fix(relinker): keep PT_GNU_EH_FRAME in the relinked executable
The segment filter dropped every header in the PT_LOOS..PT_HIOS range, which includes PT_GNU_EH_FRAME. The unwinders find the executable's unwind tables through that header, so no C++ exception thrown in the main executable could be caught on Linux. The header is kept only when the output program header table still fits in the input's table; otherwise it is dropped as before, with a warning. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01HeC9bA3n74TzJRYv9AgBE8
This commit is contained in:
clem-gb
parent
cba8d86da8
commit
d16cac0ab2
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@ -206,6 +206,8 @@ if(BUILD_TESTING)
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${CMAKE_CURRENT_SOURCE_DIR}/relinker/tests/test_tls_diagnostics.py $<TARGET_FILE:relinker>)
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add_test(NAME linux_load_alignment COMMAND ${Python3_EXECUTABLE}
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${CMAKE_CURRENT_SOURCE_DIR}/relinker/tests/test_linux_load_alignment.py $<TARGET_FILE:relinker>)
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add_test(NAME linux_eh_frame_header COMMAND ${Python3_EXECUTABLE}
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${CMAKE_CURRENT_SOURCE_DIR}/relinker/tests/test_linux_eh_frame_header.py $<TARGET_FILE:relinker>)
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add_test(NAME linux_dynamic_strings COMMAND ${Python3_EXECUTABLE}
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${CMAKE_CURRENT_SOURCE_DIR}/relinker/tests/test_linux_dynamic_strings.py $<TARGET_FILE:relinker>)
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add_test(NAME executable_segments COMMAND ${Python3_EXECUTABLE}
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@ -62,6 +62,7 @@ inline constexpr std::uint32_t PT_DYNAMIC = 2;
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inline constexpr std::uint32_t PT_INTERP = 3;
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inline constexpr std::uint32_t PT_NOTE = 4;
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inline constexpr std::uint32_t PT_PHDR = 6;
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inline constexpr std::uint32_t PT_GNU_EH_FRAME = 0x6474e550;
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inline constexpr std::uint32_t PT_GNU_RELRO = 0x6474e552;
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inline constexpr std::uint32_t PF_X = 0x1;
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inline constexpr std::uint32_t PF_W = 0x2;
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@ -2,6 +2,7 @@
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#include <elfpatcher/general/ElfConstants.hpp>
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#include <domain/Types.hpp>
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#include <cstdint>
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#include <iostream>
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#include <string>
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namespace Elfpatcher {
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@ -131,10 +132,19 @@ std::uint16_t ProgramHeaderLayoutBuilder::WriteLayout(
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const ProgramHeaderLayoutRequest& request
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) const {
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std::uint16_t keptCount = 0;
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std::uint16_t frameCount = 0;
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for (const auto& ph : request.OriginalHeaders) {
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if (_segmentFilter->ShouldSkip(ph))
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continue;
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keptCount++;
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if (ph.Type == PT_GNU_EH_FRAME)
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frameCount++;
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}
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const bool keepFrames = keptCount + kSyntheticProgramHeaderCount < request.PhNum;
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if (!keepFrames && frameCount > 0) {
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keptCount -= frameCount;
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std::cerr << "WARNING: No free program header slot for PT_GNU_EH_FRAME; C++ exceptions thrown in the executable cannot be caught.\n";
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}
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const std::uint16_t neededPh = keptCount + kSyntheticProgramHeaderCount;
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@ -175,7 +185,7 @@ std::uint16_t ProgramHeaderLayoutBuilder::WriteLayout(
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writtenPh++;
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for (const auto& ph : request.OriginalHeaders) {
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if (_segmentFilter->ShouldSkip(ph))
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if (_segmentFilter->ShouldSkip(ph) || (!keepFrames && ph.Type == PT_GNU_EH_FRAME))
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continue;
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const std::size_t phEntOff = static_cast<std::size_t>(request.PhOff) + writtenPh * request.PhEntSize;
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if (ph.Type == PT_LOAD) {
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@ -12,6 +12,7 @@ bool SegmentFilter::_isSceSpecificSegment(const std::uint32_t type) const {
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bool SegmentFilter::ShouldSkip(const Domain::ProgramHeader& ph) const {
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if (ph.Type == PT_OS_PROCPARAM) return false;
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if (ph.Type == PT_GNU_EH_FRAME) return false;
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if (_isSceSpecificSegment(ph.Type)) return true;
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if (ph.Type == PT_DYNAMIC) return true;
