kernel/linux.git/Documentation/riscv, branch v5.15.208

riscv: Move early dtb mapping into the fixmap region

2023-04-30T23:23:24+00:00

commit ef69d2559fe91f23d27a3d6fd640b5641787d22e upstream. riscv establishes 2 virtual mappings: - early_pg_dir maps the kernel which allows to discover the system memory - swapper_pg_dir installs the final mapping (linear mapping included) We used to map the dtb in early_pg_dir using DTB_EARLY_BASE_VA, and this mapping was not carried over in swapper_pg_dir. It happens that early_init_fdt_scan_reserved_mem() must be called before swapper_pg_dir is setup otherwise we could allocate reserved memory defined in the dtb. And this function initializes reserved_mem variable with addresses that lie in the early_pg_dir dtb mapping: when those addresses are reused with swapper_pg_dir, this mapping does not exist and then we trap. The previous "fix" was incorrect as early_init_fdt_scan_reserved_mem() must be called before swapper_pg_dir is set up otherwise we could allocate in reserved memory defined in the dtb. So move the dtb mapping in the fixmap region which is established in early_pg_dir and handed over to swapper_pg_dir. This patch had to be backported because: - the documentation for sv57 is not present here (as sv48/57 are not present) - handling of sv48/57 is not needed (as not present) Fixes: 922b0375fc93 ("riscv: Fix memblock reservation for device tree blob") Fixes: 8f3a2b4a96dc ("RISC-V: Move DT mapping outof fixmap") Fixes: 50e63dd8ed92 ("riscv: fix reserved memory setup") Reported-by: Conor Dooley Link: https://lore.kernel.org/all/f8e67f82-103d-156c-deb0-d6d6e2756f5e@microchip.com/ Signed-off-by: Alexandre Ghiti Reviewed-by: Conor Dooley Tested-by: Conor Dooley Link: https://lore.kernel.org/r/20230329081932.79831-2-alexghiti@rivosinc.com Cc: stable@vger.kernel.org # 5.15.x Signed-off-by: Palmer Dabbelt Signed-off-by: Greg Kroah-Hartman

riscv: Ensure BPF_JIT_REGION_START aligned with PMD size

2021-06-19T04:10:05+00:00

Andreas reported commit fc8504765ec5 ("riscv: bpf: Avoid breaking W^X") breaks booting with one kind of defconfig, I reproduced a kernel panic with the defconfig: [ 0.138553] Unable to handle kernel paging request at virtual address ffffffff81201220 [ 0.139159] Oops [#1] [ 0.139303] Modules linked in: [ 0.139601] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.13.0-rc5-default+ #1 [ 0.139934] Hardware name: riscv-virtio,qemu (DT) [ 0.140193] epc : __memset+0xc4/0xfc [ 0.140416] ra : skb_flow_dissector_init+0x1e/0x82 [ 0.140609] epc : ffffffff8029806c ra : ffffffff8033be78 sp : ffffffe001647da0 [ 0.140878] gp : ffffffff81134b08 tp : ffffffe001654380 t0 : ffffffff81201158 [ 0.141156] t1 : 0000000000000002 t2 : 0000000000000154 s0 : ffffffe001647dd0 [ 0.141424] s1 : ffffffff80a43250 a0 : ffffffff81201220 a1 : 0000000000000000 [ 0.141654] a2 : 000000000000003c a3 : ffffffff81201258 a4 : 0000000000000064 [ 0.141893] a5 : ffffffff8029806c a6 : 0000000000000040 a7 : ffffffffffffffff [ 0.142126] s2 : ffffffff81201220 s3 : 0000000000000009 s4 : ffffffff81135088 [ 0.142353] s5 : ffffffff81135038 s6 : ffffffff8080ce80 s7 : ffffffff80800438 [ 0.142584] s8 : ffffffff80bc6578 s9 : 0000000000000008 s10: ffffffff806000ac [ 0.142810] s11: 0000000000000000 t3 : fffffffffffffffc t4 : 0000000000000000 [ 0.143042] t5 : 0000000000000155 t6 : 00000000000003ff [ 0.143220] status: 0000000000000120 badaddr: ffffffff81201220 cause: 000000000000000f [ 0.143560] [] __memset+0xc4/0xfc [ 0.143859] [] init_default_flow_dissectors+0x22/0x60 [ 0.144092] [] do_one_initcall+0x3e/0x168 [ 0.144278] [] kernel_init_freeable+0x1c8/0x224 [ 0.144479] [] kernel_init+0x12/0x110 [ 0.144658] [] ret_from_exception+0x0/0xc [ 0.145124] ---[ end trace f1e9643daa46d591 ]--- After some investigation, I think I found the root cause: commit 2bfc6cd81bd ("move kernel mapping outside of linear mapping") moves BPF JIT region after the kernel: | #define BPF_JIT_REGION_START PFN_ALIGN((unsigned long)&_end) The &_end is unlikely aligned with PMD size, so the front bpf jit region sits with part of kernel .data section in one PMD size mapping. But kernel is mapped in PMD SIZE, when bpf_jit_binary_lock_ro() is called to make the first bpf jit prog ROX, we will make part of kernel .data section RO too, so when we write to, for example memset the .data section, MMU will trigger a store page fault. To fix the issue, we need to ensure the BPF JIT region is PMD size aligned. This patch acchieve this goal by restoring the BPF JIT region to original position, I.E the 128MB before kernel .text section. The modification to kasan_init.c is inspired by Alexandre. Fixes: fc8504765ec5 ("riscv: bpf: Avoid breaking W^X") Reported-by: Andreas Schwab Signed-off-by: Jisheng Zhang Signed-off-by: Palmer Dabbelt

