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[lldb] Support gdbserver signals
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GDB and LLDB use different signal models.  GDB uses a predefined set
of signal codes, and maps platform's signos to them.  On the other hand,
LLDB has historically simply passed native signos.

In order to improve compatibility between LLDB and gdbserver, the GDB
signal model should be used.  However, GDB does not provide a mapping
for all existing signals on Linux and unsupported signals are passed
as 'unknown'.  Limiting LLDB to this behavior could be considered
a regression.

To get the best of both worlds, use the LLDB signal model when talking
to lldb-server, and the GDB signal model otherwise.  For this purpose,
new versions of lldb-server indicate "native-signals+" via qSupported.
At the same time, we also detect older versions of lldb-server
via QThreadSuffixSupported for backwards compatibility.  If neither test
succeeds, we assume gdbserver or another implementation using GDB model.

Differential Revision: https://reviews.llvm.org/D108078
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@mgorny
mgorny committed Nov 10, 2021
1 parent 0cada82 commit 3f13723
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Showing 9 changed files with 272 additions and 11 deletions.
1 change: 1 addition & 0 deletions lldb/packages/Python/lldbsuite/test/tools/lldb-server/gdbremote_testcase.py
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Expand Up @@ -858,6 +858,7 @@ def add_qSupported_packets(self, client_features=[]):
"vfork-events",
"memory-tagging",
"qSaveCore",
"native-signals",
]

def parse_qSupported_response(self, context):
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165 changes: 164 additions & 1 deletion lldb/source/Plugins/Process/Utility/GDBRemoteSignals.cpp
View file
Expand Up @@ -15,4 +15,167 @@ GDBRemoteSignals::GDBRemoteSignals() : UnixSignals() { Reset(); }
GDBRemoteSignals::GDBRemoteSignals(const lldb::UnixSignalsSP &rhs)
: UnixSignals(*rhs) {}

void GDBRemoteSignals::Reset() { m_signals.clear(); }
void GDBRemoteSignals::Reset() {
m_signals.clear();
// clang-format off
// SIGNO NAME SUPPRESS STOP NOTIFY DESCRIPTION
// ====== ============== ======== ====== ====== ===================================================
AddSignal(1, "SIGHUP", false, true, true, "hangup");
AddSignal(2, "SIGINT", true, true, true, "interrupt");
AddSignal(3, "SIGQUIT", false, true, true, "quit");
AddSignal(4, "SIGILL", false, true, true, "illegal instruction");
AddSignal(5, "SIGTRAP", true, true, true, "trace trap (not reset when caught)");
AddSignal(6, "SIGABRT", false, true, true, "abort()/IOT trap", "SIGIOT");
AddSignal(7, "SIGEMT", false, true, true, "emulation trap");
AddSignal(8, "SIGFPE", false, true, true, "floating point exception");
AddSignal(9, "SIGKILL", false, true, true, "kill");
AddSignal(10, "SIGBUS", false, true, true, "bus error");
AddSignal(11, "SIGSEGV", false, true, true, "segmentation violation");
AddSignal(12, "SIGSYS", false, true, true, "invalid system call");
AddSignal(13, "SIGPIPE", false, true, true, "write to pipe with reading end closed");
AddSignal(14, "SIGALRM", false, false, false, "alarm");
AddSignal(15, "SIGTERM", false, true, true, "termination requested");
AddSignal(16, "SIGURG", false, true, true, "urgent data on socket");
AddSignal(17, "SIGSTOP", true, true, true, "process stop");
AddSignal(18, "SIGTSTP", false, true, true, "tty stop");
AddSignal(19, "SIGCONT", false, false, true, "process continue");
AddSignal(20, "SIGCHLD", false, false, true, "child status has changed", "SIGCLD");
AddSignal(21, "SIGTTIN", false, true, true, "background tty read");
AddSignal(22, "SIGTTOU", false, true, true, "background tty write");
AddSignal(23, "SIGIO", false, true, true, "input/output ready/Pollable event");
AddSignal(24, "SIGXCPU", false, true, true, "CPU resource exceeded");
AddSignal(25, "SIGXFSZ", false, true, true, "file size limit exceeded");
AddSignal(26, "SIGVTALRM", false, true, true, "virtual time alarm");
AddSignal(27, "SIGPROF", false, false, false, "profiling time alarm");
AddSignal(28, "SIGWINCH", false, true, true, "window size changes");
AddSignal(29, "SIGLOST", false, true, true, "resource lost");
AddSignal(30, "SIGUSR1", false, true, true, "user defined signal 1");
AddSignal(31, "SIGUSR2", false, true, true, "user defined signal 2");
AddSignal(32, "SIGPWR", false, true, true, "power failure");
AddSignal(33, "SIGPOLL", false, true, true, "pollable event");
AddSignal(34, "SIGWIND", false, true, true, "SIGWIND");
AddSignal(35, "SIGPHONE", false, true, true, "SIGPHONE");
AddSignal(36, "SIGWAITING", false, true, true, "process's LWPs are blocked");
AddSignal(37, "SIGLWP", false, true, true, "signal LWP");
AddSignal(38, "SIGDANGER", false, true, true, "swap space dangerously low");
AddSignal(39, "SIGGRANT", false, true, true, "monitor mode granted");
AddSignal(40, "SIGRETRACT", false, true, true, "need to relinquish monitor mode");
AddSignal(41, "SIGMSG", false, true, true, "monitor mode data available");
AddSignal(42, "SIGSOUND", false, true, true, "sound completed");
AddSignal(43, "SIGSAK", false, true, true, "secure attention");
AddSignal(44, "SIGPRIO", false, true, true, "SIGPRIO");

