WEBVTT 00:00.440 --> 00:05.330 Hello, my name is Stephan, and in this lecture we will embark on a journey into the realm of assembly 00:05.330 --> 00:11.270 programming, and our focus will be on understanding conditional jumps and branching. 00:11.330 --> 00:12.530 Crucial concepts. 00:13.530 --> 00:15.060 Low level programming. 00:15.060 --> 00:21.870 And to illustrate this and we will dissect the code that called the jumped ASM. 00:21.900 --> 00:27.690 Actually, we also develop it and I will explain this code line by line. 00:27.720 --> 00:31.650 So here, let's open our CSM project. 00:32.040 --> 00:35.010 The project here. 00:35.620 --> 00:37.780 Uh, we will start from zero. 00:38.130 --> 00:42.580 Uh, let's go to assembler here, create a new file. 00:42.580 --> 00:45.370 Let's jump here. 00:46.220 --> 00:47.420 And save it. 00:49.850 --> 00:52.220 Jump jumping, that is. 00:54.310 --> 01:01.210 And here, let's actually, uh, we will jump jumping that Assam at the comment here. 01:01.240 --> 01:03.270 Jumping at Assam. 01:03.400 --> 01:06.490 Exploring conditional jumps. 01:06.670 --> 01:08.620 Conditional jumps. 01:09.160 --> 01:13.330 And here we will create the extern printf. 01:13.420 --> 01:17.560 This is for declaring the external function. 01:17.650 --> 01:23.680 Uh, declare the external function printf. 01:24.250 --> 01:29.260 And here we will create a section data here with tabs. 01:29.260 --> 01:41.230 Here we will create a number one peak here 42 because this we are here defining a variable number one 01:41.980 --> 01:45.130 with the value of 42. 01:46.840 --> 01:47.380 42. 01:47.380 --> 01:50.110 And here we will also declare. 01:50.410 --> 01:52.620 Define a variable. 01:52.630 --> 01:59.170 Number two with the value of 41 here. 01:59.720 --> 02:03.230 So defining a variable. 02:03.230 --> 02:08.600 Number two with the path, the value. 02:10.020 --> 02:11.340 Value of. 02:12.340 --> 02:14.140 With the value of 41. 02:15.720 --> 02:22.200 And also we'll create the format string for comparison result one. 02:22.200 --> 02:28.560 And we will also write our code for format string for comparison result two here. 02:28.560 --> 02:29.460 So fmt. 02:30.930 --> 02:36.270 If empty one DB here a number. 02:38.850 --> 02:39.750 Number. 02:39.930 --> 02:43.560 Number one here and. 02:47.130 --> 02:48.210 Number two. 02:50.050 --> 03:00.550 So this will recreate your code like this because it's actually prints like equal or greater and equal, 03:00.580 --> 03:02.230 but it actually shows like this. 03:02.230 --> 03:05.470 So this is easier and more understandable to view here. 03:05.470 --> 03:09.580 But if we make this here and as you can see here, these are the separate characters. 03:09.760 --> 03:19.500 This shows this together, uh, to one as of one symbol shows that this is the operand, right? 03:19.510 --> 03:25.600 So logic, operand, operand and here ten and zero. 03:25.630 --> 03:26.920 So here we are. 03:26.920 --> 03:28.990 Format, string. 03:33.050 --> 03:36.230 Format string for comparison. 03:38.060 --> 03:40.580 The result one. 03:40.580 --> 03:43.940 And also we will create the form of two Again. 03:43.950 --> 03:51.410 DB here number one is less than number, one less. 03:53.070 --> 03:55.740 And, uh, number two. 03:55.740 --> 03:56.700 Number two. 03:56.730 --> 03:58.470 Here again, we. 04:02.920 --> 04:04.900 This is for formatting. 04:05.110 --> 04:06.940 Format String. 04:07.690 --> 04:09.610 For comparison. 04:09.610 --> 04:10.930 Result two. 04:11.350 --> 04:16.300 And here we start with the basics. 