CODEWITHSUNDEEP
assemblyx86-64gnu-assemblerintel-syntaxgot
Mikola Akbal
Mikola Akbal

Reputation: 161

GOTPCREL(%rip) in GAS Intel syntax

How can i write following: movq variable@GOTPCREL(%rip), %r8 in GAS Intel syntax?

.intel_syntax noprefix allows only this: mov r8, variable@GOTPCREL, it does not understand (), and resulting code is different - i receive segmentation fault. How can i specify RIP-relative addressing?

At this moment i have to use following syntax switcher:

.att_syntax
movq variable@GOTPCREL(%rip), %r8
.intel_syntax noprefix

I prefer Intel syntax, and my code uses it mostly. This switcher is inconvenience when porting code to GAS. Is it possible to write it shortly in Intel syntax?

Upvotes: 1

Views: 1911

Answers (2)

Ross Ridge
Ross Ridge

Reputation: 39621

The syntax GAS expects for RIP relative addressing when using Intel syntax is displacement[rip]. So for example:

    .att_syntax
    movq variable@GOTPCREL(%rip), %r8
    .intel_syntax noprefix
    mov r8, variable@GOTPCREL[rip]

$ as test.s
$ objdump -d -r

a.out:     file format elf64-x86-64


Disassembly of section .text:

0000000000000000 <.text>:
   0:   4c 8b 05 00 00 00 00    mov    0x0(%rip),%r8        # 0x7
                        3: R_X86_64_REX_GOTPCRELX       variable-0x4
   7:   4c 8b 05 00 00 00 00    mov    0x0(%rip),%r8        # 0xe
                        a: R_X86_64_REX_GOTPCRELX       variable-0x4

GAS will also accept [rip + displacement] and maybe some other forms.

Upvotes: 0

Jester
Jester

Reputation: 58782

It's the standard effective address syntax. As such, you write it as mov r8, [variable@GOTPCREL + rip]

Upvotes: 1

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