Hi, I'm using Yocto with the gatesgarth branches of poky and meta-xilinx to build a kernel image for a custom MicroBlaze design. This results in kernel images that silently fail to boot.
After many hours of failed attempts, I found a blog post[*] that uses buildroot for a similar setup and out of despair, I tried that. I used the latest release of buildroot (2021.02) and selected gcc 10.2.0 to match the version that is currently used in Yocto. Much to my surprise, this resulted in a toolchain that is able to build bootable kernel images. Which proofs that the FPGA design and the rest of the setup is fine. So I have two toolchains now, and I'm trying to understand what causes the difference in behavior. Funny enough, buildroot doesn't apply any patches to binutils or gcc that seem relevant for MicroBlaze, so for testing, I disabled all patches for those components on the Yocto side as well, but that didn't help either. I've also played with different TUNE_FEATURES, but AFAIU, in case of the kernel these flags are set by the kernel build system directly anyway, and hence they are the same for both toolchains. Setting BUILD_OPTIMIZATION="-Os" (which is the default in buildroot) doesn't change anything, neither does building buildroot with -O2. A recursive diff of the trees produced by the two toolchains show the following files are different, while all other binary object files are identical: ./arch/microblaze/lib/memset.o ./block/elevator.o ./fs/dcache.o ./fs/buffer.o ./fs/io_uring.o ./init/main.o ./init/version.o ./kernel/irq/irqdomain.o ./kernel/user.o ./kernel/workqueue.o ./kernel/configs.o ./lib/vsprintf.o ./lib/rhashtable.o ./mm/mincore.o ./vmlinux.o I would certainly appreciate any pointer on where to continue digging, as I need to have this working in Yocto. What MicroBlaze designs have successfully booted with meta-xilinx/gatesgarth at this point? Best regards, Daniel [*] https://numato.com/kb/saturn-microblaze-and-linux-how-run-linux-saturn-spartan-6-fpga-module-part-ii/
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