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Libraries: Add LibDeviceTree for manipulating OpenFirmware Device Trees

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Starting with header validation and a dump() method that can be used to
debug future parsing work.
This commit is contained in:
Andrew Kaster 2021-10-17 19:09:18 -06:00 • committed by Brian Gianforcaro
parent 4ffee78146
commit 644928314a
5 changed files with 214 additions and 0 deletions
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143
Userland/Libraries/LibDeviceTree/Validation.cpp Normal file
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/*
* Copyright (c) 2021, Andrew Kaster <akaster@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/Endian.h>
#include <AK/Format.h>
#include <AK/String.h>
#include <LibDeviceTree/Validation.h>
namespace DeviceTree {
bool validate_flattened_device_tree(FlattenedDeviceTreeHeader const& header, u8 const* blob_start, size_t blob_size, Verbose verbose)
{
if (header.magic != 0xD00DFEEDU) {
if (verbose == Verbose::Yes)
warnln("FDT Header has invalid magic value 0x{:08x}. Are you sure it's a flattened device tree?", header.magic);
return false;
}
if ((header.off_mem_rsvmap & ~0x7) != header.off_mem_rsvmap) {
if (verbose == Verbose::Yes)
warnln("FDT Header's MemoryReservationBlock is not 8 byte aligned! Offset: 0x{:08x}", header.off_mem_rsvmap);
return false;
}
if ((header.off_dt_struct & ~0x3) != header.off_dt_struct) {
if (verbose == Verbose::Yes)
warnln("FDT Header's StructureBlock is not 4 byte aligned! Offset: 0x{:08x}", header.off_dt_struct);
return false;
}
if (header.totalsize != blob_size) {
if (verbose == Verbose::Yes)
warnln("FDT Header total size mismatch: {}, expected {}!", header.totalsize, blob_size);
return false;
}
if (header.off_dt_struct > blob_size) {
if (verbose == Verbose::Yes)
warnln("FDT Header reports larger StructureBlock offset than possible: {} but total size is {}!", header.off_dt_struct, blob_size);
return false;
}
if (header.off_dt_strings > blob_size) {
if (verbose == Verbose::Yes)
warnln("FDT Header reports larger StringsBlock offset than possible: {} but total size is {}!", header.off_dt_strings, blob_size);
return false;
}
if (header.off_mem_rsvmap > blob_size) {
if (verbose == Verbose::Yes)
warnln("FDT Header reports larger MemoryReservationBlock offset than possible: {} but total size is {}!", header.off_mem_rsvmap, blob_size);
return false;
}
// Verify format is correct. Header --> MemoryReservation --> Structures --> Strings
if (header.off_dt_strings <= header.off_dt_struct) {
if (verbose == Verbose::Yes)
warnln("FDT Header has invalid StringsBlock offset {}, must be after v (@ {})", header.off_dt_strings, header.off_dt_struct);
return false;
}
if (header.off_dt_struct <= header.off_mem_rsvmap) {
if (verbose == Verbose::Yes)
warnln("FDT Header has invalid StructureBlock offset {}, must be after MemoryReservationBlock (@ {})", header.off_dt_struct, header.off_mem_rsvmap);
return false;
}
if (header.version != 17) {
if (verbose == Verbose::Yes)
warnln("Expected FDT header version 17, got {}", header.version);
return false;
}
if (header.last_comp_version != 16) {
if (verbose == Verbose::Yes)
warnln("Expected FDT header last compatible version 16, got {}", header.last_comp_version);
return false;
}
auto* mem_reserve_block = reinterpret_cast<FlattenedDeviceTreeReserveEntry const*>(&blob_start[header.off_mem_rsvmap]);
u64 next_block_offset = header.off_mem_rsvmap + sizeof(FlattenedDeviceTreeReserveEntry);
while ((next_block_offset < header.off_dt_struct) && (*mem_reserve_block != FlattenedDeviceTreeReserveEntry {})) {
++mem_reserve_block;
next_block_offset += sizeof(FlattenedDeviceTreeReserveEntry);
}
if (next_block_offset >= header.off_dt_strings) {
if (verbose == Verbose::Yes)
warnln("FDT malformed, MemoryReservationBlock spill into StructureBlock section!");
return false;
}
// check for overlap. Overflow not possible b/c the fields are u32
u64 structure_block_size = header.off_dt_struct + header.size_dt_struct;
if ((structure_block_size > header.off_dt_strings) || (structure_block_size > blob_size)) {
if (verbose == Verbose::Yes)
warnln("FDT Header reports invalid StructureBlock block size: {} is too large given StringsBlock offset {} and total size {}", structure_block_size, header.off_dt_strings, blob_size);
return false;
}
u64 strings_block_size = header.off_dt_strings + header.size_dt_strings;
if (strings_block_size > blob_size) {
if (verbose == Verbose::Yes)
warnln("FDT Header reports invalid StringsBlock size: {} is too large given total size {}", structure_block_size, blob_size);
return false;
}
return true;
}
bool dump(FlattenedDeviceTreeHeader const& header, u8 const* blob_start, size_t blob_size)
{
outln("/dts-v1/;");
outln("// magic: 0x{:08x}", header.magic);
outln("// totalsize: 0x{:08x} ({})", header.totalsize, header.totalsize);
outln("// off_dt_struct: 0x{:08x}", header.off_dt_struct);
outln("// off_dt_strings: 0x{:08x}", header.off_dt_strings);
outln("// off_mem_rsvmap: 0x{:08x}", header.off_mem_rsvmap);
outln("// version: 0x{:08x}", header.version);
outln("// last_comp_version: 0x{:08x}", header.last_comp_version);
outln("// boot_cpuid_phys: 0x{:08x}", header.boot_cpuid_phys);
outln("// size_dt_strings: 0x{:08x}", header.size_dt_strings);
outln("// size_dt_struct: 0x{:08x}", header.size_dt_struct);
if (!validate_flattened_device_tree(header, blob_start, blob_size, Verbose::Yes))
return false;
// Now that we know the device tree is valid, print out the rest of the information
auto* mem_reserve_block = reinterpret_cast<FlattenedDeviceTreeReserveEntry const*>(&blob_start[header.off_mem_rsvmap]);
u64 next_block_offset = header.off_mem_rsvmap + sizeof(FlattenedDeviceTreeReserveEntry);
while ((next_block_offset < header.off_dt_struct) && (*mem_reserve_block != FlattenedDeviceTreeReserveEntry {})) {
outln("/memreserve/ 0x{:08x} 0x{:08x};", mem_reserve_block->address, mem_reserve_block->size);
++mem_reserve_block;
next_block_offset += sizeof(FlattenedDeviceTreeReserveEntry);
}
return true;
}
} // namespace DeviceTree