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llvm-project/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunication.cpp
Pavel Labath 2c90c0b90c
[lldb] Extract debug server location code (#145706) 
.. from the guts of GDBRemoteCommunication to ~top level.

This is motivated by #131519 and by the fact that's impossible to guess
whether the author of a symlink intended it to be a "convenience
shortcut" -- meaning it should be resolved before looking for related
files; or an "implementation detail" -- meaning the related files should
be located near the symlink itself.

This debate is particularly ridiculous when it comes to lldb-server
running in platform mode, because it also functions as a debug server,
so what we really just need to do is to pass /proc/self/exe in a
platform-independent manner.

Moving the location logic higher up achieves that as lldb-platform (on
non-macos) can pass `HostInfo::GetProgramFileSpec`, while liblldb can
use the existing complex logic (which only worked on liblldb anyway as
lldb-platform doesn't have a lldb_private::Platform instance).

Another benefit of this patch is a reduction in dependency from
GDBRemoteCommunication to the rest of liblldb (achieved by avoiding the
Platform dependency).
2025-06-27 11:16:57 +02:00

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//===-- GDBRemoteCommunication.cpp ----------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "GDBRemoteCommunication.h"
#include "ProcessGDBRemoteLog.h"
#include "lldb/Host/Config.h"
#include "lldb/Host/FileSystem.h"
#include "lldb/Host/Host.h"
#include "lldb/Host/Pipe.h"
#include "lldb/Host/ProcessLaunchInfo.h"
#include "lldb/Host/Socket.h"
#include "lldb/Host/common/TCPSocket.h"
#include "lldb/Host/posix/ConnectionFileDescriptorPosix.h"
#include "lldb/Target/Platform.h"
#include "lldb/Utility/Event.h"
#include "lldb/Utility/FileSpec.h"
#include "lldb/Utility/Log.h"
#include "lldb/Utility/RegularExpression.h"
#include "lldb/Utility/StreamString.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Config/llvm-config.h" // for LLVM_ENABLE_ZLIB
#include "llvm/Support/Error.h"
#include "llvm/Support/ScopedPrinter.h"
#include <climits>
#include <cstring>
#include <sys/stat.h>
#include <variant>
#if HAVE_LIBCOMPRESSION
#include <compression.h>
#endif
#if LLVM_ENABLE_ZLIB
#include <zlib.h>
#endif
using namespace lldb;
using namespace lldb_private;
using namespace lldb_private::process_gdb_remote;
// GDBRemoteCommunication constructor
GDBRemoteCommunication::GDBRemoteCommunication()
: Communication(),
#ifdef LLDB_CONFIGURATION_DEBUG
m_packet_timeout(1000),
#else
m_packet_timeout(1),
#endif
m_echo_number(0), m_supports_qEcho(eLazyBoolCalculate), m_history(512),
m_send_acks(true), m_is_platform(false),
m_compression_type(CompressionType::None) {
}
// Destructor
GDBRemoteCommunication::~GDBRemoteCommunication() {
if (IsConnected()) {
Disconnect();
}
#if HAVE_LIBCOMPRESSION
if (m_decompression_scratch)
free (m_decompression_scratch);
#endif
}
char GDBRemoteCommunication::CalculcateChecksum(llvm::StringRef payload) {
int checksum = 0;
for (char c : payload)
checksum += c;
return checksum & 255;
}
size_t GDBRemoteCommunication::SendAck() {
Log *log = GetLog(GDBRLog::Packets);
ConnectionStatus status = eConnectionStatusSuccess;
char ch = '+';
const size_t bytes_written = WriteAll(&ch, 1, status, nullptr);
LLDB_LOGF(log, "<%4" PRIu64 "> send packet: %c", (uint64_t)bytes_written, ch);
m_history.AddPacket(ch, GDBRemotePacket::ePacketTypeSend, bytes_written);
return bytes_written;
}
size_t GDBRemoteCommunication::SendNack() {
Log *log = GetLog(GDBRLog::Packets);
ConnectionStatus status = eConnectionStatusSuccess;
char ch = '-';
const size_t bytes_written = WriteAll(&ch, 1, status, nullptr);
LLDB_LOGF(log, "<%4" PRIu64 "> send packet: %c", (uint64_t)bytes_written, ch);
m_history.AddPacket(ch, GDBRemotePacket::ePacketTypeSend, bytes_written);
return bytes_written;
}
GDBRemoteCommunication::PacketResult
GDBRemoteCommunication::SendPacketNoLock(llvm::StringRef payload) {
StreamString packet(0, 4, eByteOrderBig);
packet.PutChar('$');
packet.Write(payload.data(), payload.size());
packet.PutChar('#');
packet.PutHex8(CalculcateChecksum(payload));
std::string packet_str = std::string(packet.GetString());
return SendRawPacketNoLock(packet_str);
}
GDBRemoteCommunication::PacketResult
GDBRemoteCommunication::SendNotificationPacketNoLock(
llvm::StringRef notify_type, std::deque<std::string> &queue,
llvm::StringRef payload) {
PacketResult ret = PacketResult::Success;
// If there are no notification in the queue, send the notification
// packet.
