emul: added INT 0x80 hook for syscall 4 (write) for printint

1 files changed, 63 insertions, 1 deletions

diff --git a/ecomp-c/emul.c b/ecomp-c/emul.c
index f97e787..c1d819f 100644
--- a/ecomp-c/emul.c
+++ b/ecomp-c/emul.c
@@ -105,6 +105,58 @@ static int compute_p( int size )
 	return p;
 }
 
+static void handle_interrupts( uc_engine *uc, uint32_t interrupt, void *user_data )
+{
+	uint32_t eax, ebx, ecx, edx;
+	bool trace = *((bool *)user_data);
+	
+	if( trace ) {
+		printf( "INT %x\n", interrupt );
+		dump_regs( uc );
+	}
+	
+	if( interrupt != 0x80 ) {
+		return;
+	}
+
+	uc_reg_read( uc, UC_X86_REG_EAX, &eax );
+	switch( eax ) {
+		case 4: // SYSCALL_WRITE			
+		{
+			unsigned char buffer[256];
+			size_t size;
+			uc_err uerr;
+			
+			uc_reg_read( uc, UC_X86_REG_EBX, &ebx );
+			if( ebx != 1 ) {
+				fprintf( stderr, "ERROR: failed to call SYSCALL_WRITE on non-stdout (not implemented)\n" );
+				return;
+			}
+
+			uc_reg_read( uc, UC_X86_REG_ECX, &ecx );
+			uc_reg_read( uc, UC_X86_REG_EDX, &edx );
+			size = sizeof( buffer ) - 1;
+			if( edx < sizeof( buffer ) - 1 ) {
+				size = edx;
+			}
+			
+			uerr = uc_mem_read( uc, ecx, buffer, size );
+			buffer[size] = '\0';
+			if( uerr != UC_ERR_OK ) {
+				fprintf( stderr, "ERROR: failed to call uc_mem_read( ) in int x080 syscall 4 (SYSCALL_WRITE): %s\n", uc_strerror( uerr ) );
+				dump_regs( uc );
+				exit( EXIT_FAILURE );
+			}
+			
+			printf( "%*s", size, buffer );
+		    }
+		    break;
+
+		default:
+			fprintf( stderr, "WARN: unknown syscall %0x, EAX: %d\n", interrupt, eax );
+	}
+}
+
 int main( int argc, char *argv[] )
 {
 	uc_engine *uc;
@@ -355,6 +407,16 @@ int main( int argc, char *argv[] )
 	if( trace ) {
 		printf( "Single step execution:\n" );
 	}
+
+	// hook for emulating syscalls (int 0x80 on the host)
+	uc_hook hook;
+	uerr = uc_hook_add( uc, &hook, UC_HOOK_INTR, handle_interrupts, (void *)&trace, 1, 0 );
+	if( uerr != UC_ERR_OK ) {
+		fprintf( stderr, "ERROR: failed to call uc_hook_add( handle_interrupts ): %s\n", uc_strerror( uerr ) );		
+		cs_close( &cs );
+		uc_close( uc );
+		exit( EXIT_FAILURE );
+	}
 	
 	while( !terminate ) {
 
@@ -393,7 +455,7 @@ int main( int argc, char *argv[] )
 					
 			printf( "%s %s\n", instrs[n].mnemonic, instrs[n].op_str );
 		}
-				
+						
 		uerr = uc_emu_start( uc, addr, CODE_START + code_size, 0, 1 );
 		if( uerr != UC_ERR_OK ) {
 			fprintf( stderr, "ERROR: failed to call uc_emu_start( ): %s\n", uc_strerror( uerr ) );