What is the equivalent of the dollar sign from jmp $+1 in GAS syntax?

Question

I have an asm program made with intel syntax. In this program, I am using this syntax jz $+1 from INTEL (+gcc), that means that I jump into the jz instruction (which is 2 bytes). I jump 1 byte further the current instruction. I am trying to find what is the correct syntax to do the same thing in GAS AT&T syntax, but I can't find the information. Does anyone know that?

Answer 1

This is not really an RE question, but I think . is used to refer to current location in many GAS architectures.

Answer 2

you can use intel syntax if you prefer in gas and use $+1 to jump into the middle of the instruction

$ cat foo.s

.intel_syntax noprefix
.global start
        _start:
        jz $+1
        .byte 0x25,0x45,0x33,0x40,0x00

assemble

$ as -o foo.o foo.s

disassemble

$ objdump.exe -d foo.o
foo.o:     file format pe-x86-64
Disassembly of section .text:
0000000000000000 <_start>:
   0:   74 ff                   je     1 <_start+0x1>
   2:   25 45 33 40 00          and    $0x403345,%eax
   7:   90                      nop
   8:   90                      nop

link

$ ld -m i386pep -o foo foo.o

debug

$ gdb ./foo
GNU gdb (GDB) 8.2.1

(gdb) break _start
Breakpoint 1 at 0x100401000
(gdb) r
Starting program: 
[New Thread 7876.0x2614]

Breakpoint 1, 0x0000000100401000 in __rt_psrelocs_start ()
(gdb) x/2i $rip
=> 0x100401000 <__rt_psrelocs_start>:
    je     0x100401001 <__rt_psrelocs_start+1>
   0x100401002 <__rt_psrelocs_start+2>: and    $0x403345,%eax

(gdb) si
0x0000000100401001 in __rt_psrelocs_start ()
(gdb) x/2i $rip
=> 0x100401001 <__rt_psrelocs_start+1>:
    jmpq   *0x403345(%rip)        # 0x10080434c

   0x100401007 <__rt_psrelocs_start+7>: nop
(gdb)