04:16.450 --> 04:23.500 We are declaring the printf function that will help us display messages later. 04:23.500 --> 04:27.100 And in this data section we define two variables. 04:27.400 --> 04:32.200 Number one and number two which and format strings. 04:32.210 --> 04:34.570 Also Fmt one. 04:34.960 --> 04:40.590 Fmt two to prepare for our output messages. 04:40.600 --> 04:49.750 And here we will also create the section text right now, section text Global Main. 04:49.750 --> 04:57.760 We are declaring this for the global entry point of the program main here and that's it. 04:57.760 --> 05:02.710 So now we will pass the beep here and after that. 05:05.700 --> 05:07.470 It will save this. 05:12.380 --> 05:14.180 Leaving the base pointer. 05:16.120 --> 05:18.400 Maybe the base pointer here. 05:18.550 --> 05:19.270 Move. 05:21.530 --> 05:21.810 Khabib. 05:21.890 --> 05:23.190 Actually, let's do this. 05:32.520 --> 05:33.160 RB. 05:39.290 --> 05:41.060 And also RSP. 05:41.720 --> 05:43.310 Now with this. 05:47.280 --> 05:48.750 We are set. 05:49.020 --> 05:52.220 Set up the base pointer. 05:53.100 --> 06:01.320 And here, moving on this text section, we declare the global main function, which marks the entry 06:01.320 --> 06:03.780 point of our program. 06:04.050 --> 06:08.160 And we are also setting up the stack frame with the path. 06:09.710 --> 06:09.920 Uh. 06:11.190 --> 06:20.650 And move rwp rsp instructions ensuring that we have a proper execution environment. 06:20.670 --> 06:23.530 And now let's proceed with this. 06:23.580 --> 06:26.670 Here we will move the racks. 06:27.120 --> 06:27.870 Move. 06:29.700 --> 06:31.730 Tracks here. 06:31.830 --> 06:40.260 The number one here we are loading the value of number one into the register racks. 06:41.310 --> 06:44.460 But the value of. 06:45.540 --> 06:54.150 Of number one into register racks and move rb x rb x. 06:54.990 --> 06:57.510 We will write number two. 06:57.720 --> 07:06.030 Here we are loading the load, the value of number two into a register. 07:06.920 --> 07:08.770 RBCs again. 07:09.320 --> 07:18.520 And here we start loading by values of number one and number two into registers. 07:18.530 --> 07:22.520 The the racks here now holds value of. 07:23.650 --> 07:29.660 42, and RBCs contains the value of 41. 07:29.680 --> 07:30.100 Right. 07:30.100 --> 07:32.590 So these registers are. 07:33.280 --> 07:35.770 Where we will perform comparisons. 07:36.100 --> 07:40.960 Now here we will compare the values in Rax and. 07:42.190 --> 07:45.460 In order to do that, we will use this instruction. 07:45.670 --> 07:46.450 So. 07:47.370 --> 07:49.910 Racks and RBCs. 07:50.100 --> 07:52.560 And after that, here. 07:55.480 --> 08:02.650 ING cmp for comparing the values in RACs and RBC's. 08:02.650 --> 08:05.080 And here we will use the. 08:08.510 --> 08:09.440 He here? 08:10.430 --> 08:11.810 As greater. 08:14.050 --> 08:15.460 Now with this. 08:15.460 --> 08:17.200 Here we are. 08:17.740 --> 08:18.850 Uh, jump. 08:19.380 --> 08:29.360 To greater if Rax is greater than or equal to rb x. 08:30.130 --> 08:32.410 Um, and next we use this. 08:32.410 --> 08:36.100 Um, here again, I will explain this again from zero. 08:36.280 --> 08:44.830 So this we are using this CPAp instruction to compare the values in racks and as I explained here. 08:44.830 --> 08:50.860 So the interesting part is here this instruction. 08:50.860 --> 08:58.720 So if racks is greater than or equal to RB x, we jump to a greater label. 08:58.720 --> 09:03.790 Otherwise we continue with the next instruction here. 09:04.710 --> 09:05.540 The chairs. 