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base: Add Linux and GOT relative startup code on ARM

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* Linux specific startup code for base-linux ARM
* load symbols global offset table relative in order to avoid text
  relocations

issue #3466
This commit is contained in:
Sebastian Sumpf 2019-08-13 13:43:28 +02:00 committed by Christian Helmuth
parent 1bdd18a196
commit f3a7d3750f
1 changed files with 60 additions and 10 deletions
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70
repos/base/src/lib/startup/spec/arm/crt0.s
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@ -6,7 +6,7 @@
*/
/*
* Copyright (C) 2007-2017 Genode Labs GmbH
* Copyright (C) 2007-2019 Genode Labs GmbH
*
* This file is part of the Genode OS framework, which is distributed
* under the terms of the GNU Affero General Public License version 3.
@ -17,39 +17,88 @@
** .text (program code) **
**************************/
/**
* Set pointer to global offset table in given register
*/
.macro _got reg
1:
ldr \reg, 2f
add \reg, pc, \reg
b 3f
2:
.word _GLOBAL_OFFSET_TABLE_ - (1b + 12)
3:
.endm
.section ".text.crt0"
/* ld.lib.so entry for Linux */
.global _start_initial_stack
_start_initial_stack:
/* on Linux we have a valid stack pointer */
bl init_rtld
/* save stack pointer in __intial_sp GOT relative */
_got sl
ldr r4, .LGOT
ldr r4, [sl, r4]
str sp, [r4]
/* load stack pointer _stack_high GOT relative */
ldr r4, .LGOT + 8
ldr sp, [sl, r4]
b 4f
/* program entry-point */
.global _start
_start:
.global _start_initial_stack
_start_initial_stack:
/* make initial value of some registers available to higher-level code */
ldr r4, =__initial_sp
_got sl
/* save __initial_sp */
ldr r4, .LGOT
ldr r4, [sl, r4]
str sp, [r4]
ldr r4, =__initial_r0
/* r0 contains the boot info on SeL4 save in __intial_r0 */
ldr r4, .LGOT + 4
ldr r4, [sl, r4]
str r0, [r4]
/*
* Install initial temporary environment that is replaced later by the
* environment that init_main_thread creates.
* environment that init_main_thread creates, load __stack_high
*/
ldr sp, =_stack_high
ldr r4, .LGOT + 8
ldr sp, [sl, r4]
/* if this is the dynamic linker, init_rtld relocates the linker */
bl init_rtld
4:
/* create proper environment for main thread */
bl init_main_thread
/* apply environment that was created by init_main_thread */
ldr sp, =init_main_thread_result
/*
* Apply environment that was created by init_main_thread from
* init_main_thread_result
*/
ldr r4, .LGOT + 12
ldr sp, [sl, r4]
ldr sp, [sp]
/* jump into init C code instead of calling it as it should never return */
b _main
.LGOT:
.word __initial_sp(GOT)
.word __initial_r0(GOT)
.word _stack_high(GOT)
.word init_main_thread_result(GOT)
/*********************************
** .bss (non-initialized data) **
@ -62,6 +111,7 @@
.global __initial_stack_base
__initial_stack_base:
.space 4*1024
.global _stack_high
_stack_high:
/* initial value of the SP register */