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The RISC-V ISA manual used to mandate that misaligned accesses were
supported in user mode, but that requirement was removed in 2018 via
riscv-isa-manual commit 61cadb9 ("Provide new description of misaligned
load/store behavior compatible with privileged architecture."). Since
the Linux uABI was already frozen at that point it's just been demoted
to part of the uABI, but that was never written down.
Link: https://lore.kernel.org/r/20220728210715.17214-1-palmer@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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sv48 was just introduced, so add its virtual memory layout to the
documentation.
Signed-off-by: Alexandre Ghiti <alexandre.ghiti@canonical.com>
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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This subdir no longer exists: it was there to document some of the
quirks and paths forward for handling them, but those have been dealt
with as of Atish's recent patch set.
Fixes: 23b1f18326ec ("Documentation: riscv: Remove the old documentation")
Link: https://lore.kernel.org/linux-next/20220329133412.591d6882@canb.auug.org.au/
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Bagas Sanjaya <bagasdotme@gmail.com>
[Palmer: commit text]
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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The existing pmu documentation describes the limitation of perf
infrastructure in RISC-V ISA and limited feature set of perf in RISC-V.
However, SBI PMU extension and sscofpmf extension(ISA extension) allows to
implement most of the required features of perf. Remove the old
documentation which is not accurate anymore.
Reviewed-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Atish Patra <atish.patra@wdc.com>
Signed-off-by: Atish Patra <atishp@rivosinc.com>
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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Now that KASAN_SHADOW_OFFSET is defined at compile time as a config,
this value must remain constant whatever the size of the virtual address
space, which is only possible by pushing this region at the end of the
address space next to the kernel mapping.
Signed-off-by: Alexandre Ghiti <alexandre.ghiti@canonical.com>
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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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] [<ffffffff8029806c>] __memset+0xc4/0xfc
[ 0.143859] [<ffffffff8061e984>] init_default_flow_dissectors+0x22/0x60
[ 0.144092] [<ffffffff800010fc>] do_one_initcall+0x3e/0x168
[ 0.144278] [<ffffffff80600df0>] kernel_init_freeable+0x1c8/0x224
[ 0.144479] [<ffffffff804868a8>] kernel_init+0x12/0x110
[ 0.144658] [<ffffffff800022de>] 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 <schwab@linux-m68k.org>
Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
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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 <alex@ghiti.fr>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
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Add a feature list matrix for each architecture to their
respective Kernel books.
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/9c39d4dd93e05c0008205527d2c3450912f029ed.1606748711.git.mchehab+huawei@kernel.org
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
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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
...
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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 <paul.walmsley@sifive.com>
Reviewed-by: Palmer Dabbelt <palmerdabbelt@google.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Krste Asanovic <krste@berkeley.edu>
Cc: Andrew Waterman <waterman@eecs.berkeley.edu>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Jonathan Corbet <corbet@lwn.net>
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There are some typos in boot image header and riscv boot documentation.
Fix the typos.
Signed-off-by: Atish Patra <atish.patra@wdc.com>
Reviewed-by: Palmer Dabbelt <palmerdabbelt@google.com>
Link: https://lore.kernel.org/r/20191009010637.9955-1-atish.patra@wdc.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
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Correct the sequence of the magic number 2 since it's little endian.
Signed-off-by: Chester Lin <clin@suse.com>
Reviewed-by: Paul Walmsley <paul.walmsley@sifive.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
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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
...
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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 <paul.walmsley@sifive.com>
Reported-by: Palmer Dabbelt <palmer@sifive.com>
Reviewed-by: Palmer Dabbelt <palmer@sifive.com>
Cc: Atish Patra <atish.patra@wdc.com>
Cc: Karsten Merker <merker@debian.org>
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
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Convert this small file to ReST format by:
- Using a proper markup for the document title;
- marking a code block as such;
- use tags for Author and date;
- use tables for bit map fields.