if (queue.empty()) {
StreamString packet(0, 4, eByteOrderBig);
packet.PutChar('%');
packet.Write(notify_type.data(), notify_type.size());
packet.PutChar(':');
packet.Write(payload.data(), payload.size());
packet.PutChar('#');
packet.PutHex8(CalculcateChecksum(payload));
ret = SendRawPacketNoLock(packet.GetString(), true);
}
queue.push_back(payload.str());
return ret;
}
GDBRemoteCommunication::PacketResult
GDBRemoteCommunication::SendRawPacketNoLock(llvm::StringRef packet,
bool skip_ack) {
if (IsConnected()) {
Log *log = GetLog(GDBRLog::Packets);
ConnectionStatus status = eConnectionStatusSuccess;
const char *packet_data = packet.data();
const size_t packet_length = packet.size();
size_t bytes_written = WriteAll(packet_data, packet_length, status, nullptr);
if (log) {
size_t binary_start_offset = 0;
if (strncmp(packet_data, "$vFile:pwrite:", strlen("$vFile:pwrite:")) ==
0) {
const char *first_comma = strchr(packet_data, ',');
if (first_comma) {
const char *second_comma = strchr(first_comma + 1, ',');
if (second_comma)
binary_start_offset = second_comma - packet_data + 1;
}
}
// If logging was just enabled and we have history, then dump out what we
// have to the log so we get the historical context. The Dump() call that
// logs all of the packet will set a boolean so that we don't dump this
// more than once
if (!m_history.DidDumpToLog())
m_history.Dump(log);
if (binary_start_offset) {
StreamString strm;
// Print non binary data header
strm.Printf("<%4" PRIu64 "> send packet: %.*s", (uint64_t)bytes_written,
(int)binary_start_offset, packet_data);
const uint8_t *p;
// Print binary data exactly as sent
for (p = (const uint8_t *)packet_data + binary_start_offset; *p != '#';
++p)
strm.Printf("\\x%2.2x", *p);
// Print the checksum
strm.Printf("%*s", (int)3, p);
log->PutString(strm.GetString());
} else
LLDB_LOGF(log, "<%4" PRIu64 "> send packet: %.*s",
(uint64_t)bytes_written, (int)packet_length, packet_data);
}
m_history.AddPacket(packet.str(), packet_length,
GDBRemotePacket::ePacketTypeSend, bytes_written);
if (bytes_written == packet_length) {
if (!skip_ack && GetSendAcks())
return GetAck();
else
return PacketResult::Success;
} else {
LLDB_LOGF(log, "error: failed to send packet: %.*s", (int)packet_length,
packet_data);
}
}
return PacketResult::ErrorSendFailed;
}
GDBRemoteCommunication::PacketResult GDBRemoteCommunication::GetAck() {
StringExtractorGDBRemote packet;
PacketResult result = WaitForPacketNoLock(packet, GetPacketTimeout(), false);
if (result == PacketResult::Success) {
if (packet.GetResponseType() ==
StringExtractorGDBRemote::ResponseType::eAck)
return PacketResult::Success;
else
return PacketResult::ErrorSendAck;
}
return result;
}
GDBRemoteCommunication::PacketResult
GDBRemoteCommunication::ReadPacket(StringExtractorGDBRemote &response,
Timeout<std::micro> timeout,
bool sync_on_timeout) {
using ResponseType = StringExtractorGDBRemote::ResponseType;
Log *log = GetLog(GDBRLog::Packets);
for (;;) {
PacketResult result =
WaitForPacketNoLock(response, timeout, sync_on_timeout);
if (result != PacketResult::Success ||
(response.GetResponseType() != ResponseType::eAck &&
response.GetResponseType() != ResponseType::eNack))
return result;
LLDB_LOG(log, "discarding spurious `{0}` packet", response.GetStringRef());
}
}
GDBRemoteCommunication::PacketResult
GDBRemoteCommunication::WaitForPacketNoLock(StringExtractorGDBRemote &packet,
Timeout<std::micro> timeout,
bool sync_on_timeout) {
uint8_t buffer[8192];
Status error;
Log *log = GetLog(GDBRLog::Packets);
// Check for a packet from our cache first without trying any reading...
if (CheckForPacket(nullptr, 0, packet) != PacketType::Invalid)
return PacketResult::Success;
bool timed_out = false;
bool disconnected = false;
while (IsConnected() && !timed_out) {
lldb::ConnectionStatus status = eConnectionStatusNoConnection;
size_t bytes_read = Read(buffer, sizeof(buffer), timeout, status, &error);
LLDB_LOGV(log,
"Read(buffer, sizeof(buffer), timeout = {0}, "
"status = {1}, error = {2}) => bytes_read = {3}",
timeout, Communication::ConnectionStatusAsString(status), error,
bytes_read);
if (bytes_read > 0) {
if (CheckForPacket(buffer, bytes_read, packet) != PacketType::Invalid)
return PacketResult::Success;
} else {
switch (status) {
case eConnectionStatusTimedOut:
case eConnectionStatusInterrupted:
if (sync_on_timeout) {
/// Sync the remote GDB server and make sure we get a response that
/// corresponds to what we send.
