linuxthreadhelpers.cpp

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/* RageThreads helpers for threads in Linux, which are based on PIDs and TIDs. */

#include "LinuxThreadHelpers.h"
#include "Backtrace.h"
#include "RunningUnderValgrind.h"
#include <assert.h>
#include <unistd.h>
#include <stdlib.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/ptrace.h>
#include <sys/stat.h>
#include <linux/unistd.h>
#define _LINUX_PTRACE_H // hack to prevent broken linux/ptrace.h from conflicting with sys/ptrace.h
#include <sys/user.h>
#include <sys/syscall.h>

/* In Linux, we might be using PID-based or TID-based threads.  With PID-based
 * threads, getpid() returns a unique value for each thread; each thread is a
 * separate process.  Newer kernels using NPTL return the same PID for all
 * threads; these systems support a gettid() call to get a unique TID for each
 * thread. */



static bool g_bUsingNPTL = false;

#define gettid() syscall(SYS_gettid)

#ifndef _CS_GNU_LIBPTHREAD_VERSION
#define _CS_GNU_LIBPTHREAD_VERSION 3
#endif


MString ThreadsVersion()
{
	char buf[1024] = "(error)";
	int ret = confstr( _CS_GNU_LIBPTHREAD_VERSION, buf, sizeof(buf) );
	if( ret == -1 )
		return "(unknown)";

	return buf;
}

/* Crash-conditions-safe: */
bool UsingNPTL()
{
	char buf[1024] = "";
	int ret = confstr( _CS_GNU_LIBPTHREAD_VERSION, buf, sizeof(buf) );
	if( ret == -1 )
		return false;

	return !strncmp( buf, "NPTL", 4 );
}
/* Crash-conditions-safe: */
void InitializePidThreadHelpers()
{
	static bool bInitialized = false;
	if( bInitialized )
		return;
	bInitialized = true;

	g_bUsingNPTL = UsingNPTL();
}

/* waitpid(); ThreadID can be a PID or (in NPTL) a TID; doesn't care if the ID
 * is a clone() or not. */
static int waittid( int ThreadID, int *status, int options )
{
	static bool bSupportsWall = true;

	if( bSupportsWall )
	{
		int ret = waitpid( ThreadID, status, options | __WALL );
		if( ret != -1 || errno != EINVAL )
			return ret;
		bSupportsWall = false;
	}
			
	/* XXX: on 2.2, we need to use __WCLONE only if ThreadID isn't the main thread;
	 * perhaps wait and retry without it if errno == ECHILD? */
	int ret;
	ret = waitpid( ThreadID, status, options );

	return ret;
}

/* Attempt to PTRACE_ATTACH to a thread, and wait for the SIGSTOP. */
static int PtraceAttach( int ThreadID )
{
	int ret;
	ret = ptrace( PTRACE_ATTACH, ThreadID, NULL, NULL );
	if( ret == -1 )
	{
		printf("ptrace failed: %s\n", strerror(errno) );
		return -1;
	}

	/* Wait for the SIGSTOP from the ptrace call. */
	int status;
	ret = waittid( ThreadID, &status, 0 );
	if( ret == -1 )
		return -1;

//	printf( "ret %i, exited %i, signalled %i, sig %i, stopped %i, stopsig %i\n", ret, WIFEXITED(status),
//			WIFSIGNALED(status), WTERMSIG(status), WIFSTOPPED(status), WSTOPSIG(status));
	return 0;
}

static int PtraceDetach( int ThreadID )
{
	return ptrace( PTRACE_DETACH, ThreadID, NULL, NULL );
}


/* Get this thread's ID (this may be a TID or a PID). */
static uint64_t GetCurrentThreadIdInternal()
{
	/* If we're under Valgrind, neither the PID nor the TID is associated with the
	 * thread.  Return the pthread ID.  This can't be used to kill threads, etc.,
	 * but that only happens under error conditions anyway.  If we don't return a
	 * usable, unique ID, then mutexes won't work. */
	if( RunningUnderValgrind() )
		return (int) pthread_self();
	
	InitializePidThreadHelpers(); // for g_bUsingNPTL

	/* Don't keep calling gettid() if it's not supported; it'll make valgrind spam us. */
	static bool GetTidUnsupported = 0;
	if( !GetTidUnsupported )
	{
		pid_t ret = gettid();

