.img file not a multiple of 512 bytes

[Paletech35]

I am trying to follow along with the raspberry pi barebones tutorial, and I have compiled the project as described on the wiki to generate the kernel7.img file. However, the raspberry pi imaging tool will not take it as it is not a multiple of 512 bytes, and QEMU will not load it either. The file is 41012 bytes in size and my project is stored on github here under the master branch. I am trying to compile for a raspi 1 and am using the raspi1ap option on qemu. I am a little confused, what part of the code should ensure that the file is the right size? As far as i can tell the linker.ld file should be doing this but I am not sure. Thanks

[nullplan]

Is there no option to these tools to pad the input file accordingly?

Your github repo does not contain build instructions of any sort, so I don't know how you are creating the kernel. But no, the ELF file does not have to be a multiple of 4kB in size. The last thing the linker script does is to pad the BSS section to a 4kB boundary, but BSS is not stored in the file. Perhaps the file was meant to be dumped into binary form before being used? That can be done with

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objcopy -O binary kernel7.elf kernel7.bin

Many kernels use this trick, in embedded development and elsewhere. I personally dislike it, but there are cases where it is needed. Such as when running without a loader capable of loading an ELF file.

[Paletech35]

Ah sorry, it is kernel7.img, not kernel7.elf. The elf file was generated earlier in the process. I have fixed the title and post to reflect this. I compiled the kernel exactly using the process described in the barebones tutorial, using a cross compiler with arm-none-eabi as the target. I followed the instructions as closely as possible, is there anything else I might have missed?

[linuxyne]

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$ qemu-system-arm -M raspi1ap -kernel myos.elf -serial stdio
Hello, kernel World!

From the barebones:

With QEMU you do not need to objcopy the kernel into a plain binary; QEMU also supports ELF kernels:

$YOURINSTALLLOCATION/bin/qemu-system-arm -m 256 -M raspi2 -serial stdio -kernel kernel.elf

[iansjack]

You are copying the kernel to a prepared bootable SD card (rather than trying to copy it as an SD image), aren't you?