RGBCube/serenity
1
Fork 0
mirror of https://github.com/RGBCube/serenity synced 2025-07-26 07:27:45 +00:00
Code Issues Activity Actions

LibEDID: Fix handling extension maps

Browse source 
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
Download patch file Download diff file Expand all files Collapse all files

39
Userland/Libraries/LibEDID/EDID.cpp
View file

@ -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());