【基于Android的ARM汇编语言系列】之二：C/C++程序生成ARM汇编程序的过程分析

作者：郭嘉
邮箱：[e-mail]
博客：http://blog.csdn.net/allenwells
github：https://github.com/AllenWell

【基于Android的ARM汇编语言系列】章节列表

【基于Android的ARM汇编语言系列】之一：ARM汇编语言开篇
【基于Android的ARM汇编语言系列】之二：C/C++程序生成ARM汇编程序的过程分析
【基于Android的ARM汇编语言系列】之三：ARM汇编语言程序结构
【基于Android的ARM汇编语言系列】之四：ARM处理器的寻址方式
【基于Android的ARM汇编语言系列】之五：ARM指令集与Thumb指令集
【基于Android的ARM汇编语言系列】之六：NEON指令集与VFP指令集

所谓的原生程序指的是用C/C++编写的程序，下面来详细演示一下原生程序是怎么一步步生成汇编代码的。

这里编译的是一个简单的hello.c程序，如下所示：

#include <stdio.h>int main(int argc, char* argv[]){    printf("Hello ARM!\n");    return 0;}

一 预处理

预处理阶段会处理代码中的预处理指令,如下所示：

• #include
• #define
• #if

执行以下命令进行预处理，-E可以用来查看详细输出。

gcc -E hello.c -o hello.i

成成的hello.i如下所示：

# 1 "hello.c"# 1 "<built-in>"# 1 "<command-line>"# 1 "hello.c"# 1 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/stdio.h" 1# 41 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/stdio.h"# 1 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/sys/cdefs.h" 1# 59 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/sys/cdefs.h"# 1 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/sys/cdefs_elf.h" 1# 60 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/sys/cdefs.h" 2# 42 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/stdio.h" 2# 1 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/sys/_types.h" 1# 40 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/sys/_types.h"# 1 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/machine/_types.h" 1# 52 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/machine/_types.h"typedef signed char __int8_t;typedef unsigned char __uint8_t;typedef short __int16_t;typedef unsigned short __uint16_t;typedef int __int32_t;typedef unsigned int __uint32_t;typedef long long __int64_t;typedef unsigned long long __uint64_t;typedef __int8_t __int_least8_t;typedef __uint8_t __uint_least8_t;typedef __int16_t __int_least16_t;typedef __uint16_t __uint_least16_t;typedef __int32_t __int_least32_t;typedef __uint32_t __uint_least32_t;typedef __int64_t __int_least64_t;typedef __uint64_t __uint_least64_t;typedef __int32_t __int_fast8_t;typedef __uint32_t __uint_fast8_t;typedef __int32_t __int_fast16_t;typedef __uint32_t __uint_fast16_t;typedef __int32_t __int_fast32_t;typedef __uint32_t __uint_fast32_t;typedef __int64_t __int_fast64_t;typedef __uint64_t __uint_fast64_t;typedef int __intptr_t;typedef unsigned int __uintptr_t;typedef __int64_t __intmax_t;typedef __uint64_t __uintmax_t;typedef __int32_t __register_t;typedef unsigned long __vaddr_t;typedef unsigned long __paddr_t;typedef unsigned long __vsize_t;typedef unsigned long __psize_t;typedef int __clock_t;typedef int __clockid_t;typedef long __ptrdiff_t;typedef int __time_t;typedef int __timer_t;typedef __builtin_va_list __va_list;typedef int __wchar_t;typedef int __wint_t;typedef int __rune_t;typedef void * __wctrans_t;typedef void * __wctype_t;# 41 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/sys/_types.h" 2typedef unsigned long __cpuid_t;typedef __int32_t __dev_t;typedef __uint32_t __fixpt_t;typedef __uint32_t __gid_t;typedef __uint32_t __id_t;typedef __uint32_t __in_addr_t;typedef __uint16_t __in_port_t;typedef __uint32_t __ino_t;typedef long __key_t;typedef __uint32_t __mode_t;typedef __uint32_t __nlink_t;typedef __int32_t __pid_t;typedef __uint64_t __rlim_t;typedef __uint16_t __sa_family_t;typedef __int32_t __segsz_t;typedef __uint32_t __socklen_t;typedef __int32_t __swblk_t;typedef __uint32_t __uid_t;typedef __uint32_t __useconds_t;typedef __int32_t __suseconds_t;typedef union { char __mbstate8[128]; __int64_t __mbstateL;} __mbstate_t;# 43 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/stdio.h" 2# 1 "c:/android-ndk-r8/toolchains/arm-linux-androideabi-4.4.3/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.4.3/include/stdarg.h" 1 3 4# 40 "c:/android-ndk-r8/toolchains/arm-linux-androideabi-4.4.3/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.4.3/include/stdarg.h" 3 4typedef __builtin_va_list __gnuc_va_list;# 47 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/stdio.h" 2# 1 "c:/android-ndk-r8/toolchains/arm-linux-androideabi-4.4.3/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.4.3/include/stddef.h" 1 3 4# 211 "c:/android-ndk-r8/toolchains/arm-linux-androideabi-4.4.3/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.4.3/include/stddef.h" 3 4typedef unsigned int size_t;# 51 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/stdio.h" 2# 1 "c:/android-ndk-r8/toolchains/arm-linux-androideabi-4.4.3/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.4.3/include/stddef.h" 1 3 4# 149 "c:/android-ndk-r8/toolchains/arm-linux-androideabi-4.4.3/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.4.3/include/stddef.h" 3 4typedef int ptrdiff_t;# 323 "c:/android-ndk-r8/toolchains/arm-linux-androideabi-4.4.3/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.4.3/include/stddef.h" 3 4typedef unsigned int wchar_t;# 53 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/stdio.h" 2# 1 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/sys/types.h" 1# 33 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/sys/types.h"# 1 "c:/android-ndk-r8/toolchains/arm-linux-androideabi-4.4.3/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.4.3/include/stddef.h" 1 3 4# 34 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/sys/types.h" 2# 1 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/stdint.h" 1# 31 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/stdint.h"# 1 "c:/android-ndk-r8/toolchains/arm-linux-androideabi-4.4.3/prebuilt/windows/bin/../lib/gcc/arm-linux-androideabi/4.4.3/include/stddef.h" 1 3 4# 32 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/stdint.h" 2# 48 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/stdint.h"typedef __int8_t int8_t;typedef __uint8_t uint8_t;typedef __int16_t int16_t;typedef __uint16_t uint16_t;typedef __int32_t int32_t;typedef __uint32_t uint32_t;typedef __int64_t int64_t;typedef __uint64_t uint64_t;typedef int8_t int_least8_t;typedef int8_t int_fast8_t;typedef uint8_t uint_least8_t;typedef uint8_t uint_fast8_t;# 97 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/stdint.h"typedef int16_t int_least16_t;typedef int32_t int_fast16_t;typedef uint16_t uint_least16_t;typedef uint32_t uint_fast16_t;# 130 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/stdint.h"typedef int32_t int_least32_t;typedef int32_t int_fast32_t;typedef uint32_t uint_least32_t;typedef uint32_t uint_fast32_t;# 163 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/stdint.h"typedef int64_t int_least64_t;typedef int64_t int_fast64_t;typedef uint64_t uint_least64_t;typedef uint64_t uint_fast64_t;# 207 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/stdint.h"typedef int intptr_t;typedef unsigned int uintptr_t;# 232 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/stdint.h"typedef uint64_t uintmax_t;typedef int64_t intmax_t;# 268 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/stdint.h"typedef long int ssize_t;# 35 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/sys/types.h" 2# 1 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/linux/posix_types.h" 1# 15 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/linux/posix_types.h"# 1 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/linux/stddef.h" 1# 15 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/linux/stddef.h"# 1 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/linux/compiler.h" 1# 16 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/linux/stddef.h" 2# 16 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/linux/posix_types.h" 2# 32 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/linux/posix_types.h"typedef struct { unsigned long fds_bits [(1024/(8 * sizeof(unsigned long)))];} __kernel_fd_set;typedef void (*__kernel_sighandler_t)(int);typedef int __kernel_key_t;typedef int __kernel_mqd_t;# 1 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/asm/posix_types.h" 1# 15 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/asm/posix_types.h"typedef unsigned long __kernel_ino_t;typedef unsigned short __kernel_mode_t;typedef unsigned short __kernel_nlink_t;typedef