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[lldb] Check for and use ptsname_r if available 

ptsname is not thread-safe. ptsname_r is available on most (but not all)
systems -- use it preferentially.

In the patch I also improve the thread-safety of the ptsname fallback
path by wrapping it in a mutex. This should guarantee the safety of a
typical ptsname implementation using a single static buffer, as long as
all callers go through this function.

I also remove the error arguments, as the only way this function can
fail is if the "primary" fd is not valid. This is a programmer error as
this requirement is documented, and all callers ensure that is the case.

Differential Revision: https://reviews.llvm.org/D88728
This commit is contained in:
Pavel Labath 2020-10-02 13:38:09 +02:00
parent 029290f1a6
commit 3dfb949861
8 changed files with 43 additions and 70 deletions
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1
lldb/cmake/modules/LLDBGenerateConfig.cmake
View File

@ -7,6 +7,7 @@ include(CheckLibraryExists)
set(CMAKE_REQUIRED_DEFINITIONS -D_GNU_SOURCE)
check_symbol_exists(ppoll poll.h HAVE_PPOLL)
check_symbol_exists(ptsname_r stdlib.h HAVE_PTSNAME_R)
set(CMAKE_REQUIRED_DEFINITIONS)
check_symbol_exists(sigaction signal.h HAVE_SIGACTION)
check_cxx_symbol_exists(accept4 "sys/socket.h" HAVE_ACCEPT4)

2
lldb/include/lldb/Host/Config.h.cmake
View File

@ -20,6 +20,8 @@
#cmakedefine01 HAVE_PPOLL
#cmakedefine01 HAVE_PTSNAME_R
#cmakedefine01 HAVE_SIGACTION
#cmakedefine01 HAVE_PROCESS_VM_READV

13
lldb/include/lldb/Host/PseudoTerminal.h
View File

@ -105,20 +105,11 @@ public:
/// A primary pseudo terminal should already be valid prior to
/// calling this function.
///
/// \param[out] error_str
/// An pointer to an error that can describe any errors that
/// occur. This can be NULL if no error status is desired.
///
/// \return
/// The name of the secondary pseudo terminal as a NULL terminated
/// C. This string that comes from static memory, so a copy of
/// the string should be made as subsequent calls can change
/// this value. NULL is returned if this object doesn't have
/// a valid primary pseudo terminal opened or if the call to
/// \c ptsname() fails.
/// The name of the secondary pseudo terminal.
///
/// \see PseudoTerminal::OpenFirstAvailablePrimary()
const char *GetSecondaryName(char *error_str, size_t error_len) const;
std::string GetSecondaryName() const;
/// Open the first available pseudo terminal.
///

2
lldb/source/Host/common/ProcessLaunchInfo.cpp
View File

@ -222,7 +222,7 @@ llvm::Error ProcessLaunchInfo::SetUpPtyRedirection() {
return llvm::createStringError(llvm::inconvertibleErrorCode(),
"PTY::OpenFirstAvailablePrimary failed");
}
const FileSpec secondary_file_spec(m_pty->GetSecondaryName(nullptr, 0));
const FileSpec secondary_file_spec(m_pty->GetSecondaryName());
// Only use the secondary tty if we don't have anything specified for
// input and don't have an action for stdin

