llvm-project/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationClient.h
Greg Clayton 2687cd116a <rdar://problem/11052174>
<rdar://problem/11051056>

Found a race condition when sending async packets in the ProcessGDBRemote.

A little background: GDB remote clients can only send one packet at a time. You must send a packet and wait for a response. So when we continue, we obviously can't hold up the calling thread waiting for the process to stop again, so we have an async thread in the ProcessGDBRemote whose only job is to run packets that control the inferior process. When you send a continue packet, the only packet you can send is an interrupt packet (which consists of sending a CTRL+C (or a '\x03' byte)). This then stops the inferior and we can send the async packet, and then resume the target. There was a race condition that often happened during stepping where we are doing a source level single step which consists of many instruction steps and a few runs here and there when we step into a function. So the flow looks like:

inst single step
inst single step
inst single step
inst single step
inst single step
step BP and run
inst single step
inst single step
inst single step

Now if we got an async packet while the program is running we get something like:

send --> continue
send --> interrupt
recv <-- interrupt stop reply packet
send --> async packet
recv <-- async response
send --> continue again and wait for actual stop

Problems arise when this was happening when single stepping a thread where we would get:

send --> step thread 123
send --> interrupt
send --> stop reply for thread 123 (from the step)

Now we _might_ have an extra stop reply packet from the "interrupt" which we weren't checking for and we could end up with:

send --> async packet (like memory read!)
recv <-- async response (which is the interrupt stop reply packet)

Now we have the read memroy reply sitting in our buffer and waiting to be used as the reply for the next packet... 

To further complicate things, the single step should have exited the async thread since the run control is finished, but now it will continue if it was interrupted.

The fixes I checked in to two major things:
- watch for the extra stop reply if we need to
- make sure we exit from the async thread run loop when the previous run control (like the instruction level single step) is finished.

Needless to say this makes very fast stepping in Xcode much more reliable.

