After commit 49b290e430 ("riscv: prevent compressed instructions in
alternatives"), builds with LLVM's integrated assembler fail:
In file included from arch/riscv/mm/init.c:10:
In file included from ./include/linux/mm.h:29:
In file included from ./include/linux/pgtable.h:6:
In file included from ./arch/riscv/include/asm/pgtable.h:108:
./arch/riscv/include/asm/tlbflush.h:23:2: error: expected assembly-time absolute expression
ALT_FLUSH_TLB_PAGE(__asm__ __volatile__ ("sfence.vma %0" : : "r" (addr) : "memory"));
^
./arch/riscv/include/asm/errata_list.h:33:5: note: expanded from macro 'ALT_FLUSH_TLB_PAGE'
asm(ALTERNATIVE("sfence.vma %0", "sfence.vma", SIFIVE_VENDOR_ID, \
^
./arch/riscv/include/asm/alternative-macros.h:187:2: note: expanded from macro 'ALTERNATIVE'
_ALTERNATIVE_CFG(old_content, new_content, vendor_id, errata_id, CONFIG_k)
^
./arch/riscv/include/asm/alternative-macros.h:113:2: note: expanded from macro '_ALTERNATIVE_CFG'
__ALTERNATIVE_CFG(old_c, new_c, vendor_id, errata_id, IS_ENABLED(CONFIG_k))
^
./arch/riscv/include/asm/alternative-macros.h:110:2: note: expanded from macro '__ALTERNATIVE_CFG'
ALT_NEW_CONTENT(vendor_id, errata_id, enable, new_c)
^
./arch/riscv/include/asm/alternative-macros.h:99:3: note: expanded from macro 'ALT_NEW_CONTENT'
".org . - (889b - 888b) + (887b - 886b)\n" \
^
<inline asm>:26:6: note: instantiated into assembly here
.org . - (889b - 888b) + (887b - 886b)
^
This error happens because LLVM's integrated assembler has a one-pass
design, which means it cannot figure out the instruction lengths when
the .org directive is outside of the subsection that contains the
instructions, which was changed by the .option directives added by the
above change.
Move the .org directives before the .previous directive so that these
directives are always within the same subsection, which resolves the
failures and does not introduce any new issues with GNU as. This was
done for arm64 in commit 966a0acce2 ("arm64/alternatives: move length
validation inside the subsection") and commit 22315a2296 ("arm64:
alternatives: Move length validation in alternative_{insn, endif}").
While there is no error from the assembly versions of the macro, they
appear to have the same problem so just make the same change there as
well so that there are no problems in the future.
Link: https://github.com/ClangBuiltLinux/linux/issues/1640
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Link: https://lore.kernel.org/r/20220516214520.3252074-1-nathan@kernel.org
Cc: stable@vger.kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Instructions are opportunistically compressed by the RISC-V assembler
when possible, but in alternatives-blocks both the old and new content
need to be the same size, so having the toolchain do somewhat random
optimizations will cause strange side-effects like
"attempt to move .org backwards" compile-time errors.
Already a simple "and" used in alternatives assembly will cause these
mismatched code sizes.
So prevent compressed instructions to be generated in alternatives-
code and use option-push and -pop to only limit this to the relevant
code blocks
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Philipp Tomsich <philipp.tomsich@vrull.eu>
Link: https://lore.kernel.org/r/20220511192921.2223629-7-heiko@sntech.de
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
ALT_NEW_CONTENT already uses same-length assembler lines, so
extend this to the other elements as well.
This makes it more readable when these elements need to be extended
in the future.
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Philipp Tomsich <philipp.tomsich@vrull.eu>
Link: https://lore.kernel.org/r/20220511192921.2223629-6-heiko@sntech.de
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
When the alternatives were added the commit already provided a template
on how to implement 2 different alternatives for one piece of code.
Make this usable.
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Philipp Tomsich <philipp.tomsich@vrull.eu>
Link: https://lore.kernel.org/r/20220511192921.2223629-5-heiko@sntech.de
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Right now the alternatives need to be explicitly enabled and
erratas are limited to SiFive ones.
We want to use alternatives not only for patching soc erratas,
but in the future also for handling different behaviour depending
on the existence of future extensions.
So move the core alternatives over to the kernel subdirectory
and move the CONFIG_RISCV_ALTERNATIVE to be a hidden symbol
which we expect relevant erratas and extensions to just select
if needed.
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Philipp Tomsich <philipp.tomsich@vrull.eu>
Link: https://lore.kernel.org/r/20220511192921.2223629-2-heiko@sntech.de
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
alternative-macros.h defines ALT_NEW_CONTENT in its assembly part
and ALT_NEW_CONSTENT in the C part. Most likely it is the latter
that is wrong.
Fixes: 6f4eea9046
(riscv: Introduce alternative mechanism to apply errata solution)
Signed-off-by: Vitaly Wool <vitaly.wool@konsulko.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
Introduce the "alternative" mechanism from ARM64 and x86 to apply the CPU
vendors' errata solution at runtime. The main purpose of this patch is
to provide a framework. Therefore, the implementation is quite basic for
now so that some scenarios could not use this schemei, such as patching
code to a module, relocating the patching code and heterogeneous CPU
topology.
Users could use the macro ALTERNATIVE to apply an errata to the existing
code flow. In the macro ALTERNATIVE, users need to specify the manufacturer
information(vendorid, archid, and impid) for this errata. Therefore, kernel
will know this errata is suitable for which CPU core. During the booting
procedure, kernel will select the errata required by the CPU core and then
patch it. It means that the kernel only applies the errata to the specified
CPU core. In this case, the vendor's errata does not affect each other at
runtime. The above patching procedure only occurs during the booting phase,
so we only take the overhead of the "alternative" mechanism once.
This "alternative" mechanism is enabled by default to ensure that all
required errata will be applied. However, users can disable this feature by
the Kconfig "CONFIG_RISCV_ERRATA_ALTERNATIVE".
Signed-off-by: Vincent Chen <vincent.chen@sifive.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