58
lldb/source/Host/common/PseudoTerminal.cpp
View File

@ -8,9 +8,11 @@
#include "lldb/Host/PseudoTerminal.h"
#include "lldb/Host/Config.h"
#include "llvm/Support/Errc.h"
#include "llvm/Support/Errno.h"
#include <cassert>
#include <limits.h>
#include <mutex>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
@ -128,15 +130,8 @@ bool PseudoTerminal::OpenSecondary(int oflag, char *error_str,
CloseSecondaryFileDescriptor();
// Open the primary side of a pseudo terminal
const char *secondary_name = GetSecondaryName(error_str, error_len);
if (secondary_name == nullptr)
return false;
m_secondary_fd =
llvm::sys::RetryAfterSignal(-1, ::open, secondary_name, oflag);
std::string name = GetSecondaryName();
m_secondary_fd = llvm::sys::RetryAfterSignal(-1, ::open, name.c_str(), oflag);
if (m_secondary_fd < 0) {
if (error_str)
ErrnoToStr(error_str, error_len);
@ -146,32 +141,21 @@ bool PseudoTerminal::OpenSecondary(int oflag, char *error_str,
return true;
}
// Get the name of the secondary pseudo terminal. A primary pseudo terminal
// should already be valid prior to calling this function (see
// OpenFirstAvailablePrimary()).
//
// RETURNS:
// NULL if no valid primary pseudo terminal or if ptsname() fails.
// The name of the secondary pseudo terminal as a NULL terminated C string
// that comes from static memory, so a copy of the string should be
// made as subsequent calls can change this value.
const char *PseudoTerminal::GetSecondaryName(char *error_str,
size_t error_len) const {
if (error_str)
error_str[0] = '\0';
if (m_primary_fd < 0) {
if (error_str)
::snprintf(error_str, error_len, "%s",
"primary file descriptor is invalid");
return nullptr;
}
const char *secondary_name = ::ptsname(m_primary_fd);
if (error_str && secondary_name == nullptr)
ErrnoToStr(error_str, error_len);
return secondary_name;
std::string PseudoTerminal::GetSecondaryName() const {
assert(m_primary_fd >= 0);
#if HAVE_PTSNAME_R
char buf[PATH_MAX];
buf[0] = '\0';
int r = ptsname_r(m_primary_fd, buf, sizeof(buf));
assert(r == 0);
return buf;
#else
static std::mutex mutex;
std::lock_guard<std::mutex> guard(mutex);
const char *r = ptsname(m_primary_fd);
assert(r != nullptr);
return r;
#endif
}
// Fork a child process and have its stdio routed to a pseudo terminal.

32
lldb/source/Plugins/Platform/MacOSX/objcxx/PlatformiOSSimulatorCoreSimulatorSupport.mm
View File

@ -407,25 +407,21 @@ static Status HandleFileAction(ProcessLaunchInfo &launch_info,
const int master_fd = launch_info.GetPTY().GetPrimaryFileDescriptor();
if (master_fd != PseudoTerminal::invalid_fd) {
// Check in case our file action open wants to open the secondary
const char *secondary_path =
launch_info.GetPTY().GetSecondaryName(NULL, 0);
if (secondary_path) {
FileSpec secondary_spec(secondary_path);
if (file_spec == secondary_spec) {
int secondary_fd =
launch_info.GetPTY().GetSecondaryFileDescriptor();
if (secondary_fd == PseudoTerminal::invalid_fd)
secondary_fd =
launch_info.GetPTY().OpenSecondary(O_RDWR, nullptr, 0);
if (secondary_fd == PseudoTerminal::invalid_fd) {
error.SetErrorStringWithFormat(
"unable to open secondary pty '%s'", secondary_path);
return error; // Failure
}
[options setValue:[NSNumber numberWithInteger:secondary_fd]
forKey:key];
return error; // Success
FileSpec secondary_spec(launch_info.GetPTY().GetSecondaryName());
if (file_spec == secondary_spec) {
int secondary_fd =
launch_info.GetPTY().GetSecondaryFileDescriptor();
if (secondary_fd == PseudoTerminal::invalid_fd)
secondary_fd =
launch_info.GetPTY().OpenSecondary(O_RDWR, nullptr, 0);
if (secondary_fd == PseudoTerminal::invalid_fd) {
error.SetErrorStringWithFormat(
"unable to open secondary pty '%s'", secondary_path);
return error; // Failure
}
[options setValue:[NSNumber numberWithInteger:secondary_fd]
forKey:key];
return error; // Success
}
}
Status posix_error;

3
lldb/source/Plugins/Process/FreeBSD/ProcessFreeBSD.cpp
View File

@ -380,8 +380,7 @@ Status ProcessFreeBSD::DoLaunch(Module *module,
FileSpec stdout_file_spec{};
FileSpec stderr_file_spec{};
const FileSpec dbg_pts_file_spec{
launch_info.GetPTY().GetSecondaryName(NULL, 0)};
const FileSpec dbg_pts_file_spec{launch_info.GetPTY().GetSecondaryName()};
file_action = launch_info.GetFileActionForFD(STDIN_FILENO);
stdin_file_spec =

2
lldb/source/Plugins/Process/gdb-remote/ProcessGDBRemote.cpp
View File

@ -818,7 +818,7 @@ Status ProcessGDBRemote::DoLaunch(lldb_private::Module *exe_module,
// does a lot of output.
if ((!stdin_file_spec || !stdout_file_spec || !stderr_file_spec) &&
pty.OpenFirstAvailablePrimary(O_RDWR | O_NOCTTY, nullptr, 0)) {
FileSpec secondary_name{pty.GetSecondaryName(nullptr, 0)};
FileSpec secondary_name(pty.GetSecondaryName());
if (!stdin_file_spec)
stdin_file_spec = secondary_name;