llvm-svn: 153629
2012-03-29 01:55:41 +00:00

391 lines
12 KiB
C++

//===-- GDBRemoteCommunicationClient.h --------------------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#ifndef liblldb_GDBRemoteCommunicationClient_h_
#define liblldb_GDBRemoteCommunicationClient_h_
// C Includes
// C++ Includes
#include <vector>
// Other libraries and framework includes
// Project includes
#include "lldb/Core/ArchSpec.h"
#include "lldb/Target/Process.h"
#include "GDBRemoteCommunication.h"
typedef enum
{
eBreakpointSoftware = 0,
eBreakpointHardware,
eWatchpointWrite,
eWatchpointRead,
eWatchpointReadWrite
} GDBStoppointType;
class GDBRemoteCommunicationClient : public GDBRemoteCommunication
{
public:
//------------------------------------------------------------------
// Constructors and Destructors
//------------------------------------------------------------------
GDBRemoteCommunicationClient(bool is_platform);
virtual
~GDBRemoteCommunicationClient();
//------------------------------------------------------------------
// After connecting, send the handshake to the server to make sure
// we are communicating with it.
//------------------------------------------------------------------
bool
HandshakeWithServer (lldb_private::Error *error_ptr);
size_t
SendPacketAndWaitForResponse (const char *send_payload,
StringExtractorGDBRemote &response,
bool send_async);
size_t
SendPacketAndWaitForResponse (const char *send_payload,
size_t send_length,
StringExtractorGDBRemote &response,
bool send_async);
lldb::StateType
SendContinuePacketAndWaitForResponse (ProcessGDBRemote *process,
const char *packet_payload,
size_t packet_length,
StringExtractorGDBRemote &response);
virtual bool
GetThreadSuffixSupported ();
void
QueryNoAckModeSupported ();
bool
SendAsyncSignal (int signo);
bool
SendInterrupt (lldb_private::Mutex::Locker &locker,
uint32_t seconds_to_wait_for_stop,
bool &timed_out);
lldb::pid_t
GetCurrentProcessID ();
bool
GetLaunchSuccess (std::string &error_str);
uint16_t
LaunchGDBserverAndGetPort ();
//------------------------------------------------------------------
/// Sends a GDB remote protocol 'A' packet that delivers program
/// arguments to the remote server.
///
/// @param[in] argv
/// A NULL terminated array of const C strings to use as the
/// arguments.
///
/// @return
/// Zero if the response was "OK", a positive value if the
/// the response was "Exx" where xx are two hex digits, or
/// -1 if the call is unsupported or any other unexpected
/// response was received.
//------------------------------------------------------------------
int
SendArgumentsPacket (char const *argv[]);
//------------------------------------------------------------------
/// Sends a "QEnvironment:NAME=VALUE" packet that will build up the
/// environment that will get used when launching an application
/// in conjunction with the 'A' packet. This function can be called
/// multiple times in a row in order to pass on the desired
/// environment that the inferior should be launched with.
///
/// @param[in] name_equal_value
/// A NULL terminated C string that contains a single environment
/// in the format "NAME=VALUE".
///
/// @return
/// Zero if the response was "OK", a positive value if the
/// the response was "Exx" where xx are two hex digits, or
/// -1 if the call is unsupported or any other unexpected
/// response was received.
//------------------------------------------------------------------
int
SendEnvironmentPacket (char const *name_equal_value);
int
SendLaunchArchPacket (const char *arch);
//------------------------------------------------------------------
/// Sends a "vAttach:PID" where PID is in hex.
///
/// @param[in] pid
/// A process ID for the remote gdb server to attach to.
///
/// @param[out] response
/// The response received from the gdb server. If the return
/// value is zero, \a response will contain a stop reply
/// packet.
///
/// @return
/// Zero if the attach was successful, or an error indicating
/// an error code.
//------------------------------------------------------------------
int
SendAttach (lldb::pid_t pid,
StringExtractorGDBRemote& response);
//------------------------------------------------------------------
/// Sets the path to use for stdin/out/err for a process
/// that will be launched with the 'A' packet.
///
/// @param[in] path
/// The path to use for stdin/out/err
///
/// @return
/// Zero if the for success, or an error code for failure.
//------------------------------------------------------------------
int
SetSTDIN (char const *path);
int
SetSTDOUT (char const *path);
int
SetSTDERR (char const *path);
//------------------------------------------------------------------
/// Sets the disable ASLR flag to \a enable for a process that will
/// be launched with the 'A' packet.
///
/// @param[in] enable
/// A boolean value indicating wether to disable ASLR or not.
///
/// @return
/// Zero if the for success, or an error code for failure.
//------------------------------------------------------------------
int
SetDisableASLR (bool enable);
//------------------------------------------------------------------
/// Sets the working directory to \a path for a process that will
/// be launched with the 'A' packet.