long __kernel_off_t;typedef int __kernel_pid_t;typedef unsigned short __kernel_ipc_pid_t;typedef unsigned short __kernel_uid_t;typedef unsigned short __kernel_gid_t;typedef unsigned int __kernel_size_t;typedef int __kernel_ssize_t;typedef int __kernel_ptrdiff_t;typedef long __kernel_time_t;typedef long __kernel_suseconds_t;typedef long __kernel_clock_t;typedef int __kernel_timer_t;typedef int __kernel_clockid_t;typedef int __kernel_daddr_t;typedef char * __kernel_caddr_t;typedef unsigned short __kernel_uid16_t;typedef unsigned short __kernel_gid16_t;typedef unsigned int __kernel_uid32_t;typedef unsigned int __kernel_gid32_t;typedef unsigned short __kernel_old_uid_t;typedef unsigned short __kernel_old_gid_t;typedef unsigned short __kernel_old_dev_t;typedef long long __kernel_loff_t;typedef struct { int __val[2];} __kernel_fsid_t;# 42 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/linux/posix_types.h" 2# 38 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/sys/types.h" 2# 1 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/asm/types.h" 1# 17 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/asm/types.h"typedef unsigned short umode_t;typedef __signed__ char __s8;typedef unsigned char __u8;typedef __signed__ short __s16;typedef unsigned short __u16;typedef __signed__ int __s32;typedef unsigned int __u32;typedef __signed__ long long __s64;typedef unsigned long long __u64;# 39 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/sys/types.h" 2# 1 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/linux/types.h" 1# 21 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/linux/types.h"typedef __u16 __le16;typedef __u16 __be16;typedef __u32 __le32;typedef __u32 __be32;typedef __u64 __le64;typedef __u64 __be64;struct ustat { __kernel_daddr_t f_tfree; __kernel_ino_t f_tinode; char f_fname[6]; char f_fpack[6];};# 40 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/sys/types.h" 2# 1 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/machine/kernel.h" 1# 34 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/machine/kernel.h"typedef unsigned long __kernel_blkcnt_t;typedef unsigned long __kernel_blksize_t;typedef unsigned long __kernel_fsblkcnt_t;typedef unsigned long __kernel_fsfilcnt_t;typedef unsigned int __kernel_id_t;# 41 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/sys/types.h" 2typedef __u32 __kernel_dev_t;# 52 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/sys/types.h"typedef __kernel_blkcnt_t blkcnt_t;typedef __kernel_blksize_t blksize_t;typedef __kernel_clock_t clock_t;typedef __kernel_clockid_t clockid_t;typedef __kernel_dev_t dev_t;typedef __kernel_fsblkcnt_t fsblkcnt_t;typedef __kernel_fsfilcnt_t fsfilcnt_t;typedef __kernel_gid32_t gid_t;typedef __kernel_id_t id_t;typedef __kernel_ino_t ino_t;typedef __kernel_key_t key_t;typedef __kernel_mode_t mode_t;typedef __kernel_nlink_t nlink_t;typedef __kernel_off_t off_t;typedef __kernel_loff_t loff_t;typedef loff_t off64_t;typedef __kernel_pid_t pid_t;# 99 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/sys/types.h"typedef __kernel_suseconds_t suseconds_t;typedef __kernel_time_t time_t;typedef __kernel_uid32_t uid_t;typedef signed long useconds_t;typedef __kernel_daddr_t daddr_t;typedef __kernel_timer_t timer_t;typedef __kernel_mqd_t mqd_t;typedef __kernel_caddr_t caddr_t;typedef unsigned int uint_t;typedef unsigned int uint;# 1 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/sys/sysmacros.h" 1# 36 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/sys/sysmacros.h"static __inline__ int major(dev_t _dev){  return (_dev >> 8) & 0xfff;}static __inline__ int minor(dev_t _dev){  return (_dev & 0xff) | ((_dev >> 12) & 0xfff00);}static __inline__ dev_t makedev(int __ma, int __mi){  return ((__ma & 0xfff) << 8) | (__mi & 0xff) | ((__mi & 0xfff00) << 12);}# 114 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/sys/types.h" 2typedef unsigned char u_char;typedef unsigned short u_short;typedef unsigned int u_int;typedef unsigned long u_long;typedef uint32_t u_int32_t;typedef uint16_t u_int16_t;typedef