09:05.580 --> 09:09.210 We will load the format string for the second message. 09:09.210 --> 09:10.290 So move. 09:13.510 --> 09:16.000 Audi Fm2. 09:18.120 --> 09:22.050 This is for loading the format string. 09:23.640 --> 09:28.890 Praying for for the second message move. 09:31.740 --> 09:32.220 Zero. 09:34.430 --> 09:34.790 Zero. 09:34.790 --> 09:35.720 This is. 09:36.970 --> 09:40.270 This is for clearing racks here. 09:40.450 --> 09:45.010 No xmm registers in. 09:46.090 --> 09:48.310 All here. 09:49.420 --> 09:51.760 And we will call the print. 09:53.840 --> 09:54.470 Grand theft. 09:59.210 --> 10:01.560 This is this calls the printf. 10:05.480 --> 10:06.800 Number one. 10:07.070 --> 10:08.420 Number one. 10:08.720 --> 10:11.720 Less than number two. 10:12.690 --> 10:13.980 And GMP. 10:16.280 --> 10:18.170 BMP exit. 10:18.410 --> 10:21.350 So here this jump. 10:22.220 --> 10:24.220 To the table. 10:24.300 --> 10:30.020 So if the comparison condition didn't met here. 10:30.700 --> 10:32.260 Uh, wasn't or wasn't mad. 10:32.310 --> 10:42.160 Uh, we moved here, so we load the format, string Fmt into the RDA register and we clear rax since 10:42.190 --> 10:46.300 no error mem registers are involved here. 10:47.260 --> 10:50.140 Um or XMM registers involved here. 10:50.140 --> 10:55.060 And we then call the printf function to display the number. 10:55.090 --> 10:58.450 One is less than number two. 10:59.110 --> 11:09.400 Following that, we perform unconditional jump to the x label here and now we will use this greeter 11:09.400 --> 11:10.390 function here. 11:15.010 --> 11:16.370 And that's it. 11:16.390 --> 11:17.350 Move. 11:18.590 --> 11:21.720 R the i fmt one. 11:21.740 --> 11:22.780 Here we are. 11:22.790 --> 11:26.510 Load loading the format string. 11:27.620 --> 11:30.040 Spring for the first. 11:31.060 --> 11:34.780 Message and again, move racks. 11:35.590 --> 11:36.220 Zero. 11:36.550 --> 11:39.880 And here we are clearing clear the Or. 11:40.000 --> 11:40.230 Yeah. 11:40.240 --> 11:43.900 Clear the racks again and we will. 11:43.900 --> 11:44.560 We are. 11:44.590 --> 11:47.040 We will call the print. 11:47.050 --> 11:47.590 Print. 11:55.860 --> 11:56.600 Here we are. 11:56.610 --> 12:00.360 Call call printf to display. 12:00.930 --> 12:07.530 Display number one, greater than or equal to number two. 12:08.820 --> 12:12.930 So if the comparison condition didn't met we. 12:13.790 --> 12:23.270 When the racks greater than or equal to are accident meant we arrive at the greater label. 12:24.040 --> 12:31.510 Here we load the format string Fmt one into RDA register and clear Rax once more. 12:31.510 --> 12:39.940 So we then call the print function to display the message number one now greater than or equal to number 12:39.940 --> 12:40.540 two. 12:40.630 --> 12:43.510 And after that we will also. 12:44.990 --> 12:47.750 Create the exit label. 12:50.360 --> 12:51.590 Exit label. 12:51.680 --> 12:54.890 So here we will actually down here. 12:54.890 --> 12:56.840 So here we will move. 12:58.750 --> 12:59.380 RSP. 13:00.520 --> 13:01.990 RVP here. 13:02.170 --> 13:07.990 RVP Here we are restoring the stack pointer. 13:12.310 --> 13:15.280 Uh, pop up here. 13:15.370 --> 13:16.180 Here we are. 13:16.180 --> 13:20.530 Restore restoring the bass pointer again. 13:21.680 --> 13:22.580 Pointer. 13:22.790 --> 13:28.040 And we are now we're going to return from the main function. 13:28.890 --> 13:29.670 And. 13:30.600 --> 13:33.740 Brett here and we will not add anything here. 13:33.750 --> 13:35.580 Just go to command. 