Looking for a string in memory

[AlfaOmega08]

In the SMBIOS Specification, is written that the SMBIOS table starts with the "_SM_" string.
Now, I need an algorithm to find this string in memory.

I've tried with:

Code: Select all

int *mem;
mem = (int *) 0xF0000;

while (*mem < 0xFFFFF) {
	if (*mem == '_') {
		monitor << "Found a '_'";
		i++;
	}
	*mem++;
}

But it didn't work. It doesn't find any "_";
How can I find all the string???

[Ready4Dis]

Where to start...

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char *mem = (char*)0xF0000;
while (mem < 0xFFFFF) //mem == addr of mem, *mem = data stored at pointed to location!
{
  if (mem[0] == '_' && mem[1] == 'S' && mem[2] == 'M' && mem[3] == '_')
 {
  monitor << "Found it!"
  break;
 }
 mem+=4;  //Is it 4 byte aligned, then increment by 4 instead, or whatever alignment it has
}

The other way you can do is like this (assuming 4-byte alignment)

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uint32 *mem (uint*)0xF0000;  //32-bit unsigned...
uint32 val = ('_'<<24) + ('M'<<16) + ('S'<<8) + '_'; //Make dword
while  (mem < 0xFFFFF)
{
 if (*mem == val)
 {
   monitor << "Found it";
 }
 ++mem; //Increments mem by 4-bytes since it's a 32-bit int!
}

[AlfaOmega08]

Each method give me error on the while line:
error: ISO C++ forbids comparison between pointer and integer

[cyr1x]

You should know how to fix this problem if you know the language properly.
Please learn your language first before you tackle something like an operating system.
But anyway here's the fix:

Code: Select all

while ((unsinged int)mem < 0xFFFFF) 

[AlfaOmega08]

Ok now it works (on vmware not on bochs)

Thanks