Documentation: riscv: Add documentation that describes the VM layout

2021-04-26T15:25:05+00:00

This new document presents the RISC-V virtual memory layout and is based one the x86 one: it describes the different limits of the different regions of the virtual address space. Signed-off-by: Alexandre Ghiti Signed-off-by: Palmer Dabbelt

docs: archis: add a per-architecture features list

2020-12-03T22:10:15+00:00

Add a feature list matrix for each architecture to their respective Kernel books. Signed-off-by: Mauro Carvalho Chehab Link: https://lore.kernel.org/r/9c39d4dd93e05c0008205527d2c3450912f029ed.1606748711.git.mchehab+huawei@kernel.org Signed-off-by: Jonathan Corbet

Merge tag 'docs-5.6' of git://git.lwn.net/linux

2020-01-29T23:27:31+00:00

Pull documentation updates from Jonathan Corbet: "It has been a relatively quiet cycle for documentation, but there's still a couple of things of note: - Conversion of the NFS documentation to RST - A new document on how to help with documentation (and a maintainer profile entry too) Plus the usual collection of typo fixes, etc" * tag 'docs-5.6' of git://git.lwn.net/linux: (40 commits) docs: filesystems: add overlayfs to index.rst docs: usb: remove some broken references scripts/find-unused-docs: Fix massive false positives docs: nvdimm: use ReST notation for subsection zram: correct documentation about sysfs node of huge page writeback Documentation: zram: various fixes in zram.rst Add a maintainer entry profile for documentation Add a document on how to contribute to the documentation docs: Keep up with the location of NoUri Documentation: Call out example SYM_FUNC_* usage as x86-specific Documentation: nfs: fault_injection: convert to ReST Documentation: nfs: pnfs-scsi-server: convert to ReST Documentation: nfs: convert pnfs-block-server to ReST Documentation: nfs: idmapper: convert to ReST Documentation: convert nfsd-admin-interfaces to ReST Documentation: nfs-rdma: convert to ReST Documentation: nfsroot.rst: COSMETIC: refill a paragraph Documentation: nfsroot.txt: convert to ReST Documentation: convert nfs.txt to ReST Documentation: filesystems: convert vfat.txt to RST ...

Documentation: riscv: add patch acceptance guidelines

2020-01-05T05:49:01+00:00

Formalize, in kernel documentation, the patch acceptance policy for arch/riscv. In summary, it states that as maintainers, we plan to only accept patches for new modules or extensions that have been frozen or ratified by the RISC-V Foundation. We've been following these guidelines for the past few months. In the meantime, we've received quite a bit of feedback that it would be helpful to have these guidelines formally documented. Based on a suggestion from Matthew Wilcox, we also add a link to this file to Documentation/process/index.rst, to make this document easier to find. The format of this document has also been changed to align to the format outlined in the maintainer entry profiles, in accordance with comments from Jon Corbet and Dan Williams. Signed-off-by: Paul Walmsley Reviewed-by: Palmer Dabbelt Cc: Palmer Dabbelt Cc: Albert Ou Cc: Krste Asanovic Cc: Andrew Waterman Cc: Matthew Wilcox Cc: Dan Williams Cc: Jonathan Corbet

RISC-V: Typo fixes in image header and documentation.

