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fix(relinker): align ELF64 section header tables #10852

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Merged
oneandonlydean merged 2 commits into from
Oct 26, 2026
Merged

fix(relinker): align ELF64 section header tables #10852

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03f3829
fix(relinker): align ELF64 section header tables
Mherberts Oct 25, 2026
d15fe22
test(relinker): require the exact section string table size
Mherberts Oct 25, 2026
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1 change: 1 addition & 0 deletions core/relinker/elfpatcher/src/general/SectionHeaderTableBuilder.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -103,6 +103,7 @@ void SectionHeaderTableBuilder::WriteTable(
for (const char i : kShStrTabBlob)
buf.push_back(static_cast<std::uint8_t>(i));

Io::AlignBuffer(buf, std::size_t{8});
const auto shOff = static_cast<std::uint64_t>(buf.size());
buf.resize(buf.size() + kShdrEntrySize * kSectionHeaderCount, 0);

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28 changes: 27 additions & 1 deletion core/relinker/elfpatcher/tests/SectionRangeTests.cpp
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Original file line number Diff line number Diff line change
@@ -1,6 +1,8 @@
#include <elfpatcher/general/SectionHeaderTableBuilder.hpp>
#include <elfpatcher/general/ElfConstants.hpp>
#include <io/ByteWriter.hpp>
#include <io/BufferUtils.hpp>
#include <algorithm>
#include <iostream>
#include <limits>
#include <stdexcept>
Expand Down Expand Up @@ -29,6 +31,30 @@ int main() {
auto empty = valid; empty.StubOffset = 384; empty.StubSize = 0;
bytes = Fixture(); builder.WriteTable(bytes, empty);
Require(Io::ReadU64(bytes, Io::ReadU64(bytes, 40) + 5 * 64 + 16) == 0x1100);
for (std::size_t tail = 0; tail < 8; ++tail) {
bytes = Fixture();
bytes.resize(512 + tail, 0xa5);
const auto original = bytes;
const auto originalSize = bytes.size();
builder.WriteTable(bytes, valid);
const auto alignedTable = Io::ReadU64(bytes, 40);
if (alignedTable % 8 != 0)
throw std::runtime_error("ELF64 section header table is not 8-byte aligned");
const auto stringOffset = Io::ReadU64(bytes, alignedTable + 64 + 24);
const auto stringSize = Io::ReadU64(bytes, alignedTable + 64 + 32);
const auto stringEnd = stringOffset + stringSize;
Require(stringOffset == originalSize && stringSize == sizeof(Elfpatcher::kShStrTabBlob));
Require(stringEnd <= alignedTable && alignedTable - stringEnd < 8);
Require(bytes[stringOffset] == 0 && bytes[stringEnd - 1] == 0);
Require(std::equal(original.begin() + 64, original.end(), bytes.begin() + 64));
Require(std::all_of(bytes.begin() + stringEnd, bytes.begin() + alignedTable,
[](const auto byte) { return byte == 0; }));
Require(bytes.size() == alignedTable + Io::ReadU16(bytes, 60) * 64);
Require(Io::ReadU64(bytes, alignedTable + 2 * 64 + 24) == valid.DynStrOffset);
Require(Io::ReadU64(bytes, alignedTable + 3 * 64 + 24) == valid.DynSymOffset);
Require(Io::ReadU64(bytes, alignedTable + 4 * 64 + 24) == valid.DynamicSegmentOffset);
Require(Io::ReadU64(bytes, alignedTable + 5 * 64 + 24) == valid.StubOffset);
}
for (int kind = 0; kind < 11; ++kind) {
bytes = Fixture(); auto request = valid;
switch (kind) {
Expand All @@ -49,6 +75,6 @@ int main() {
try { builder.WriteTable(bytes, request); } catch (const std::runtime_error&) { rejected = true; }
Require(rejected && bytes == before);
}
std::cout << "13 section range cases passed\n";
std::cout << "21 section range and alignment cases passed\n";
} catch (const std::exception& error) { std::cerr << error.what() << '\n'; return 1; }
}
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