///
/// Sends a "qEcho" packet and makes sure it gets the exact packet
/// echoed back. If the qEcho packet isn't supported, we send a qC
/// packet and make sure we get a valid thread ID back. We use the
/// "qC" packet since its response if very unique: is responds with
/// "QC%x" where %x is the thread ID of the current thread. This
/// makes the response unique enough from other packet responses to
/// ensure we are back on track.
///
/// This packet is needed after we time out sending a packet so we
/// can ensure that we are getting the response for the packet we
/// are sending. There are no sequence IDs in the GDB remote
/// protocol (there used to be, but they are not supported anymore)
/// so if you timeout sending packet "abc", you might then send
/// packet "cde" and get the response for the previous "abc" packet.
/// Many responses are "OK" or "" (unsupported) or "EXX" (error) so
/// many responses for packets can look like responses for other
/// packets. So if we timeout, we need to ensure that we can get
/// back on track. If we can't get back on track, we must
/// disconnect.
bool sync_success = false;
bool got_actual_response = false;
// We timed out, we need to sync back up with the
char echo_packet[32];
int echo_packet_len = 0;
RegularExpression response_regex;
if (m_supports_qEcho == eLazyBoolYes) {
echo_packet_len = ::snprintf(echo_packet, sizeof(echo_packet),
"qEcho:%u", ++m_echo_number);
std::string regex_str = "^";
regex_str += echo_packet;
regex_str += "$";
response_regex = RegularExpression(regex_str);
} else {
echo_packet_len =
::snprintf(echo_packet, sizeof(echo_packet), "qC");
response_regex =
RegularExpression(llvm::StringRef("^QC[0-9A-Fa-f]+$"));
}
PacketResult echo_packet_result =
SendPacketNoLock(llvm::StringRef(echo_packet, echo_packet_len));
if (echo_packet_result == PacketResult::Success) {
const uint32_t max_retries = 3;
uint32_t successful_responses = 0;
for (uint32_t i = 0; i < max_retries; ++i) {
StringExtractorGDBRemote echo_response;
echo_packet_result =
WaitForPacketNoLock(echo_response, timeout, false);
if (echo_packet_result == PacketResult::Success) {
++successful_responses;
if (response_regex.Execute(echo_response.GetStringRef())) {
sync_success = true;
break;
} else if (successful_responses == 1) {
// We got something else back as the first successful
// response, it probably is the response to the packet we
// actually wanted, so copy it over if this is the first
// success and continue to try to get the qEcho response
packet = echo_response;
got_actual_response = true;
}
} else if (echo_packet_result == PacketResult::ErrorReplyTimeout)
continue; // Packet timed out, continue waiting for a response
else
break; // Something else went wrong getting the packet back, we
// failed and are done trying
}
}
// We weren't able to sync back up with the server, we must abort
// otherwise all responses might not be from the right packets...
if (sync_success) {
// We timed out, but were able to recover
if (got_actual_response) {
// We initially timed out, but we did get a response that came in
// before the successful reply to our qEcho packet, so lets say
// everything is fine...
return PacketResult::Success;
}
} else {
disconnected = true;
Disconnect();
}
} else {
timed_out = true;
}
break;
case eConnectionStatusSuccess:
// printf ("status = success but error = %s\n",
// error.AsCString("<invalid>"));
break;
case eConnectionStatusEndOfFile:
case eConnectionStatusNoConnection:
case eConnectionStatusLostConnection:
case eConnectionStatusError:
disconnected = true;
Disconnect();
break;
}
}
}
packet.Clear();
if (disconnected)
return PacketResult::ErrorDisconnected;
if (timed_out)
return PacketResult::ErrorReplyTimeout;
else
return PacketResult::ErrorReplyFailed;
}
bool GDBRemoteCommunication::DecompressPacket() {
Log *log = GetLog(GDBRLog::Packets);
if (!CompressionIsEnabled())
return true;
size_t pkt_size = m_bytes.size();
// Smallest possible compressed packet is $N#00 - an uncompressed empty
// reply, most commonly indicating an unsupported packet. Anything less than
// 5 characters, it's definitely not a compressed packet.
if (pkt_size < 5)
return true;
if (m_bytes[0] != '$' && m_bytes[0] != '%')
return true;
if (m_bytes[1] != 'C' && m_bytes[1] != 'N')
return true;
size_t hash_mark_idx = m_bytes.find('#');
if (hash_mark_idx == std::string::npos)
return true;
if (hash_mark_idx + 2 >= m_bytes.size())
return true;
if (!::isxdigit(m_bytes[hash_mark_idx + 1]) ||
!::isxdigit(m_bytes[hash_mark_idx + 2]))
return true;
size_t content_length =
pkt_size -
5; // not counting '$', 'C' | 'N', '#', & the two hex checksum chars
size_t content_start = 2; // The first character of the
// compressed/not-compressed text of the packet
size_t checksum_idx =
hash_mark_idx +
1; // The first character of the two hex checksum characters
// Normally size_of_first_packet == m_bytes.size() but m_bytes may contain
// multiple packets. size_of_first_packet is the size of the initial packet
// which we'll replace with the decompressed version of, leaving the rest of
// m_bytes unmodified.
size_t size_of_first_packet = hash_mark_idx + 3;
// Compressed packets ("$C") start with a base10 number which is the size of
// the uncompressed payload, then a : and then the compressed data. e.g.
