235 lines
4.4 KiB
ArmAsm
235 lines
4.4 KiB
ArmAsm
.section .text.crt
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.globl _start
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.globl _exit.crt0
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.globl watchdogTrigger
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#ifdef __thumb__
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# define subs sub
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# define adds add
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#endif
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_start:
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/* get current PC , in R7 */
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bl _start_pc
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_start_pc:
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/* get PC from LR and correct it, used as PIC pointer r7+r9 onwards */
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mov r7, lr
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mov r0, #1
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bic r7, r7, r0
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ldr r0, .BASE
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subs r7, r7, r0
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mov r9, r7
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/* check for detailed relocation info and relocate */
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bl relocate
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/* set stack and frame pointer */
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ldr r1, .SP
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add r1, r7
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mov r0, #7
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bic r1, r0
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mov r0, #0
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mov sp, r1
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mov fp, r0
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/* clear .bss-section */
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ldr r4, .BSS_S
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ldr r5, .BSS_E
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mov r0, #0
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b bss_check
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bss_clear:
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strb r0, [r7, r4]
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add r4, r4, #1
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bss_check:
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cmp r5, r4
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bne bss_clear
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bss_done:
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/* correct global-offset-table, .got */
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/* correct data with relocations, .data.rel - with limitations */
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ldr r4, .RELOC_S
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ldr r5, .RELOC_E
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b got_check
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got:
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ldr r3, [r7, r4]
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add r3, r7
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str r3, [r7, r4]
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add r4, r4, #4
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got_check:
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cmp r5, r4
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bne got
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got_done:
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/* initialize Watchdog */
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ldr r3, .WDG_INIT
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cmp r3, #0
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beq wdg_init_done
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add r3, r7
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bl crt0_veneer
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wdg_init_done:
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/* register the WatchdogHook */
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ldr r3, .WDG_TRIGGER
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ldr r4, .WDG_HOOK
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cmp r3, #0
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beq wdg_hook_done
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add r3, r7
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wdg_hook_done:
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str r3, [r7, r4]
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/* initialization of e.g. static objects */
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ldr r4, .INIT_S
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ldr r5, .INIT_E
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b init_check
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init:
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ldr r3, [r7,r4]
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add r3, r7
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bl crt0_veneer
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add r4, r4, #4
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init_check:
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cmp r5, r4
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bne init
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init_done:
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gomain:
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ldr r3, .MAIN
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add r3, r7
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bl crt0_veneer
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nop
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_exit.crt0:
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b _exit.crt0
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crt0_veneer:
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/* make a THUMB/ARM generic veneer call to r3 */
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/* lr is set by preceding bl instruction */
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mov r0, #0
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mov r1, #0
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bx r3
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.org 0xFC
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_start_secondary:
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/* get current PC , in R7 */
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bl _start_secondary_pc
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.align 1
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_start_secondary_pc:
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/* get PC from LR and correct it - _start_secondary-_start = 0x100 = 2*0x80 */
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mov r7, lr
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mov r0, #1
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bic r7, r7, r0
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subs r7, r7, #0x4
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ldr r0, .BASE
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subs r7, r7, r0
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subs r7, r7, #0x80
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subs r7, r7, #0x80
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mov r9, r7
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/* set stack and frame pointer */
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/* SP is placed 0xF0 bytes after SP of Core0 */
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ldr r1, .SP
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add r1, r7
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add r1, r1, #0xf0
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mov r0, #0
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mov sp, r1
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mov fp, r0
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ldr r3, .BACKGROUND
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add r3, r9
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bl crt0_veneer
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nop
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b _exit.crt0
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.align 2
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.BASE:
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.word RAMSTART+0x4+0x4
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.SP:
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.word __stack_end
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.BSS_S:
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.word __bss_start
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.BSS_E:
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.word __bss_end
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.INIT_S:
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.word __init_array_start
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.INIT_E:
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.word __init_array_end
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.RELOC_S:
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.word __simple_relocate_start
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.RELOC_E:
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.word __simple_relocate_end
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.DATA_S:
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.word __data_vaddr
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.DATA_LADDR:
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.word __data_laddr
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.DATA_SIZE:
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.word __data_size
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#ifndef WATCHDOG
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.WDG_INIT:
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.word 0x0
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.WDG_TRIGGER:
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.word 0x0
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#else
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.WDG_INIT:
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.word WatchdogInit
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.WDG_TRIGGER:
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.word WatchdogTrigger
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#endif
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.WDG_HOOK:
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.word watchdogTrigger
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.MAIN:
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.word main
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.BACKGROUND:
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.word background
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relocate:
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ldr r4, .REL_DYN_S
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ldr r5, .REL_DYN_E
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cmp r4, r5
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beq relocate_done
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ldr r6, .DYNSYM_S
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add r4, r4, r7
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add r5, r5, r7
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add r6, r6, r7
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b relocate_check
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relocate_do:
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ldr r0, [r4]
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ldr r1, [r7, r0]
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ldrb r2, [r4, #4]
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cmp r2, #23
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beq relocate_fix_rel
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cmp r2, #2
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beq relocate_fix_abs
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b _exit.crt0
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relocate_fix_abs:
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ldr r2, [r4, #4]
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lsr r2, #4
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add r2, r2, r6
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ldr r2, [r2, #4]
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add r1, r1, r2
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/* intended fall-through */
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relocate_fix_rel:
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add r1, r1, r7
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str r1, [r7, r0]
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relocate_next:
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add r4, r4, #8
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relocate_check:
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cmp r4, r5
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bne relocate_do
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mov r7, #0
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relocate_done:
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bx r14
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.align 2
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.REL_DYN_S:
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.word _rel_dyn_start
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.REL_DYN_E:
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.word _rel_dyn_end
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.DYNSYM_S:
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.word _dynsym_start
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.section .data
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watchdogTrigger:
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.word 0x0
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.section .text
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.weak background
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background:
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1:
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b 1b
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