On 3/1/23 06:52, Palmer Dabbelt wrote: > On Tue, 28 Feb 2023 05:51:24 PST (-0800), gerg@xxxxxxxxxx wrote: >> The following changes add the ability to run ELF format binaries when >> running RISC-V in nommu mode. That support is actually part of the >> ELF-FDPIC loader, so these changes are all about making that work on >> RISC-V. >> >> The first issue to deal with is making the ELF-FDPIC loader capable of >> handling 64-bit ELF files. As coded right now it only supports 32-bit >> ELF files. >> >> Secondly some changes are required to enable and compile the ELF-FDPIC >> loader on RISC-V and to pass the ELF-FDPIC mapping addresses through to >> user space when execing the new program. >> >> These changes have not been used to run actual ELF-FDPIC binaries. >> It is used to load and run normal ELF - compiled -pie format. Though the >> underlying changes are expected to work with full ELF-FDPIC binaries if >> or when that is supported on RISC-V in gcc. >> >> To avoid needing changes to the C-library (tested with uClibc-ng >> currently) there is a simple runtime dynamic loader (interpreter) >> available to do the final relocations, https://github.com/gregungerer/uldso. >> The nice thing about doing it this way is that the same program >> binary can also be loaded with the usual ELF loader in MMU linux. >> >> The motivation here is to provide an easy to use alternative to the >> flat format binaries normally used for RISC-V nommu based systems. >> >> Signed-off-by: Greg Ungerer <gerg@xxxxxxxxxx> >> --- >> >> arch/riscv/include/asm/elf.h | 11 +++++++++- >> arch/riscv/include/asm/mmu.h | 4 +++ >> arch/riscv/include/uapi/asm/ptrace.h | 5 ++++ >> fs/Kconfig.binfmt | 2 - >> fs/binfmt_elf_fdpic.c | 38 +++++++++++++++++------------------ >> include/linux/elf-fdpic.h | 14 +++++++++++- >> include/uapi/linux/elf-fdpic.h | 15 +++++++++++++ >> 7 files changed, 67 insertions(+), 22 deletions(-) > > Adding Damien, as IIRC he's had some hacked up userspace bits for the > K210. I'm yet to get anything running, but it'd be great if we get this > to a point where I can actually boot test this on QEMU (I'm just doing > builds now). +Niklas Niklas, didn't you add a nommu qemu build for buildroot ? Can't find the config though... > > Given that it's the second week of the merge window and this is a bunch > of new uABI it seems best to hold off until the next cycle. I poked > around and don't see anything wrong, but I'll try and take a more > detailed look after the merge window. Does any riscv compiler support nommu fdpic now ? When doing the work on the k210, there was no support at all, hence the statically linked user binaries used (no shared text for libraries). -- Damien Le Moal Western Digital Research
