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// Copyright 2019 The Pigweed Authors
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy of
// the License at
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations under
// the License.
#pragma once
#ifdef __cplusplus
#include <cstdint>
#include "pw_preprocessor/arch.h"
#include "pw_preprocessor/compiler.h"
namespace pw::cpu_exception::cortex_m {
// The PC, LR, and PSR registers are not captured when the program stack
// pointer is in an MPU-protected or otherwise invalid memory region. In
// these situations, the registers are set to 0xFFFF'FFFF to indicate they
// are invalid.
// 0xFFFFFFFF is an illegal LR value, which is why it was selected for
// this purpose. PC and PSR values of 0xFFFFFFFF are dubious too, so this
// constant is clear enough at suggesting that the registers weren't
// properly captured.
constexpr uintptr_t kUndefinedPcLrOrPsrRegValue = 0xFFFF'FFFF;
// This is dictated by ARMv7-M architecture. Do not change.
struct ExceptionRegisters {
uint32_t r0;
uint32_t r1;
uint32_t r2;
uint32_t r3;
uint32_t r12;
uint32_t lr; // Link register, note this may be invalid.
uint32_t pc; // Program counter, note this may be invalid.
uint32_t psr; // Program status register, note this may be invalid.
static_assert(sizeof(ExceptionRegisters) == (sizeof(uint32_t) * 8),
"There's unexpected padding.");
// This is dictated by ARMv7-M architecture. Do not change.
struct ExceptionRegistersFpu {
uint32_t s0;
uint32_t s1;
uint32_t s2;
uint32_t s3;
uint32_t s4;
uint32_t s5;
uint32_t s6;
uint32_t s7;
uint32_t s8;
uint32_t s9;
uint32_t s10;
uint32_t s11;
uint32_t s12;
uint32_t s13;
uint32_t s14;
uint32_t s15;
uint32_t fpscr;
uint32_t reserved;
static_assert(sizeof(ExceptionRegistersFpu) == (sizeof(uint32_t) * 18),
"There's unexpected padding.");
// Bit in the PSR that indicates CPU added an extra word on the stack to
// align it during context save for an exception.
inline constexpr uint32_t kPsrExtraStackAlignBit = (1 << 9);
// This is dictated by this module, and shouldn't change often.
// Note that the order of entries in this struct is very important (as the
// values are populated in assembly).
// NOTE: Memory mapped registers are NOT restored upon fault return!
struct ExtraRegisters {
// Memory mapped registers.
uint32_t cfsr;
uint32_t mmfar;
uint32_t bfar;
uint32_t icsr;
uint32_t hfsr;
uint32_t shcsr;
// Special registers.
uint32_t exc_return;
uint32_t msp;
uint32_t psp;
uint32_t control;
uint32_t msplim;
uint32_t psplim;
// General purpose registers.
uint32_t r4;
uint32_t r5;
uint32_t r6;
uint32_t r7;
uint32_t r8;
uint32_t r9;
uint32_t r10;
uint32_t r11;
static_assert(sizeof(ExtraRegisters) ==
(sizeof(uint32_t) * 20),
(sizeof(uint32_t) * 18),
"There's unexpected padding.");
} // namespace pw::cpu_exception::cortex_m
struct pw_cpu_exception_State {
pw::cpu_exception::cortex_m::ExtraRegisters extended;
pw::cpu_exception::cortex_m::ExceptionRegisters base;
// TODO(amontanez): FPU registers may or may not be here as well. Make the
// availability of the FPU registers a compile-time configuration when FPU
// register support is added.
#else // !__cplusplus
typedef struct pw_cpu_exception_State pw_cpu_exception_State;
#endif // __cplusplus