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the `__runtime_fixup_32` function does not handle the case where `val` is
zero correctly (as might occur when patching a nommu kernel and referring
to a physical address below the 4GiB boundary whose upper 32 bits are all
zero) because nothing in the existing logic prevents the code from taking
the `else` branch of both nop-checks and emitting two `nop` instructions.
This leaves random garbage in the register that is supposed to receive the
upper 32 bits of the pointer instead of zero that when combined with the
value for the lower 32 bits yields an invalid pointer and causes a kernel
panic when that pointer is eventually accessed.
The author clearly considered the fact that if the `lui` is converted into
a `nop` that the second instruction needs to be adjusted to become an `li`
instead of an `addi`, hence introducing the `addi_insn_mask` variable, but
didn't follow that logic through fully to the case where the `else` branch
executes. To fix it just adjust the logic to ensure that the second `else`
branch is not taken if the first instruction will be patched to a `nop`.
Fixes: a44fb5722199 ("riscv: Add runtime constant support")
Signed-off-by: Charles Mirabile <cmirabil@redhat.com>
Reviewed-by: Charlie Jenkins <charlie@rivosinc.com>
Tested-by: Charlie Jenkins <charlie@rivosinc.com>
Link: https://lore.kernel.org/r/20250530211422.784415-2-cmirabil@redhat.com
Signed-off-by: Palmer Dabbelt <palmer@dabbelt.com>
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.option arch clobbers .option norvc. Prevent gas from emitting
compressed instructions in the runtime const alternative blocks by
setting .option norvc after .option arch. This issue starts appearing on
gcc 15, which adds zca to the march.
Reported by: Klara Modin <klarasmodin@gmail.com>
Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
Fixes: a44fb5722199 ("riscv: Add runtime constant support")
Closes: https://lore.kernel.org/all/cc8f3525-20b7-445b-877b-2add28a160a2@gmail.com/
Tested-by: Klara Modin <klarasmodin@gmail.com>
Link: https://lore.kernel.org/r/20250331-fix_runtime_const_norvc-v1-1-89bc62687ab8@rivosinc.com
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
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Old toolchain like gcc 8.5.0 does not support zba, so we must check that
the toolchain supports this extension before using it in the kernel.
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202503281836.8pntHm6I-lkp@intel.com/
Link: https://lore.kernel.org/r/20250328115422.253670-1-alexghiti@rivosinc.com
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
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Implement the runtime constant infrastructure for riscv. Use this
infrastructure to generate constants to be used by the d_hash()
function.
This is the riscv variant of commit 94a2bc0f611c ("arm64: add 'runtime
constant' support") and commit e3c92e81711d ("runtime constants: add
x86 architecture support").
[ alex: Remove trailing whitespace ]
Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Tested-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Link: https://lore.kernel.org/r/20250319-runtime_const_riscv-v10-2-745b31a11d65@rivosinc.com
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
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