Memory test program

Forum: Linux
eduardo 
Hi there,

I need to write a program to check consistency of memory... the problem is:
I don't have any idea about how to do that. xD


Could someone post some useful link or useful tool that will help me?

Thanks in advance!

davef 
Good afternoon eduardo,

Like a check for bad blocks in flash?

Consistency means everything is the same.  So, you want to check that every
memory location in flash is working?

Another test could be when you are close to using all the memory, ie RAM.
Some terms here are "stack paint" and "stack canary".  I can give you an
example if that is what you are after.

Dave

Oleg 
Hi davef! i get errors like Segmentation fault and Unable to handle kernel
paging request at virtual address. This errors happens if i run rootfs form
NAND flash and NFS. So i decided to check my RAM. What program can i use?

davef 
I use this technique on a 8bit 32K FLASH 2K RAM device.

The idea is to fill all of ram with a character like  0xC5 (would need to
be changed to something bigger for a 32 bit machine) and periodically check
that you have some 0xC5s left or you know you have run out of RAM.

here is the code:

***
#define STACK_CANARY 0xc5

// stack monitoring variables
extern uint8_t _end;
extern uint8_t __stack;
(these must be extern because they live somewhere in the startup code)

void StackPaint(void) __attribute__ ((naked)) __attribute__ ((section
(".init1")));
void StackPaint(void);

now in main.c

// stack monitoring pointer
   const uint8_t *p = &_end;
   uint16_t c = 0;

and then somewhere you place this code and execute it every so many seconds

// stack count
while(*p == STACK_CANARY && p <= &__stack)
{
   p++;
   c++;
}
// we are running low on RAM
if(c < 100) // more like 1000 or 10000
{
   turn on a LED;
}

and then the function:

void StackPaint(void)
{
   uint8_t *p = &_end;

   while(p <= &__stack)
   {
      *p = STACK_CANARY;
      p++;
   }
}
***

Now, there must be code more suitable for use on our platform.  All the
variables would need to be made BIGGER, I don't know if _end and __stack
even exist in our environment and who knows if:
void StackPaint(void) __attribute__ ((naked)) __attribute__ ((section
(".init1")));

is even relevant for this platform.  The device I use it on has a Harvard
architecture.

I guess this would also tell you if a RAM memory location failed as either
it wouldn't have a 0xC5 in it or it wouldn't read that memory position
correctly.

Good luck in your search for a more suitable tool.

Dave


Good luck i

eduardo 
Thanks for the responses Dave!

I found a useful link:
http://www.cyberciti.biz/tips/howto-linux-server-memory-check.html

davef 
That looks more appropriate.  Tell us how well it works.

Dave