AddSignal(45, "SIG33", false, false, false, "real-time event 33");
AddSignal(46, "SIG34", false, false, false, "real-time event 34");
AddSignal(47, "SIG35", false, false, false, "real-time event 35");
AddSignal(48, "SIG36", false, false, false, "real-time event 36");
AddSignal(49, "SIG37", false, false, false, "real-time event 37");
AddSignal(50, "SIG38", false, false, false, "real-time event 38");
AddSignal(51, "SIG39", false, false, false, "real-time event 39");
AddSignal(52, "SIG40", false, false, false, "real-time event 40");
AddSignal(53, "SIG41", false, false, false, "real-time event 41");
AddSignal(54, "SIG42", false, false, false, "real-time event 42");
AddSignal(55, "SIG43", false, false, false, "real-time event 43");
AddSignal(56, "SIG44", false, false, false, "real-time event 44");
AddSignal(57, "SIG45", false, false, false, "real-time event 45");
AddSignal(58, "SIG46", false, false, false, "real-time event 46");
AddSignal(59, "SIG47", false, false, false, "real-time event 47");
AddSignal(60, "SIG48", false, false, false, "real-time event 48");
AddSignal(61, "SIG49", false, false, false, "real-time event 49");
AddSignal(62, "SIG50", false, false, false, "real-time event 50");
AddSignal(63, "SIG51", false, false, false, "real-time event 51");
AddSignal(64, "SIG52", false, false, false, "real-time event 52");
AddSignal(65, "SIG53", false, false, false, "real-time event 53");
AddSignal(66, "SIG54", false, false, false, "real-time event 54");
AddSignal(67, "SIG55", false, false, false, "real-time event 55");
AddSignal(68, "SIG56", false, false, false, "real-time event 56");
AddSignal(69, "SIG57", false, false, false, "real-time event 57");
AddSignal(70, "SIG58", false, false, false, "real-time event 58");
AddSignal(71, "SIG59", false, false, false, "real-time event 59");
AddSignal(72, "SIG60", false, false, false, "real-time event 60");
AddSignal(73, "SIG61", false, false, false, "real-time event 61");
AddSignal(74, "SIG62", false, false, false, "real-time event 62");
AddSignal(75, "SIG63", false, false, false, "real-time event 63");

