damien-lemoal/buildroot

buildroot fork

buildroot's Issues

Elf2flt relocation problem on newer kernels

Hi, I'm recently tweaking kernels and toolchains for 32-bit RISC-V No-MMU systems, I faced the same problem and I guess I came up with some solutions. So far I only tried 32-bit, but I guess they can apply to 64-bit as well.

On 5.9.4 kernel, seems relocation is done to wrong addresses during load_flat_file in fs/binfmt_flat.c, this is quite stubborn, after modifying datapos by 0x20 like this:

		datapos = ALIGN(realdatastart +
				MAX_SHARED_LIBS * sizeof(u32),
				FLAT_DATA_ALIGN) - 0x20; 

meanwhile change elf2flt.ld script like this on line 50:

	. = . + 4; /* add this */
	. = ALIGN(0x20) ;
	_etext = . ;

Then busybox can run without noticeable problem. I keep kernel executable file formats configuration like this, with unrelated stuff all disabled:

[*] Kernel support for scripts starting with #!     
[*] Kernel support for flat binaries                
[ ] Enable support for very old legacy flat binaries
[ ] Enable ZFLAT support                            
[ ] Enable shared FLAT support                      
[ ] Kernel support for MISC binaries                
[ ] Enable core dump support                                                                         

On latest(5.17) kernel, seems other changes have taken place, and busybox can run without any modification in kernel source or the linker script, so using latest kernel for this project seems a good choice(if 64-bit can also work). If you are interested in 32-bit support(I verified on both QEMU and custom FPGA rv32ima softcore), I'll clean my modified code up and PR.

Which defconfig should I use for k210?

I'd like to build nommu linux for maixduino. Which defconfig should I use?