282 lines
9.6 KiB
ArmAsm
282 lines
9.6 KiB
ArmAsm
/*********************************************************************
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* SEGGER Microcontroller GmbH *
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* The Embedded Experts *
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**********************************************************************
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* *
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* (c) 2014 - 2022 SEGGER Microcontroller GmbH *
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* *
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* www.segger.com Support: support@segger.com *
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* *
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**********************************************************************
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* *
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* All rights reserved. *
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* *
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* Redistribution and use in source and binary forms, with or *
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* without modification, are permitted provided that the following *
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* condition is met: *
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* *
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* - Redistributions of source code must retain the above copyright *
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* notice, this condition and the following disclaimer. *
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* *
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND *
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* CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, *
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* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF *
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* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE *
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* DISCLAIMED. IN NO EVENT SHALL SEGGER Microcontroller BE LIABLE FOR *
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* ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR *
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT *
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* OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; *
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* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF *
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* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT *
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE *
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* USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH *
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* DAMAGE. *
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* *
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**********************************************************************
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-------------------------- END-OF-HEADER -----------------------------
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File : SEGGER_THUMB_Startup.s
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Purpose : Generic runtime init startup code for ARM CPUs running
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in THUMB mode.
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Designed to work with the SEGGER linker to produce
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smallest possible executables.
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This file does not normally require any customization.
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Additional information:
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Preprocessor Definitions
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FULL_LIBRARY
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If defined then
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- argc, argv are set up by calling SEGGER_SEMIHOST_GetArgs().
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- the exit symbol is defined and executes on return from main.
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- the exit symbol calls destructors, atexit functions and then
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calls SEGGER_SEMIHOST_Exit().
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If not defined then
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- argc and argv are not valid (main is assumed to not take parameters)
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- the exit symbol is defined, executes on return from main and
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halts in a loop.
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*/
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.syntax unified
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/*********************************************************************
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*
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* Defines, configurable
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*
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**********************************************************************
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*/
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#ifndef APP_ENTRY_POINT
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#define APP_ENTRY_POINT main
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#endif
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#ifndef ARGSSPACE
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#define ARGSSPACE 128
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#endif
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/*********************************************************************
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*
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* Macros
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*
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**********************************************************************
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*/
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//
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// Declare a label as function symbol (without switching sections)
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//
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.macro MARK_FUNC Name
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.global \Name
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.thumb_func
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.code 16
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\Name:
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.endm
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//
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// Declare a regular function.
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// Functions from the startup are placed in the init section.
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//
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.macro START_FUNC Name
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.section .init.\Name, "ax"
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.global \Name
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.balign 2
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.thumb_func
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.code 16
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\Name:
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.endm
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//
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// Declare a weak function
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//
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.macro WEAK_FUNC Name
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.section .init.\Name, "ax", %progbits
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.weak \Name
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.balign 2
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.thumb_func
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.code 16
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\Name:
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.endm
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//
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// Mark the end of a function and calculate its size
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//
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.macro END_FUNC name
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.size \name,.-\name
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.endm
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/*********************************************************************
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*
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* Externals
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*
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**********************************************************************
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*/
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.extern APP_ENTRY_POINT // typically main
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/*********************************************************************
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*
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* Global functions
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*
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**********************************************************************
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*/
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/*********************************************************************
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*
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* _start
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*
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* Function description
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* Entry point for the startup code.
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* Usually called by the reset handler.
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* Performs all initialisation, based on the entries in the
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* linker-generated init table, then calls main().
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* It is device independent, so there should not be any need for an
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* end-user to modify it.
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*
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* Additional information
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* At this point, the stack pointer should already have been
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* initialized
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* - by hardware (such as on Cortex-M),
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* - by the device-specific reset handler,
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* - or by the debugger (such as for RAM Code).
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*/
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#undef L
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#define L(label) .L_start_##label
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START_FUNC _start
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//
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// Call linker init functions which in turn performs the following:
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// * Perform segment init
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// * Perform heap init (if used)
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// * Call constructors of global Objects (if any exist)
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//
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ldr R4, =__SEGGER_init_table__ // Set table pointer to start of initialization table
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L(RunInit):
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ldr R0, [R4] // Get next initialization function from table
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adds R4, R4, #4 // Increment table pointer to point to function arguments
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blx R0 // Call initialization function
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b L(RunInit)
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//
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MARK_FUNC __SEGGER_init_done
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MARK_FUNC __startup_complete
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//
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// Time to call main(), the application entry point.
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//
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#ifndef FULL_LIBRARY
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//
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// In a real embedded application ("Free-standing environment"),
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// main() does not get any arguments,
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// which means it is not necessary to init R0 and R1.
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//
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bl APP_ENTRY_POINT // Call to application entry point (usually main())
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END_FUNC _start
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//
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// end of _start
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// Fall-through to exit if main ever returns.
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//
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MARK_FUNC exit
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//
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// In a free-standing environment, if returned from application:
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// Loop forever.
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//
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b .
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.size exit,.-exit
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#else
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//
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// In a hosted environment,
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// we need to load R0 and R1 with argc and argv, in order to handle
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// the command line arguments.
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// This is required for some programs running under control of a
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// debugger, such as automated tests.
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//
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movs R0, #ARGSSPACE
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ldr R1, =__SEGGER_init_arg_data
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bl SEGGER_SEMIHOST_GetArgs
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ldr R1, =__SEGGER_init_arg_data
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bl APP_ENTRY_POINT // Call to application entry point (usually main())
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bl exit // Call exit function
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b . // If we unexpectedly return from exit, hang.
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END_FUNC _start
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#endif
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//
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#ifdef FULL_LIBRARY
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/*********************************************************************
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*
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* exit
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*
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* Function description
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* Exit of the system.
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* Called on return from application entry point or explicit call
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* to exit.
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*
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* Additional information
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* In a hosted environment exit gracefully, by
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* saving the return value,
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* calling destructurs of global objects,
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* calling registered atexit functions,
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* and notifying the host/debugger.
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*/
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#undef L
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#define L(label) .L_exit_##label
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WEAK_FUNC exit
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mov R5, R0 // Save the exit parameter/return result
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//
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// Call destructors
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//
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ldr R0, =__dtors_start__ // Pointer to destructor list
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ldr R1, =__dtors_end__
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L(Loop):
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cmp R0, R1
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beq L(End) // Reached end of destructor list? => Done
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ldr R2, [R0] // Load current destructor address into R2
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adds R0, R0, #4 // Increment pointer
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push {R0-R1} // Save R0 and R1
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blx R2 // Call destructor
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pop {R0-R1} // Restore R0 and R1
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b L(Loop)
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L(End):
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//
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// Call atexit functions
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//
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bl __SEGGER_RTL_execute_at_exit_fns
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//
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// Call debug_exit with return result/exit parameter
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//
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mov R0, R5
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bl SEGGER_SEMIHOST_Exit
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//
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// If execution is not terminated, loop forever
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//
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L(ExitLoop):
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b L(ExitLoop) // Loop forever.
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END_FUNC exit
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#endif
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#ifdef FULL_LIBRARY
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.bss
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__SEGGER_init_arg_data:
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.space ARGSSPACE
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.size __SEGGER_init_arg_data, .-__SEGGER_init_arg_data
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.type __SEGGER_init_arg_data, %object
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#endif
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/*************************** End of file ****************************/
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