diff options
Diffstat (limited to 'libgloss/arm/crt0.S')
| -rw-r--r-- | libgloss/arm/crt0.S | 359 |
1 files changed, 359 insertions, 0 deletions
diff --git a/libgloss/arm/crt0.S b/libgloss/arm/crt0.S new file mode 100644 index 0000000..7f36b12 --- /dev/null +++ b/libgloss/arm/crt0.S @@ -0,0 +1,359 @@ +#include "swi.h" + +/* ANSI concatenation macros. */ +#define CONCAT(a, b) CONCAT2(a, b) +#define CONCAT2(a, b) a ## b + +#ifdef __USER_LABEL_PREFIX__ +#define FUNCTION( name ) CONCAT (__USER_LABEL_PREFIX__, name) +#else +#error __USER_LABEL_PREFIX is not defined +#endif + +/* .text is used instead of .section .text so it works with arm-aout too. */ + .text + .code 32 + .align 0 + + .global _mainCRTStartup + .global _start + .global start +start: +_start: +_mainCRTStartup: + +/* Start by setting up a stack */ +#ifdef ARM_RDP_MONITOR + /* Issue Demon SWI to read stack info */ + swi SWI_GetEnv /* Returns command line in r0 */ + mov sp,r1 /* and the highest memory address in r1 */ + ldr sl, .LC2 /* stack limit is at end of data */ + add sl, sl, #256 /* allow slop for stack overflow handling */ + /* and small frames */ +#else +#ifdef ARM_RDI_MONITOR + /* Issue Angel SWI to read stack info */ + mov r0, #AngelSWI_Reason_HeapInfo + adr r1, .LC0 /* point at ptr to 4 words to receive data */ + swi AngelSWI_ARM /* We are always in ARM mode for startup */ + ldr r0, .LC0 /* point at values read */ + ldr sp, [r0, #8] + ldr sl, [r0, #12] + add sl, sl, #256 /* allow slop for stack overflow handling */ + /* and small frames */ +#else + /* Set up the stack pointer to a fixed value */ + /* Changes by toralf: + - Allow linker script to provide stack via __stack symbol - see + defintion of .Lstack + - Provide "hooks" that may be used by the application to add + custom init code - see .Lhwinit and .Lswinit + - Go through all execution modes and set up stack for each of them. + Loosely based on init.s from ARM/Motorola example code. + Note: Mode switch via CPSR is not allowed once in non-privileged + mode, so we take care not to enter "User" to set up its sp, + and also skip most operations if already in that mode. */ + + ldr r3, .Lstack + cmp r3, #0 + ldreq r3, .LC0 + /* Note: This 'mov' is essential when starting in User, and ensures we + always get *some* sp value for the initial mode, even if we + have somehow missed it below (in which case it gets the same + value as FIQ - not ideal, but better than nothing.) */ + mov sp, r3 + mrs r2, CPSR + tst r2, #0x0F /* Test mode bits - in User of all are 0 */ + beq .LC23 /* "eq" means r2 AND #0x0F is 0 */ + msr CPSR_c, #0xD1 /* FIRQ mode, interrupts disabled */ + mov sp, r3 + sub sl, sp, #0x1000 /* This mode also has its own sl (see below) */ + + mov r3, sl + msr CPSR_c, #0xD7 /* Abort mode, interrupts disabled */ + mov sp, r3 + sub r3, r3, #0x1000 + + msr CPSR_c, #0xDB /* Undefined mode, interrupts disabled */ + mov sp, r3 + sub r3, r3, #0x1000 + + msr CPSR_c, #0xD2 /* IRQ mode, interrupts disabled */ + mov sp, r3 + sub r3, r3, #0x2000 + + msr CPSR_c, #0xD3 /* Supervisory mode, interrupts disabled */ + mov sp, r3 + sub r3, r3, #0x8000 /* Min size 32k */ + bic r3, r3, #0x00FF /* Align with current 64k block */ + bic r3, r3, #0xFF00 + + str