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LibEDID: Fix handling extension maps

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We weren't properly iterating the extension blocks and thought we
encountered an unexpected extension map block, when we really should
have just skipped over it.
This commit is contained in:
Tom 2022-01-24 11:00:51 -07:00 • committed by Linus Groh
parent 18fc54fc34
commit a821aa5f50
2 changed files with 164 additions and 17 deletions
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39
Userland/Libraries/LibEDID/EDID.cpp
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@ -141,7 +141,7 @@ struct [[gnu::packed]] EDID {
u8 checksum;
};
enum ExtensionBlockTag : u8 {
enum class ExtensionBlockTag : u8 {
CEA_861 = 0x2,
VideoTimingBlock = 0x10,
DisplayInformation = 0x40,
@ -220,8 +220,10 @@ public:
ErrorOr<IterationDecision> for_each_dtd(Function<IterationDecision(Parser::DetailedTiming const&)> callback) const
{
u8 dtd_start = m_edid.read_host(&m_block->cea861extension.dtd_start_offset);
if (dtd_start <= 4)
if (dtd_start < 4) {
// dtd_start == 4 means there are no data blocks, but there are still DTDs
return IterationDecision::Continue;
}
if (dtd_start > offsetof(Definitions::ExtensionBlock, checksum) - sizeof(Definitions::DetailedTiming))
return Error::from_string_literal("CEA 861 extension block has invalid DTD list"sv);
@ -488,35 +490,39 @@ ErrorOr<IterationDecision> Parser::for_each_extension_block(Function<IterationDe
if (sizeof(Definitions::EDID) + (size_t)raw_extension_block_count * sizeof(Definitions::ExtensionBlock) > m_bytes.size())
return Error::from_string_literal("Truncated EDID");
auto validate_block_checksum = [&](Definitions::ExtensionBlock const& extension_map) {
auto validate_block_checksum = [&](Definitions::ExtensionBlock const& block) {
u8 checksum = 0x0;
auto* bytes = (u8 const*)&extension_map;
for (size_t i = 0; i < sizeof(extension_map); i++)
auto* bytes = (u8 const*)&block;
for (size_t i = 0; i < sizeof(block); i++)
checksum += bytes[i];
return checksum == 0;
};
size_t offset = sizeof(Definitions::EDID);
auto* raw_extension_blocks = (Definitions::ExtensionBlock const*)(m_bytes.data() + offset);
auto* raw_extension_blocks = (Definitions::ExtensionBlock const*)(m_bytes.data() + sizeof(Definitions::EDID));
Definitions::ExtensionBlock const* current_extension_map = nullptr;
unsigned raw_index = 0;
if (m_revision <= 3) {
if (raw_extension_block_count > 1) {
current_extension_map = &raw_extension_blocks[0];
if (read_host(&current_extension_map->tag) != Definitions::ExtensionBlockTag::ExtensionBlockMap)
raw_index++;
if (read_host(&current_extension_map->tag) != (u8)Definitions::ExtensionBlockTag::ExtensionBlockMap)
return Error::from_string_literal("Did not find extension map at block 1"sv);
if (!validate_block_checksum(*current_extension_map))
return Error::from_string_literal("Extension block map checksum mismatch"sv);
}
} else if (read_host(&raw_extension_blocks[0].tag) == Definitions::ExtensionBlockTag::ExtensionBlockMap) {
} else if (read_host(&raw_extension_blocks[0].tag) == (u8)Definitions::ExtensionBlockTag::ExtensionBlockMap) {
current_extension_map = &raw_extension_blocks[0];
raw_index++;
}
for (unsigned raw_index = 0; raw_index < raw_extension_block_count; raw_index++) {
for (; raw_index < raw_extension_block_count; raw_index++) {
auto& raw_block = raw_extension_blocks[raw_index];
u8 tag = read_host(&raw_block.tag);
if (current_extension_map && raw_index == 127) {
if (tag != Definitions::ExtensionBlockTag::ExtensionBlockMap)
if (tag != (u8)Definitions::ExtensionBlockTag::ExtensionBlockMap)
return Error::from_string_literal("Did not find extension map at block 128"sv);
current_extension_map = &raw_extension_blocks[127];
if (!validate_block_checksum(*current_extension_map))
@ -524,17 +530,16 @@ ErrorOr<IterationDecision> Parser::for_each_extension_block(Function<IterationDe
continue;
}
if (tag == Definitions::ExtensionBlockTag::ExtensionBlockMap)
if (tag == (u8)Definitions::ExtensionBlockTag::ExtensionBlockMap)
return Error::from_string_literal("Unexpected extension map encountered"sv);
if (!validate_block_checksum(raw_block))
return Error::from_string_literal("Extension block checksum mismatch"sv);
size_t offset = (u8 const*)&raw_block - m_bytes.data();
IterationDecision decision = callback(raw_index + 1, tag, raw_block.block.revision, m_bytes.slice(offset, sizeof(Definitions::ExtensionBlock)));
if (decision != IterationDecision::Continue)
return decision;
offset += sizeof(Definitions::ExtensionBlock);
}
return IterationDecision::Continue;
}
@ -1033,7 +1038,7 @@ ErrorOr<IterationDecision> Parser::for_each_detailed_timing(Function<IterationDe
Optional<Error> extension_error;
auto result = for_each_extension_block([&](u8 block_id, u8 tag, u8, ReadonlyBytes bytes) {
if (tag != Definitions::ExtensionBlockTag::CEA_861)
if (tag != (u8)Definitions::ExtensionBlockTag::CEA_861)
return IterationDecision::Continue;
CEA861ExtensionBlock cea861(*this, (Definitions::ExtensionBlock const*)bytes.data());
@ -1077,7 +1082,7 @@ ErrorOr<IterationDecision> Parser::for_each_short_video_descriptor(Function<Iter
{
Optional<Error> extension_error;
auto result = for_each_extension_block([&](u8 block_id, u8 tag, u8, ReadonlyBytes bytes) {
if (tag != Definitions::ExtensionBlockTag::CEA_861)
if (tag != (u8)Definitions::ExtensionBlockTag::CEA_861)
return IterationDecision::Continue;
CEA861ExtensionBlock cea861(*this, (Definitions::ExtensionBlock const*)bytes.data());
@ -1113,7 +1118,7 @@ ErrorOr<IterationDecision> Parser::for_each_display_descriptor(Function<Iteratio
Optional<Error> extension_error;
auto result = for_each_extension_block([&](u8, u8 tag, u8, ReadonlyBytes bytes) {
if (tag != Definitions::ExtensionBlockTag::CEA_861)
if (tag != (u8)Definitions::ExtensionBlockTag::CEA_861)
return IterationDecision::Continue;
CEA861ExtensionBlock cea861(*this, (Definitions::ExtensionBlock const*)bytes.data());