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/* Copyright (C) 2025 Wildfire Games.
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be included
* in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
#include "precompiled.h"
#include "lib/sysdep/os/win/acpi.h"
#include "lib/byte_order.h"
#include "lib/module_init.h"
#include "lib/sysdep/os/win/wfirmware.h"
#include <atomic>
#include <cctype>
#pragma pack(1)
typedef const volatile u8* PCV_u8;
typedef const volatile AcpiTable* PCV_AcpiTable;
//-----------------------------------------------------------------------------
// table
static AcpiTable* AllocateTable(size_t size)
{
ENSURE(size >= sizeof(AcpiTable));
return (AcpiTable*)malloc(size);
}
template<typename T>
static void DeallocateTable(const T* table)
{
free((void*)table);
}
// return 8-bit checksum of a buffer (should be 0)
static u8 ComputeChecksum(PCV_u8 buf, size_t numBytes)
{
// (can't use std::accumulate - we need 8-bit wraparound)
u8 sum = 0;
for(PCV_u8 p = buf; p < buf+numBytes; p++)
sum = u8((sum + *p) & 0xFF);
return sum;
}
static bool ValidateTable(const AcpiTable* table, const char* signature = 0)
{
if(!table)
return false;
// caller knowns the signature; make sure it matches
if(signature)
{
if(memcmp(table->signature, signature, 4) != 0)
return false;
}
// no specific signature is called for, just validate the characters.
else
{
for(size_t i = 0; i < 4; i++)
{
const char c = table->signature[i];
// "ASF!" and "____" have been encountered
if(!isalpha(c) && c != '_' && c != '!')
return false;
}
}
// must be at least as large as the common header
if(table->size < sizeof(AcpiTable))
return false;
// checksum of table must be 0
// .. AMIBIOS OEMB table has an incorrect checksum (off-by-one),
// so don't complain about any OEM tables (ignored anyway).
const bool isOemTable = (memcmp(table->signature, "OEM", 3) == 0);
if(!isOemTable)
{
if(ComputeChecksum((PCV_u8)table, table->size) != 0)
return false;
}
return true;
}
static void AllocateAndCopyTables(std::atomic<const AcpiTable**>& tables, size_t& numTables)
{
const wfirmware::Provider provider = FOURCC_BE('A','C','P','I');
const wfirmware::TableIds tableIDs = wfirmware::GetTableIDs(provider);
numTables = tableIDs.size();
tables = new const AcpiTable*[numTables];
for(size_t i = 0; i < numTables; i++)
{
wfirmware::Table table = wfirmware::GetTable(provider, tableIDs[i]);
ENSURE(!table.empty());
tables[i] = AllocateTable(table.size());
memcpy((void*)tables[i], &table[0], table.size());
}
// to prevent callers from choking on invalid tables, we
// zero out the corresponding tables[] entries.
for(size_t i = 0; i < numTables; i++)
{
if(!ValidateTable(tables[i]))
{
DeallocateTable(tables[i]);
tables[i] = 0;
}
}
}
//-----------------------------------------------------------------------------
// note: avoid global std::map etc. because we may be called before _cinit
static std::atomic<const AcpiTable**> tables{ nullptr }; // tables == nullptr <=> not initialized
static const AcpiTable* invalidTables; // tables == &invalidTables => init failed
static size_t numTables;
void acpi_Shutdown()
{
if(tables)
{
for(size_t i = 0; i < numTables; i++)
DeallocateTable(tables[i]);
SAFE_ARRAY_DELETE(tables);
numTables = 0;
}
}
const AcpiTable* acpi_GetTable(const char* signature)
{
const AcpiTable** initial{ nullptr };
if(tables.compare_exchange_strong(initial, &invalidTables))
AllocateAndCopyTables(tables, numTables);
// (typically only a few tables, linear search is OK)
for(size_t i = 0; i < numTables; i++)
{
const AcpiTable* table = tables[i];
if(!table)
continue; // skip invalid tables, e.g. OEM (see above)
if(strncmp(table->signature, signature, 4) == 0)
return table;
}
return 0; // no matching AND valid table found
}
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