// $C1024:<binary>#00 Update content_start and content_length to only include
// the <binary> part of the packet.
uint64_t decompressed_bufsize = ULONG_MAX;
if (m_bytes[1] == 'C') {
size_t i = content_start;
while (i < hash_mark_idx && isdigit(m_bytes[i]))
i++;
if (i < hash_mark_idx && m_bytes[i] == ':') {
i++;
content_start = i;
content_length = hash_mark_idx - content_start;
std::string bufsize_str(m_bytes.data() + 2, i - 2 - 1);
errno = 0;
decompressed_bufsize = ::strtoul(bufsize_str.c_str(), nullptr, 10);
if (errno != 0 || decompressed_bufsize == ULONG_MAX) {
m_bytes.erase(0, size_of_first_packet);
return false;
}
}
}
if (GetSendAcks()) {
char packet_checksum_cstr[3];
packet_checksum_cstr[0] = m_bytes[checksum_idx];
packet_checksum_cstr[1] = m_bytes[checksum_idx + 1];
packet_checksum_cstr[2] = '\0';
long packet_checksum = strtol(packet_checksum_cstr, nullptr, 16);
long actual_checksum = CalculcateChecksum(
llvm::StringRef(m_bytes).substr(1, hash_mark_idx - 1));
bool success = packet_checksum == actual_checksum;
if (!success) {
LLDB_LOGF(log,
"error: checksum mismatch: %.*s expected 0x%2.2x, got 0x%2.2x",
(int)(pkt_size), m_bytes.c_str(), (uint8_t)packet_checksum,
(uint8_t)actual_checksum);
}
// Send the ack or nack if needed
if (!success) {
SendNack();
m_bytes.erase(0, size_of_first_packet);
return false;
} else {
SendAck();
}
}
if (m_bytes[1] == 'N') {
// This packet was not compressed -- delete the 'N' character at the start
// and the packet may be processed as-is.
m_bytes.erase(1, 1);
return true;
}
// Reverse the gdb-remote binary escaping that was done to the compressed
// text to guard characters like '$', '#', '}', etc.
std::vector<uint8_t> unescaped_content;
unescaped_content.reserve(content_length);
size_t i = content_start;
while (i < hash_mark_idx) {
if (m_bytes[i] == '}') {
i++;
unescaped_content.push_back(m_bytes[i] ^ 0x20);
} else {
unescaped_content.push_back(m_bytes[i]);
}
i++;
}
uint8_t *decompressed_buffer = nullptr;
size_t decompressed_bytes = 0;
if (decompressed_bufsize != ULONG_MAX) {
decompressed_buffer = (uint8_t *)malloc(decompressed_bufsize);
if (decompressed_buffer == nullptr) {
m_bytes.erase(0, size_of_first_packet);
return false;
}
}
#if HAVE_LIBCOMPRESSION
if (m_compression_type == CompressionType::ZlibDeflate ||
m_compression_type == CompressionType::LZFSE ||
m_compression_type == CompressionType::LZ4 ||
m_compression_type == CompressionType::LZMA) {
compression_algorithm compression_type;
if (m_compression_type == CompressionType::LZFSE)
compression_type = COMPRESSION_LZFSE;
else if (m_compression_type == CompressionType::ZlibDeflate)
compression_type = COMPRESSION_ZLIB;
else if (m_compression_type == CompressionType::LZ4)
compression_type = COMPRESSION_LZ4_RAW;
else if (m_compression_type == CompressionType::LZMA)
compression_type = COMPRESSION_LZMA;
if (m_decompression_scratch_type != m_compression_type) {
if (m_decompression_scratch) {
free (m_decompression_scratch);
m_decompression_scratch = nullptr;
}
size_t scratchbuf_size = 0;
if (m_compression_type == CompressionType::LZFSE)
scratchbuf_size = compression_decode_scratch_buffer_size (COMPRESSION_LZFSE);
else if (m_compression_type == CompressionType::LZ4)
scratchbuf_size = compression_decode_scratch_buffer_size (COMPRESSION_LZ4_RAW);
else if (m_compression_type == CompressionType::ZlibDeflate)
scratchbuf_size = compression_decode_scratch_buffer_size (COMPRESSION_ZLIB);
else if (m_compression_type == CompressionType::LZMA)
scratchbuf_size =
compression_decode_scratch_buffer_size(COMPRESSION_LZMA);
if (scratchbuf_size > 0) {
m_decompression_scratch = (void*) malloc (scratchbuf_size);
m_decompression_scratch_type = m_compression_type;
}
}
if (decompressed_bufsize != ULONG_MAX && decompressed_buffer != nullptr) {
decompressed_bytes = compression_decode_buffer(
decompressed_buffer, decompressed_bufsize,
