MSVC inline assembly

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bcdsys

Joined: 04 Aug 2008
Posts: 41

bcdsys 26 Oct 2008, 04:00

I have c code and in it I have character array and IMAGE_SECTION_HEADER struct and need copy first 8 bytes from struct to char array. Tried in c but can't get stupid useless type casts to work! Tried inline asm, but it has different syntax to fasm and can't get pointer to char array. Can anyone help? Also, is there anything in c that I can just move memory around without stupid compiler errors?

26 Oct 2008, 04:00

bcdsys

Joined: 04 Aug 2008
Posts: 41

bcdsys 26 Oct 2008, 04:04

here is asm code tested

Code:

__asm {
           mov esi, section_header
             mov edi, section_name_ptr
           mov ecx, 2
          cld
         rep movsd
   }

c code version:

Code:

section_name[0] = ((DWORD*) &section_header)[0];
section_name[4] = ((DWORD*) &section_header)[1];

asm version not compile, c code compile but incorrect result, verified cause this line
can anyone help?

26 Oct 2008, 04:04

Kain

Joined: 26 Oct 2003
Posts: 108

Kain 26 Oct 2008, 06:12

Have you checked your indexing? Maybe it should be section_name[1]

For the asm part, it looks like you're moving the address of the pointer variable (section_name_ptr) into edi rather than the address of section_name which should be the contents of the section_name_ptr. You probably need to dereference the dword at edi.

26 Oct 2008, 06:12

bcdsys

Joined: 04 Aug 2008
Posts: 41

bcdsys 26 Oct 2008, 12:35

problem fixed
used:

Code:

((DWORD*) section_name)[0] = ((DWORD*) &section_header)[0];
((DWORD*) section_name)[1] = ((DWORD*) &section_header)[1];

26 Oct 2008, 12:35

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