iofunc_mmap()
Handle an _IO_MMAP message
Synopsis:
#include <sys/iofunc.h> int iofunc_mmap ( resmgr_context_t * hdr, io_mmap_t * msg, iofunc_ocb_t * ocb, iofunc_attr_t * attr );
Arguments:
- hdr
- A pointer to a resmgr_context_t structure that the resource-manager library uses to pass context information between functions.
- msg
- A pointer to the io_mmap_t structure that contains the message that the resource manager received; see below.
- ocb
- A pointer to the iofunc_ocb_t structure for the Open Control Block that was created when the client opened the resource.
- attr
- A pointer to the iofunc_attr_t structure that describes the characteristics of the device that's associated with your resource manager.
Library:
libc
Use the -l c option to qcc to link against this library. This library is usually included automatically.
Description:
The iofunc_mmap() helper function provides functionality for the _IO_MMAP message. The _IO_MMAP message is an outcall from the Memory Manager (a part of the QNX Neutrino microkernel's procnto ).
Note that if the Process Manager is to be able to execute from this resource, then you must use the iofunc_mmap() function.
io_mmap_t structure
The io_mmap_t structure holds the _IO_MMAP message received by the resource manager:
struct _io_mmap { uint16_t type; uint16_t combine_len; uint32_t prot; uint64_t offset; struct _msg_info info; uint32_t zero[6]; }; struct _io_mmap_reply { uint32_t zero; uint32_t flags; uint64_t offset; int32_t coid; int32_t fd; }; typedef union { struct _io_mmap i; struct _io_mmap_reply o; } io_mmap_t;
The I/O message structures are unions of an input message (coming to the resource manager) and an output or reply message (going back to the client).
The i member is a structure of type _io_mmap that contains the following members:
- type
- _IO_MMAP.
- combine_len
- If the message is a combine message, _IO_COMBINE_FLAG is set in this member.
- prot
- The access capabilities that the client wants to use for the memory
region being mapped.
This can be a combination of at least the following protection bits, as
defined in <sys/mman.h>:
- PROT_EXEC — the region can be executed.
- PROT_NOCACHE — disable caching of the region (e.g. so it can be used to access dual-ported memory).
- PROT_NONE — the region can't be accessed.
- PROT_READ — the region can be read.
- PROT_WRITE — the region can be written.
- offset
- The offset into shared memory of the location that the client wants to start mapping.
- info
- A pointer to a _msg_info , structure that contains information about the message received by the resource manager.
The o member of the io_mmap_t structure is a structure of type _io_mmap_reply that contains the following members:
- flags
- Reserved for future use.
- offset
- Reserved for future use.
- coid
- A file descriptor that the process manager can use to access the mapped file.
- fd
- Reserved for future use.
Returns:
- A nonpositive value (i.e. ≤ 0)
- Successful completion.
- EROFS
- An attempt to memory map (mmap) a read-only file, using the PROT_WRITE page protection mode.
- EACCES
- The client doesn't have the appropriate permissions.
- ENOMEM
- Insufficient memory exists to allocate internal resources required to effect the mapping.
Classification:
Safety: | |
---|---|
Cancellation point | No |
Interrupt handler | No |
Signal handler | Yes |
Thread | Yes |