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Kernel: Add safe atomic functions
This allows us to perform atomic operations on potentially unsafe user space pointers.
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10 changed files with 573 additions and 166 deletions
120
Kernel/Arch/i386/SafeMem.h
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Kernel/Arch/i386/SafeMem.h
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/*
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* Copyright (c) 2020, the SerenityOS developers.
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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 without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <AK/Atomic.h>
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#include <AK/Optional.h>
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#include <AK/Types.h>
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#pragma once
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namespace Kernel {
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struct RegisterState;
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[[nodiscard]] bool safe_memcpy(void* dest_ptr, const void* src_ptr, size_t n, void*& fault_at);
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[[nodiscard]] ssize_t safe_strnlen(const char* str, size_t max_n, void*& fault_at);
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[[nodiscard]] bool safe_memset(void* dest_ptr, int c, size_t n, void*& fault_at);
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[[nodiscard]] Optional<u32> safe_atomic_fetch_add_relaxed(volatile u32* var, u32 val);
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[[nodiscard]] Optional<u32> safe_atomic_exchange_relaxed(volatile u32* var, u32 val);
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[[nodiscard]] Optional<u32> safe_atomic_load_relaxed(volatile u32* var);
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[[nodiscard]] bool safe_atomic_store_relaxed(volatile u32* var, u32 val);
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[[nodiscard]] Optional<bool> safe_atomic_compare_exchange_relaxed(volatile u32* var, u32& expected, u32 val);
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[[nodiscard]] ALWAYS_INLINE Optional<u32> safe_atomic_fetch_and_relaxed(volatile u32* var, u32 val)
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{
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auto expected_value = safe_atomic_load_relaxed(var);
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if (!expected_value.has_value())
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return {}; // fault
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u32& expected = expected_value.value();
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for (;;) {
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auto result = safe_atomic_compare_exchange_relaxed(var, expected, expected & val);
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if (!result.has_value())
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return {}; // fault
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if (result.value())
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return expected; // exchanged
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// This is only so that we don't saturate the bus...
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AK::atomic_thread_fence(AK::MemoryOrder::memory_order_acquire);
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}
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}
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[[nodiscard]] ALWAYS_INLINE Optional<u32> safe_atomic_fetch_and_not_relaxed(volatile u32* var, u32 val)
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{
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auto expected_value = safe_atomic_load_relaxed(var);
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if (!expected_value.has_value())
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return {}; // fault
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u32& expected = expected_value.value();
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for (;;) {
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auto result = safe_atomic_compare_exchange_relaxed(var, expected, expected & ~val);
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if (!result.has_value())
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return {}; // fault
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if (result.value())
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return expected; // exchanged
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// This is only so that we don't saturate the bus...
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AK::atomic_thread_fence(AK::MemoryOrder::memory_order_acquire);
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}
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}
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[[nodiscard]] ALWAYS_INLINE Optional<u32> safe_atomic_fetch_or_relaxed(volatile u32* var, u32 val)
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{
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auto expected_value = safe_atomic_load_relaxed(var);
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if (!expected_value.has_value())
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return {}; // fault
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u32& expected = expected_value.value();
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for (;;) {
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auto result = safe_atomic_compare_exchange_relaxed(var, expected, expected | val);
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if (!result.has_value())
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return {}; // fault
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if (result.value())
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return expected; // exchanged
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// This is only so that we don't saturate the bus...
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AK::atomic_thread_fence(AK::MemoryOrder::memory_order_acquire);
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}
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}
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[[nodiscard]] ALWAYS_INLINE Optional<u32> safe_atomic_fetch_xor_relaxed(volatile u32* var, u32 val)
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{
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auto expected_value = safe_atomic_load_relaxed(var);
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if (!expected_value.has_value())
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return {}; // fault
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u32& expected = expected_value.value();
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for (;;) {
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auto result = safe_atomic_compare_exchange_relaxed(var, expected, expected ^ val);
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if (!result.has_value())
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return {}; // fault
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if (result.value())
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return expected; // exchanged
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// This is only so that we don't saturate the bus...
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AK::atomic_thread_fence(AK::MemoryOrder::memory_order_acquire);
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}
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}
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bool handle_safe_access_fault(RegisterState& regs, u32 fault_address);
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}
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