		/* If this fails with ENOSYS, we're on a kernel before gettid, or we're
		 * under valgrind.  If we don't have NPTL, then just use getpid().  If
		 * we're on NPTL and don't have gettid(), something's wrong. */
		if( ret != -1 )
			return ret;

		assert( !g_bUsingNPTL );
		GetTidUnsupported = true;
	}

	return getpid();
}

uint64_t GetCurrentThreadId()
{
#if defined(HAVE_TLS)
	/* This is called each time we lock a mutex, and gettid() is a little slow, so
	 * cache the result if we support TLS. */
	if( RageThread::GetSupportsTLS() )
	{
		static thread_local uint64_t cached_tid = 0;
		static thread_local bool cached = false;
		if( !cached )
		{
			cached_tid = GetCurrentThreadIdInternal();
			cached = true;
		}
		return cached_tid;
	}
#endif

	return GetCurrentThreadIdInternal();
}

int SuspendThread( uint64_t ThreadID )
{
	/*
	 * Linux: We can't simply kill(SIGSTOP) (or tkill), since that will stop all processes
	 * (grr).  We can ptrace(PTRACE_ATTACH) the process to stop it, and PTRACE_DETACH
	 * to restart it.
	 */
	return PtraceAttach( int(ThreadID) );
	// kill( ThreadID, SIGSTOP );
}

int ResumeThread( uint64_t ThreadID )
{
	return PtraceDetach( int(ThreadID) );
	// kill( ThreadID, SIGSTOP );
}


/* Get a BacktraceContext for a thread.  ThreadID must not be the current thread.
 *
 * tid() is a PID (from getpid) or a TID (from gettid).  Note that this may have kernel compatibility
 * problems, because NPTL is new and its interactions with ptrace() aren't well-defined.
 * If we're on a non-NPTL system, tid is a regular PID.
 *
 * This call leaves the given thread suspended, so the returned context doesn't become invalid.
 * ResumeThread() can be used to resume a thread after this call. */
#if defined(CRASH_HANDLER)
bool GetThreadBacktraceContext( uint64_t ThreadID, BacktraceContext *ctx )
{
	/* Can't GetThreadBacktraceContext the current thread. */
	assert( ThreadID != GetCurrentThreadId() );

	/* Attach to the thread.  This may fail with EPERM.  This can happen for at least
	 * two common reasons: the process might be in a debugger already, or *we* might
	 * already have attached to it via SuspendThread.
	 *
	 * If it's in a debugger, we won't be able to ptrace(PTRACE_GETREGS). If
	 * it's us that attached, we will. */
	if( PtraceAttach( int(ThreadID) ) == -1 )
	{
		if( errno != EPERM )
		{
//	CHECKPOINT_M( ssprintf( "%s (pid %i tid %i locking tid %i)",
//			strerror(errno), getpid(), (int)GetCurrentThreadId(), 
//int(ThreadID) ) );
			return false;
		}
	}

	user_regs_struct regs;
	if( ptrace( PTRACE_GETREGS, pid_t(ThreadID), NULL, &regs ) == -1 )
		return false;

	ctx->pid = pid_t(ThreadID);
#if defined(CPU_X86_64)
	ctx->ip = (void *) regs.rip;
	ctx->bp = (void *) regs.rbp;
	ctx->sp = (void *) regs.rsp;
#elif defined(CPU_X86)
	ctx->ip = (void *) regs.eip;
	ctx->bp = (void *) regs.ebp;
	ctx->sp = (void *) regs.esp;
#else
#error GetThreadBacktraceContext: which arch?
#endif

	return true;
}
#endif

/*
 * (c) 2004 Glenn Maynard
 * All rights reserved.
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, and/or sell copies of the Software, and to permit persons to
 * whom the Software is furnished to do so, provided that the above
 * copyright notice(s) and this permission notice appear in all copies of
 * the Software and that both the above copyright notice(s) and this
 * permission notice appear in supporting documentation.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT OF
 * THIRD PARTY RIGHTS. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR HOLDERS
 * INCLUDED IN THIS NOTICE BE LIABLE FOR ANY CLAIM, OR ANY SPECIAL INDIRECT
 * OR CONSEQUENTIAL DAMAGES, OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
 * OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
 * OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 * PERFORMANCE OF THIS SOFTWARE.
 */