2019-12-19T16:32:45+00:00

There are some typos in boot image header and riscv boot documentation. Fix the typos. Signed-off-by: Atish Patra Reviewed-by: Palmer Dabbelt Link: https://lore.kernel.org/r/20191009010637.9955-1-atish.patra@wdc.com Signed-off-by: Jonathan Corbet

riscv-docs: correct the sequence of the magic number 2 since it's little endian

2019-10-03T16:51:42+00:00

Correct the sequence of the magic number 2 since it's little endian. Signed-off-by: Chester Lin Reviewed-by: Paul Walmsley Signed-off-by: Jonathan Corbet

Merge tag 'docs-5.4' of git://git.lwn.net/linux

2019-09-17T23:22:26+00:00

Pull documentation updates from Jonathan Corbet: "It's a somewhat calmer cycle for docs this time, as the churn of the mass RST conversion is happily mostly behind us. - A new document on reproducible builds. - We finally got around to zapping the documentation for hardware support that was removed in 2004; one doesn't want to rush these things. - The usual assortment of fixes, typo corrections, etc" * tag 'docs-5.4' of git://git.lwn.net/linux: (67 commits) Documentation: kbuild: Add document about reproducible builds docs: printk-formats: Stop encouraging use of unnecessary %h[xudi] and %hh[xudi] Documentation: Add "earlycon=sbi" to the admin guide doc:lock: remove reference to clever use of read-write lock devices.txt: improve entry for comedi (char major 98) docs: mtd: Update spi nor reference driver doc: arm64: fix grammar dtb placed in no attributes region Documentation: sysrq: don't recommend 'S' 'U' before 'B' mailmap: Update email address for Quentin Perret docs: ftrace: clarify when tracing is disabled by the trace file docs: process: fix broken link Documentation/arm/samsung-s3c24xx: Remove stray U+FEFF character to fix title Documentation/arm/sa1100/assabet: Fix 'make assabet_defconfig' command Documentation/arm/sa1100: Remove some obsolete documentation docs/zh_CN: update Chinese howto.rst for latexdocs making Documentation: virt: Fix broken reference to virt tree's index docs: Fix typo on pull requests guide kernel-doc: Allow anonymous enum Documentation: sphinx: Don't parse socket() as identifier reference Documentation: sphinx: Add missing comma to list of strings ...

riscv: modify the Image header to improve compatibility with the ARM64 header

2019-09-14T02:03:52+00:00

Part of the intention during the definition of the RISC-V kernel image header was to lay the groundwork for a future merge with the ARM64 image header. One error during my original review was not noticing that the RISC-V header's "magic" field was at a different size and position than the ARM64's "magic" field. If the existing ARM64 Image header parsing code were to attempt to parse an existing RISC-V kernel image header format, it would see a magic number 0. This is undesirable, since it's our intention to align as closely as possible with the ARM64 header format. Another problem was that the original "res3" field was not being initialized correctly to zero. Address these issues by creating a 32-bit "magic2" field in the RISC-V header which matches the ARM64 "magic" field. RISC-V binaries will store "RSC\x05" in this field. The intention is that the use of the existing 64-bit "magic" field in the RISC-V header will be deprecated over time. Increment the minor version number of the file format to indicate this change, and update the documentation accordingly. Fix the assembler directives in head.S to ensure that reserved fields are properly zero-initialized. Signed-off-by: Paul Walmsley Reported-by: Palmer Dabbelt Reviewed-by: Palmer Dabbelt Cc: Atish Patra Cc: Karsten Merker Link: https://lore.kernel.org/linux-riscv/194c2f10c9806720623430dbf0cc59a965e50448.camel@wdc.com/T/#u Link: https://lore.kernel.org/linux-riscv/mhng-755b14c4-8f35-4079-a7ff-e421fd1b02bc@palmer-si-x1e/T/#t