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/*
* Copyright (c) 2023, Andrew Kaster <akaster@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/ByteBuffer.h>
#include <AK/Error.h>
#include <AK/IterationDecision.h>
#include <AK/MemoryStream.h>
#include <AK/StringView.h>
#include <LibDeviceTree/FlattenedDeviceTree.h>
namespace DeviceTree {
static ErrorOr<StringView> read_string_view(ReadonlyBytes bytes, StringView error_string)
{
auto len = strnlen(reinterpret_cast<char const*>(bytes.data()), bytes.size());
if (len == bytes.size()) {
return Error::from_string_view_or_print_error_and_return_errno(error_string, EINVAL);
}
return StringView { bytes.slice(0, len) };
}
ErrorOr<void> walk_device_tree(FlattenedDeviceTreeHeader const& header, ReadonlyBytes raw_device_tree, DeviceTreeCallbacks callbacks)
{
ReadonlyBytes struct_bytes { raw_device_tree.data() + header.off_dt_struct, header.size_dt_struct };
FixedMemoryStream stream(struct_bytes);
char const* begin_strings_block = reinterpret_cast<char const*>(raw_device_tree.data() + header.off_dt_strings);
FlattenedDeviceTreeTokenType prev_token = EndNode;
StringView current_node_name;
while (!stream.is_eof()) {
auto current_token = TRY(stream.read_value<BigEndian<u32>>());
switch (current_token) {
case BeginNode: {
current_node_name = TRY(read_string_view(struct_bytes.slice(stream.offset()), "Non-null terminated name for FDT_BEGIN_NODE token!"sv));
size_t const consume_len = round_up_to_power_of_two(current_node_name.length() + 1, 4);
TRY(stream.discard(consume_len));
if (callbacks.on_node_begin) {
if (IterationDecision::Break == TRY(callbacks.on_node_begin(current_node_name)))
return {};
}
break;
}
case EndNode:
if (callbacks.on_node_end) {
if (IterationDecision::Break == TRY(callbacks.on_node_end(current_node_name)))
return {};
}
break;
case Property: {
if (prev_token == EndNode) {
return Error::from_string_view_or_print_error_and_return_errno("Invalid node sequence, FDT_PROP after FDT_END_NODE"sv, EINVAL);
}
auto len = TRY(stream.read_value<BigEndian<u32>>());
auto nameoff = TRY(stream.read_value<BigEndian<u32>>());
if (nameoff >= header.size_dt_strings) {
return Error::from_string_view_or_print_error_and_return_errno("Invalid name offset in FDT_PROP"sv, EINVAL);
}
size_t const prop_name_max_len = header.size_dt_strings - nameoff;
size_t const prop_name_len = strnlen(begin_strings_block + nameoff, prop_name_max_len);
if (prop_name_len == prop_name_max_len) {
return Error::from_string_view_or_print_error_and_return_errno("Non-null terminated name for FDT_PROP token!"sv, EINVAL);
}
StringView prop_name(begin_strings_block + nameoff, prop_name_len);
if (len >= stream.remaining()) {
return Error::from_string_view_or_print_error_and_return_errno("Property value length too large"sv, EINVAL);
}
ReadonlyBytes prop_value;
if (len != 0) {
prop_value = { struct_bytes.slice(stream.offset()).data(), len };
size_t const consume_len = round_up_to_power_of_two(static_cast<u32>(len), 4);
TRY(stream.discard(consume_len));
}
if (callbacks.on_property) {
if (IterationDecision::Break == TRY(callbacks.on_property(prop_name, prop_value)))
return {};
}
break;
}
case NoOp:
if (callbacks.on_noop) {
if (IterationDecision::Break == TRY(callbacks.on_noop()))
return {};
}
break;
case End: {
if (prev_token == BeginNode || prev_token == Property) {
return Error::from_string_view_or_print_error_and_return_errno("Invalid node sequence, FDT_END after BEGIN_NODE or PROP"sv, EINVAL);
}
if (!stream.is_eof()) {
return Error::from_string_view_or_print_error_and_return_errno("Expected EOF at FTD_END but more data remains"sv, EINVAL);
}
if (callbacks.on_end) {
return callbacks.on_end();
}
return {};
}
default:
return Error::from_string_view_or_print_error_and_return_errno("Invalid token"sv, EINVAL);
}
prev_token = static_cast<FlattenedDeviceTreeTokenType>(static_cast<u32>(current_token));
}
return Error::from_string_view_or_print_error_and_return_errno("Unexpected end of stream"sv, EINVAL);
}
static ErrorOr<ReadonlyBytes> slow_get_property_raw(StringView name, FlattenedDeviceTreeHeader const& header, ReadonlyBytes raw_device_tree)
{
// Name is a path like /path/to/node/property
Vector<StringView, 16> path;
TRY(name.for_each_split_view('/', SplitBehavior::Nothing, [&path](StringView view) -> ErrorOr<void> {
if (path.size() == path.capacity()) {
return Error::from_errno(ENAMETOOLONG);
}
// This can never fail as all entries go into the inline buffer, enforced by the check above.
