it from being unmounted until the mapping is removed.

Parameters

addr	Address previously returned by mmap().
length	Length of the mapped region.

Returns

0 on success, or -1 on error.

Remove a previously created memory mapping.

< Max number of mounted TARFS filesystems

Definition at line 72 of file posix.c.

References tarfs_fs::fs_size, tarfs_fs::fs_vaddr, log, tarf_munmap(), tarfs_getfs(), tarfs_lock(), TARFS_MAX_FS, and tarfs_unlock().