AddSignal(76, "SIGCANCEL", false, true, true, "LWP internal signal");

AddSignal(77, "SIG32", false, false, false, "real-time event 32");
AddSignal(78, "SIG64", false, false, false, "real-time event 64");
AddSignal(79, "SIG65", false, false, false, "real-time event 65");
AddSignal(80, "SIG66", false, false, false, "real-time event 66");
AddSignal(81, "SIG67", false, false, false, "real-time event 67");
AddSignal(82, "SIG68", false, false, false, "real-time event 68");
AddSignal(83, "SIG69", false, false, false, "real-time event 69");
AddSignal(84, "SIG70", false, false, false, "real-time event 70");
AddSignal(85, "SIG71", false, false, false, "real-time event 71");
AddSignal(86, "SIG72", false, false, false, "real-time event 72");
AddSignal(87, "SIG73", false, false, false, "real-time event 73");
AddSignal(88, "SIG74", false, false, false, "real-time event 74");
AddSignal(89, "SIG75", false, false, false, "real-time event 75");
AddSignal(90, "SIG76", false, false, false, "real-time event 76");
AddSignal(91, "SIG77", false, false, false, "real-time event 77");
AddSignal(92, "SIG78", false, false, false, "real-time event 78");
AddSignal(93, "SIG79", false, false, false, "real-time event 79");
AddSignal(94, "SIG80", false, false, false, "real-time event 80");
AddSignal(95, "SIG81", false, false, false, "real-time event 81");
AddSignal(96, "SIG82", false, false, false, "real-time event 82");
AddSignal(97, "SIG83", false, false, false, "real-time event 83");
AddSignal(98, "SIG84", false, false, false, "real-time event 84");
AddSignal(99, "SIG85", false, false, false, "real-time event 85");
AddSignal(100, "SIG86", false, false, false, "real-time event 86");
AddSignal(101, "SIG87", false, false, false, "real-time event 87");
AddSignal(102, "SIG88", false, false, false, "real-time event 88");
AddSignal(103, "SIG89", false, false, false, "real-time event 89");
AddSignal(104, "SIG90", false, false, false, "real-time event 90");
AddSignal(105, "SIG91", false, false, false, "real-time event 91");
AddSignal(106, "SIG92", false, false, false, "real-time event 92");
AddSignal(107, "SIG93", false, false, false, "real-time event 93");
AddSignal(108, "SIG94", false, false, false, "real-time event 94");
AddSignal(109, "SIG95", false, false, false, "real-time event 95");
AddSignal(110, "SIG96", false, false, false, "real-time event 96");
AddSignal(111, "SIG97", false, false, false, "real-time event 97");
AddSignal(112, "SIG98", false, false, false, "real-time event 98");
AddSignal(113, "SIG99", false, false, false, "real-time event 99");
AddSignal(114, "SIG100", false, false, false, "real-time event 100");
AddSignal(115, "SIG101", false, false, false, "real-time event 101");
AddSignal(116, "SIG102", false, false, false, "real-time event 102");
AddSignal(117, "SIG103", false, false, false, "real-time event 103");
AddSignal(118, "SIG104", false, false, false, "real-time event 104");
AddSignal(119, "SIG105", false, false, false, "real-time event 105");
AddSignal(120, "SIG106", false, false, false, "real-time event 106");
AddSignal(121, "SIG107", false, false, false, "real-time event 107");
AddSignal(122, "SIG108", false, false, false, "real-time event 108");
AddSignal(123, "SIG109", false, false, false, "real-time event 109");
AddSignal(124, "SIG110", false, false, false, "real-time event 110");
AddSignal(125, "SIG111", false, false, false, "real-time event 111");
AddSignal(126, "SIG112", false, false, false, "real-time event 112");
AddSignal(127, "SIG113", false, false, false, "real-time event 113");
AddSignal(128, "SIG114", false, false, false, "real-time event 114");
AddSignal(129, "SIG115", false, false, false, "real-time event 115");
AddSignal(130, "SIG116", false, false, false, "real-time event 116");
AddSignal(131, "SIG117", false, false, false, "real-time event 117");
AddSignal(132, "SIG118", false, false, false, "real-time event 118");
AddSignal(133, "SIG119", false, false, false, "real-time event 119");
AddSignal(134, "SIG120", false, false, false, "real-time event 120");
AddSignal(135, "SIG121", false, false, false, "real-time event 121");
AddSignal(136, "SIG122", false, false, false, "real-time event 122");
AddSignal(137, "SIG123", false, false, false, "real-time event 123");
AddSignal(138, "SIG124", false, false, false, "real-time event 124");
AddSignal(139, "SIG125", false, false, false, "real-time event 125");
AddSignal(140, "SIG126", false, false, false, "real-time event 126");
AddSignal(141, "SIG127", false, false, false, "real-time event 127");

