What is the prolog / epilog code for the assembly executed with rbp / rsp / leave?

Question

I'm just starting to learn assembly for mac using the GCC compiler to build my code. Unfortunately, there are VERY limited resources for learning how to do this if you are a beginner. I finally managed to find a simple code sample that I could start tearing my mind apart, and I got it to build and run correctly. Here is the code:

.text                                           # start of code indicator.
.globl _main                                    # make the main function visible to the outside.
_main:                                          # actually label this spot as the start of our main function.
    push    %rbp                            # save the base pointer to the stack.
    mov     %rsp, %rbp                      # put the previous stack pointer into the base pointer.
    subl    $8, %esp                        # Balance the stack onto a 16-byte boundary.
    movl    $0, %eax                        # Stuff 0 into EAX, which is where result values go.
    leave                                   # leave cleans up base and stack pointers again.
    ret

Comments explain some things in the code (I understand what lines 2-5 do), but I don't understand what that means. I understand the basics of what registers and each register here ( rbp, rsp, espand eax) is used and how big they are, I also know the (usually) what is the stack, but it still goes over my head. Can someone tell me what exactly this is doing? Also, can someone point me towards a good beginner's tutorial?

Answer 1

- , LIFO. ( , ) , x86 x86-64 . . Wikibooks x86 ( , - 32- x86- Intel, - 64 - x86-64 AT & T).

, ( Intel):

push %rbp

rbp , 8 rsp ( rbp 8 ), rbp [ss:rsp].

, Intel push rbp :

sub rsp, 8
mov [ss:rsp], rbp

:

mov     %rsp, %rbp

. rsp rbp.

subl    $8, %esp

8 esp esp. , . 32- (eax, ebx, ecx, edx, ebp, esp, esi edi)) x86-64 32 64- (rax, rbx, rcx, rdx, rbp, rsp, rsi rdi) , - 4 , ( Intel):

sub rsp,8
and rsp,0x00000000ffffffff

: sub esp,8 .

4 . 4 . leave sane rsp. x86-64 esp (, , ). :

subq    $8, %rsp

( $8 ). Wikibooks x86 ( , 32- x86 Intel, 64- x86-64 AT & T).

:

movl    $0, %eax

. 0 eax. .

leave

mov rsp, rbp, pop rbp.

ret

, , rip , [ss:rsp], , , 8 rsp.