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Add a small refinement to the qSymbol:: support in lldb. 

This is a packet which allows the remote gdb stub to ask for the address
of a symbol in the process.  lldb sends the packet (offering to provide
addresses for symbol names) after every solib loaded.  I changed lldb so
that once the stub has indicated that it doesn't need any more symbol
addresses, lldb will stop sending the qSymbol:: packet on new solib loads.

This can yield a performance benefit over slower communication links when
there are many solibs involved.

<rdar://problem/23310049> 

llvm-svn: 257569
This commit is contained in:
Jason Molenda 2016-01-13 04:08:10 +00:00
parent c8c39ea822
commit 50018d3cf5
2 changed files with 48 additions and 1 deletions
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48
lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationClient.cpp
View File

@ -101,6 +101,7 @@ GDBRemoteCommunicationClient::GDBRemoteCommunicationClient() :
m_supports_QEnvironment (true),
m_supports_QEnvironmentHexEncoded (true),
m_supports_qSymbol (true),
m_qSymbol_requests_done (false),
m_supports_qModuleInfo (true),
m_supports_jThreadsInfo (true),
m_curr_pid (LLDB_INVALID_PROCESS_ID),
@ -377,6 +378,7 @@ GDBRemoteCommunicationClient::ResetDiscoverableSettings (bool did_exec)
m_supports_QEnvironment = true;
m_supports_QEnvironmentHexEncoded = true;
m_supports_qSymbol = true;
m_qSymbol_requests_done = false;
m_supports_qModuleInfo = true;
m_host_arch.Clear();
m_os_version_major = UINT32_MAX;
@ -4443,11 +4445,42 @@ GDBRemoteCommunicationClient::ReadExtFeature (const lldb_private::ConstString ob
// qSymbol:<sym_name> The target requests the value of symbol sym_name (hex encoded).
// LLDB may provide the value by sending another qSymbol packet
// in the form of"qSymbol:<sym_value>:<sym_name>".
//
// Three examples:
//
// lldb sends: qSymbol::
// lldb receives: OK
// Remote gdb stub does not need to know the addresses of any symbols, lldb does not
// need to ask again in this session.
//
// lldb sends: qSymbol::
// lldb receives: qSymbol:64697370617463685f71756575655f6f666673657473
// lldb sends: qSymbol::64697370617463685f71756575655f6f666673657473
// lldb receives: OK
// Remote gdb stub asks for address of 'dispatch_queue_offsets'. lldb does not know
// the address at this time. lldb needs to send qSymbol:: again when it has more
// solibs loaded.
//
// lldb sends: qSymbol::
// lldb receives: qSymbol:64697370617463685f71756575655f6f666673657473
// lldb sends: qSymbol:2bc97554:64697370617463685f71756575655f6f666673657473
// lldb receives: OK
// Remote gdb stub asks for address of 'dispatch_queue_offsets'. lldb says that it
// is at address 0x2bc97554. Remote gdb stub sends 'OK' indicating that it does not
// need any more symbols. lldb does not need to ask again in this session.
void
GDBRemoteCommunicationClient::ServeSymbolLookups(lldb_private::Process *process)
{
if (m_supports_qSymbol)
// Set to true once we've resolved a symbol to an address for the remote stub.
// If we get an 'OK' response after this, the remote stub doesn't need any more
// symbols and we can stop asking.
bool symbol_response_provided = false;
// Is this the inital qSymbol:: packet?
bool first_qsymbol_query = true;
if (m_supports_qSymbol && m_qSymbol_requests_done == false)
{
Mutex::Locker locker;
if (GetSequenceMutex(locker, "GDBRemoteCommunicationClient::ServeSymbolLookups() failed due to not getting the sequence mutex"))
@ -4459,9 +4492,15 @@ GDBRemoteCommunicationClient::ServeSymbolLookups(lldb_private::Process *process)
{
if (response.IsOKResponse())
{
if (symbol_response_provided || first_qsymbol_query)
{
m_qSymbol_requests_done = true;
}
// We are done serving symbols requests
return;
}
first_qsymbol_query = false;
if (response.IsUnsupportedResponse())
{
@ -4541,7 +4580,14 @@ GDBRemoteCommunicationClient::ServeSymbolLookups(lldb_private::Process *process)
packet.Clear();
packet.PutCString("qSymbol:");
if (symbol_load_addr != LLDB_INVALID_ADDRESS)
{
packet.Printf("%" PRIx64, symbol_load_addr);
symbol_response_provided = true;
}
else
{
symbol_response_provided = false;
}
packet.PutCString(":");
packet.PutBytesAsRawHex8(symbol_name.data(), symbol_name.size());
continue; // go back to the while loop and send "packet" and wait for another response

1
lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationClient.h
View File

@ -619,6 +619,7 @@ protected:
m_supports_QEnvironment:1,
m_supports_QEnvironmentHexEncoded:1,
m_supports_qSymbol:1,
m_qSymbol_requests_done:1,
m_supports_qModuleInfo:1,
m_supports_jThreadsInfo:1;