13:36.000 --> 13:38.910 Write that return from the. 13:40.430 --> 13:41.930 A main function. 13:41.930 --> 13:45.350 And finally, we reach the exit label. 13:46.160 --> 13:49.280 This is where we wrap up our program. 13:49.370 --> 13:56.180 We restore the stack pointer, RSP and base pointer rb. 13:56.480 --> 13:57.290 Oops, sorry. 13:57.290 --> 14:01.610 Not RB rb here to their original values. 14:01.610 --> 14:10.610 So we then use the pop rb p instruction to clean up the stack frame and read instruction. 14:11.120 --> 14:19.850 The read instruction gracefully exits the main function and in conclusion, our journey through does 14:19.850 --> 14:25.340 jumping that ACM has unveiled the mechanisms of conditional jumps and branching. 14:25.370 --> 14:32.150 So we have explored how assembly code can make decisions based on conditions influencing program flow. 14:33.070 --> 14:40.690 And these fundamental concepts lay the foundation for understanding more complex programming challenges 14:40.840 --> 14:43.100 and optimizing the code. 14:43.120 --> 14:49.720 So now when we click on this here, and as you can see here, we will get an error. 14:50.650 --> 15:01.570 You are getting this error because instruction we wrote the 64 bit assembly code, but here as default, 15:01.570 --> 15:06.970 the CSM comes with the 32 bit instruction. 15:07.880 --> 15:08.840 Or selected. 15:08.840 --> 15:13.370 And in order to fix that, we will go to settings here. 15:14.040 --> 15:14.550 Um. 15:15.520 --> 15:18.730 World here from settings world and here. 15:18.730 --> 15:22.090 As you can see, we have mode here click on 64. 15:22.970 --> 15:28.520 And assembler click on NSM because NSM best for this purposes. 15:28.730 --> 15:38.030 And as you can see here, when we click on 32 bit x86, we are getting this M 32 here. 15:38.030 --> 15:43.100 But when we click on 64 bit, as you can see it, it also changes here. 15:44.060 --> 15:52.210 It also changed l 32 two from 32 to x l 64. 15:52.220 --> 15:54.890 So now apply this here. 15:56.200 --> 15:57.220 And click okay. 15:57.250 --> 15:58.720 Now let's run our program again. 15:58.720 --> 16:04.120 And as you can see here, we'll start it and build successfully. 16:04.120 --> 16:12.820 And our output is number one, is greater than or equal to number two. 16:12.820 --> 16:14.200 And the program finished. 16:14.230 --> 16:17.710 Normally, execution time is 0.001. 16:17.710 --> 16:26.680 So we can also go to our folder where we compile this assembly here, the CD jump. 16:27.900 --> 16:28.380 LZ. 16:28.380 --> 16:30.300 And as you can see here, we have jumping. 16:30.960 --> 16:35.040 We can also create a separate Makefile and just compile it. 16:35.070 --> 16:37.110 But in this case we will not do that. 16:37.230 --> 16:42.420 And as you can see here, our code is works and when we. 16:44.040 --> 16:47.940 Here on test the program executing program finished. 16:47.970 --> 16:52.320 Normally the execution time is 0.0001. 16:53.250 --> 16:55.110 And this is our output. 16:55.110 --> 17:03.060 So remember, mastering this building blocks will empower you to delve deeper into the intricacies, 17:03.060 --> 17:11.540 intricacies, world of assembly programming and keep practicing, experimenting and pushing your boundaries. 17:11.550 --> 17:19.410 So the journey has just begun in this lecture here, and thank you for joining me in this enlightening 17:19.410 --> 17:20.460 exploration. 17:20.460 --> 17:28.530 Until next time, keep coding and keep expanding your programming, programming skills and happy learning 17:28.560 --> 17:30.180 awaiting you in next lecture.