While here, fix a broken reference for a document with is
planned but is not here yet.
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Reviewed-by: Atish Patra <atish.patra@wdc.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
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git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux
Pull RISC-V updates from Paul Walmsley:
- Hugepage support
- "Image" header support for RISC-V kernel binaries, compatible with
the current ARM64 "Image" header
- Initial page table setup now split into two stages
- CONFIG_SOC support (starting with SiFive SoCs)
- Avoid reserving memory between RAM start and the kernel in
setup_bootmem()
- Enable high-res timers and dynamic tick in the RV64 defconfig
- Remove long-deprecated gate area stubs
- MAINTAINERS updates to switch to the newly-created shared RISC-V git
tree, and to fix a get_maintainers.pl issue for patches involving
SiFive E-mail addresses
Also, one integration fix to resolve a build problem introduced during
in the v5.3-rc1 merge window:
- Fix build break after macro-to-function conversion in
asm-generic/cacheflush.h
* tag 'riscv/for-v5.3-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux:
riscv: fix build break after macro-to-function conversion in generic cacheflush.h
RISC-V: Add an Image header that boot loader can parse.
RISC-V: Setup initial page tables in two stages
riscv: remove free_initrd_mem
riscv: ccache: Remove unused variable
riscv: Introduce huge page support for 32/64bit kernel
x86, arm64: Move ARCH_WANT_HUGE_PMD_SHARE config in arch/Kconfig
RISC-V: Fix memory reservation in setup_bootmem()
riscv: defconfig: enable SOC_SIFIVE
riscv: select SiFive platform drivers with SOC_SIFIVE
arch: riscv: add config option for building SiFive's SoC resource
riscv: Remove gate area stubs
MAINTAINERS: change the arch/riscv git tree to the new shared tree
MAINTAINERS: don't automatically patches involving SiFive to the linux-riscv list
RISC-V: defconfig: Enable NO_HZ_IDLE and HIGH_RES_TIMERS
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Now that several arch documents were converted to ReST,
add their indexes to Documentation/index.rst and remove the
:orphan: from them.
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
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Currently, the last stage boot loaders such as U-Boot can accept only
uImage which is an unnecessary additional step in automating boot
process.
Add an image header that boot loader understands and boot Linux from
flat Image directly.
This header is based on ARM64 boot image header and provides an
opportunity to combine both ARM64 & RISC-V image headers in future.
Also make sure that PE/COFF header can co-exist in the same image so
that EFI stub can be supported for RISC-V in future. EFI specification
needs PE/COFF image header in the beginning of the kernel image in order
to load it as an EFI application. In order to support EFI stub, code0
should be replaced with "MZ" magic string and res4(at offset 0x3c)
should point to the rest of the PE/COFF header (which will be added
during EFI support).
Tested on both QEMU and HiFive Unleashed using OpenSBI + U-Boot + Linux.
Signed-off-by: Atish Patra <atish.patra@wdc.com>
Reviewed-by: Karsten Merker <merker@debian.org>
Tested-by: Karsten Merker <merker@debian.org> (QEMU+OpenSBI+U-Boot)
Tested-by: Kevin Hilman <khilman@baylibre.com> (OpenSBI + U-Boot + Linux)
[paul.walmsley@sifive.com: fixed whitespace in boot-image-header.txt;
converted structure comment to kernel-doc format and added some detail]
Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>
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The conversion here is trivial:
- Adjust the document title's markup
- Do some whitespace alignment;
- mark literal blocks;
- Use ReST way to markup indented lists.
At its new index.rst, let's add a :orphan: while this is not linked to
the main index.rst file, in order to avoid build warnings.
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
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Reviewed-by: Alex Solomatnikov <sols@sifive.com>
Cc: Nick Hu <nickhu@andestech.com>
Cc: Greentime Hu <greentime@andestech.com>
Signed-off-by: Alan Kao <alankao@andestech.com>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
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