(uint8_t *)unescaped_content.data(), unescaped_content.size(),
m_decompression_scratch, compression_type);
}
}
#endif
#if LLVM_ENABLE_ZLIB
if (decompressed_bytes == 0 && decompressed_bufsize != ULONG_MAX &&
decompressed_buffer != nullptr &&
m_compression_type == CompressionType::ZlibDeflate) {
z_stream stream;
memset(&stream, 0, sizeof(z_stream));
stream.next_in = (Bytef *)unescaped_content.data();
stream.avail_in = (uInt)unescaped_content.size();
stream.total_in = 0;
stream.next_out = (Bytef *)decompressed_buffer;
stream.avail_out = decompressed_bufsize;
stream.total_out = 0;
stream.zalloc = Z_NULL;
stream.zfree = Z_NULL;
stream.opaque = Z_NULL;
if (inflateInit2(&stream, -15) == Z_OK) {
int status = inflate(&stream, Z_NO_FLUSH);
inflateEnd(&stream);
if (status == Z_STREAM_END) {
decompressed_bytes = stream.total_out;
}
}
}
#endif
if (decompressed_bytes == 0 || decompressed_buffer == nullptr) {
if (decompressed_buffer)
free(decompressed_buffer);
m_bytes.erase(0, size_of_first_packet);
return false;
}
std::string new_packet;
new_packet.reserve(decompressed_bytes + 6);
new_packet.push_back(m_bytes[0]);
new_packet.append((const char *)decompressed_buffer, decompressed_bytes);
new_packet.push_back('#');
if (GetSendAcks()) {
uint8_t decompressed_checksum = CalculcateChecksum(
llvm::StringRef((const char *)decompressed_buffer, decompressed_bytes));
char decompressed_checksum_str[3];
snprintf(decompressed_checksum_str, 3, "%02x", decompressed_checksum);
new_packet.append(decompressed_checksum_str);
} else {
new_packet.push_back('0');
new_packet.push_back('0');
}
m_bytes.replace(0, size_of_first_packet, new_packet.data(),
new_packet.size());
free(decompressed_buffer);
return true;
}
GDBRemoteCommunication::PacketType
GDBRemoteCommunication::CheckForPacket(const uint8_t *src, size_t src_len,
StringExtractorGDBRemote &packet) {
// Put the packet data into the buffer in a thread safe fashion
std::lock_guard<std::recursive_mutex> guard(m_bytes_mutex);
Log *log = GetLog(GDBRLog::Packets);
if (src && src_len > 0) {
if (log && log->GetVerbose()) {
StreamString s;
LLDB_LOGF(log, "GDBRemoteCommunication::%s adding %u bytes: %.*s",
__FUNCTION__, (uint32_t)src_len, (uint32_t)src_len, src);
}
m_bytes.append((const char *)src, src_len);
}
bool isNotifyPacket = false;
// Parse up the packets into gdb remote packets
if (!m_bytes.empty()) {
// end_idx must be one past the last valid packet byte. Start it off with
// an invalid value that is the same as the current index.
size_t content_start = 0;
size_t content_length = 0;
size_t total_length = 0;
size_t checksum_idx = std::string::npos;
// Size of packet before it is decompressed, for logging purposes
size_t original_packet_size = m_bytes.size();
if (CompressionIsEnabled()) {
if (!DecompressPacket()) {
packet.Clear();
return GDBRemoteCommunication::PacketType::Standard;
}
}
switch (m_bytes[0]) {
case '+': // Look for ack
case '-': // Look for cancel
case '\x03': // ^C to halt target
content_length = total_length = 1; // The command is one byte long...
break;
case '%': // Async notify packet
isNotifyPacket = true;
[[fallthrough]];
case '$':
// Look for a standard gdb packet?
{
size_t hash_pos = m_bytes.find('#');
if (hash_pos != std::string::npos) {
if (hash_pos + 2 < m_bytes.size()) {
checksum_idx = hash_pos + 1;
// Skip the dollar sign
content_start = 1;
// Don't include the # in the content or the $ in the content
// length
content_length = hash_pos - 1;
total_length =
hash_pos + 3; // Skip the # and the two hex checksum bytes
} else {
// Checksum bytes aren't all here yet
content_length = std::string::npos;
}
}
}
break;
default: {
// We have an unexpected byte and we need to flush all bad data that is
// in m_bytes, so we need to find the first byte that is a '+' (ACK), '-'
// (NACK), \x03 (CTRL+C interrupt), or '$' character (start of packet
// header) or of course, the end of the data in m_bytes...
