sergiotarxz/nuttx
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

Add README files and configuration support for the shared memory logic

Browse Source
This commit is contained in:
Gregory Nutt 2014-09-23 07:11:47 -06:00
parent 826f703669
commit 242d5f2068
10 changed files with 656 additions and 423 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
Documentation/README.html
View File

@ -8,7 +8,7 @@
<tr align="center" bgcolor="#e4e4e4">
<td>
<h1><big><font color="#3c34ec"><i>NuttX README Files</i></font></big></h1>
<p>Last Updated: September 9, 2014</p>
<p>Last Updated: September 23, 2014</p>
</td>
</tr>
</table>
@ -281,6 +281,8 @@
| |- libxx/
| | `- <a href="http://sourceforge.net/p/nuttx/git/ci/master/tree/nuttx/libxx/README.txt"><b><i>README.txt</i></b></a>
| |- mm/
| | |- shm/
| | | `- <a href="http://sourceforge.net/p/nuttx/git/ci/master/tree/nuttx/mm/shm/README.txt"><b><i>README.txt</i></b></a>
| | `- <a href="http://sourceforge.net/p/nuttx/git/ci/master/tree/nuttx/mm/README.txt"><b><i>README.txt</i></b></a>
| |- net/
| | `- <a href="http://sourceforge.net/p/nuttx/git/ci/master/tree/nuttx/net/README.txt"><b><i>README.txt</i></b></a>

2
README.txt
View File

@ -1149,6 +1149,8 @@ nuttx
|- libxx/
| `- README.txt
|- mm/
| |- shm/
| | `- README.txt
| `- README.txt
|- net/
| `- README.txt

36
arch/Kconfig
View File

@ -199,6 +199,12 @@ config ARCH_HEAP_VBASE
---help---
The virtual address of the beginning of the heap region.
config ARCH_SHM_VBASE
hex "Virtual heap base"
depends on MM_SHM
---help---
The virtual address of the beginning of the shared memory region.
config ARCH_TEXT_NPAGES
int "Max .text pages"
default 1
@ -223,6 +229,36 @@ config ARCH_HEAP_NPAGES
This, along with knowledge of the page size, determines the size of
the heap virtual address space. Default is 1.
if MM_SHM
config ARCH_SHM_MAXREGIONS
int "Max shared memory regions"
default 1
---help---
The maximum number of regions that can allocated for the shared
memory space. This hard-coded value permits static allocation of
the shared memory data structures and serves no other purpose.
Default is 1.
The size of the virtual shared memory address space is then
determined by the product of the maximum number of regions, the
maximum number of pages per region, and the configured size of
each page.
config ARCH_SHM_NPAGES
int "Max shared memory pages"
default 1
---help---
The maximum number of pages that can allocated per region for the shared memory
region. Default is 1.
The size of the virtual shared memory address space is then
determined by the product of the maximum number of regions, the
maximum number of pages per region, and the configured size of
each page.
endif # MM_SHM
config ARCH_STACK_DYNAMIC
bool "Dynamic user stack"
default n

