Re: Programmatic use of load module
- From: "ssubbarayan" <ssubba@xxxxxxxxx>
- Date: 11 Sep 2005 22:02:35 -0700
Jeanseb wrote:
> Hello,
>
> I have read the windriver tech tip 4179, which explains how to
> programmaticaly load modules from RAM/ROM.
>
> I am interested in doing this, since I want to split my code in
> multiple modules on my standalone application: updating my code would
> only require updating a couple of modules (the link to my standalone
> application has a very limited bandwidth). Also at startup, I would be
> able to load different modules, and chose which version of my code to
> run.
>
> However, I have encoutered 2 major problems:
>
> 1) I intend to load code modules from flash from UsrAppInit. There is a
> problem though: from UsrAppInit, I cannot invoke any function from the
> modules I intend to load, since these functions are not defined in the
> scope of the bootable image. I have tried a forward declaration of
> these functions (using extern, which works for downloadable
> applications) but the code just does not compile ("undefined
> reference").
>
> 2) When modules have a cyclic relationship - Module A invokes Module B,
> and Module B invokes Module A - the sequential VxWorks loader does not
> work. Since loading Module A first will generate errors due to
> undefined symbols from Module B, and vice versa. I have tried to
> declare a "fake" module B in module A (create an empty library, used to
> register Module B symbols in the symbol table). Then I load module B to
> overwrite the fake symbols defined by module A. The idea is to
> pre-register module B's symbols when module A is loaded.
> >From what I read in the VxWorks user's guide on page 259, this is
> possible: "The system symbol table allows name clashes to occur. For
> example, suppose a function func exists in the system. A second symbol
> named func is added to the system symbol table as part of a load. From
> this point, all links to func are to the most recently loaded
> symbol...". I have tried multiple options for the loader, but it just
> does not work: the symbols defined by module B, even if they use the
> same name do not overwrite the fake symbols defined by module A.
>
> Could someone help me please?
>
> Thank you in advance!
>
> Jean-Sebastien
Jean,
There are some info I have gathered from this group which may be
relevant to your query.I am pasting it below for your reference.I
believe it will be of help to you,Though I am not exactly sure how far
this will be solving your query.
Collected info:
--------------------------------------------------
Hi,
I have two VxWorks images in flash. I boot from one of the images. I
image
I boot from to transfer the second image into RAM and run it. I can
transfer the second image into RAM but I am not sure how to run it.
Can anybody offer any ideas?
Dan J
Michael R. Kesti (mkesti@xxxxxx)
After the second image is loaded into memory (presumably using
loadModule()
or loadModuleAt() ), use symFindByName() to locate that image's entry
point
and then call the entry point.
Is loadModuleAt() not used for loading .out files? I have a bootable
VxWorks image?
Dan J
Bill Pringlemeir (spam_account@xxxxxxxxxxxx)
This is true. You will have to make a modification to the vxWorks RAM
image. Specifically, you have to look at if it is going to setup
memory mappings. For instance, the RAM image may assume that it is
loaded at a particular memory address. Is the RAM image compressed,
etc. You also didn't mention if the RAM image was pre-built, you are
creating it with the project, or via a makefile.
In any case, there are several possibilities. You jump to the first of
the image. This is usually romInit.s, etc. If the image is not
compressed and just assumes that it is loaded at the right place, then
a jump to "usrInit()" might work. Some images have this address
placed at a fixed offset in the image.
btw, there was no way for Michael to know that you are loading a
binary image versus a elf/coff file. Can you see the need to give
more info?
fwiw,
Bill Pringlemeir.
shafi (shafi4u@xxxxxxxxxxxxxx)
Jump to the starting entry routine location on the second image you
loaded on the RAM. check bootConfig.c sample file. That's what it does
there using a function 'go' to jump and execute the image loaded.
----------------------------- ends here----------------
Query 2:
JT (mail@xxxxxxxxx)
163)Hi,
I am trying to keep my VxWorks image and my application image separate.
Maybe that is really not necessary, but in our product we will quite
often
be upgrading the application. So I thought it would be a good idea to
keep
the VxWorks image (boot-image), separate from the application.
The problem is: How do I link the VxWorks-image to my application image
when
my application image is changing all the time?
My plan is to place the application image on the target hard disk. This
provides for easy means for our customers to upgrade to new versions of
our
application. The VxWorks image will then, in usrAppInit(), perform a
loadModule() to load our application module from disk to memory.
The plan is then to call "MyApplicationStart()". However, I can not
link the
VxWorks image directly to my application, as the application will
change
over and over again, and thus the address of MyApplicationStart().
Therefore
I get problems when builing the VxWorks image.
So, what is the best way to achieve this? Could I search for
MyApplicationStart() in the SymTable after performing the loadModule?
Or is
there any other way of linking the VxWorks-image to something that will
be
dynamically loaded?
Thanks for any help!
Best regards,
Jostein Trones
1
Tapani Leppänen (tapani.leppanen@xxxxxxxxxxxxxxxxxxxxxx)
I dont know about the "best way", but this is what we do. We load the
VxWorks image separately and use startup script in boot parameter to
specify
script file. That file loads our application and starts it.
example of bootparams
.........
target name (tn) : phobos
startup script (s) : /flashDisk/test.sct
other (o) : ei
..........
example of test.sct file
-----------
cd "/flashDisk/contcom/bin"
ld <update
applicationInit(2)
-----------
regards,
Tapani
JT (mail@xxxxxxxxx)
Hi, thanks!