const size_t bytes_len = m_bytes.size();
bool done = false;
uint32_t idx;
for (idx = 1; !done && idx < bytes_len; ++idx) {
switch (m_bytes[idx]) {
case '+':
case '-':
case '\x03':
case '%':
case '$':
done = true;
break;
default:
break;
}
}
LLDB_LOGF(log, "GDBRemoteCommunication::%s tossing %u junk bytes: '%.*s'",
__FUNCTION__, idx - 1, idx - 1, m_bytes.c_str());
m_bytes.erase(0, idx - 1);
} break;
}
if (content_length == std::string::npos) {
packet.Clear();
return GDBRemoteCommunication::PacketType::Invalid;
} else if (total_length > 0) {
// We have a valid packet...
assert(content_length <= m_bytes.size());
assert(total_length <= m_bytes.size());
assert(content_length <= total_length);
size_t content_end = content_start + content_length;
bool success = true;
if (log) {
// If logging was just enabled and we have history, then dump out what
// we have to the log so we get the historical context. The Dump() call
// that logs all of the packet will set a boolean so that we don't dump
// this more than once
if (!m_history.DidDumpToLog())
m_history.Dump(log);
bool binary = false;
// Only detect binary for packets that start with a '$' and have a
// '#CC' checksum
if (m_bytes[0] == '$' && total_length > 4) {
for (size_t i = 0; !binary && i < total_length; ++i) {
unsigned char c = m_bytes[i];
if (!llvm::isPrint(c) && !llvm::isSpace(c)) {
binary = true;
}
}
}
if (binary) {
StreamString strm;
// Packet header...
if (CompressionIsEnabled())
strm.Printf("<%4" PRIu64 ":%" PRIu64 "> read packet: %c",
(uint64_t)original_packet_size, (uint64_t)total_length,
m_bytes[0]);
else
strm.Printf("<%4" PRIu64 "> read packet: %c",
(uint64_t)total_length, m_bytes[0]);
for (size_t i = content_start; i < content_end; ++i) {
// Remove binary escaped bytes when displaying the packet...
const char ch = m_bytes[i];
if (ch == 0x7d) {
// 0x7d is the escape character. The next character is to be
// XOR'd with 0x20.
const char escapee = m_bytes[++i] ^ 0x20;
strm.Printf("%2.2x", escapee);
} else {
strm.Printf("%2.2x", (uint8_t)ch);
}
}
// Packet footer...
strm.Printf("%c%c%c", m_bytes[total_length - 3],
m_bytes[total_length - 2], m_bytes[total_length - 1]);
log->PutString(strm.GetString());
} else {
if (CompressionIsEnabled())
LLDB_LOGF(log, "<%4" PRIu64 ":%" PRIu64 "> read packet: %.*s",
(uint64_t)original_packet_size, (uint64_t)total_length,
(int)(total_length), m_bytes.c_str());
else
LLDB_LOGF(log, "<%4" PRIu64 "> read packet: %.*s",
(uint64_t)total_length, (int)(total_length),
m_bytes.c_str());
}
}
m_history.AddPacket(m_bytes, total_length,
GDBRemotePacket::ePacketTypeRecv, total_length);
// Copy the packet from m_bytes to packet_str expanding the run-length
// encoding in the process.
auto maybe_packet_str =
ExpandRLE(m_bytes.substr(content_start, content_end - content_start));
if (!maybe_packet_str) {
m_bytes.erase(0, total_length);
packet.Clear();
return GDBRemoteCommunication::PacketType::Invalid;
}
packet = StringExtractorGDBRemote(*maybe_packet_str);
if (m_bytes[0] == '$' || m_bytes[0] == '%') {
assert(checksum_idx < m_bytes.size());
if (::isxdigit(m_bytes[checksum_idx + 0]) ||
::isxdigit(m_bytes[checksum_idx + 1])) {
if (GetSendAcks()) {
const char *packet_checksum_cstr = &m_bytes[checksum_idx];
char packet_checksum = strtol(packet_checksum_cstr, nullptr, 16);
char actual_checksum = CalculcateChecksum(
llvm::StringRef(m_bytes).slice(content_start, content_end));
success = packet_checksum == actual_checksum;
if (!success) {
LLDB_LOGF(log,
"error: checksum mismatch: %.*s expected 0x%2.2x, "
"got 0x%2.2x",
(int)(total_length), m_bytes.c_str(),
(uint8_t)packet_checksum, (uint8_t)actual_checksum);
}
// Send the ack or nack if needed
if (!success)
SendNack();
else
SendAck();
}
} else {
success = false;
LLDB_LOGF(log, "error: invalid checksum in packet: '%s'\n",
m_bytes.c_str());
}
}
m_bytes.erase(0, total_length);
packet.SetFilePos(0);
if (isNotifyPacket)
return GDBRemoteCommunication::PacketType::Notify;
else
return GDBRemoteCommunication::PacketType::Standard;
}
}
packet.Clear();
return GDBRemoteCommunication::PacketType::Invalid;
}
Status GDBRemoteCommunication::StartDebugserverProcess(
std::variant<llvm::StringRef, shared_fd_t> comm,
ProcessLaunchInfo &launch_info, const Args *inferior_args) {
Log *log = GetLog(GDBRLog::Process);
Args &debugserver_args = launch_info.GetArguments();
#if !defined(__APPLE__)
// First argument to lldb-server must be mode in which to run.
debugserver_args.AppendArgument("gdbserver");
#endif
// use native registers, not the GDB registers
debugserver_args.AppendArgument("--native-regs");
if (launch_info.GetLaunchInSeparateProcessGroup())
debugserver_args.AppendArgument("--setsid");
llvm::SmallString<128> named_pipe_path;
// socket_pipe is used by debug server to communicate back either
// TCP port or domain socket name which it listens on. However, we're not
// interested in the actualy value here.
