Date: Wed, 4 Jul 2012 16:32:02 -0700 From: Colin Barnabas <colin.barnabas@gmail.com> To: FreeBSD Hackers <freebsd-hackers@freebsd.org> Subject: GAS AT&T linkage issue Message-ID: <20120704233202.GA9910@hs1.VERBENA>
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I've been dabbling in assembly and decided to try AT&T syntax and
the GAS assembler. I'm trying to get a cpuid test program
running. It assembles fine if I give the command:
as -o cpuid.o cpuid.s
But starts complaining when I try to link it with:
ld -o cpuid cpuid.o
Which produces these errors:
cpuid.o: In function `_start':
(.text+0x10): undefined reference to `ebx'
cpuid.o: In function `_start':
(.text+0x18): undefined reference to `edx'
cpuid.o: In function `_start':
(.text+0x20): undefined reference to `ecx'
Im running FreeBSD 9.0-RELEASE amd64 and here is the text I am
using:
#cpuid.s Sample program to extract the processor Vendor ID
.section .data
output:
.ascii "The processor Vendor ID is 'xxxxxxxxxxxx'\n"
.section .text
.globl _start
_start:
movl $0, %eax
cpuid
movl $output, %edi
movl $ebx, 28(%edi)
movl $edx, 32(%edi)
movl $ecx, 36(%edi)
movl $4, %eax
movl $1, %ebx
movl $output, %ecx
movl $42, %edx
int $0x80
movl $1, %eax
movl $0, %ebx
int $0x80
Any advice would be appreciated.
--
Colin Barnabas
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