94 lines
3.8 KiB
C
94 lines
3.8 KiB
C
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// Copyright 2020 Espressif Systems (Shanghai) PTE LTD
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#include "sdkconfig.h"
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#include "soc/rtc_cntl_reg.h"
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#pragma once
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#ifdef __cplusplus
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extern "C" {
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#endif
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/**
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* @brief Assert a condition is true, in a way that should be resistant to fault injection for
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* single fault attacks.
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*
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* - Expands CONDITION multiple times (condition must have no side effects)
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* - Compiler is told all registers are invalid before evaluating CONDITION each time, to avoid a fault
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* causing a misread of a register used in all three evaluations of CONDITION.
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* - If CONDITION is ever false, a system reset is triggered.
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*
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* @note Place this macro after a "normal" check of CONDITION that will fail with a normal error
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* message. This is the fallback in case a fault injection attack skips or corrupts the result of
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* that check. (Although ensure that an attacker can't use fault injection to skip past the "normal"
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* error message, to avoid this check entirely.)
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*
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* @note This macro increases binary size and is slow and should be used sparingly.
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*
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* @note This macro does not guarantee fault injection resistance. In particular CONDITION must be
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* chosen carefully - a fault injection attack which sets CONDITION to true will not be detected by
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* this macro. Care must also be taken that an attacker can't use a fault to completely bypass calling
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* whatever function tests ESP_FAULT_ASSERT.
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*
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* @note This is difficult to debug as a failure triggers an instant software reset, and UART output
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* is often truncated (as FIFO is not flushed). Define the ESP_FAULT_ASSERT_DEBUG macro to debug any
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* failures of this macro due to software bugs.
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*
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* @param CONDITION A condition which will evaluate true unless an attacker used fault injection to skip or corrupt some other critical system calculation.
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*
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*/
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#define ESP_FAULT_ASSERT(CONDITION) do { \
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asm volatile ("" ::: "memory"); \
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if(!(CONDITION)) _ESP_FAULT_RESET(); \
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asm volatile ("" ::: "memory"); \
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if(!(CONDITION)) _ESP_FAULT_RESET(); \
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asm volatile ("" ::: "memory"); \
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if(!(CONDITION)) _ESP_FAULT_RESET(); \
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} while(0)
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// Uncomment this macro to get debug output if ESP_FAULT_ASSERT() fails
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//
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// Note that uncommenting this macro reduces the anti-FI effectiveness
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//
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//#define ESP_FAULT_ASSERT_DEBUG
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/* Internal macro, purpose is to trigger a system reset if an inconsistency due to fault injection
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is detected.
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Illegal instruction opcodes are there as a fallback to crash the CPU in case it doesn't
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reset as expected.
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*/
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#ifndef ESP_FAULT_ASSERT_DEBUG
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#define _ESP_FAULT_RESET() do { \
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REG_WRITE(RTC_CNTL_OPTIONS0_REG, RTC_CNTL_SW_SYS_RST); \
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asm volatile("ill; ill; ill;"); \
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} while(0)
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#else // ESP_FAULT_ASSERT_DEBUG
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#warning "Enabling ESP_FAULT_ASSERT_DEBUG makes ESP_FAULT_ASSERT() less effective"
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#define _ESP_FAULT_RESET() do { \
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ets_printf("ESP_FAULT_ASSERT %s:%d\n", __FILE__, __LINE__); \
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asm volatile("ill;"); \
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} while(0)
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#endif // ESP_FAULT_ASSERT_DEBUG
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#ifdef __cplusplus
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}
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#endif
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