uint8_t u_int8_t;typedef uint64_t u_int64_t;# 56 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/stdio.h" 2# 78 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/stdio.h"typedef off_t fpos_t;# 87 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/stdio.h"struct __sbuf { unsigned char *_base; int _size;};# 119 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/stdio.h"typedef struct __sFILE { unsigned char *_p; int _r; int _w; short _flags; short _file; struct __sbuf _bf; int _lbfsize; void *_cookie; int (*_close)(void *); int (*_read)(void *, char *, int); fpos_t (*_seek)(void *, fpos_t, int); int (*_write)(void *, const char *, int); struct __sbuf _ext; unsigned char *_up; int _ur; unsigned char _ubuf[3]; unsigned char _nbuf[1]; struct __sbuf _lb; int _blksize; fpos_t _offset;} FILE;extern FILE __sF[];# 223 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/stdio.h"void clearerr(FILE *);int fclose(FILE *);int feof(FILE *);int ferror(FILE *);int fflush(FILE *);int fgetc(FILE *);int fgetpos(FILE *, fpos_t *);char *fgets(char *, int, FILE *);FILE *fopen(const char *, const char *);int fprintf(FILE *, const char *, ...);int fputc(int, FILE *);int fputs(const char *, FILE *);size_t fread(void *, size_t, size_t, FILE *);FILE *freopen(const char *, const char *, FILE *);int fscanf(FILE *, const char *, ...);int fseek(FILE *, long, int);int fseeko(FILE *, off_t, int);int fsetpos(FILE *, const fpos_t *);long ftell(FILE *);off_t ftello(FILE *);size_t fwrite(const void *, size_t, size_t, FILE *);int getc(FILE *);int getchar(void);char *gets(char *);extern int sys_nerr;extern char *sys_errlist[];void perror(const char *);int printf(const char *, ...);int putc(int, FILE *);int putchar(int);int puts(const char *);int remove(const char *);int rename(const char *, const char *);void rewind(FILE *);int scanf(const char *, ...);void setbuf(FILE *, char *);int setvbuf(FILE *, char *, int, size_t);int sprintf(char *, const char *, ...);int sscanf(const char *, const char *, ...);FILE *tmpfile(void);char *tmpnam(char *);int ungetc(int, FILE *);int vfprintf(FILE *, const char *, __va_list);int vprintf(const char *, __va_list);int vsprintf(char *, const char *, __va_list);int snprintf(char *, size_t, const char *, ...)  __attribute__((__format__ (printf, 3, 4)))  __attribute__((__nonnull__ (3)));int vfscanf(FILE *, const char *, __va_list)  __attribute__((__format__ (scanf, 2, 0)))  __attribute__((__nonnull__ (2)));int vscanf(const char *, __va_list)  __attribute__((__format__ (scanf, 1, 0)))  __attribute__((__nonnull__ (1)));int vsnprintf(char *, size_t, const char *, __va_list)  __attribute__((__format__ (printf, 3, 0)))  __attribute__((__nonnull__ (3)));int vsscanf(const char *, const char *, __va_list)  __attribute__((__format__ (scanf, 2, 0)))  __attribute__((__nonnull__ (2)));# 302 "c:/android-ndk-r8/platforms/android-14/arch-arm/usr/include/stdio.h"FILE *fdopen(int, const char *);int fileno(FILE *);int pclose(FILE *);FILE *popen(const char *, const char *);void flockfile(FILE *);int ftrylockfile(FILE *);void funlockfile(FILE *);int getc_unlocked(FILE *);int getchar_unlocked(void);int putc_unlocked(int, FILE *);int putchar_unlocked(int);char *tempnam(const char *, const char *);int asprintf(char **, const char *, ...)  __attribute__((__format__ (printf, 2, 3)))  __attribute__((__nonnull__ (2)));char *fgetln(FILE *, size_t *);int fpurge(FILE *);int getw(FILE *);int putw(int, FILE *);void setbuffer(FILE *, char *, int);int setlinebuf(FILE *);int vasprintf(char **, const char *, __va_list)  __attribute__((__format__ (printf, 2, 0)))  __attribute__((__nonnull__ (2)));FILE *funopen(const void *,  int (*)(void *, char *, int),  int (*)(void *, const char *, int),  fpos_t (*)(void *, fpos_t, int),  int (*)(void *));int __srget(FILE *);int __swbuf(int, FILE *);static __inline int __sputc(int _c, FILE *_p) { if (--_p->_w >= 0 || (_p->_w >= _p->_lbfsize && (char)_c != '\n'))  return (*_p->_p++ = _c); else  return (__swbuf(_c, _p));}# 2 "hello.c" 2int main(int argc, char* argv[]){ printf("Hello ARM!\n"); return 0;}