35
include/nuttx/addrenv.h
View File

@ -168,11 +168,42 @@
/* A single page scratch region used for temporary mappings */
# define ARCH_SCRATCH_VBASE ARCH_STACK_VEND
# define __ARCH_SHM_VBASE ARCH_STACK_VEND
#else
/* A single page scratch region used for temporary mappings */
# define ARCH_SCRATCH_VBASE ARCH_HEAP_VEND
# define __ARCH_SHM_VBASE ARCH_HEAP_VEND
#endif
/* Shared memory regions */
#ifdef CONFIG_MM_SHM
# ifndef CONFIG_ARCH_SHM_VBASE
# error CONFIG_ARCH_SHM_VBASE not defined
# define CONFIG_ARCH_SHM_VBASE __ARCH_SHM_VBASE
# endif
# if (CONFIG_ARCH_SHM_VBASE & CONFIG_MM_MASK) != 0
# error CONFIG_ARCH_SHM_VBASE not aligned to page boundary
# endif
# ifndef CONFIG_ARCH_SHM_MAXREGIONS
# warning CONFIG_ARCH_SHM_MAXREGIONS not defined
# define CONFIG_ARCH_SHM_MAXREGIONS 1
# endif
# ifndef CONFIG_ARCH_SHM_NPAGES
# warning CONFIG_ARCH_SHM_NPAGES not defined
# define CONFIG_ARCH_SHM_NPAGES 1
# endif
# define ARCH_SHM_REGIONSIZE (CONFIG_ARCH_SHM_NPAGES * CONFIG_MM_PGSIZE)
# define ARCH_SHM_SIZE (CONFIG_ARCH_SHM_MAXREGIONS * ARCH_SHM_REGIONSIZE)
# define ARCH_SHM_VEND (CONFIG_ARCH_SHM_VBASE + ARCH_SHM_SIZE)
# define ARCH_SCRATCH_VBASE ARCH_SHM_VEND
#else
# define ARCH_SCRATCH_VBASE __ARCH_SHM_VBASE
#endif
/* There is no need to use the scratch memory region if the page pool memory

19
mm/Kconfig
View File

@ -79,15 +79,6 @@ config HEAP2_SIZE
endif # ARCH_HAVE_HEAP2
config MM_SHM
bool "Shared memory support"
default n
depends on BUILD_KERNEL && EXPERIMENTAL
---help---
Build in support for the shared memory interfaces shmget(), shmat(),
shmctl(), and shmdt().
config GRAN
bool "Enable Granule Allocator"
default n
@ -158,3 +149,13 @@ config DEBUG_PGALLOC
allocation logic.
endif # MM_PGALLOC
config MM_SHM
bool "Shared memory support"
default n
depends on MM_PGALLOC && BUILD_KERNEL && EXPERIMENTAL
---help---
Build in support for the shared memory interfaces shmget(), shmat(),
shmctl(), and shmdt().

43
mm/README.txt
View File

@ -5,6 +5,8 @@ This directory contains the NuttX memory management logic. This include:
1) Standard Memory Management Functions:
Standard Functions:
The standard memory management functions as prototyped in stdlib.h as
specified in the Base definitions volume of IEEE Std 1003.1-2001. This
include the files:
@ -61,6 +63,17 @@ This directory contains the NuttX memory management logic. This include:
In fact, the standard malloc(), realloc(), free() use this same mechanism,
but with a global heap structure called g_mmheap.
User/Kernel Heaps
This multiple heap capability is exploited in some of the more complex NuttX
build configurations to provide separate kernel-mode and user-mode heaps.
Sub-Directories:
mm/mm_heap - Holds the common base logic for all heap allocators
mm/umm_heap - Holds the user-mode memory allocation interfaces
mm/kmm_heap - Holds the kernel-mode memory allocation interfaces
2) Granule Allocator.
A non-standard granule allocator is also available in this directory The
@ -110,3 +123,33 @@ This directory contains the NuttX memory management logic. This include:
The actual memory allocates will be 64 byte (wasting 17 bytes) and
will be aligned at least to (1 << log2align).
Sub-Directories:
mm/mm_gran - Holds the granule allocation logic
3) Page Allocator
The page allocator is an application of the granule allocator. It is a
special purpose memory allocator intended to allocate physical memory
pages for use with systems that have a memory management unit (MMU).
Sub-Directories:
mm/mm_gran - The page allocator cohabits the same directory as the
granule allocator.
4) Shared Memory Management
When NuttX is build in kernel mode with a separate, privileged, kernel-
mode address space and multiple, unprivileged, user-mode address spaces,
then shared memory regions must also be managed. Shared memory regions
are user-accessible memory regions that can be attached into the user
process address space for sharing between user process.
Sub-Directories:
mm/shm - The shared memory logic
The shared memory management logic has its own README file that can be
found at nuttx/mm/shm/README.txt.

