/********************************************************************* * SEGGER Microcontroller GmbH * * The Embedded Experts * ********************************************************************** * * * (c) 2014 - 2020 SEGGER Microcontroller GmbH * * * * www.segger.com Support: support@segger.com * * * ********************************************************************** * * * All rights reserved. * * * * Redistribution and use in source and binary forms, with or * * without modification, are permitted provided that the following * * condition is met: * * * * - Redistributions of source code must retain the above copyright * * notice, this condition and the following disclaimer. * * * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND * * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, * * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF * * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE * * DISCLAIMED. IN NO EVENT SHALL SEGGER Microcontroller BE LIABLE FOR * * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR * * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT * * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; * * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF * * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE * * USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH * * DAMAGE. * * * ********************************************************************** -------------------------- END-OF-HEADER ----------------------------- File : SEGGER_THUMB_Startup.s Purpose : Generic runtime init startup code for ARM CPUs running in THUMB mode. Designed to work with the SEGGER linker to produce smallest possible executables. This file does not normally require any customization. Additional information: Preprocessor Definitions FULL_LIBRARY If defined then - argc, argv are setup by the debug_getargs. - the exit symbol is defined and executes on return from main. - the exit symbol calls destructors, atexit functions and then debug_exit. If not defined then - argc and argv are not valid (main is assumed to not take parameters) - the exit symbol is defined, executes on return from main and loops */ .syntax unified /********************************************************************* * * Defines, configurable * ********************************************************************** */ #ifndef APP_ENTRY_POINT #define APP_ENTRY_POINT main #endif #ifndef ARGSSPACE #define ARGSSPACE 128 #endif /********************************************************************* * * Externals * ********************************************************************** */ .extern APP_ENTRY_POINT // typically main /********************************************************************* * * Global functions * ********************************************************************** */ /********************************************************************* * * _start * * Function description * Entry point for the startup code. * Usually called by the reset handler. * Performs all initialisation, based on the entries in the * linker-generated init table, then calls main(). * It is device independent, so there should not be any need for an * end-user to modify it. * * Additional information * At this point, the stack pointer should already have been * initialized: * - For typical programs executiong from flash, the stack pointer * has already been loaded from vector table at offset 0. * - In other cases, such as RAM Code, this is done by the debugger * or the device-specific startup code / reset handler. */ .section .init, "ax" .balign 2 .global _start .thumb_func .code 16 _start: // // Call linker init functions which in turn performs the following: // * Perform segment init // * Perform heap init (if used) // * Call constructors of global Objects (if any exist) // ldr R4, =__SEGGER_init_table__ // Set table pointer to start of initialization table __SEGGER_init_run_loop: ldr R0, [R4] // Get next initialization function from table adds R4, R4, #4 // Increment table pointer to point to function arguments blx R0 // Call initialization function b.n __SEGGER_init_run_loop // .thumb_func .global __SEGGER_init_done __SEGGER_init_done: // // Time to call main(), the application entry point. // #ifndef FULL_LIBRARY // // In a real embedded application ("Free-standing environment"), // main() does not get any arguments, // which means it is not necessary to init R0 and R1. // bl APP_ENTRY_POINT // Call to application entry point (usually main()) // // Fall-through to exit if main ever returns. // .global exit .thumb_func exit: // // In a free-standing environment, if returned from application: // Loop forever. // b . #else // // In a hosted environment, // we need to load R0 and R1 with argc and argv, in order to handle // the command line arguments. // This is required for some programs running under control of a // debugger, such as automated tests. // movs R0, #ARGSSPACE ldr R1, =args bl SEGGER_SEMIHOST_GetArgs ldr R1, =args bl APP_ENTRY_POINT // Call to application entry point (usually main()) // // Fall-through to exit if main ever returns. // .global exit .thumb_func exit: // // In a hosted environment exit gracefully, by // saving the return value, // calling destructurs of global objects, // calling registered atexit functions, // and notifying the host/debugger. // mov R5, R0 // Save the exit parameter/return result // // Call destructors // ldr R0, =__dtors_start__ // Pointer to destructor list ldr R1, =__dtors_end__ dtorLoop: cmp R0, R1 beq dtorEnd // Reached end of destructor list? => Done ldr R2, [R0] // Load current destructor address into R2 add R0, #4 // Increment pointer push {R0-R1} // Save R0 and R1 blx R2 // Call destructor pop {R0-R1} // Restore R0 and R1 b dtorLoop dtorEnd: // // Call atexit functions // bl __SEGGER_RTL_execute_at_exit_fns // // Call debug_exit with return result/exit parameter // mov R0, R5 bl SEGGER_SEMIHOST_Exit // // If execution is not terminated, loop forever // exit_loop: b exit_loop // Loop forever. #endif #ifdef FULL_LIBRARY .bss args: .space ARGSSPACE #endif /*************************** End of file ****************************/