二 编译

编译阶段编译器会检查代码规范性，以及是否有语法错误等。

执行以下命令进行编译，-S可以用来查看编译器输出。

gcc -S hello.i -o hello.s

生成的hello.s文件如下所示：

    .arch armv5te    .fpu softvfp    .eabi_attribute 20, 1    .eabi_attribute 21, 1    .eabi_attribute 23, 3    .eabi_attribute 24, 1    .eabi_attribute 25, 1    .eabi_attribute 26, 2    .eabi_attribute 30, 6    .eabi_attribute 18, 4    .file   "hello.c"    .section    .rodata    .align  2.LC0:    .ascii  "Hello ARM!\000"    .text    .align  2    .global main    .type   main, %functionmain:    @ args = 0, pretend = 0, frame = 8    @ frame_needed = 1, uses_anonymous_args = 0    stmfd   sp!, {fp, lr}    add fp, sp, #4    sub sp, sp, #8    str r0, [fp, #-8]    str r1, [fp, #-12]    ldr r3, .L3.LPIC0:    add r3, pc, r3    mov r0, r3    bl  puts(PLT)    mov r3, #0    mov r0, r3    sub sp, fp, #4    ldmfd   sp!, {fp, pc}.L4:    .align  2.L3:    .word   .LC0-(.LPIC0+8)    .size   main, .-main    .ident  "GCC: (GNU) 4.4.3"    .section    .note.GNU-stack,"",%progbits