I actually got it to work myself, in a different way. In usrAppInit()
(in
the VxWorks image), I use loadModule() to load our application module,
then
I use symFindByName() to find the address of my start-function.
Works well!
Thanks for your input!
-jostein
forums_mp@xxxxxxxxxxx)
----------------------- ends here---------------
Query 3:
Hi Everyone.
Did you use 'loadModule()' in vxWorks 5.5?
After loadModule(), I want to start a task in the module.
what do I do?
Example>
/*--------------------------------------------------*/
/* Source Code */
void foo(void)
{
printf("Hello!");
}
in foo.o
/*--------------------------------------------------*/
/* LoadModule */
void usrAppInit (void)
{
fdX = open ("/devX/foo.o", O_RDONLY);
loadModule (fdX, LOAD_ALL_SYMBOLS);
close (fdX);
}
and
I want to start foo function..
Help me!
Use symFindByName to get the address of foo() and call that address.
-----------------------------------------------ends here--------------
Query 4:
272)Hi,
I'm attempting to load a .out file into RAM and extract a smbol from
the
module using symFindByName. I cannot work out how I find a value for
the
first parameter (SYMTAB_ID symTblId) to this function for the symbol
table
I haver loaded using loadModule?
Any suggestions?
Daniel.
#include <symLib.h>
#include <sysSymtbl.h>
f()
{
char * pValue;
SM_TYPE pType;
if (symFindByName(sysSymTbl, "whatever", &pValue, &pType) == OK) {
...
}
else
; /* error */
Hi,
If the .out file I load already contains some symbols that are already
in
the symbol table, how will the OS cope. I want the symbols in the .out
file
to take presedence.
I have noticed when you download an two versions of an .out file to a
target
the shell displays an option with the version of the symbol you want to
invoke if you attempt to run a function for example.
Regards,
Daniel
Hi,
For some reason, the loadModule function returns a failure. I transfer
a
..out file from flash into RAM using the 'write' function with an
associated
file descriptor. I then pass this file descriptor to the loadModule
function and a NULL value is returned.
Why might this happen? Could it be because I'm running the test code
as a
downloadable object as well? Something to do with the symbol table
setup?
Regards,
Daniel
See below for the code I'm using. I have created a file called
File.out
which contains a symbol I want to call (called 'main').
I download another piece of test code called loader in an .out file and
run
it from the shell. It attempts to load the File.out
file and extract the symbol but fails the loadModule function. I can
use
the ld < File.out from the shell to load the file from
my host o the host but I need to be able to do this just the target.
Any idea's why the loadModule function fails?
Daniel.
#include "pxlib.h"
#include "ioLib.h"
#include "loadlib.h"
#include "ramDrv.h"
#include "dosFsLib.h"
#include "symLib.h"
#include "sysSymtbl.h"
void loader(void)
{
char fullFileNameForRAM[46];
int fd;
FUNCPTR start;
UINT8 symType;
int tid;
STATUS rc;
char buff[100];
// Extract the .out file with the 'main' symbol
// out of flash (BSP function). The flash
// file system doesn't support file descriptors
PX_Ptr px = PX::GetPX();
PXFlashObject_Ptr fobj = px->GetFlashObject("File.out");
// Check the file was successfully
// retrieved.
if(fobj != 0)
{
// Create a RAM device
BLK_DEV* blk = ramDevCreate(0, 1024, 0, 50176, 0);
if(blk != NULL)
{
// Create a file system
DOS_VOL_DESC* pVolDesc= dosFsMkfs("/ram", blk);
// Construct the file name for the
// fd to be created
memset(fullFileNameForRAM, 0, 46);
strcat(fullFileNameForRAM, (const char*)"/ram/File.out");
fd = creat(fullFileNameForRAM, 2);
// Write the contents of the flash file (.out)
// to the fd
write(fd, (char*)fobj->GetData(), fobj->GetSize()));
// Attempt to load the symbols
// THIS IS WHERE IS FAILS
if((loadModule(fd, LOAD_ALL_SYMBOLS)) == NULL)
{
printf("Error in load module\n");
}
else
{
printf("No error in loading\n");
}
if(symFindByName(sysSymTbl, "main", (char**)&start, &symType)
==
OK)
{
printf("Symbol found\n");
}
else
{
printf("Symbol not found\n");
}
}
else
{
printf("RAM Device creation failed\n");
}
}
else
{
printf("Failure to extract file from Flash\n");
}
}
Could be that this is the problem. main is a name you should not use in
VxWorks, as it is reserved for the OS itself. Try it again with the
main
symbol renamed to (for example) my_main.
What is the value of errno after the call to loadModule?
Kind regards,
Johan
--------------------------------------------------------------
Hope you would have understood it from the above 4 querys how to do
it.Another alternative is to google here with in this group for 2
functions LoadModule() and SymFindByName() which will further help you
to know about dynamic loading.
Regards,
s.subbarayan
.
- References:
- Programmatic use of load module
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