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0203dea024
Added replacement for the Boot ROM `_xtos_set_exception_handler` to handle installing our replacement `_xtos_c_wrapper_handler`. Simplified install in the non 32-bit exception module to make use of the improved `_xtos_set_exception_handler` Reorganized and improved comments.
114 lines
4.2 KiB
C++
114 lines
4.2 KiB
C++
/*
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* Adaptation of _xtos_set_exception_handler for Arduino ESP8266 core
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*
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* This replacement for the Boot ROM `_xtos_set_exception_handler` is used to
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* install our replacement `_xtos_c_wrapper_handler`. This change protects the
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* value of `excvaddr` from corruption.
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*
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*
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* Details
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*
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* The issue, the Boot ROM "C" wrapper for exception handlers,
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* `_xtos_c_wrapper_handler`, turns interrupts back on. This leaves `excvaddr`
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* exposed to possible overwrite before it is read. For example, if an interrupt
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* is taken during the exception handler processing and the ISR handler
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* generates a new exception, the original value of `excvaddr` is lost. To
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* address this issue we have a replacement `_xtos_c_wrapper_handler` in file
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* `exc-c-wrapper-handler.S`.
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*
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* An overview, of an exception at entry: New interrupts are blocked by EXCM
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* being set. Once cleared, interrupts above the current INTLEVEL and exceptions
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* (w/o creating a DoubleException) can occur.
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*
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* Using our replacement for `_xtos_c_wrapper_handler`, INTLEVEL is raised to 15
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* with EXCM cleared.
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*
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* The original Boot ROM `_xtos_c_wrapper_handler` at entry would set INTLEVEL
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* to 3 with EXCM cleared, save registers, then do a `rsil 0` (interrupts fully
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* enabled!) just before calling the registered "C" Exception handler. Our
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* replacement keeps INTLEVEL at 15. This is needed to support the Arduino model
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* of interrupts disabled while an ISR runs.
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*
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* And we also need it for umm_malloc to work safely with an IRAM heap from an
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* ISR call. While malloc() will supply DRAM for all allocation from an ISR, we
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* want free() to safely operate from an ISR to avoid a leak potential.
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*
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* If an exception handler needs interrupts enabled, it would be done after it
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* has consumed the value of `excvaddr`. Whether such action is safe is left to
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* the exception handler writer to determine. However, with our current
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* architecture, I am not convinced it can be done safely.
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*
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*/
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#if defined(NON32XFER_HANDLER) || defined(MMU_IRAM_HEAP) || defined(NEW_EXC_C_WRAPPER)
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/*
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* The original module source code came from:
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* https://github.com/qca/open-ath9k-htc-firmware/blob/master/sboot/magpie_1_1/sboot/athos/src/xtos/exc-sethandler.c
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*
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* It has been revised to use Arduino ESP8266 core includes, types, and
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* formating.
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*/
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/* exc-sethandler.c - register an exception handler in XTOS */
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/*
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* Copyright (c) 1999-2006 Tensilica Inc.
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*
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the
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* "Software"), to deal in the Software without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sublicense, and/or sell copies of the Software, and to
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* permit persons to whom the Software is furnished to do so, subject to
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* the following conditions:
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*
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* The above copyright notice and this permission notice shall be included
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* in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
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* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
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* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
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* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*/
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#include <Arduino.h>
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#include "esp8266_undocumented.h"
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extern "C" {
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/*
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* Register a C handler for the specified general exception
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* (specified EXCCAUSE value).
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*/
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fn_c_exception_handler_t _xtos_set_exception_handler(int cause, fn_c_exception_handler_t fn)
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{
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fn_c_exception_handler_t ret;
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if( (unsigned) cause >= XCHAL_EXCCAUSE_NUM )
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return 0;
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if( fn == 0 )
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fn = &_xtos_p_none;
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ret = _xtos_c_handler_table[cause];
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_xtos_exc_handler_table[cause] = ( (fn == &_xtos_p_none)
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? &_xtos_unhandled_exception
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: &_xtos_c_wrapper_handler );
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_xtos_c_handler_table[cause] = fn;
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if( ret == &_xtos_p_none )
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ret = 0;
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return ret;
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}
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};
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#endif
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