How do I use RIP Relative Addressing in a Linux assembly program for the AMD64 archtitecture? I am looking for a simple example (a Hello world program) that uses the AMD64 RIP relative adressing mode.
For example the following 64-bit assembly program would work with normal (absolute addressing):
.text
.global _start
_start:
mov $0xd, %rdx
mov $msg, %rsi
pushq $0x1
pop %rax
mov %rax, %rdi
syscall
xor %rdi, %rdi
pushq $0x3c
pop %rax
syscall
.data
msg:
.ascii "Hello world!\n"
I am guessing that the same program using RIP Relative Addressing would be something like:
.text
.global _start
_start:
mov $0xd, %rdx
mov msg(%rip), %rsi
pushq $0x1
pop %rax
mov %rax, %rdi
syscall
xor %rdi, %rdi
pushq $0x3c
pop %rax
syscall
msg:
.ascii "Hello world!\n"
The normal version runs fine when compiled with:
as -o hello.o hello.s && ld -s -o hello hello.o && ./hello
But I can't get the RIP version working.
Any ideas?
--- edit ----
Stephen Canon's answer makes the RIP version work.
Now when I disassemble the executable of the RIP version I get:
objdump -d hello
0000000000400078 <.text>:
400078: 48 c7 c2 0d 00 00 00 mov $0xd,%rdx
40007f: 48 8d 35 10 00 00 00 lea 0x10(%rip),%rsi # 0x400096
400086: 6a 01 pushq $0x1
400088: 58 pop %rax
400089: 48 89 c7 mov %rax,%rdi
40008c: 0f 05 syscall
40008e: 48 31 ff xor %rdi,%rdi
400091: 6a 3c pushq $0x3c
400093: 58 pop %rax
400094: 0f 05 syscall
400096: 48 rex.W
400097: 65 gs
400098: 6c insb (%dx),%es:(%rdi)
400099: 6c insb (%dx),%es:(%rdi)
40009a: 6f outsl %ds:(%rsi),(%dx)
40009b: 20 77 6f and %dh,0x6f(%rdi)
40009e: 72 6c jb 0x40010c
4000a0: 64 21 0a and %ecx,%fs:(%rdx)
Which shows what I was trying to accomplish: lea 0x10(%rip),%rsi loads the address 17 bytes after the lea instruction which is address 0x400096 where the Hello world string can be found and thus resulting in position independent code.
RIP is the instruction pointer register, which contains the address of the location immediately following the current instructionbut theleainstruction is seven bytes long, not one. – fadedbee