mmapobj - map a file object in the appropriate manner
#include <sys/mman.h>
int mmapobj(int fd, uint_t flags, mmapobj_result_t *storage,
uint_t *elements, void *arg);
fd
The open file descriptor for the file to be mapped.
flags
Indicates that the default behavior of
mmapobj()
should be modified accordingly. Available flags are:
MMOBJ_INTERPRET
Interpret the contents of the file descriptor instead of
just mapping it as a single image. This flag can be used only with ELF
and AOUT files.
MMOBJ_PADDING
When mapping in the file descriptor, add an additional
mapping before the lowest mapping and after the highest mapping. The size of
this padding is at least as large as the amount pointed to by arg.
These mappings will be private to the process, will not reserve any swap space
and will have no protections. To use this address space, the protections for
it will need to be changed. This padding request will be ignored for the
AOUT format.
storage
A pointer to the mmapobj_result_t array where the
mapping data will be copied out after a successful mapping of fd.
elements
A pointer to the number of mmapobj_result_t
elements pointed to by storage. On return, elements contains the
number of mappings required to fully map the requested object. If the original
value of elements is too small, E2BIG is returned and
elements is modified to contain the number of mappings necessary.
arg
A pointer to additional information that might be
associated with the specific request. Only the MMOBJ_PADDING request
uses this argument. If MMOBJ_PADDING is not specified, arg must
be NULL.
The mmapobj() function establishes a set of mappings between a process's
address space and a file. By default, mmapobj() maps the whole file as
a single, private, read-only mapping. The MMOBJ_INTERPRET flag
instructs mmapobj() to attempt to interpret the file and map the file
according to the rules for that file format. The following ELF and
AOUT formats are supported:
ET_EXEC and AOUT executables
This format results in one or more mappings whose size,
alignment and protections are as described by the file's program header
information. The address of each mapping is explicitly defined by the file's
program headers.
ET_DYN and AOUT shared objects
This format results in one or more mappings whose size,
alignment and protections are as described by the file's program header
information. The base address of the initial mapping is chosen by
mmapobj(). The addresses of adjacent mappings are based off of this
base address as defined by the file's program headers.
ET_REL and ET_CORE
This format results in a single, read-only mapping that
covers the whole file. The base address of this mapping is chosen by
mmapobj().
The mmapobj() function will not map over any currently used
mappings within the process, except for the case of an ELF ET_EXEC
file for which a previous reservation has been made via /dev/null.
The most common way to make such a reservation would be with an
mmap() of /dev/null.
Mappings created with mmapobj() can be processed
individually by other system calls such as munmap(2).
The mmapobj_result structure contains the following
members:
typedef struct mmapobj_result {
caddr_t mr_addr; /* mapping address */
size_t mr_msize; /* mapping size */
size_t mr_fsize; /* file size */
size_t mr_offset; /* offset into file */
uint_t mr_prot; /* the protections provided */
uint_t mr_flags; /* info on the mapping */
} mmapobj_result_t;
The macro MR_GET_TYPE(mr_flags) must be used when
looking for the above flags in the value of mr_flags.
Values for mr_flags include:
MR_PADDING 0x1 /* this mapping represents requested padding */
MR_HDR_ELF 0x2 /* the ELF header is mapped at mr_addr */
MR_HDR_AOU 0x3 /* the AOUT header is mapped at mr_addr */
When MR_PADDING is set, mr_fsize and
mr_offset will both be 0.
The mr_fsize member represents the amount of the file that
is mapped into memory with this mapping.
The mr_offset member is the offset into the mapping where
valid data begins.
The mr_msize member represents the size of the memory
mapping starting at mr_addr. This size may include unused data prior
to mr_offset that exists to satisfy the alignment requirements of
this segment. This size may also include any non-file data that are required
to provide NOBITS data (typically .bss). The system reserves
the right to map more than mr_msize bytes of memory but only
mr_msize bytes will be available to the caller of
mmapobj().
Upon successful completion, 0 is returned and elements contains the
number of program headers that are mapped for fd. The data describing
these elements are copied to storage such that the first elements
members of the storage array contain valid mapping data.
On failure, -1 is returned and errno is set to indicate the
error. No data is copied to storage.
The mmapobj() function will fail if:
E2BIG
The elements argument was not large enough to hold
the number of loadable segments in fd. The elements argument
will be modified to contain the number of segments required.
EACCES
The file system containing the fd to be mapped
does not allow execute access, or the file descriptor pointed to by fd
is not open for reading.
EADDRINUSE
The mapping requirements overlap an object that is
already used by the process.
EAGAIN
There is insufficient room to reserve swap space for the
mapping.
The file to be mapped is already locked using advisory or
mandatory record locking. See fcntl(2).
EBADF
The fd argument is not a valid open file
descriptor.
EFAULT
The storage, arg, or elements
argument points to an invalid address.
EINVAL
The
flags argument contains an invalid flag.
MMOBJ_PADDING was not specified in flags and
arg was non-null.
ENODEV
The fd argument refers to an object for which
mmapobj() is meaningless, such as a terminal.
ENOMEM
Insufficient memory is available to hold the program
headers.
Insufficient memory is available in the address space to create
the mapping.
ENOTSUP
The current user data model does not match the
fd
to be interpreted; thus, a 32-bit process that tried to use
mmapobj()
to interpret a 64-bit object would return
ENOTSUP.
The fd argument is a file whose type can not be interpreted
and MMOBJ_INTERPRET was specified in flags.
The ELF header contains an unaligned e_phentsize
value.
ENOSYS
An unsupported filesystem operation was attempted while
trying to map in the object.
See attributes(7) for descriptions of the following attributes:
| ATTRIBUTE
TYPE |
ATTRIBUTE VALUE |
| Interface Stability |
Private |
| MT-Level |
Async-Signal-Safe |
ld.so.1(1), fcntl(2), memcntl(2), mmap(2),
mprotect(2), munmap(2), madvise(3C), mlockall(3C),
msync(3C), elf(3ELF), a.out(5), attributes(7)
Linker and Libraries Guide