On Thu, Jul 30, 2020 at 4:04 AM Heinrich Schuchardt <xypron.g...@gmx.de> wrote: > > On 30.07.20 12:16, Sean Anderson wrote: > > On 7/30/20 6:03 AM, Heinrich Schuchardt wrote: > >> Dear Sean, > >> > >> when trying to run grubriscv64.efi from the > >> trini/u-boot-gitlab-ci-runner:bionic-20200526-18Jun2020 Docker image on > >> a MAIXDUINO the relocations are not naturally aligned: > >> > >> lib/efi_loader/efi_image_loader.c(133) efi_loader_relocate(): > >> > >> efi_reloc 000000008030a000, offset 0x101e, type 10 > >> > >> Here we are trying to change an u64 at 0x8030B01E: > >> > >> uint64_t *x64 = efi_reloc + offset; > >> *x64 += (uint64_t)delta; > >> > >> This leads to an exception in function efi_loader_relocate(): > >> > >> Unhandled exception: Load address misaligned > >> EPC: 00000000805a95ac RA: 00000000805a953a TVAL: 000000008030b01e > >> EPC: 000000008001c5ac RA: 000000008001c53a reloc > >> > >> The GRUB image is available here: > >> > >> https://gist.github.com/xypron/522a91962248e9c3888d8554cb61ad2c/raw/b959661626b38a738673a9efb2f398b2fabd5c77/grubriscv64.efi > >> > >> On QEMU the GRUB image is executed without problems: > >> > >> https://gitlab.denx.de/u-boot/custodians/u-boot-efi/-/jobs/132919 > >> > >> The UEFI specification requires for the ARM platform that unaligned > >> support is enabled. This is why we have implemented function > >> allow_unaligned(). > >> > >> On RISC-V we have not yet implemented allow_unaligned() yet. Is there a > >> way to switch RISCV64 CPUs especially the Kendryte K210 into a mode > >> supporting unaligned access? > > > > AFAIK RISC-V has no requirement that un-aligned loads/stores complete. I > > believe the recommended solution is to install a trap handler which > > completes the un-aligned load through a series of aligned loads and then > > returns back to the application. For an example of such an > > implementation, check out arch/riscv/kernel/traps_misaligned.c in Linux. > > This may be too complex for U-Boot, so perhaps you can simply disallow > > unaligned accesses? > > > > --Sean > > > > Working around the problem inside U-Boot is easy (just some memcpy() > calls) but the GRUB image itself also makes unaligned accesses: > > Unhandled exception: Load address misaligned > EPC: 000000008030b004 RA: 00000000805a4eca TVAL: 000000008030b02e > EPC: 000000007fd7e004 RA: 0000000080017eca reloc > > UEFI image [0x000000008030a000:0x0000000080433fff] pc=0x1004 > > This is what I found in "RISC-V Unprivileged ISA V20191213" > > "Loads and stores where the effective address is not naturally > aligned to the referenced datatype (i.e., on a four-byte boundary for > 32-bit accesses, and a two-byte boundary for 16-bit accesses) have > behavior dependent on the EEI. An EEI may guarantee that misaligned > loads and stores are fully supported, and so the software running inside > the execution environment will never experience a contained or fatal > address-misaligned trap." > > @Leif > Should GRUB be built with -mstrict-align for RISC-V? >
That shouldn't be necessary. Any real board with an MMU that can boot Linux needs a SBI provider such as OpenSBI. OpenSBI already implements a misaligned handler. Are we planning to support EFI booting for NoMMU platforms ? As per my understanding runtime services need to be mapped through kernel page tables. > @Ard > How about the EFI part of the Linux kernel? > > Best regards > > Heinrich -- Regards, Atish _______________________________________________ Grub-devel mailing list Grub-devel@gnu.org https://lists.gnu.org/mailman/listinfo/grub-devel
