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5c3943bf38
In the beginning of the interrupt handler, we had previously checked if the current handler had grabbed an IST stack from the IDT/TSS. If it was, it saved this value and set it to 0 in the IDT, then restored it at the end. Now this is an atomic action. This is unlikely to make a difference unless the interrupt handler is itself interrupted by an exception before being able to swap the IDT value, but such a situation is now impossible.
82 lines
2.5 KiB
C++
82 lines
2.5 KiB
C++
#pragma once
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/// \file idt.h
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/// Definitions relating to a CPU's IDT table
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#include <stdint.h>
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#include "assert.h"
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class IDT
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{
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public:
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IDT();
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/// Get the currently running CPU's IDT
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static IDT & current();
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/// Set the global NMI handler. Must happen before creating
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/// any IDTs.
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static void set_nmi_handler(uintptr_t address);
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/// Install this IDT to the current CPU
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void install() const;
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/// Add the IST entries listed in the ISR table into the IDT.
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/// This can't be done until after memory is set up so the
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/// stacks can be created.
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void add_ist_entries();
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/// Get the IST entry used by an entry, clearing it in the process.
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/// \arg i Which IDT entry to look in
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/// \returns The IST index used by entry i, or 0 for none
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inline uint8_t get_ist(uint8_t i) {
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return __atomic_exchange_n(&m_entries[i].ist, 0, __ATOMIC_SEQ_CST);
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}
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/// Restore the IST entry used by an entry when done using it.
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/// \arg i Which IDT entry to restore
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/// \arg ist The IST index for entry i, or 0 for none
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inline void return_ist(uint8_t i, uint8_t ist) {
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if (!ist) return;
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uint8_t expected = 0;
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bool result = __atomic_compare_exchange_n(
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&m_entries[i].ist, &expected, ist,
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false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
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kassert(result, "Tried to overwrite a non-zero IST value in IDT");
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}
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/// Set the IST entry used by an entry. This should not be called
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/// by interrupt handlers.
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/// \arg i Which IDT entry to set
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/// \arg ist The IST index for entry i, or 0 for none
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inline void set_ist(uint8_t i, uint8_t ist) { m_entries[i].ist = ist; }
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/// Get the IST entries that are used by this table, as a bitmap
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static uint8_t used_ist_entries();
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/// Dump debug information about the IDT to the console.
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/// \arg index Which entry to print, or -1 for all entries
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void dump(unsigned index = -1) const;
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private:
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void set(uint8_t i, void (*handler)(), uint16_t selector, uint8_t flags);
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struct descriptor
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{
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uint16_t base_low;
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uint16_t selector;
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uint8_t ist;
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uint8_t flags;
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uint16_t base_mid;
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uint32_t base_high;
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uint32_t reserved; // must be zero
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} __attribute__ ((packed, aligned(16)));
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struct ptr
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{
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uint16_t limit;
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descriptor *base;
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} __attribute__ ((packed, aligned(4)));
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descriptor m_entries[256];
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ptr m_ptr;
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};
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