Messages in this thread | | | From | Andrew Kirilenko <> | Subject | Re: Searching for string problems | Date | Wed, 23 Apr 2003 21:25:22 +0300 |
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Hello!
> > > scan: movw %cs, %ax > > > movw %ax, %ds > > > movw %ax, %es > > > movw $where_in_BIOS_to_start, %bx > > > cld > > > 1: movw $cl_id_str, %si # Offset of search string > > > movw $cl_id_end, %cx # Offset of string end + 1 > > > subw %si, %cx # String length > > > decw %cx # Don't look for the \0 > > > movw %bx, %di # ES:DI = where to look > > > repz cmpsb # Loop while the same > > > jz found # Found the string > > > incb %bx # Next starting offset > > > cmpb $_BIOS_END, %bx # Check for limit > > > jb 1b # Continue > > > never_found_anywhere: > > > > > > found: > > > > I've written something similar to this before - and it wont' work, so > > I've reimplemented it. The problem is, that I don't know how to set ES > > properly. I only know, that BIOS data (and code) is located in > > 0xe000..0xf000 (real address). > > Yeah. So. I set ES and DS to be exactly where CS is. This means that > if your &!)(^$&_ code executes it will work. So, instead of trying > it, you just blindly ignore it and state that it won't work. > > Bullshit. I do this for a living and I gave you some valuable time > which you rejected out-of-hand. Have fun.
Of course, I've tried your code as well - the same result! Sorry, if you haven't understand me.
The problem is, that I don't know where this BIOS code is relative to current code segment (CS). I only know (hope), that it should be in 0x0:0xe000...0x0:0xf000. I have tried to set ES to 0 (xor %ax, %ax; mov %ax, %es) - no luck as well. BTW, `strings /dev/mem | grep "REQUESTED STRING"` founds it perfectly...
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