///
/// @param[in] path
/// The path to a directory to use when launching our processs
///
/// @return
/// Zero if the for success, or an error code for failure.
//------------------------------------------------------------------
int
SetWorkingDir (char const *path);
lldb::addr_t
AllocateMemory (size_t size, uint32_t permissions);
bool
DeallocateMemory (lldb::addr_t addr);
lldb_private::Error
GetMemoryRegionInfo (lldb::addr_t addr,
lldb_private::MemoryRegionInfo &range_info);
const lldb_private::ArchSpec &
GetHostArchitecture ();
bool
GetVContSupported (char flavor);
void
ResetDiscoverableSettings();
bool
GetHostInfo (bool force = false);
bool
GetOSVersion (uint32_t &major,
uint32_t &minor,
uint32_t &update);
bool
GetOSBuildString (std::string &s);
bool
GetOSKernelDescription (std::string &s);
lldb_private::ArchSpec
GetSystemArchitecture ();
bool
GetHostname (std::string &s);
bool
GetSupportsThreadSuffix ();
bool
GetProcessInfo (lldb::pid_t pid,
lldb_private::ProcessInstanceInfo &process_info);
uint32_t
FindProcesses (const lldb_private::ProcessInstanceInfoMatch &process_match_info,
lldb_private::ProcessInstanceInfoList &process_infos);
bool
GetUserName (uint32_t uid, std::string &name);
bool
GetGroupName (uint32_t gid, std::string &name);
bool
HasFullVContSupport ()
{
return GetVContSupported ('A');
}
bool
HasAnyVContSupport ()
{
return GetVContSupported ('a');
}
uint32_t
SetPacketTimeout (uint32_t packet_timeout)
{
const uint32_t old_packet_timeout = m_packet_timeout;
m_packet_timeout = packet_timeout;
return old_packet_timeout;
}
bool
GetStopReply (StringExtractorGDBRemote &response);
bool
GetThreadStopInfo (uint32_t tid,
StringExtractorGDBRemote &response);
bool
SupportsGDBStoppointPacket (GDBStoppointType type)
{
switch (type)
{
case eBreakpointSoftware: return m_supports_z0;
case eBreakpointHardware: return m_supports_z1;
case eWatchpointWrite: return m_supports_z2;
case eWatchpointRead: return m_supports_z3;
case eWatchpointReadWrite: return m_supports_z4;
default: break;
}
return false;
}
uint8_t
SendGDBStoppointTypePacket (GDBStoppointType type, // Type of breakpoint or watchpoint
bool insert, // Insert or remove?
lldb::addr_t addr, // Address of breakpoint or watchpoint
uint32_t length); // Byte Size of breakpoint or watchpoint
void
TestPacketSpeed (const uint32_t num_packets);
// This packet is for testing the speed of the interface only. Both
// the client and server need to support it, but this allows us to
// measure the packet speed without any other work being done on the
// other end and avoids any of that work affecting the packet send
// and response times.
bool
SendSpeedTestPacket (uint32_t send_size,
uint32_t recv_size);
bool
SetCurrentThread (int tid);
bool
SetCurrentThreadForRun (int tid);
lldb_private::LazyBool
SupportsAllocDeallocMemory () const
{
return m_supports_alloc_dealloc_memory;
}
size_t
GetCurrentThreadIDs (std::vector<lldb::tid_t> &thread_ids,
bool &sequence_mutex_unavailable);
bool
GetInterruptWasSent () const
{
return m_interrupt_sent;
}
protected:
//------------------------------------------------------------------
// Classes that inherit from GDBRemoteCommunicationClient can see and modify these
//------------------------------------------------------------------
lldb_private::LazyBool m_supports_not_sending_acks;
lldb_private::LazyBool m_supports_thread_suffix;
lldb_private::LazyBool m_supports_vCont_all;
lldb_private::LazyBool m_supports_vCont_any;
lldb_private::LazyBool m_supports_vCont_c;
lldb_private::LazyBool m_supports_vCont_C;
lldb_private::LazyBool m_supports_vCont_s;
lldb_private::LazyBool m_supports_vCont_S;
lldb_private::LazyBool m_qHostInfo_is_valid;
lldb_private::LazyBool m_supports_alloc_dealloc_memory;
lldb_private::LazyBool m_supports_memory_region_info;
bool
m_supports_qProcessInfoPID:1,
m_supports_qfProcessInfo:1,
m_supports_qUserName:1,
m_supports_qGroupName:1,
m_supports_qThreadStopInfo:1,
m_supports_z0:1,
m_supports_z1:1,
m_supports_z2:1,
m_supports_z3:1,
m_supports_z4:1;
lldb::tid_t m_curr_tid; // Current gdb remote protocol thread index for all other operations
lldb::tid_t m_curr_tid_run; // Current gdb remote protocol thread index for continue, step, etc
// If we need to send a packet while the target is running, the m_async_XXX
// member variables take care of making this happen.
lldb_private::Mutex m_async_mutex;
lldb_private::Predicate<bool> m_async_packet_predicate;
std::string m_async_packet;
StringExtractorGDBRemote m_async_response;
int m_async_signal; // We were asked to deliver a signal to the inferior process.
bool m_interrupt_sent;
lldb_private::ArchSpec m_host_arch;
uint32_t m_os_version_major;
uint32_t m_os_version_minor;
uint32_t m_os_version_update;
std::string m_os_build;
std::string m_os_kernel;
std::string m_hostname;
bool
DecodeProcessInfoResponse (StringExtractorGDBRemote &response,
lldb_private::ProcessInstanceInfo &process_info);
private:
//------------------------------------------------------------------
// For GDBRemoteCommunicationClient only
//------------------------------------------------------------------
DISALLOW_COPY_AND_ASSIGN (GDBRemoteCommunicationClient);
};
#endif // liblldb_GDBRemoteCommunicationClient_h_