Help with Assembly. Segmentation fault when compiling samples on Mac OS X_问答_开发者

I'm trying to learn assembly using Dr Paul Carter's pcasm book: http://www.drpaulcarter.com/pcasm/

The author doesn't packaged Mac OS X samples, then I've started using from linux sources. Here is the first sample, that uses his library asm_io.

I'm getting Segmentation Fault when running it. Why? What need to be changed to run in mac?

I think if you know asm, maybe you can tell me what's happening.

Here's the sources.

asm_io.asm:

;
; file: asm_io.asm
; Assembly I/O routines
; To assemble for DJGPP
;   nasm -f coff -d COFF_TYPE asm_io.asm
; To assemble for Borland C++ 5.x
;   nasm -f obj -d OBJ_TYPE asm_io.asm
; To assemble for Microsoft Visual Studio
;   nasm -f win32 -d COFF_TYPE asm_io.asm
; To assemble for Linux
;   nasm -f elf -d ELF_TYPE asm_io.asm
; To assemble for Watcom
;   nasm -f obj -d OBJ_TYPE -d WATCOM asm_io.asm
; IMPORTANT NOTES FOR WATCOM
;   The Watcom compiler's C library does not use the
;   standard C calling convention. For example, the
;   putchar() function gets its argument from the
;   the value of EAX, not the stack.


%define NL 10
%define CF_MASK 00000001h
%define PF_MASK 00000004h
%define AF_MASK 00000010h
%define ZF_MASK 00000040h
%define SF_MASK 00000080h
%define DF_MASK 00000400h
%define OF_MASK 00000800h


;
; Linux C doesn't put underscores on labels
;
%ifdef ELF_TYPE
  %define _scanf   scanf
  %define _printf  printf
  %define _getchar getchar
  %define _putchar putchar
%endif

;
; Watcom puts underscores at end of label
;
%ifdef WATCOM
  %define _scanf   scanf_
  %define _printf  printf_
  %define _getchar getchar_
  %define _putchar putchar_
%endif

%ifdef OBJ_TYPE
segment .data public align=4 class=data use32
%else
segment .data
%endif

int_format     db  "%i", 0
string_format       db  "%s", 0
reg_format     db  "Register Dump # %d", NL
      db  "EAX = %.8X EBX = %.8X ECX = %.8X EDX = %.8X", NL
                    db  "ESI = %.8X EDI = %.8X EBP = %.8X ESP = %.8X", NL
                    db  "EIP = %.8X FLAGS = %.4X %s %s %s %s %s %s %s", NL
             db  0
carry_flag     db  "CF", 0
zero_flag     db  "ZF", 0
sign_flag     db  "SF", 0
parity_flag     db "PF", 0
overflow_flag     db "OF", 0
dir_flag     db "DF", 0
aux_carry_flag     db "AF", 0
unset_flag     db "  ", 0
mem_format1         db  "Memory Dump # %d Address = %.8X", NL, 0
mem_format2         db  "%.8X ", 0
mem_format3         db  "%.2X ", 0
stack_format        db  "Stack Dump # %d", NL
             db  "EBP = %.8X ESP = %.8X", NL, 0
stack_line_format   db  "%+4d  %.8X  %.8X", NL, 0
math_format1        db  "Math Coprocessor Dump # %d Control Word = %.4X"
                    db  " Status Word = %.4X", NL, 0
valid_st_format     db  "ST%d: %.10g", NL, 0
invalid_st_format   db  "ST%d: Invalid ST", NL, 0
empty_st_format     db  "ST%d: Empty", NL, 0

