#include "global.h"

#include "RageLog.h"
#include "SignalHandler.h"
#include "GetSysInfo.h"

#include <stdlib.h>
#include <unistd.h>
#include <sys/mman.h>
#include <errno.h>

static vector<SignalHandler::handler> handlers;
SaveSignals *saved_sigs;
static bool initted = false;

static int signals[] = {
	SIGALRM, SIGBUS, SIGFPE, SIGHUP, SIGILL, SIGINT, SIGABRT, SIGPIPE,
	SIGQUIT, SIGSEGV, SIGTRAP, SIGTERM, SIGVTALRM, SIGXCPU, SIGXFSZ,
#if defined(HAVE_DECL_SIGPWR) && HAVE_DECL_SIGPWR
	SIGPWR,
#endif
	-1
};

/*
 * Store signals and restore them.  This lets us clean up after libraries
 * that like to mess with our signal handler.  (Of course, if we undo
 * signal handlers for libraries, we need to be sure to handle whatever it
 * was cleaning up by hand.)
 */

SaveSignals::SaveSignals()
{
	/* Store the old signal handlers. */
	for(int i = 0; signals[i] != -1; ++i)
	{
		struct sigaction sa;
		sigaction(signals[i], NULL, &sa);
		old_handlers.push_back(sa);
	}
}

SaveSignals::~SaveSignals()
{
	/* Restore the old signal handlers. */
	for(unsigned i = 0; i < old_handlers.size(); ++i)
		sigaction(signals[i], &old_handlers[i], NULL);
}

static void SigHandler( int signal, siginfo_t *si, void *ucp )
{
	for(unsigned i = 0; i < handlers.size(); ++i)
		handlers[i]( signal, si, (const ucontext_t *) ucp );
}

static int find_stack_direction2( char *p )
{
	char c;
	return (&c > p) ? +1:-1;
}

static int find_stack_direction()
{
	char c;
	return find_stack_direction2( &c );
}

/* Create a stack with a barrier page at the end to guard against stack overflow. */
static void *CreateStack( int size )
{
	const long PageSize = sysconf(_SC_PAGESIZE);

	/* Round size up to the nearest PageSize. */
	size += PageSize-1;
	size -= (size%PageSize);

	/* mmap always returns page-aligned data.
	 *
	 * mmap entries always show up individually in /proc/#/maps.  We could use posix_memalign as
	 * a fallback, but we'd have to put a barrier page on both sides to guarantee that. */
	char *p = NULL;
	p = (char *) mmap( NULL, size+PageSize, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0 );

	if( p == (void *) -1 )
		return NULL;
	// if( posix_memalign( (void**) &p, PageSize, RealSize ) != 0 )
	//	return NULL;

	if( find_stack_direction() < 0 )
	{
		/* The stack grows towards smaller addresses.  Protect the first page. */
		mprotect( p, PageSize, PROT_NONE );
		p += PageSize;
	}
	else
	{
		/* The stack grows towards larger addresses.  Protect the last page. */
		mprotect( p+size, PageSize, PROT_NONE );
	}

	return p;
}

/* Hook up events to fatal signals, so we can clean up if we're killed. */
void SignalHandler::OnClose(handler h)
{
	if(saved_sigs == NULL)
	{
		saved_sigs = new SaveSignals;

		/* Allocate a separate signal stack.  This makes the crash handler work
		 * if we run out of stack space. */
		/* Ugh.  Signal stack + pthreads + Linux 2.4 = crash or hang. */
		CString system;
		int version;
		GetKernel( system, version );

		const int AltStackSize = 1024*64;
		void *p = NULL;
		if( version > 20500 )
			p = CreateStack( AltStackSize );

		if( p != NULL )
		{
			stack_t ss;
			ss.ss_sp = p;
			ss.ss_size = AltStackSize;
			ss.ss_flags = 0;
			if( sigaltstack( &ss, NULL ) == -1 )
			{
				LOG->Info( "sigaltstack failed: %s", strerror(errno) );
				p = NULL; /* no SA_ONSTACK */
			}
		}
		
		/* Set up our signal handlers. */
		for(int i = 0; signals[i] != -1; ++i)
		{
			struct sigaction sa;

			sa.sa_sigaction = SigHandler;
			sa.sa_flags = p != NULL? SA_ONSTACK:0;
			sa.sa_flags |= SA_NODEFER;
			sa.sa_flags |= SA_SIGINFO;
			sigemptyset(&sa.sa_mask);

			sigaction(signals[i], &sa, NULL);
		}
	}
	handlers.push_back(h);
}


/* Written by Glenn Maynard.  Public domain, copyrighting a simple signal handler
 * is dumb. */