diff options
Diffstat (limited to 'libc/sysdeps/linux/arm/crt1.S')
| -rw-r--r-- | libc/sysdeps/linux/arm/crt1.S | 161 |
1 files changed, 161 insertions, 0 deletions
diff --git a/libc/sysdeps/linux/arm/crt1.S b/libc/sysdeps/linux/arm/crt1.S new file mode 100644 index 000000000..3bea01e73 --- /dev/null +++ b/libc/sysdeps/linux/arm/crt1.S @@ -0,0 +1,161 @@ +/* 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 + + For uClinux it looks like this: + + argc argument counter (integer) + argv char *argv[] + envp char *envp[] + 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 ARM Procedure Calling Standard Role + + a1 r0 argument 1 / integer result / scratch register / argc + a2 r1 argument 2 / scratch register / argv + a3 r2 argument 3 / scratch register / envp + a4 r3 argument 4 / scratch register + v1 r4 register variable + v2 r5 register variable + v3 r6 register variable + v4 r7 register variable + v5 r8 register variable + sb/v6 r9 static base / register variable + sl/v7 r10 stack limit / stack chunk handle / reg. variable + fp r11 frame pointer + ip r12 scratch register / new-sb in inter-link-unit calls + sp r13 lower end of current stack frame + lr r14 link address / scratch register + pc r15 program counter +*/ + +#include <features.h> + +.text + .global _start + .type _start,%function + .type _init,%function + .type _fini,%function + .type main,%function + .type __uClibc_main,%function + + +.text +_start: + /* clear the frame pointer */ + mov fp, #0 + +#ifdef __PIC__ + /* Store the address of main in r0 */ + adr r5, .L_main + ldr r0, .L_main + add r0, r0, r5 + +#else + /* Store the address of main in r0 */ + ldr r0, =main +#endif + +#ifdef __ARCH_HAS_MMU__ + + /* Load register r1 (argc) from the stack to its final resting place */ + ldr r1, [sp], #4 + + /* Copy argv pointer into r2 -- which its final resting place */ + mov r2, sp +#else + /* + * uClinux stacks look a little different from normal + * MMU-full Linux stacks (for no good reason) + */ + /* pull argc, argv and envp off the stack */ + ldr r1,[sp, #0] + ldr r2,[sp, #4] +#endif + +#ifdef __PIC__ + /* Store the address of _init in r3 */ + adr r5, .L_init + ldr r3, .L_init + add r3, r3, r5 + + /* Push _fini onto the stack as an argument to main() */ + ldr r4, .L_init + 4 + add r4, r4, r5 + stmfd sp!, {r4} + + /* Push rtld_fini onto the stack as an argument to main() */ + ldr r4, .L_init + 8 + add r4, r4, r5 + stmfd sp!, {r4} +#else + /* Store the address of _init in r3 as an argument to main() */ + ldr r3, =_init + + /* Push _fini onto the stack as an argument to main() */ + ldr r4, =_fini + stmfd sp!, {r4} + + /* Push rtld_fini onto the stack as an argument to main() */ + ldr r4, =rtld_fini + stmfd sp!, {r4} +#endif + + /* We need to call __uClibc_main which should not return. + __uClibc_main (int (*main) (int, char **, char **), int argc, + char **argv, void (*init) (void), void (*fini) (void), + void (*rtld_fini) (void), void *stack_end) + */ + bl __uClibc_main + + /* Crash if somehow `exit' returns anyways. */ + bl abort + +#ifdef __PIC__ +.L_init: + .word _init + .word _fini + .word rtld_fini +.L_main: + .word main +#endif + +/* We need this stuff to make gdb behave itself, otherwise + gdb will choke with SIGILL when trying to debug apps. +*/ + .section ".note.ABI-tag", "a" + .align 4 + .long 1f - 0f + .long 3f - 2f + .long 1 +0: .asciz "GNU" +1: .align 4 +2: .long 0 + .long 2,0,0 +3: .align 4 + +/* Define a symbol for the first piece of initialized data. */ + .data + .globl __data_start +__data_start: + .long 0 + .weak data_start + data_start = __data_start + |