// The only reason for using the pipe is to serve as a synchronization point -
// once data is written to the pipe, debug server is up and running.
Pipe socket_pipe;
// If a url is supplied then use it
if (shared_fd_t *comm_fd = std::get_if<shared_fd_t>(&comm)) {
LLDB_LOG(log, "debugserver communicates over fd {0}", comm_fd);
assert(*comm_fd != SharedSocket::kInvalidFD);
debugserver_args.AppendArgument(llvm::formatv("--fd={0}", *comm_fd).str());
// Send "comm_fd" down to the inferior so it can use it to communicate back
// with this process.
launch_info.AppendDuplicateFileAction((int64_t)*comm_fd, (int64_t)*comm_fd);
} else {
llvm::StringRef url = std::get<llvm::StringRef>(comm);
LLDB_LOG(log, "debugserver listens on: {0}", url);
debugserver_args.AppendArgument(url);
#if defined(__APPLE__)
// Using a named pipe as debugserver does not support --pipe.
Status error = socket_pipe.CreateWithUniqueName("debugserver-named-pipe",
named_pipe_path);
if (error.Fail()) {
LLDB_LOG(log, "named pipe creation failed: {0}", error);
return error;
}
debugserver_args.AppendArgument(llvm::StringRef("--named-pipe"));
debugserver_args.AppendArgument(named_pipe_path);
#else
// Using an unnamed pipe as it's simpler.
Status error = socket_pipe.CreateNew();
if (error.Fail()) {
LLDB_LOG(log, "unnamed pipe creation failed: {0}", error);
return error;
}
pipe_t write = socket_pipe.GetWritePipe();
debugserver_args.AppendArgument(llvm::StringRef("--pipe"));
debugserver_args.AppendArgument(llvm::to_string(write));
launch_info.AppendDuplicateFileAction((int64_t)write, (int64_t)write);
#endif
}
Environment host_env = Host::GetEnvironment();
std::string env_debugserver_log_file =
host_env.lookup("LLDB_DEBUGSERVER_LOG_FILE");
if (!env_debugserver_log_file.empty()) {
debugserver_args.AppendArgument(
llvm::formatv("--log-file={0}", env_debugserver_log_file).str());
}
#if defined(__APPLE__)
const char *env_debugserver_log_flags = getenv("LLDB_DEBUGSERVER_LOG_FLAGS");
if (env_debugserver_log_flags) {
debugserver_args.AppendArgument(
llvm::formatv("--log-flags={0}", env_debugserver_log_flags).str());
}
#else
std::string env_debugserver_log_channels =
host_env.lookup("LLDB_SERVER_LOG_CHANNELS");
if (!env_debugserver_log_channels.empty()) {
debugserver_args.AppendArgument(
llvm::formatv("--log-channels={0}", env_debugserver_log_channels)
.str());
}
#endif
// Add additional args, starting with LLDB_DEBUGSERVER_EXTRA_ARG_1 until an
// env var doesn't come back.
uint32_t env_var_index = 1;
bool has_env_var;
do {
char env_var_name[64];
snprintf(env_var_name, sizeof(env_var_name),
"LLDB_DEBUGSERVER_EXTRA_ARG_%" PRIu32, env_var_index++);
std::string extra_arg = host_env.lookup(env_var_name);
has_env_var = !extra_arg.empty();
if (has_env_var) {
debugserver_args.AppendArgument(llvm::StringRef(extra_arg));
LLDB_LOGF(log,
"GDBRemoteCommunication::%s adding env var %s contents "
"to stub command line (%s)",
__FUNCTION__, env_var_name, extra_arg.c_str());
}
} while (has_env_var);
if (inferior_args && inferior_args->GetArgumentCount() > 0) {
debugserver_args.AppendArgument(llvm::StringRef("--"));
debugserver_args.AppendArguments(*inferior_args);
}
// Copy the current environment to the gdbserver/debugserver instance
launch_info.GetEnvironment() = host_env;
// Close STDIN, STDOUT and STDERR.
launch_info.AppendCloseFileAction(STDIN_FILENO);
launch_info.AppendCloseFileAction(STDOUT_FILENO);
launch_info.AppendCloseFileAction(STDERR_FILENO);
// Redirect STDIN, STDOUT and STDERR to "/dev/null".
