//-------------------------------------------------------------------
//	segvtrap.cpp
//
//	This program shows how a signal-handler can be used to help
//	diagnose the cause of a 'Segmentation Violation' exception.
//
//	programmer: ALLAN CRUSE
//	written on: 11 MAY 2005
//-------------------------------------------------------------------

#include <stdio.h>	// for printf() 
#include <stdlib.h>	// for exit() 
#include <signal.h>	// for sigaction()

void my_sigaction( int signum, siginfo_t *si, void *data )
{
	struct sigcontext	*sc = (struct sigcontext *)((int)data+20);

	// display CPU registers
	printf( "\nsignal %d ", signum );
	printf( "EFLAGS=%08lX ", sc->eflags );
	printf( "\n" );
	printf( "EAX=%08lX ", sc->eax );
	printf( "EBX=%08lX ", sc->ebx );
	printf( "ESP=%08lX ", sc->esp );
	printf( "SS=%04lX ", sc->ss );
	printf( "ES=%04lX ", sc->es );
	printf( "\n" );
	printf( "ECX=%08lX ", sc->ecx );
	printf( "EDX=%08lX ", sc->edx );
	printf( "EIP=%08lX ", sc->eip );
	printf( "CS=%04lX ", sc->cs );
	printf( "FS=%04lX ", sc->fs );
	printf( "\n" );
	printf( "ESI=%08lX ", sc->esi );
	printf( "EDI=%08lX ", sc->edi );
	printf( "EBP=%08lX ", sc->ebp );
	printf( "DS=%04lX ", sc->ds );
	printf( "GS=%04lX ", sc->gs );
	printf( "\n" );

	// display stack-values
	unsigned long	*lp = (unsigned long *)sc->esp;
	printf( "\n[SS:ESP]  " );
	for (int i = 0; i < 5; i++) printf( "%08X ", lp[i] );

	// display instruction-stream
	unsigned char	*ip = (unsigned char *)sc->eip;
	printf( "\n[CS:EIP]  " );
	for (int i = 0; i < 15; i++) printf( "%02X ", ip[i] );
	printf( "\n\n" );

	// terminate this program with status-code 1
	exit( 1 );
}


int main( int argc, char **argv )
{
	// install our signal-handler
	static struct sigaction	sa = {0};
	sigemptyset( &sa.sa_mask );
	sa.sa_flags = SA_SIGINFO;
	sa.sa_sigaction = my_sigaction;
	sigaction( SIGSEGV, &sa, NULL );

	// setup registers with demonstration values
	asm(" movl $0xAAAAAAAA, %eax ");
	asm(" movl $0xBBBBBBBB, %ebx ");
	asm(" movl $0xCCCCCCCC, %ecx ");
	asm(" movl $0xDDDDDDDD, %edx ");
	asm(" movl $0xEEEEEEEE, %esi ");
	asm(" movl $0xFFFFFFFF, %edi ");
	
	// try to execute a privileged instruction
	asm(" hlt ");	
	
	// terminate this program with status-code 0
	exit( 0 );
}