117
mm/shm/README.txt Executable file
View File

@ -0,0 +1,117 @@
Shared Memory Support
=====================
Prerequisites
-------------
These features must be enabled before shared memory support can be
provided:
CONFIG_ARCH_ADDRENV=y - Support for per-task address environment using a
MMU.
CONFIG_BUILD_KERNEL=y - Support for protected kernel-/user-space memory
regions must be provided by the MMU.
CONFIG_GRAN=y - The granule allocation is the allocation underlying all
paged allocations.
CONFIG_GRAN_SINGLE=n - Multiple granule allocators are needed: One for
the physical page allocation and one virtual page allocator for each
process.
CONFIG_MM_PGALLOC=y - Enables the physical page allocator
CONFIG_MM_PGSIZE - Determines the size of one page that can be mapped by
the MMU.
And then finally:
CONFIG_MM_SHM=y - Enables shared memory support
CONFIG_ARCH_SHM_VBASE - The virtual address of the beginning of the
shared memory region.
CONFIG_ARCH_SHM_MAXREGIONS - The maximum number of regions that can
allocated for the shared memory space. This hard-coded value permits
static allocation of the shared memory data structures and serves no
other purpose. Default is 1.
CONFIG_ARCH_SHM_NPAGES - The maximum number of pages that can allocated
for the shared memory region. Default is 1.
The size of the virtual shared memory address space is then determined by
the product of the maximum number of regions, the maximum number of pages
per region, and the configured size of each page.
Concepts
--------
Each process has a task group structure, struct task_group_s, that holds
information common to all threads in the group. If CONFIG_MM_SHM=y, then
this includes data structures for the per-process shared memory virtual
page allocator.
A memory region is accessed using:
int shmget(key_t key, size_t size, int shmflg);
by a lookup using internal shared memory data sets with key as the lookup
match value. On success, shmget returns the shared memory identifier for
the match -- in this implementation that identifier is simply the table
index of the match.
If the memory region does not exist, it may also be created by shmget (if
the IPC_CREAT bit is set in the shmflag). When a shared memory region is
created, the following things happen:
- A new entry is set aside in the internal data set. The key value is
assigned to the entry and the table index is the new shared memory
identifier.
- The requested size is rounded up to rounded up to full pages, each of
size CONFIG_MM_PGSIZE.
- A set of physical pages are allocated and the physical address of
these pages is retained in the internel data set.
Now the key maps to and shared memory identifier (the table index) and
the table index provides access to the list of physical pages making up
the shared memory region.
NOTE: An improved implementation my perform a "lazy" back up of the
physical memory, i.e., do not allocate the physical memory until the
memory is required, for example, when a page fault occurs when a
application tries to allocate the memory.
A shared memory region is destroyed via:
int shmctl(int shmid, int cmd, struct shmid_ds *buf);
In order for a process to make use of the memory region, it must be
"attached" the the process using:
FAR void *shmat(int shmid, FAR const void *shmaddr, int shmflg);
shmat() returns the virtual address where the shared memory can be found
in the user process. Attaching the shared memory region involves the
following steps:
- Use the shmid as a table index to look up the mapping in the shared
memory internal data structures.
- Allocate a virtual address spaces of the same size as the physical
address space using the per-process virtual shared memory virtual
page allocator that can be found in the calling process' task group
structure.
- Use platform specific interfaces to mapy the physical memory to the
selected virtual address space, and
- Return the allocated virtual base address to the caller.
The memory region can be detached from the user process using:
int shmdt(FAR const void *shmaddr);
Relevant header files:
---------------------
include/sys/shm.h - Shared memory interface declarations
include/sys/ipc.h - Provides additional definitions used by the shared
memory interfaces
include/nuttx/addrenv.h - Defines the virtual address space of the
process.
include/nuttx/pgalloc.h - Page allocator interfaces
mm/shm/shm.h - Internal shared memory definitions. This includes the
definitions of the internal shared memory data structures.

3
mm/shm/shmctl.c
View File

@ -75,7 +75,8 @@
*
* - IPC_STAT
* Place the current value of each member of the shmid_ds data
* structure associated with shmid into the structure pointed to by buf.
* structure associated with shmid into the structure pointed to by
* buf.
* - IPC_SET
* Set the value of the following members of the shmid_ds data
* structure associated with shmid to the corresponding value found