;
; code is put in the _TEXT segment
;
%ifdef OBJ_TYPE
segment text public align=1 class=code use32
%else
segment .text
%endif
 global read_int, print_int, print_string, read_char
 global  print_char, print_nl, sub_dump_regs, sub_dump_mem
        global  sub_dump_math, sub_dump_stack
        extern  _scanf, _printf, _getchar, _putchar

read_int:
 enter 4,0
 pusha
 pushf

 lea eax, [ebp-4]
 push eax
 push dword int_format
 call _scanf
 pop ecx
 pop ecx

 popf
 popa
 mov eax, [ebp-4]
 leave
 ret

print_int:
 enter 0,0
 pusha
 pushf

 push eax
 push dword int_format
 call _printf
 pop ecx
 pop ecx

 popf
 popa
 leave
 ret

print_string:
 enter 0,0
 pusha
 pushf

 push eax
 push    dword string_format
 call _printf
 pop ecx
 pop ecx

 popf
 popa
 leave
 ret

read_char:
 enter 4,0
 pusha
 pushf

 call _getchar
 mov [ebp-4], eax

 popf
 popa
 mov eax, [ebp-4]
 leave
 ret

print_char:
 enter 0,0
 pusha
 pushf

%ifndef WATCOM
 push eax
%endif
 call _putchar
%ifndef WATCOM
 pop ecx
%endif

 popf
 popa
 leave
 ret


print_nl:
 enter 0,0
 pusha
 pushf

%ifdef WATCOM
 mov eax, 10  ; WATCOM doesn't use the stack here
%else
 push dword 10 ; 10 == ASCII code for \n
%endif
 call _putchar
%ifndef WATCOM
 pop ecx
%endif
 popf
 popa
 leave
 ret


sub_dump_regs:
 enter   4,0
 pusha
 pushf
 mov     eax, [esp]      ; read FLAGS back off stack
 mov [ebp-4], eax    ; save flags

;
; show which FLAGS are set
;
 test eax, CF_MASK
 jz cf_off
 mov eax, carry_flag
 jmp short push_cf
cf_off:
 mov eax, unset_flag
push_cf:
 push eax

 test dword [ebp-4], PF_MASK
 jz pf_off
 mov eax, parity_flag
 jmp short push_pf
pf_off:
 mov eax, unset_flag
push_pf:
 push eax

 test dword [ebp-4], AF_MASK
 jz af_off
 mov eax, aux_carry_flag
 jmp short push_af
af_off:
 mov eax, unset_flag
push_af:
 push eax

 test dword [ebp-4], ZF_MASK
 jz zf_off
 mov eax, zero_flag
 jmp short push_zf
zf_off:
 mov eax, unset_flag
push_zf:
 push eax

 test dword [ebp-4], SF_MASK
 jz sf_off
 mov eax, sign_flag
 jmp short push_sf
sf_off:
 mov eax, unset_flag
push_sf:
 push eax

 test dword [ebp-4], DF_MASK
 jz df_off
 mov eax, dir_flag
 jmp short push_df
df_off:
 mov eax, unset_flag
push_df:
 push eax

 test dword [ebp-4], OF_MASK
 jz of_off
 mov eax, overflow_flag
 jmp short push_of
of_off:
 mov eax, unset_flag
push_of:
 push eax

 push    dword [ebp-4]   ; FLAGS
 mov eax, [ebp+4]
 sub eax, 10         ; EIP on stack is 10 bytes ahead of orig
 push eax             ; EIP
 lea     eax, [ebp+12]
 push    eax             ; original ESP
 push    dword [ebp]     ; original EBP
        push    edi
        push    esi
 push    edx
 push ecx
 push ebx
 push dword [ebp-8]   ; original EAX
 push dword [ebp+8]   ; # of dump
 push dword reg_format
 call _printf
 add esp, 76
 popf
 popa
 leave
 ret     4

sub_dump_stack:
 enter   0,0
 pusha
 pushf

 lea     eax, [ebp+20]
 push    eax             ; original ESP
 push    dword [ebp]     ; original EBP
 push dword [ebp+8]   ; # of dump
 push dword stack_format
 call _printf
 add esp, 16

 mov ebx, [ebp] ; ebx = original ebp
 mov eax, [ebp+16]   ; eax = # dwords above ebp
 shl eax, 2          ; eax *= 4
 add ebx, eax ; ebx = & highest dword in stack to display
 mov edx, [ebp+16]
 mov ecx, edx
 add ecx, [ebp+12]
 inc ecx  ; ecx = # of dwords to display

stack_line_loop:
 push edx
 push ecx  ; save ecx & edx

 push dword [ebx] ; value on stack
 push ebx  ; address of value on stack
 mov eax, edx
 sal eax, 2  ; eax = 4*edx
 push eax  ; offset from ebp
 push dword stack_line_format
 call _printf
 add esp, 16