AddSignal(142, "SIGINFO", false, true, true, "information request");
AddSignal(143, "unknown", false, true, true, "unknown signal");

AddSignal(145, "EXC_BAD_ACCESS", false, true, true, "could not access memory");
AddSignal(146, "EXC_BAD_INSTRUCTION", false, true, true, "illegal instruction/operand");
AddSignal(147, "EXC_ARITHMETIC", false, true, true, "arithmetic exception");
AddSignal(148, "EXC_EMULATION", false, true, true, "emulation instruction");
AddSignal(149, "EXC_SOFTWARE", false, true, true, "software generated exception");
AddSignal(150, "EXC_BREAKPOINT", false, true, true, "breakpoint");

AddSignal(151, "SIGLIBRT", false, true, true, "librt internal signal");

// clang-format on
}
3 changes: 2 additions & 1 deletion lldb/source/Plugins/Process/Utility/GDBRemoteSignals.h
View file
Expand Up @@ -13,7 +13,8 @@

namespace lldb_private {

/// Empty set of Unix signals to be filled by PlatformRemoteGDBServer
/// Initially carries signals defined by the GDB Remote Serial Protocol.
/// Can be filled with platform's signals through PlatformRemoteGDBServer.
class GDBRemoteSignals : public UnixSignals {
public:
GDBRemoteSignals();
Expand Down
15 changes: 15 additions & 0 deletions lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationClient.cpp
View file
Expand Up @@ -283,6 +283,7 @@ void GDBRemoteCommunicationClient::ResetDiscoverableSettings(bool did_exec) {
m_supports_qXfer_features_read = eLazyBoolCalculate;
m_supports_qXfer_memory_map_read = eLazyBoolCalculate;
m_supports_augmented_libraries_svr4_read = eLazyBoolCalculate;
m_uses_native_signals = eLazyBoolCalculate;
m_supports_qProcessInfoPID = true;
m_supports_qfProcessInfo = true;
m_supports_qUserName = true;
Expand Down Expand Up @@ -333,6 +334,7 @@ void GDBRemoteCommunicationClient::GetRemoteQSupported() {
m_supports_QPassSignals = eLazyBoolNo;
m_supports_memory_tagging = eLazyBoolNo;
m_supports_qSaveCore = eLazyBoolNo;
m_uses_native_signals = eLazyBoolNo;

