diff options
Diffstat (limited to 'libc/sysdeps/linux/arm/crt0pic.S')
| -rw-r--r-- | libc/sysdeps/linux/arm/crt0pic.S | 67 |
1 files changed, 40 insertions, 27 deletions
diff --git a/libc/sysdeps/linux/arm/crt0pic.S b/libc/sysdeps/linux/arm/crt0pic.S index a668ac31f..04b1cb755 100644 --- a/libc/sysdeps/linux/arm/crt0pic.S +++ b/libc/sysdeps/linux/arm/crt0pic.S @@ -1,21 +1,49 @@ +/* When we enter this piece of code, the program stack looks like this: + argc argument counter (integer) + argv[0] program name (pointer) + argv[1...N] program args (pointers) + argv[argc-1] end of args (integer) + NULL + env[0...N] environment variables (pointers) + NULL + + When we are done here, we want + a1=argc + a2=argv[0] + a3=argv[argc+1] + +ARM register quick reference: + + Name Number APCS Role + + a1 0 argument 1 / integer result / scratch register / argc + a2 1 argument 2 / scratch register / argv + a3 2 argument 3 / scratch register / envp + a4 3 argument 4 / scratch register + v1 4 register variable + v2 5 register variable + v3 6 register variable + v4 7 register variable + v5 8 register variable + sb/v6 9 static base / register variable + sl/v7 10 stack limit / stack chunk handle / reg. variable + fp 11 frame pointer + ip 12 scratch register / new-sb in inter-link-unit calls + sp 13 lower end of current stack frame + lr 14 link address / scratch register + pc 15 program counter +*/ + .text .align 2 .global __environ .global _start .global exit .global main - .global __libc_init - .global __init_stdio - .global __stdio_close_all - .global _void_void_null_func .type _start,%function .type exit,%function .type main,%function - .type __libc_init,%function - .type __init_stdio,%function - .type __stdio_close_all,%function - .type _void_void_null_func,%function @@ -23,21 +51,18 @@ @ r1 = argv @ r2 = envp @ sl = data segment +#define BASEREG r9 .text _start: @ adjust the data segment base pointer ldr r3,=__data_start sub sl,sl,r3 - mov r9,sl + mov BASEREG,sl ldr r3, .L3 - str r2,[r9,r3] + str r2,[BASEREG,r3] - /* Tell libc to initialize whatever it needs */ - bl __libc_init - bl __init_stdio - /* pull argc, argv and envp off the stack */ ldr r0,[sp, #0] ldr r1,[sp, #4] @@ -47,21 +72,9 @@ _start: /* ldr r0,=0 */ bl exit -_void_void_null_func: - mov pc, lr - -.weak __libc_init -__libc_init = _void_void_null_func - -.weak __init_stdio -__init_stdio = _void_void_null_func - -.weak __stdio_close_all -__stdio_close_all = _void_void_null_func - .align 2 .L3: - .word environ + .word __environ .data |