这里便是ARM汇编代码了，后续的文章会详细介绍这些代码的具体含义。

三 汇编

汇编阶段汇编器会将汇编代码汇编成二进制目标文件。

执行以下命令进行汇编：

gcc -c hello.s -o hello.o

生成的hello.o文件，用IDAPro反汇编以后如下所示：

;; +-------------------------------------------------------------------------+; |   This file has been generated by The Interactive Disassembler (IDA)    |; |           Copyright (c) 2011 Hex-Rays, <[e-mail]>           |; |                      License info: 48-327F-7274-B7                      |; |                            ESET spol. s r.o.                            |; +-------------------------------------------------------------------------+;; Input MD5   : B0821B68099D81DC63D478051984E2D8; Input CRC32 : 68360FC1; File Name   : C:\Users\Administrator\Desktop\【Android SDK程序逆向分析与破解系列】\相关资料\Android软件安全与逆向分析【丰生强】\Android软件安全与逆向分析【丰生强】随书光盘\chapter6\6.2\6.2.2\hello\hello.o; Format      : ELF for ARM (Relocatable);; EABI version: 5;; Source File : 'hello.c'; Processor       : ARM; Target assembler: Generic assembler for ARM; Byte sex        : Little endian; Segment type: Pure codeAREA .text, CODECODE32; Attributes: bp-based frameEXPORT mainmainvar_C= -0xCvar_8= -8STMFD   SP!, {R11,LR}ADD     R11, SP, #4SUB     SP, SP, #8STR     R0, [R11,#var_8]STR     R1, [R11,#var_C]LDR     R3, =(aHelloArm-0x20) ; "Hello ARM!"ADD     R3, PC, R3      ; "Hello ARM!"MOV     R0, R3          ; sBL      puts            ; PIC modeMOV     R3, #0MOV     R0, R3SUB     SP, R11, #4LDMFD   SP!, {R11,PC}; End of function main

四 链接

链接阶段会调用链接器将二进制的目标文件链接成Android平台可执行的ARM原生程序。

执行以下命令进行链接：

gcc hello.o -o hello

这个过程还需要链接其他目标文件，参数配置见以下Makefile脚本：

NDK_ROOT=c:/android-ndk-r8TOOLCHAINS_ROOT=$(NDK_ROOT)/toolchains/arm-linux-androideabi-4.4.3/prebuilt/windowsTOOLCHAINS_PREFIX=$(TOOLCHAINS_ROOT)/bin/arm-linux-androideabiTOOLCHAINS_INCLUDE=$(TOOLCHAINS_ROOT)/lib/gcc/arm-linux-androideabi/4.4.3/include-fixedPLATFORM_ROOT=$(NDK_ROOT)/platforms/android-14/arch-armPLATFORM_INCLUDE=$(PLATFORM_ROOT)/usr/includePLATFORM_LIB=$(PLATFORM_ROOT)/usr/libSYSROOT=$(PLATFORM_ROOT)MODULE_NAME=helloRM=delFLAGS=-I$(TOOLCHAINS_INCLUDE) \    -I$(PLATFORM_INCLUDE) \    -L$(PLATFORM_LIB) \OBJS=$(MODULE_NAME).o \    $(PLATFORM_LIB)/crtbegin_dynamic.o \    $(PLATFORM_LIB)/crtend_android.oall:    $(TOOLCHAINS_PREFIX)-gcc $(FLAGS) -E $(MODULE_NAME).c -o $(MODULE_NAME).i    $(TOOLCHAINS_PREFIX)-gcc $(FLAGS) -S $(MODULE_NAME).i -o $(MODULE_NAME).s    $(TOOLCHAINS_PREFIX)-gcc $(FLAGS) -c $(MODULE_NAME).s -o $(MODULE_NAME).o    $(TOOLCHAINS_PREFIX)-gcc $(FLAGS) -nostdlib -lgcc -Bdynamic -lc $(OBJS) -o $(MODULE_NAME)clean:    $(RM) *.oinstall:    adb push $(MODULE_NAME) /data/local/    adb shell chmod 755 /data/local/$(MODULE_NAME)

生成的可执行文件hello用IDAPro反汇编如下所示：

; Segment type: Pure codeAREA .text, CODE, ALIGN=4; ORG 0x82E0CODE32; Attributes: bp-based frameEXPORT mainmainvar_C= -0xCvar_8= -8STMFD   SP!, {R11,LR}ADD     R11, SP, #4SUB     SP, SP, #8STR     R0, [R11,#var_8]STR     R1, [R11,#var_C]LDR     R3, =(aHelloArm - 0x8300)ADD     R3, PC, R3      ; "Hello ARM!"MOV     R0, R3          ; sBL      putsMOV     R3, #0MOV     R0, R3SUB     SP, R11, #4LDMFD   SP!, {R11,PC}; End of function main

从以上过程可以看出，经过编译后C代码就转换成了汇编代码，因此可以直接编写汇编代码来开发ARM程序。Android NDK支持直接使用ARM汇编语言编写以.s结尾的文件作为程序的源文件，同时还允许使用C代码与ARM汇编代码进行混合编程。