 pop ecx
 pop edx

 sub ebx, 4
 dec edx
 loop stack_line_loop

 popf
 popa
 leave
 ret     12


sub_dump_mem:
 enter 0,0
 pusha
 pushf

 push dword [ebp+12]
 push dword [ebp+16]
 push dword mem_format1
 call _printf
 add esp, 12  
 mov esi, [ebp+12]      ; address
 and esi, 0FFFFFFF0h    ; move to start of paragraph
 mov ecx, [ebp+8]
 inc ecx
mem_outer_loop:
 push ecx
 push esi
 push dword mem_format2
 call _printf
 add esp, 8

 xor ebx, ebx
mem_hex_loop:
 xor eax, eax
 mov al, [esi + ebx]
 push eax
 push dword mem_format3
 call _printf
 add esp, 8
 inc ebx
 cmp ebx, 16
 jl mem_hex_loop

 mov eax, '"'
 call print_char
 xor ebx, ebx
mem_char_loop:
 xor eax, eax
 mov al, [esi+ebx]
 cmp al, 32
 jl non_printable
 cmp al, 126
 jg non_printable
 jmp short mem_char_loop_continue
non_printable:
 mov eax, '?'
mem_char_loop_continue:
 call print_char

 inc ebx
 cmp ebx, 16
 jl mem_char_loop

 mov eax, '"'
 call print_char
 call print_nl

 add esi, 16
 pop ecx
 loop mem_outer_loop

 popf
 popa
 leave
 ret 12

; function sub_dump_math
;   prints out state of math coprocessor without modifying the coprocessor
;   or regular processor state
; Parameters:
;  dump number - dword at [ebp+8]
; Local variables:
;   ebp-108 start of fsave buffer
;   ebp-116 temp double
; Notes: This procedure uses the Pascal convention.
;   fsave buffer structure:
;   ebp-108   control word
;   ebp-104   status word
;   ebp-100   tag word
;   ebp-80    ST0
;   ebp-70    ST1
;   ebp-60    ST2 ...
;   ebp-10    ST7
;
sub_dump_math:
 enter 116,0
 pusha
 pushf

 fsave [ebp-108] ; save coprocessor state to memory
 mov eax, [ebp-104]  ; status word
 and eax, 0FFFFh
 push eax
 mov eax, [ebp-108]  ; control word
 and eax, 0FFFFh
 push eax
 push dword [ebp+8]
 push dword math_format1
 call _printf
 add esp, 16
;
; rotate tag word so that tags in same order as numbers are
; in the stack
;
 mov cx, [ebp-104] ; ax = status word
 shr cx, 11
 and cx, 7           ; cl = physical state of number on stack top
 mov bx, [ebp-100]   ; bx = tag word
 shl     cl,1  ; cl *= 2
 ror bx, cl  ; move top of stack tag to lowest bits

 mov edi, 0  ; edi = stack number of number
 lea esi, [ebp-80]   ; esi = address of ST0
 mov ecx, 8          ; ecx = loop counter
tag_loop:
 push ecx
 mov ax, 3
 and ax, bx  ; ax = current tag
 or ax, ax  ; 00 -> valid number
 je valid_st
 cmp ax, 1  ; 01 -> zero
 je zero_st
 cmp ax, 2  ; 10 -> invalid number
 je invalid_st
 push edi  ; 11 -> empty
 push dword empty_st_format
 call _printf
 add esp, 8
 jmp short cont_tag_loop
zero_st:
 fldz
 jmp short print_real
valid_st:
 fld tword [esi]
print_real:
 fstp qword [ebp-116]
 push dword [ebp-112]
 push dword [ebp-116]
 push edi
 push dword valid_st_format
 call _printf
 add esp, 16
 jmp short cont_tag_loop
invalid_st:
 push edi
 push dword invalid_st_format
 call _printf
 add esp, 8
cont_tag_loop:
 ror bx, 2  ; mov next tag into lowest bits
 inc edi
 add esi, 10         ; mov to next number on stack
 pop ecx
 loop    tag_loop

 frstor [ebp-108]       ; restore coprocessor state
 popf
 popa
 leave
 ret 4

asm_io.inc:

 extern  read_int, print_int, print_string
 extern read_char, print_char, print_nl
 extern  sub_dump_regs, sub_dump_mem, sub_dump_math, sub_dump_stack

