On 12/05/2011 8.21, Sudheer Divakaran wrote: > On Thu, May 12, 2011 at 10:02 AM, Sudheer Divakaran > <inbox1.sudheer@xxxxxxxxx> wrote: >> Hi Vikram, >> >> On Thu, May 12, 2011 at 9:02 AM, Vikram Narayanan<vikram186@xxxxxxxxx> wrote: >>> On Thu, May 12, 2011 at 1:51 AM, Mulyadi Santosa >>> <mulyadi.santosa@xxxxxxxxx> wrote: >>>> On Thu, May 12, 2011 at 03:11, Vikram Narayanan<vikram186@xxxxxxxxx> wrote: >>>>> Yes. I agree. But how who converts the ELF binary to raw binary so >>>>> that the processor understands. Or how is it actually done? >>>> >>>> OK I try my best to understand your question :) >>>> >>>> i think I got it...you probably guessed that vmlinux created first, >>>> then vmlinuz... AFAIK, it's the other way around...or more precisely, >>>> not both. >>> >>> I think you got it wrong. I will try to put my question more elaborately. >>> 1) The system is on and BIOS code runs. It gives the control to the >>> boot loader, say GRUB. >>> 2) Grub picks up the kernel from the specific partition. (i.e a >>> vmlinuz image), which denotes that it is compressed. >>> 3) There are uncompression routines in the kernel itself, If I am not >>> wrong. So the kernel uncompresses itself. >>> 4) Now the uncompressed thing is the vmlinux image, right? >>> 5) The vmlinux is in ELF format. Correct? >>> 6) If the OS boots and if u try to run an ELF file, the loader knows >>> how to load that in the RAM. (I mean it knows how to interpret the ELF >>> format) >>> 7) Coming back to the vmlinux image, Who takes care of the loading activity.? >>> 8) Who recognizes that the image is ELF format and do the necessary >>> things accordingly.? >>> >>> Hope I have my question clear now. >>> >> >> >> >> If understand your question correctly, you believe that the >> uncompressed kernel is in elf format. correct?. it is in binary >> format, so elf interpretation is not required, #5 is wrong. >> >> You can see this by building the kernel using 'make V=1' and note the >> following line in the output, >> >> "arch/x86/boot/tools/build arch/x86/boot/setup.bin >> arch/x86/boot/vmlinux.bin CURRENT> arch/x86/boot/bzImage" >> >> means bzImage is made out of two binary files extracted from the elf images. > > One more info I want to clarify is, vmlinux.bin mentioned in the > above snippet contains the compressed binary image and some other > routines. Just go through the 'make V=1' output, you can see that the > build process is actually compressing binary file extracted from the > vmlinux elf image, which is again combined with some object files, > creates another elf and again extracts the binary and finally combined > with the setup.bin to create the final bzImage. So, elf interpretation > doesn't happen on the uncompressed code. > Let's put some order here. The image that almost all bootloaders use is arch/x86/boot/bzImage which is made of a setup binary file (executable) joined with some compressed code (the real kernel) which is uncompressed in memory by the setup binary. The big suggestion I can give is to check the hidden files which end with .cmd. There is one of these for every object created by the compilation process. For example there is a file called .bzImage.cmd which tell you how bzImage was made: arch/x86/boot/tools/build -b arch/x86/boot/setup.bin arch/x86/boot/vmlinux.bin CURRENT > arch/x86/boot/bzImage NOTE: I refer to a quite old kernel here, it's likely that the compilation process has changed somehow. You can proceed now in reverse order to find how bzImage was made (if I understand correctly that is the one you are interested in). Here is how is made on my kernel tree: bzImage: arch/x86/boot/tools/build -b arch/x86/boot/setup.bin arch/x86/boot/vmlinux.bin CURRENT > arch/x86/boot/bzImage arch/x86/boot/vmlinux.bin: objcopy -O binary -R .note -R .comment -S arch/x86/boot/compressed/vmlinux arch/x86/boot/vmlinux.bin arch/x86/boot/compressed/vmlinux: ld -m elf_i386 -T arch/x86/boot/compressed/vmlinux_32.lds arch/x86/boot/compressed/head_32.o arch/x86/boot/compressed/misc.o arch/x86/boot/compressed/piggy.o -o arch/x86/boot/compressed/vmlinux arch/x86/boot/compressed/piggy.o: ld -m elf_i386 -r --format binary --oformat elf32-i386 -T arch/x86/boot/compressed/vmlinux.scr arch/x86/boot/compressed/vmlinux.bin.gz -o arch/x86/boot/compressed/piggy.o arch/x86/boot/compressed/vmlinux.bin.gz: gzip -f -9 < arch/x86/boot/compressed/vmlinux.bin > arch/x86/boot/compressed/vmlinux.bin.gz arch/x86/boot/compressed/vmlinux.bin: objcopy -O binary -R .note -R .comment -S vmlinux arch/x86/boot/compressed/vmlinux.bin vmlinux: ld -m elf_i386 --build-id -o vmlinux -T arch/x86/kernel/vmlinux.lds arch/x86/kernel/head_32.o arch/x86/kernel/init_task.o init/built-in.o --start-group usr/built-in.o arch/x86/kernel/built-in.o arch/x86/mm/built-in.o arch/x86/mach-default/built-in.o arch/x86/crypto/built-in.o arch/x86/vdso/built-in.o kernel/built-in.o mm/built-in.o fs/built-in.o ipc/built-in.o security/built-in.o crypto/built-in.o block/built-in.o lib/lib.a arch/x86/lib/lib.a lib/built-in.o arch/x86/lib/built-in.o drivers/built-in.o sound/built-in.o arch/x86/math-emu/built-in.o arch/x86/pci/built-in.o arch/x86/power/built-in.o net/built-in.o --end-group .tmp_kallsyms2.o NOTE: there are 2 vmlinux (vmlinux and arch\x86\boot\compressed\vmlinux) and 2 vmlinux.bin (arch\x86\boot\compressed\vmlinux.bin and arch\x86\boot\vmlinux.bin) which are not the same Hope this helps Regards Luca Ellero _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
