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