software | Windows |
The instruction pointer is called ip in 16-bit mode, eip in 32-bit mode,,
and rip in 64-bit mode. The instruction pointer register points to the
memory address which the processor will next attempt to execute; it
cannot be directly accessed in 16-bit or 32-bit mode, but a sequence
like the following can be written to put the address of next_line into
eax:
call next_line
next_line:
pop eax
source :
http://en.wikipedia.org/wiki/X86_assembly_language
software | GNU/Linux |
(gdb) info registers
rax 0xfffffffffffffdfc -516
rbx 0x5dc 1500
rcx 0xffffffffffffffff -1
rdx 0x5dc 1500
rsi 0x1 1
rdi 0x7fff09cf5780 140733357971328
rbp 0x2051160 0x2051160
rsp 0x7fff09cf5730 0x7fff09cf5730
r8 0x0 0
r9 0xffffffff 4294967295
r10 0x8 8
r11 0x246 582
r12 0x7fff09cf5780 140733357971328
r13 0x7fff09cf5790 140733357971344
r14 0x0 0
r15 0x1 1
rip 0x7f2e947000c8 0x7f2e947000c8 <*__GI___poll+24>
eflags 0x246 [ PF ZF IF ]
cs 0x33 51
ss 0x2b 43
ds 0x0 0
es 0x0 0
fs 0x0 0
gs 0x0 0
(gdb)
rip 0x7f2e947000c8 0x7f2e947000c8 <*__GI___poll+24>
The RIP register is the instruction pointer register. In 64-bit mode, the
RIP register is extended to 64 bits to support 64-bit offsets. In 32-bit
x86 architecture, the instruction pointer register is the EIP register.
source:
http://developers.sun.com/solaris/articles/x64_dbx.html
| Related Discussion |
Hi...I'm teaching myself some AMD 64 bit assembler programing and I'm
curious about RIP relative addressing. The docs that I've read state
"You are recommended to use RIP relative addressing whenever possible
to reduce code size" now my question is, is this the code size reduction
they are talking about
Code:
example code 1 RIP-relative addressing
.section .data
mydata: .long 0
.section .bss
.section .text
.global _start
_start:
movq $64, mydata(%rdi)
Code:
example code 2
.section .data
mydata: .long 0
.section .bss
.section .text
.global _start
_start:
movq $64, mydata
and the results
Code:
example 1 RIP-relative addressing
code1: file format elf64-x86-64
Disassembly of section .text:
00000000004000b0 <_start>:
4000b0: 48 c7 87 bc 00 60 00 movq $0x40,0x6000bc(%rdi)
4000b7: 40 00 00 00
Code:
example 2
code2: file format elf64-x86-64
Disassembly of section .text:
00000000004000b0 <_start>:
4000b0: 48 c7 04 25 bc 00 60 movq $0x40,0x6000bc
4000b7: 00 40 00 00 00
are we talking about a one byte reduction in code size every time I use RIP relative addressing?
source :
http://www.linuxforums.org/forum/linux-programming-scripting/131795-amd-64-bit-rip-relative-addressing.html
| Variation |
How RIP/EIP relative addressing works in 32-bit mode
In 32-bit programs you can't do this :
mov al, [eip]
But you will have to do something like this instead :
call $ + 5
pop ebx
add ebx, 1 + 1 + 1 + 1 ; POP + ADD + ModRM + imm8
mov al, [ebx] ; EBX is now pointing to this instruction!
How RIP/EIP relative addressing works in 64-bit mode
In 64-bit programs you are allowed to write this :
mov al, [rip]
source :
http://www.codegurus.be/codegurus/Programming/riprelativeaddressing_en.htm
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