![]() We’ll write one that simply writes “Hello” to the screen, then hangs. We can now write a first version of our second-stage boot loader, just to prove that our concept works. In order to build your code, you can now do: $ mingw32-makeĪnd to clean everything up except the source code, do: $ mingw32-make clean The second-stage boot loader In short, makefiles allow you to describe dependencies. If any of these files change, then boot.o must be recompiled. These instructions tells make that the boot.o object file depends on the files boot.s, bootsector.s, functions.s and macros.s. Note, for instance, the lines: boot.o : boot.s bootsector.s functions.s macros.s $(AS) -o boot.o boot.s text 2ndstage.out 2ndstage.bin 2ndstage.out : 2ndstage.o $(LD) -o 2ndstage.out 2ndstage.o -Ttext 0x0 2ndstage.o : 2ndstage.s bootsector.s functions.s macros.s $(AS) -o 2ndstage.o 2ndstage.s clean : del *.o del *.out del *.bin text boot.out boot.bin boot.out : boot.o $(LD) -o boot.out boot.o -Ttext 0x7c00 boot.o : boot.s bootsector.s functions.s macros.s $(AS) -o boot.o boot.s 2ndstage.bin : 2ndstage.out objcopy -O binary -j. Here is a makefile for our boot loader code: AS := asĪll : boot.bin 2ndstage.bin boot.bin : boot.out objcopy -O binary -j. GNU make determines automatically which files have changed, and compiles only those files. And worst of all, you’ll always compile everything, including files that haven’t changed, which might get slow if you have a lot of code. Also, you have no way of cleaning up intermediary files. You’ll write many batchfiles with similar instructions. Bochs cmos image file code#Imagine your code growing, so that you have many subdirectories with many files that need to be compiled. Better yet, the GNU toolchain comes with a solution: makefiles. Instead of typing all this at the command prompt each time you test, you’d be better off placing the instructions in a batch file. $ ld -o 2ndstage.out 2ndstage.o -Ttext 0x0 In order to compile our five files, and turn them into a disk image we can test with Bochs, we need quite a few instructions: $ as -o boot.o boot.s Since we now have to compile each file separately, we’ll tie the build process together with a makefile.
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