r3, [r3, #-4] /* Move value into user mode sp without */ + ldmdb r3, {sp}^ /* changing modes, via '^' form of ldm */ + + orr r2, r2, #0xC0 /* Back to original mode, presumably SVC, */ + msr CPSR_c, r2 /* with FIQ/IRQ disable bits forced to 1 */ +.LC23: + /* Setup a default stack-limit in-case the code has been + compiled with "-mapcs-stack-check". Hard-wiring this value + is not ideal, since there is currently no support for + checking that the heap and stack have not collided, or that + this default 64k is enough for the program being executed. + However, it ensures that this simple crt0 world will not + immediately cause an overflow event: */ + sub sl, r3, #64 << 10 /* Still assumes 256bytes below sl */ +#endif +#endif + /* Zero the memory in the .bss section. */ + mov a2, #0 /* Second arg: fill value */ + mov fp, a2 /* Null frame pointer */ + mov r7, a2 /* Null frame pointer for Thumb */ + + ldr a1, .LC1 /* First arg: start of memory block */ + ldr a3, .LC2 + sub a3, a3, a1 /* Third arg: length of block */ + + +#ifdef __thumb__ /* Enter Thumb mode.... */ + + add a4, pc, #1 /* Get the address of the Thumb block */ + bx a4 /* Go there and start Thumb decoding */ + + .code 16 + .global __change_mode + .thumb_func +__change_mode: +#endif + + bl FUNCTION (memset) +#if !defined (ARM_RDP_MONITOR) && !defined (ARM_RDI_MONITOR) +/* Changes by toralf: Taken from libgloss/m68k/crt0.S + * initialize target specific stuff. Only execute these + * functions it they exist. + */ + ldr r3, .Lhwinit + cmp r3, #0 + beq .LC24 + mov lr, pc + mov pc, r3 +.LC24: + ldr r3, .Lswinit + cmp r3, #0 + beq .LC25 + mov lr, pc + mov pc, r3 +.LC25: + mov r0, #0 /* no arguments */ + mov r1, #0 /* no argv either */ +#else + /* Need to set up standard file handles */ + bl FUNCTION (initialise_monitor_handles) + +#ifdef ARM_RDP_MONITOR + swi SWI_GetEnv /* sets r0 to point to the command line */ + mov r1, r0 +#else + mov r0, #AngelSWI_Reason_GetCmdLine + adr r1, .LC30 /* Space for command line */ + swi AngelSWI + ldr r1, .LC30 +#endif + /* Parse string at r1 */ + mov r0, #0 /* count of arguments so far */ + /* Push a NULL argument onto the end of the list. */ +#ifdef __thumb__ + push {r0} +#else + stmfd sp!, {r0} +#endif +.LC10: +/* Skip leading blanks */ +#ifdef __thumb__ + ldrb r3, [r1] + add r1, #1 +#else + ldrb r3, [r1], #1 +#endif + cmp r3, #0 + beq .LC12 + cmp r3, #' ' + beq .LC10 + +/* See whether we are scanning a string */ + cmp r3, #'"' +#ifdef __thumb__ + beq .LC20 + cmp r3, #'\'' + bne .LC21 +.LC20: + mov r2, r3 + b .LC22 + +.LC21: + mov r2, #' ' /* terminator type */ + sub r1, r1, #1 /* adjust back to point at start char */ +.LC22: +#else + cmpne r3, #'\'' + moveq r2, r3 + movne r2, #' ' /* terminator type */ + subne r1, r1, #1 /* adjust back to point at start char */ +#endif + +/* Stack a pointer to the current argument */ +#ifdef __thumb__ + push {r1} +#else + stmfd sp!, {r1} +#endif + add r0, r0, #1 +.LC11: +#ifdef __thumb__ + ldrb r3, [r1] + add r1, #1 +#else + ldrb r3, [r1], #1 +#endif + cmp r3, #0 + beq .LC12 + cmp r2, r3 /* reached terminator? */ + bne .LC11 + mov r2, #0 + sub r3, r1, #1 + strb r2, [r3] /* terminate the arg string */ + b .LC10 + +.LC12: + mov r1, sp /* point at stacked arg