https://github.com/felipepiovezan updated https://github.com/llvm/llvm-project/pull/172022
>From a0a13a6cbffb62d3b49e422de10fbcfd5259fca1 Mon Sep 17 00:00:00 2001 From: Felipe de Azevedo Piovezan <[email protected]> Date: Tue, 9 Dec 2025 14:34:26 +0000 Subject: [PATCH 1/2] [lldb] Respect max packet size limits for MultiMemRead in ProcessGDBRemote Servers advertise what their maximum packet size is, MultiMemRead needs to respect that. Depends on https://github.com/llvm/llvm-project/pull/172020 --- .../Process/gdb-remote/ProcessGDBRemote.cpp | 63 ++++++++++++++----- 1 file changed, 48 insertions(+), 15 deletions(-) diff --git a/lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp b/lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp index d1b0ead74701b..45d3b111ed194 100644 --- a/lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp +++ b/lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp @@ -2790,6 +2790,23 @@ size_t ProcessGDBRemote::DoReadMemory(addr_t addr, void *buf, size_t size, return 0; } +/// Returns the number of ranges that is safe to request using MultiMemRead +/// while respecting max_packet_size. +static uint64_t ComputeNumRangesMultiMemRead( + uint64_t max_packet_size, + llvm::ArrayRef<Range<lldb::addr_t, size_t>> ranges) { + // Each range is specified by two numbers (~16 ASCII characters) and one + // comma. + constexpr uint64_t range_overhead = 33; + uint64_t current_size = 0; + for (auto [idx, range] : llvm::enumerate(ranges)) { + uint64_t potential_size = current_size + range.size + range_overhead; + if (potential_size > max_packet_size) + return idx; + } + return ranges.size(); +} + llvm::SmallVector<llvm::MutableArrayRef<uint8_t>> ProcessGDBRemote::ReadMemoryRanges( llvm::ArrayRef<Range<lldb::addr_t, size_t>> ranges, @@ -2797,22 +2814,38 @@ ProcessGDBRemote::ReadMemoryRanges( if (!m_gdb_comm.GetMultiMemReadSupported()) return Process::ReadMemoryRanges(ranges, buffer); - llvm::Expected<StringExtractorGDBRemote> response = - SendMultiMemReadPacket(ranges); - if (!response) { - LLDB_LOG_ERROR(GetLog(GDBRLog::Process), response.takeError(), - "MultiMemRead error response: {0}"); - return Process::ReadMemoryRanges(ranges, buffer); - } - - llvm::StringRef response_str = response->GetStringRef(); - const unsigned expected_num_ranges = ranges.size(); + const llvm::ArrayRef<Range<lldb::addr_t, size_t>> original_ranges = ranges; llvm::SmallVector<llvm::MutableArrayRef<uint8_t>> memory_regions; - if (llvm::Error error = ParseMultiMemReadPacket( - response_str, buffer, expected_num_ranges, memory_regions)) { - LLDB_LOG_ERROR(GetLog(GDBRLog::Process), std::move(error), - "MultiMemRead error parsing response: {0}"); - return Process::ReadMemoryRanges(ranges, buffer); + + while (!ranges.empty()) { + uint64_t num_ranges = + ComputeNumRangesMultiMemRead(m_max_memory_size, ranges); + if (num_ranges == 0) { + LLDB_LOG( + GetLog(GDBRLog::Process), + "MultiMemRead has a range bigger than maximum allowed by remote"); + return Process::ReadMemoryRanges(original_ranges, buffer); + } + + auto ranges_for_request = ranges.take_front(num_ranges); + ranges = ranges.drop_front(num_ranges); + + llvm::Expected<StringExtractorGDBRemote> response = + SendMultiMemReadPacket(ranges_for_request); + if (!response) { + LLDB_LOG_ERROR(GetLog(GDBRLog::Process), response.takeError(), + "MultiMemRead error response: {0}"); + return Process::ReadMemoryRanges(original_ranges, buffer); + } + + llvm::StringRef response_str = response->GetStringRef(); + const unsigned expected_num_ranges = ranges_for_request.size(); + if (llvm::Error error = ParseMultiMemReadPacket( + response_str, buffer, expected_num_ranges, memory_regions)) { + LLDB_LOG_ERROR(GetLog(GDBRLog::Process), std::move(error), + "MultiMemRead error parsing response: {0}"); + return Process::ReadMemoryRanges(original_ranges, buffer); + } } return memory_regions; } >From 95b70895369b6e4ea301da1c644383cb6c46a9de Mon Sep 17 00:00:00 2001 From: Felipe de Azevedo Piovezan <[email protected]> Date: Sun, 14 Dec 2025 10:39:10 +0000 Subject: [PATCH 2/2] fixup! address review comments --- .../Process/gdb-remote/ProcessGDBRemote.cpp | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) diff --git a/lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp b/lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp index 45d3b111ed194..bae07245bdfa6 100644 --- a/lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp +++ b/lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp @@ -2795,14 +2795,20 @@ size_t ProcessGDBRemote::DoReadMemory(addr_t addr, void *buf, size_t size, static uint64_t ComputeNumRangesMultiMemRead( uint64_t max_packet_size, llvm::ArrayRef<Range<lldb::addr_t, size_t>> ranges) { - // Each range is specified by two numbers (~16 ASCII characters) and one + // Each range is specified by two numbers (up to 16 ASCII characters) and one // comma. constexpr uint64_t range_overhead = 33; uint64_t current_size = 0; for (auto [idx, range] : llvm::enumerate(ranges)) { uint64_t potential_size = current_size + range.size + range_overhead; - if (potential_size > max_packet_size) + if (potential_size > max_packet_size) { + if (idx == 0) + LLDB_LOG(GetLog(GDBRLog::Process), + "MultiMemRead input has a range (base = {0:x}, size = {1}) " + "bigger than the maximum allowed by remote", + range.base, range.size); return idx; + } } return ranges.size(); } @@ -2820,12 +2826,8 @@ ProcessGDBRemote::ReadMemoryRanges( while (!ranges.empty()) { uint64_t num_ranges = ComputeNumRangesMultiMemRead(m_max_memory_size, ranges); - if (num_ranges == 0) { - LLDB_LOG( - GetLog(GDBRLog::Process), - "MultiMemRead has a range bigger than maximum allowed by remote"); + if (num_ranges == 0) return Process::ReadMemoryRanges(original_ranges, buffer); - } auto ranges_for_request = ranges.take_front(num_ranges); ranges = ranges.drop_front(num_ranges); _______________________________________________ lldb-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits
