WEBVTT 00:00.320 --> 00:04.850 Hello, my name is Stephan, and in this lecture we will develop another assembly program. 00:04.850 --> 00:12.470 And now that you have a firm grasp of GDB and know what an assembly program looks like, let's add some 00:12.470 --> 00:13.430 complexity. 00:13.460 --> 00:18.920 In this lecture I will show you how to obtain the length of a string variable. 00:19.100 --> 00:26.300 I will show you how to print integer and floating point values using printf and I will expand your knowledge 00:26.300 --> 00:28.210 of GDB commands. 00:28.220 --> 00:36.530 So now here we will firstly open CSM or you can also choose another text editor so you don't need much 00:36.530 --> 00:39.410 about creating or developing assembly code. 00:39.620 --> 00:43.070 And let's actually use the CSM here. 00:43.070 --> 00:44.720 Now create a new project here. 00:44.720 --> 00:47.270 Let's delete this project, save it somewhere. 00:47.270 --> 00:51.170 In this case, let's actually our project name is going to be kicking. 00:52.340 --> 00:52.910 That's it. 00:52.940 --> 00:57.500 Now save it as the name of kicking that --. 00:57.950 --> 00:58.580 That's it. 00:58.580 --> 01:00.740 And here is our code. 01:00.770 --> 01:03.860 Now we will firstly comment it out. 01:03.860 --> 01:05.840 Our the. 01:07.350 --> 01:11.400 Assembly program, name, file name, RSM here. 01:11.430 --> 01:18.810 Now we will firstly add this data section in it here because we will add the two variables. 01:18.810 --> 01:21.510 It's actually two variables, but we will add four variables. 01:21.510 --> 01:27.270 The two variables is for the our string and string. 01:27.300 --> 01:33.810 And the second variables is the length of the first string and the length of the second string. 01:33.810 --> 01:43.260 Now here we will firstly write this the message MSG one db here. 01:43.650 --> 01:44.850 Hello world. 01:45.000 --> 01:48.240 Let's actually case sensitive words here. 01:48.390 --> 01:51.930 Hello world and ten zero. 01:52.900 --> 01:54.950 And a comma and zero here. 01:54.970 --> 01:56.560 So what? 01:56.800 --> 01:58.540 So this is something new, right? 01:58.540 --> 02:00.790 So we added zero for the null terminated. 02:01.240 --> 02:04.990 But here we added ten, which I will explain right now. 02:04.990 --> 02:10.390 So this is the string with an L and zero. 02:12.000 --> 02:15.060 The string width and zero here. 02:15.690 --> 02:17.340 We will also have the. 02:19.000 --> 02:20.240 Message one. 02:20.260 --> 02:21.670 Length here. 02:21.790 --> 02:23.170 Actually, length is okay. 02:23.170 --> 02:32.380 So we will write here and what we're going to do, we will take this message variable minus message 02:32.380 --> 02:33.670 one, minus one. 02:33.670 --> 02:38.770 So this is for measuring the length minus the zero here. 02:38.770 --> 02:40.450 So measure. 02:41.550 --> 02:43.320 Measure the length. 02:44.200 --> 02:49.240 Of message one and minus. 02:50.030 --> 02:50.810 The zero. 02:51.020 --> 02:54.560 And we will also create our string too. 02:55.490 --> 02:58.400 We will name it MSG two. 02:58.460 --> 03:02.750 Here we will write it DB right here. 03:02.750 --> 03:09.530 And our message is going to be kicking and alive this here. 03:09.740 --> 03:10.610 So. 03:12.130 --> 03:12.430 Here. 03:12.430 --> 03:13.390 We will also. 03:15.270 --> 03:17.750 All this again, ten and zero. 03:17.750 --> 03:23.540 Remember, this ten is for new line and is for nation. 03:24.200 --> 03:26.920 So we will terminate our string after new line. 03:26.930 --> 03:27.320 Right. 03:27.320 --> 03:32.840 So string with L and zero here. 03:35.720 --> 03:39.680 And after that, we will also create the search tool. 03:39.680 --> 03:40.610 Len, here. 03:40.640 --> 03:43.610 This is going to be, again, equal here. 03:43.700 --> 03:48.590 And here we will again measure the length and we will miss the zero. 03:48.770 --> 03:51.740 So a message to. 03:52.710 --> 03:54.720 Minus one here. 03:55.740 --> 03:58.560 So this is for the measure. 03:59.450 --> 04:03.110 The length of message to. 04:04.980 --> 04:06.300 Plus minus. 04:08.070 --> 04:08.970 The zero. 04:10.260 --> 04:13.770 And here we will create some radius. 04:13.770 --> 04:15.510 So this is the radius. 04:15.510 --> 04:21.870 And pi is actually the terminology for you, which you will learn by the end of this section. 04:21.990 --> 04:25.990 I will explain this terminologies deeply later. 04:26.010 --> 04:27.540 So radius. 04:28.340 --> 04:31.790 Be cool not to be here and. 04:31.790 --> 04:34.550 357. 04:35.410 --> 04:37.300 And we will add comments. 04:37.300 --> 04:41.080 But as I say, they I will explain this further. 04:41.380 --> 04:42.700 String not. 04:44.080 --> 04:44.530 This. 04:45.600 --> 04:46.830 Is playable. 04:49.200 --> 04:49.470 Again. 04:49.470 --> 04:51.090 We will copy this. 04:55.540 --> 04:57.730 And we will again create a P here. 04:57.760 --> 04:58.270 P. 04:59.640 --> 05:03.270 BQ 3.14 and again. 05:10.180 --> 05:12.850 So now our section data is completed. 05:12.850 --> 05:17.620 Now we will also create the section which we will not use. 05:17.950 --> 05:20.050 We will not notice anything here. 05:20.200 --> 05:29.050 Section The main where our main function will live here is section text and we will create a global 05:29.080 --> 05:29.890 main. 05:30.620 --> 05:34.970 Now let's start developing our main function. 05:34.970 --> 05:40.220 So in our main function we will again add the we will push the. 05:41.170 --> 05:42.510 R p. 05:42.520 --> 05:43.330 P. 05:44.240 --> 05:47.150 This is the function prologue. 05:47.190 --> 05:48.170 Actually, we can. 05:50.770 --> 05:53.500 Less taps, though, because we will not have. 05:55.820 --> 05:56.750 The strings here. 05:57.620 --> 05:59.360 These are just instructions. 05:59.480 --> 06:01.670 So here, this is the. 06:03.610 --> 06:05.860 Function prologue. 06:08.680 --> 06:09.190 Move. 06:11.180 --> 06:13.520 Are BP RSP. 06:13.550 --> 06:16.580 This is, again a function prologue as well. 06:19.140 --> 06:19.950 Move. 06:22.760 --> 06:23.360 One. 06:25.510 --> 06:27.070 I always add this here. 06:39.600 --> 06:40.020 Here. 06:40.020 --> 06:45.510 So Rex1 is as we did in previous lectures. 06:45.510 --> 06:48.060 This is for right writing here. 06:48.450 --> 06:50.100 One is right. 06:50.700 --> 06:53.070 And we will again move here. 06:53.430 --> 06:54.170 Ready? 06:55.340 --> 06:59.960 As for to write on the console. 07:04.080 --> 07:05.970 To STD out. 07:06.990 --> 07:07.190 Out. 07:07.200 --> 07:07.650 Out here. 07:07.650 --> 07:08.700 So move. 07:09.880 --> 07:11.080 RSI. 07:12.520 --> 07:13.420 Message one. 07:13.420 --> 07:14.740 First, we will use this message. 07:14.740 --> 07:15.240 One. 07:15.250 --> 07:16.300 So this is the. 07:19.730 --> 07:23.660 String to display and after that. 07:25.510 --> 07:26.490 We will again. 07:26.500 --> 07:27.520 We will move. 07:30.720 --> 07:32.310 Are the eggs. 07:32.550 --> 07:39.870 And after that we will again print the length of this message one string, and after that we will apply 07:39.870 --> 07:42.480 the same for the message to here. 07:42.750 --> 07:44.820 Message one length. 07:44.850 --> 07:45.540 Here. 07:47.690 --> 07:49.100 This is the length. 07:50.820 --> 07:53.070 Of the string here. 07:53.070 --> 07:56.160 Actually, we let's actually add tabs. 07:57.180 --> 07:58.410 More tabs here. 07:59.640 --> 08:02.370 Doesn't look good here for display purposes. 08:03.550 --> 08:04.960 And that's it. 08:04.970 --> 08:09.260 After that, we will call the syscall to display the string. 08:09.280 --> 08:10.960 Display the string. 08:10.960 --> 08:12.760 So these are the comments, as you know. 08:14.280 --> 08:17.010 So we will again instead of writing. 08:17.040 --> 08:19.830 Actually we can write it out here. 08:19.830 --> 08:24.180 So rax one, it's for one. 08:25.010 --> 08:25.940 Right. 08:26.930 --> 08:28.300 Of I. 08:30.240 --> 08:35.940 Are thy one is for the STD out. 08:39.470 --> 08:41.120 STD out. 08:43.190 --> 08:44.390 And after that. 08:45.030 --> 08:45.600 It's called. 08:48.860 --> 08:54.430 Tracks RDA and after that we will need to add RSA again. 08:54.560 --> 08:55.880 Message to. 08:56.950 --> 09:02.620 Um, this is the string to display and move again. 09:02.650 --> 09:04.420 Ah, the X. 09:04.840 --> 09:07.870 This is the message to Len. 09:08.590 --> 09:11.980 And again, this is the length of the string. 09:12.220 --> 09:15.610 Length of the string. 09:19.380 --> 09:20.520 Length out a string. 09:21.240 --> 09:21.960 And. 09:24.580 --> 09:25.420 After that. 09:25.420 --> 09:26.190 That's it. 09:26.200 --> 09:26.890 We will. 09:28.530 --> 09:29.960 You can call the syscall. 09:31.790 --> 09:33.500 So this is for. 09:34.710 --> 09:40.870 Displaying this string again, the second string which is kicking in the live display. 09:40.890 --> 09:48.000 So you might be wondering where we will use this radius and pi here, which we will use that right now. 09:51.110 --> 09:54.350 And this is the skull is display. 09:55.430 --> 09:57.290 The ring. 09:58.770 --> 10:03.690 And after that, this is the last year, so we will develop the function. 10:03.690 --> 10:04.470 Epilogue. 10:04.620 --> 10:05.100 Function. 10:05.100 --> 10:05.590 Epilogue. 10:05.610 --> 10:09.300 Again, we will add exit and success exit code again. 10:09.300 --> 10:13.980 And after that we will again call the syscall to quit the program. 10:13.980 --> 10:14.490 Right. 10:14.490 --> 10:15.300 So. 10:16.360 --> 10:20.880 After calling the Siskel here again, we will call it one more time. 10:20.890 --> 10:28.150 After completing these four lines of code, we will firstly create a two function epilogue Our BP. 10:29.840 --> 10:31.760 Are here. 10:32.480 --> 10:33.320 Cases here. 10:37.990 --> 10:38.910 Bob, I. 10:38.950 --> 10:39.370 Okay. 10:39.370 --> 10:40.630 You can't hear my voice. 10:40.990 --> 10:41.370 Okay. 10:41.630 --> 10:42.130 Beep. 10:42.730 --> 10:43.540 I just scared. 10:43.540 --> 10:47.530 I thought this ten minutes of work just for nothing. 10:48.530 --> 10:50.030 And here are BP. 10:50.540 --> 10:53.360 This is the function epilogue. 10:54.700 --> 10:56.850 And again move RB. 10:58.200 --> 11:02.550 Here are BP again without the BP. 11:02.580 --> 11:03.780 Here just BP. 11:05.030 --> 11:08.680 This is the function epilogue as well. 11:08.690 --> 11:14.450 And after that we will move the racks which we did in previous code here. 11:14.450 --> 11:20.360 This is for the 60 means exit, and after that we will again call. 11:20.360 --> 11:31.210 Lastly, rest instruction is called RDA and this is for the zero, which is the success exit code as. 11:32.040 --> 11:34.200 Exit code and after that. 11:36.170 --> 11:37.130 Port here. 11:37.130 --> 11:40.140 And after that we will call the syscall. 11:40.160 --> 11:41.660 And that's. 11:42.490 --> 11:43.540 Uh, quit. 11:43.750 --> 11:44.500 This is just a quick. 11:44.500 --> 11:45.930 So our program is done. 11:45.940 --> 11:54.550 So this type of programming to your, uh, you can write it in your, um, favorite editor and save 11:54.580 --> 11:56.260 as kicking the ACM. 11:56.260 --> 12:01.090 And now in next lecture, we will create the make file here. 12:01.090 --> 12:03.250 So I'm waiting you in next lecture.