path.unchecked_append(view);
return {};
}));
bool check_property_name = path.size() == 1; // Properties on root node should be checked immediately
ssize_t current_path_idx = -1; // Start "before" the root FDT_BEGIN_NODE tag
ReadonlyBytes found_property_value;
DeviceTreeCallbacks callbacks = {
.on_node_begin = [&](StringView token_name) -> ErrorOr<IterationDecision> {
if (current_path_idx < 0) {
++current_path_idx; // Root node
return IterationDecision::Continue;
}
if (token_name == path[current_path_idx]) {
++current_path_idx;
if (current_path_idx == static_cast<ssize_t>(path.size() - 1)) {
check_property_name = true;
}
}
return IterationDecision::Continue;
},
.on_node_end = [&](StringView) -> ErrorOr<IterationDecision> {
if (check_property_name) {
// Not found, but we were looking for the property
return Error::from_errno(EINVAL);
}
return IterationDecision::Continue;
},
.on_property = [&](StringView property_name, ReadonlyBytes property_value) -> ErrorOr<IterationDecision> {
if (check_property_name && property_name == path[current_path_idx]) {
found_property_value = property_value;
return IterationDecision::Break;
}
return IterationDecision::Continue;
},
.on_noop = nullptr,
.on_end = [&]() -> ErrorOr<void> {
return Error::from_string_view_or_print_error_and_return_errno("Property not found"sv, EINVAL);
}
};
TRY(walk_device_tree(header, raw_device_tree, move(callbacks)));
return found_property_value;
}
template<typename T>
ErrorOr<T> slow_get_property(StringView name, FlattenedDeviceTreeHeader const& header, ReadonlyBytes raw_device_tree)
{
[[maybe_unused]] auto bytes = TRY(slow_get_property_raw(name, header, raw_device_tree));
if constexpr (IsVoid<T>) {
return {};
} else if constexpr (IsArithmetic<T>) {
if (bytes.size() != sizeof(T)) {
return Error::from_errno(EINVAL);
}
return *bit_cast<T*>(bytes.data());
} else {
static_assert(IsSame<T, StringView>);
return T(bytes);
}
}
template ErrorOr<void> slow_get_property(StringView name, FlattenedDeviceTreeHeader const& header, ReadonlyBytes raw_device_tree);
template ErrorOr<u32> slow_get_property(StringView name, FlattenedDeviceTreeHeader const& header, ReadonlyBytes raw_device_tree);
template ErrorOr<u64> slow_get_property(StringView name, FlattenedDeviceTreeHeader const& header, ReadonlyBytes raw_device_tree);
template ErrorOr<StringView> slow_get_property(StringView name, FlattenedDeviceTreeHeader const& header, ReadonlyBytes raw_device_tree);
} // namespace DeviceTree
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