pointers */ + /* We've now got the stacked args in order reverse the */ +#ifdef __thumb__ + mov r2, r0 + lsl r2, #2 + add r2, sp + mov r3, sp +.LC15: cmp r2, r3 + bls .LC14 + sub r2, #4 + ldr r4, [r2] + ldr r5, [r3] + str r5, [r2] + str r4, [r3] + add r3, #4 + b .LC15 +.LC14: +#else + add r2, sp, r0, LSL #2 /* End of args */ + mov r3, sp /* Start of args */ +.LC13: cmp r2, r3 + ldrhi r4,[r2, #-4] /* Reverse ends of list */ + ldrhi r5, [r3] + strhi r5, [r2, #-4]! + strhi r4, [r3], #4 + bhi .LC13 +#endif +#endif + +#ifdef __USES_INITFINI__ + /* Some arm/elf targets use the .init and .fini sections + to create constructors and destructors, and for these + targets we need to call the _init function and arrange + for _fini to be called at program exit. */ + mov r4, r0 + mov r5, r1 + ldr r0, .Lfini + bl FUNCTION (atexit) + bl FUNCTION (_init) + mov r0, r4 + mov r1, r5 +#endif + bl FUNCTION (main) + + bl FUNCTION (exit) /* Should not return. */ + +#ifdef __thumb__ + /* Come out of Thumb mode. This code should be redundant. */ + + mov a4, pc + bx a4 + + .code 32 + .global change_back +change_back: + /* Halt the execution. This code should never be executed. */ + /* With no debug monitor, this probably aborts (eventually). + With a Demon debug monitor, this halts cleanly. + With an Angel debug monitor, this will report 'Unknown SWI'. */ + swi SWI_Exit +#endif + + /* For Thumb, constants must be after the code since only + positive offsets are supported for PC relative addresses. */ + + .align 0 +.LC0: +#ifdef ARM_RDI_MONITOR + .word HeapBase +#else +#ifndef ARM_RDP_MONITOR + /* Changes by toralf: Provide alternative "stack" variable whose value + may be defined externally; .Lstack will be used instead of .LC0 if + it points to a non-0 value. Also set up references to "hooks" that + may be used by the application to provide additional init code. */ + +#ifdef __pe__ + .word 0x800000 +#else + .word 0x80000 /* Top of RAM on the PIE board. */ +#endif +.Lstack: + .word __stack +.Lhwinit: + .word FUNCTION (hardware_init_hook) +.Lswinit: + .word FUNCTION (software_init_hook) + + /* Set up defaults for the above variables in the form of weak symbols + - so that application will link correctly, and get value 0 in + runtime (meaning "ignore setting") for the variables, when the user + does not provide the symbols. (The linker uses a weak symbol if, + and only if, a normal version of the same symbol isn't provided + e.g. by a linker script or another object file.) */ + + .set __stack, 0 + .set FUNCTION (hardware_init_hook), 0 + .set FUNCTION (software_init_hook), 0 + + .weak __stack + .weak FUNCTION (hardware_init_hook) + .weak FUNCTION (software_init_hook) +#endif + +#endif +.LC1: + .word __bss_start__ +.LC2: + .word __bss_end__ +#ifdef __USES_INITFINI__ +.Lfini: + .word FUNCTION(_fini) +#endif +#ifdef ARM_RDI_MONITOR +.LC30: + .word CommandLine + .word 255 + +/* Workspace for Angel calls. */ + .data +/* Data returned by monitor SWI. */ +.global __stack_base__ +HeapBase: .word 0 +HeapLimit: .word 0 +__stack_base__: .word 0 +StackLimit: .word 0 +CommandLine: .space 256,0 /* Maximum length of 255 chars handled. */ +#endif + +#ifdef __pe__ + .section .idata$3 + .long 0,0,0,0,0,0,0,0 +#endif |