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if (ph.Type == PT_NOTE && ph.MappedAddress == 0 && ph.FileSize > 0) return true;
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@ -0,0 +1,72 @@
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from pathlib import Path
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import struct
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import subprocess
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import sys
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import tempfile
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PT_LOAD = 1
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PT_DYNAMIC = 2
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PT_GNU_EH_FRAME = 0x6474E550
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PT_SCE_VERSION = 0x6FFFFF01
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EH_FRAME_HEADER = (PT_GNU_EH_FRAME, 4, 0x4800, 0x800, 0x800, 16, 16, 4)
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def fixture(header_count):
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image = bytearray(0x8000)
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image[:16] = b"\x7fELF\x02\x01\x01" + bytes(9)
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struct.pack_into("<HHIQQQIHHHHHH", image, 16,
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3, 62, 1, 0x4000, 64, 0, 0, 64, 56, header_count, 64, 0, 0)
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image[0x4000:0x4006] = b"\xb8\x2a\x00\x00\x00\xc3"
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tags = [(5, 0x600), (10, 1), (6, 0x620), (11, 24), (7, 0x700), (8, 0), (9, 24), (0, 0)]
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struct.pack_into("<IIQQQQQQ", image, 64,
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PT_LOAD, 5, 0x4000, 0, 0, 0x1000, 0x1000, 0x4000)
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struct.pack_into("<IIQQQQQQ", image, 120,
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PT_DYNAMIC, 6, 0x600 + 0x4000, 0x600, 0x600, len(tags) * 16, len(tags) * 16, 8)
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struct.pack_into("<IIQQQQQQ", image, 176, *EH_FRAME_HEADER)
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for index in range(3, header_count):
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struct.pack_into("<IIQQQQQQ", image, 64 + index * 56, PT_SCE_VERSION, 0, 0, 0, 0, 0, 0, 1)
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for index, tag in enumerate(tags):
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struct.pack_into("<qQ", image, 0x4600 + index * 16, *tag)
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struct.pack_into("<BBBBQI", image, 0x4800, 1, 0, 3, 0, 0x900, 0)
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return image
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def program_headers(elf):
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phoff, = struct.unpack_from("<Q", elf, 0x20)
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phentsize, phnum = struct.unpack_from("<HH", elf, 0x36)
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return [struct.unpack_from("<IIQQQQQQ", elf, phoff + index * phentsize) for index in range(phnum)]
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def relink(relinker, directory, name, image):
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source = Path(directory) / (name + ".elf")
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output = Path(directory) / (name + ".out")
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source.write_bytes(image)
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result = subprocess.run([str(relinker), "--skip-sce-module", str(source), str(output)], capture_output=True, text=True, timeout=20)
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assert result.returncode == 0, (name, result.returncode, result.stdout, result.stderr)
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return result, output.read_bytes()
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def main():
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relinker = Path(sys.argv[1]).resolve()
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with tempfile.TemporaryDirectory(prefix="anyps5-eh-frame-") as directory:
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image = fixture(7)
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result, elf = relink(relinker, directory, "spare-slot", image)
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assert "PT_GNU_EH_FRAME" not in result.stderr, result.stderr
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headers = program_headers(elf)
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frames = [header for header in headers if header[0] == PT_GNU_EH_FRAME]
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assert frames == [EH_FRAME_HEADER], ("PT_GNU_EH_FRAME must be kept unchanged", headers)
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offset, size = EH_FRAME_HEADER[2], EH_FRAME_HEADER[5]
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assert elf[offset:offset + size] == image[offset:offset + size], "eh_frame_hdr bytes changed"
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assert all(header[0] != PT_SCE_VERSION for header in headers), headers
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for header_count in (5, 6):
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result, elf = relink(relinker, directory, "full-slots-" + str(header_count), fixture(header_count))
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headers = program_headers(elf)
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assert all(header[0] != PT_GNU_EH_FRAME for header in headers), (header_count, headers)
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assert len(headers) == 6, (header_count, headers)
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assert "No free program header slot for PT_GNU_EH_FRAME" in result.stderr, (header_count, result.stderr)
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print("Linux eh_frame header test passed")
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if __name__ == "__main__":
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main()
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