%macro  dump_regs 1
 push   dword %1
 call   sub_dump_regs
%endmacro


;
; usage: dump_mem label, start-address, # paragraphs
%macro  dump_mem 3
 push  dword %1
 push  dword %2
 push  dword %3
 call  sub_dump_mem
%endmacro

%macro dump_math 1
 push  dword %1
 call  sub_dump_math
%endmacro

%macro  dump_stack 3
 push  dword %3
        push     dword %2
 push  dword %1
        call     sub_dump_stack
%endmacro

first.asm

;
; file: first.asm
; First assembly program. This program asks for two integers as
; input and prints out their sum.
;
; To create executable:
; Using djgpp:
; nasm -f coff 开发者_C百科first.asm
; gcc -o first first.o driver.c asm_io.o
;
; Using Linux and gcc:
; nasm -f elf first.asm
; gcc -o first first.o driver.c asm_io.o
;
; Using Borland C/C++
; nasm -f obj first.asm
; bcc32 first.obj driver.c asm_io.obj
;
; Using MS C/C++
; nasm -f win32 first.asm
; cl first.obj driver.c asm_io.obj
;
; Using Open Watcom
; nasm -f obj first.asm
; wcl386 first.obj driver.c asm_io.obj

%include "asm_io.inc"
;
; initialized data is put in the .data segment
;
segment .data
;
; These labels refer to strings used for output
;
prompt1 db    "Enter a number: ", 0       ; don't forget nul terminator
prompt2 db    "Enter another number: ", 0
outmsg1 db    "You entered ", 0
outmsg2 db    " and ", 0
outmsg3 db    ", the sum of these is ", 0


;
; uninitialized data is put in the .bss segment
;
segment .bss
;
; These labels refer to double words used to store the inputs
;
input1  resd 1
input2  resd 1



;
; code is put in the .text segment
;
segment .text
        global  _asm_main
_asm_main:
        enter   0,0               ; setup routine
        pusha

        mov     eax, prompt1      ; print out prompt
        call    print_string

        call    read_int          ; read integer
        mov     [input1], eax     ; store into input1

        mov     eax, prompt2      ; print out prompt
        call    print_string

        call    read_int          ; read integer
        mov     [input2], eax     ; store into input2

        mov     eax, [input1]     ; eax = dword at input1
        add     eax, [input2]     ; eax += dword at input2
        mov     ebx, eax          ; ebx = eax
        dump_regs 1               ; dump out register values
        dump_mem 2, outmsg1, 1    ; dump out memory
;
; next print out result message as series of steps
;
        mov     eax, outmsg1
        call    print_string      ; print out first message
        mov     eax, [input1]     
        call    print_int         ; print out input1
        mov     eax, outmsg2
        call    print_string      ; print out second message
        mov     eax, [input2]
        call    print_int         ; print out input2
        mov     eax, outmsg3
        call    print_string      ; print out third message
        mov     eax, ebx
        call    print_int         ; print out sum (ebx)
        call    print_nl          ; print new-line

        popa
        mov     eax, 0            ; return back to C
        leave                     
        ret

drive.c:

#include "cdecl.h"

int PRE_CDECL asm_main( void ) POST_CDECL;

int main()
{
  int ret_status;
  ret_status = asm_main();
  return ret_status;
}

Now I compile it using:

nasm -f macho first.asm

nasm -f macho asm_io.asm

gcc first.o asm_io.o driver.c -o first -arch i386

Then run: ./first

Segmentation fault

It happens only when I'm using asm_io lib.

Thank you,

Daniel Koch

You seem to be using 32-bit assembly code here. One big difference among 32-bit Mac OS X and 32-bit Windows or Linux is that Mac requires the stack to be 16-byte aligned whenever you CALL a function. In other words, at the point in your code where you have a CALL instruction, it is required that ESP = #######0h.

The following may be interesting reads:

http://blogs.embarcadero.com/eboling/2009/05/20/5607