m_max_packet_size = UINT64_MAX; // It's supposed to always be there, but if
// not, we assume no limit
Expand Down Expand Up @@ -379,6 +381,8 @@ void GDBRemoteCommunicationClient::GetRemoteQSupported() {
m_supports_memory_tagging = eLazyBoolYes;
else if (x == "qSaveCore+")
m_supports_qSaveCore = eLazyBoolYes;
else if (x == "native-signals+")
m_uses_native_signals = eLazyBoolYes;
// Look for a list of compressions in the features list e.g.
// qXfer:features:read+;PacketSize=20000;qEcho+;SupportedCompressions=zlib-
// deflate,lzma
Expand Down Expand Up @@ -4220,3 +4224,14 @@ void GDBRemoteCommunicationClient::OnRunPacketSent(bool first) {
GDBRemoteClientBase::OnRunPacketSent(first);
m_curr_tid = LLDB_INVALID_THREAD_ID;
}

bool GDBRemoteCommunicationClient::UsesNativeSignals() {
if (m_uses_native_signals == eLazyBoolCalculate)
GetRemoteQSupported();
if (m_uses_native_signals == eLazyBoolYes)
return true;

// If the remote didn't indicate native-signal support explicitly,
// check whether it is an old version of lldb-server.
return GetThreadSuffixSupported();
}
3 changes: 3 additions & 0 deletions lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationClient.h
View file
Expand Up @@ -433,6 +433,8 @@ class GDBRemoteCommunicationClient : public GDBRemoteClientBase {

bool GetMemoryTaggingSupported();

bool UsesNativeSignals();

lldb::DataBufferSP ReadMemoryTags(lldb::addr_t addr, size_t len,
int32_t type);

Expand Down Expand Up @@ -555,6 +557,7 @@ class GDBRemoteCommunicationClient : public GDBRemoteClientBase {
LazyBool m_supports_multiprocess = eLazyBoolCalculate;
LazyBool m_supports_memory_tagging = eLazyBoolCalculate;
LazyBool m_supports_qSaveCore = eLazyBoolCalculate;
LazyBool m_uses_native_signals = eLazyBoolCalculate;

bool m_supports_qProcessInfoPID : 1, m_supports_qfProcessInfo : 1,
m_supports_qUserName : 1, m_supports_qGroupName : 1,
Expand Down
1 change: 1 addition & 0 deletions lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationServerCommon.cpp
View file
Expand Up @@ -1346,5 +1346,6 @@ std::vector<std::string> GDBRemoteCommunicationServerCommon::HandleFeatures(
llvm::formatv("PacketSize={0}", max_packet_size),
"QStartNoAckMode+",
"qEcho+",
"native-signals+",
};
}
20 changes: 12 additions & 8 deletions lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp
View file
Expand Up @@ -607,14 +607,6 @@ Status ProcessGDBRemote::DoConnectRemote(llvm::StringRef remote_url) {
__FUNCTION__, GetID(),
GetTarget().GetArchitecture().GetTriple().getTriple().c_str());

if (error.Success()) {
PlatformSP platform_sp = GetTarget().GetPlatform();
if (platform_sp && platform_sp->IsConnected())
SetUnixSignals(platform_sp->GetUnixSignals());
else
SetUnixSignals(UnixSignals::Create(GetTarget().GetArchitecture()));
}

return error;
}

Expand Down Expand Up @@ -980,6 +972,18 @@ void ProcessGDBRemote::DidLaunchOrAttach(ArchSpec &process_arch) {
if (StructuredData::Array *supported_packets =
m_gdb_comm.GetSupportedStructuredDataPlugins())
MapSupportedStructuredDataPlugins(*supported_packets);

// If connected to LLDB ("native-signals+"), use signal defs for
// the remote platform. If connected to GDB, just use the standard set.
if (!m_gdb_comm.UsesNativeSignals()) {
SetUnixSignals(std::make_shared<GDBRemoteSignals>());
} else {
PlatformSP platform_sp = GetTarget().GetPlatform();
if (platform_sp && platform_sp->IsConnected())
SetUnixSignals(platform_sp->GetUnixSignals());
else
SetUnixSignals(UnixSignals::Create(GetTarget().GetArchitecture()));
}
}

void ProcessGDBRemote::MaybeLoadExecutableModule() {
Expand Down

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