Hi

I am trying the first examples on my AMD64 platform.
cpuid.s works out of the box (the debugging with gdb and the call to info registers show different registers but that is to be expected with a different architecture).

The problems start with cpuid2.s. I modified the code to have it compiled on AMD64 (as was complaining about pushl) according to http://www.x86-64.org/documentation/assembly as follows:

# Using printf from libc
.section .data
output:
        .asciz "The processor Vendor ID is '%s'\n"

.section .bss
        .lcomm buffer, 12
.section .text
.globl _start
_start:
        nop
        movq $0, %rax
        cpuid
        movq $buffer, %rdi
        movq %rbx, (%rdi)
        movq %rdx, 4 (%rdi)
        movq %rcx, 8 (%rdi)
        pushq $buffer
        pushq $output
        call printf
        addq $8, %rsp
        pushq $0
        call exit

The call to the linker is a little different because it links with the 64-bit loader instead:
ld -dynamic-linker /lib64/ld-linux-x86-64.so.2 -lc -o cpuid2_x86_64 cpuid2_x86_64.o

Now running the binaries:
$ ./cpuid2_x86_64
AuthenticAMD

My question is this: why printf does not display the first part of the string? What happened to the stack?

I can't find any documentation about libc calls on AMD64.

Thank you.