launch_info.AppendSuppressFileAction(STDIN_FILENO, true, false);
launch_info.AppendSuppressFileAction(STDOUT_FILENO, false, true);
launch_info.AppendSuppressFileAction(STDERR_FILENO, false, true);
if (log) {
StreamString string_stream;
Platform *const platform = nullptr;
launch_info.Dump(string_stream, platform);
LLDB_LOG(log, "launch info for gdb-remote stub:\n{0}",
string_stream.GetData());
}
if (Status error = Host::LaunchProcess(launch_info); error.Fail()) {
LLDB_LOG(log, "launch failed: {0}", error);
return error;
}
if (std::holds_alternative<shared_fd_t>(comm))
return Status();
Status error;
if (named_pipe_path.size() > 0) {
error = socket_pipe.OpenAsReader(named_pipe_path);
if (error.Fail()) {
LLDB_LOG(log, "failed to open named pipe {0} for reading: {1}",
named_pipe_path, error);
}
}
if (socket_pipe.CanWrite())
socket_pipe.CloseWriteFileDescriptor();
assert(socket_pipe.CanRead());
// Read data from the pipe -- and ignore it (see comment above).
while (error.Success()) {
char buf[10];
if (llvm::Expected<size_t> num_bytes =
socket_pipe.Read(buf, std::size(buf), std::chrono::seconds(10))) {
if (*num_bytes == 0)
break;
} else {
error = Status::FromError(num_bytes.takeError());
}
}
if (error.Fail()) {
LLDB_LOG(log, "failed to synchronize on pipe {0}: {1}", named_pipe_path,
error);
}
socket_pipe.Close();
if (named_pipe_path.size() > 0) {
if (Status err = socket_pipe.Delete(named_pipe_path); err.Fail())
LLDB_LOG(log, "failed to delete pipe {0}: {1}", named_pipe_path, err);
}
return error;
}
void GDBRemoteCommunication::DumpHistory(Stream &strm) { m_history.Dump(strm); }
GDBRemoteCommunication::ScopedTimeout::ScopedTimeout(
GDBRemoteCommunication &gdb_comm, std::chrono::seconds timeout)
: m_gdb_comm(gdb_comm), m_saved_timeout(0), m_timeout_modified(false) {
auto curr_timeout = gdb_comm.GetPacketTimeout();
// Only update the timeout if the timeout is greater than the current
// timeout. If the current timeout is larger, then just use that.
if (curr_timeout < timeout) {
m_timeout_modified = true;
m_saved_timeout = m_gdb_comm.SetPacketTimeout(timeout);
}
}
GDBRemoteCommunication::ScopedTimeout::~ScopedTimeout() {
// Only restore the timeout if we set it in the constructor.
if (m_timeout_modified)
m_gdb_comm.SetPacketTimeout(m_saved_timeout);
}
void llvm::format_provider<GDBRemoteCommunication::PacketResult>::format(
const GDBRemoteCommunication::PacketResult &result, raw_ostream &Stream,
StringRef Style) {
using PacketResult = GDBRemoteCommunication::PacketResult;
switch (result) {
case PacketResult::Success:
Stream << "Success";
break;
case PacketResult::ErrorSendFailed:
Stream << "ErrorSendFailed";
break;
case PacketResult::ErrorSendAck:
Stream << "ErrorSendAck";
break;
case PacketResult::ErrorReplyFailed:
Stream << "ErrorReplyFailed";
break;
case PacketResult::ErrorReplyTimeout:
Stream << "ErrorReplyTimeout";
break;
case PacketResult::ErrorReplyInvalid:
Stream << "ErrorReplyInvalid";
break;
case PacketResult::ErrorReplyAck:
Stream << "ErrorReplyAck";
break;
case PacketResult::ErrorDisconnected:
Stream << "ErrorDisconnected";
break;
case PacketResult::ErrorNoSequenceLock:
Stream << "ErrorNoSequenceLock";
break;
}
}
std::optional<std::string>
GDBRemoteCommunication::ExpandRLE(std::string packet) {
// Reserve enough byte for the most common case (no RLE used).
std::string decoded;
decoded.reserve(packet.size());
for (std::string::const_iterator c = packet.begin(); c != packet.end(); ++c) {
if (*c == '*') {
if (decoded.empty())
return std::nullopt;
// '*' indicates RLE. Next character will give us the repeat count and
// previous character is what is to be repeated.
char char_to_repeat = decoded.back();
// Number of time the previous character is repeated.
if (++c == packet.end())
return std::nullopt;
int repeat_count = *c + 3 - ' ';
// We have the char_to_repeat and repeat_count. Now push it in the
// packet.
for (int i = 0; i < repeat_count; ++i)
decoded.push_back(char_to_repeat);
} else if (*c == 0x7d) {
// 0x7d is the escape character. The next character is to be XOR'd with
// 0x20.
if (++c == packet.end())
return std::nullopt;
char escapee = *c ^ 0x20;
decoded.push_back(escapee);
} else {
decoded.push_back(*c);
}
}
return decoded;
}
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