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a6aab01882
When the insn framework is used to encode an AND/ORR/EOR instruction, aarch64_encode_immediate() is used to pick the immr imms values. If the immediate is a 64bit mask, with bit 63 set, and zeros in any of the upper 32 bits, the immr value is incorrectly calculated meaning the wrong mask is generated. For example, 0x8000000000000001 should have an immr of 1, but 32 is used, meaning the resulting mask is 0x0000000300000000. It would appear eBPF is unable to hit these cases, as build_insn()'s imm value is a s32, so when used with BPF_ALU64, the sign-extended u64 immediate would always have all-1s or all-0s in the upper 32 bits. KVM does not generate a va_mask with any of the top bits set as these VA wouldn't be usable with TTBR0_EL2. This happens because the rotation is calculated from fls(~imm), which takes an unsigned int, but the immediate may be 64bit. Use fls64() so the 64bit mask doesn't get truncated to a u32. Signed-off-by: James Morse <james.morse@arm.com> Brown-paper-bag-for: Marc Zyngier <maz@kernel.org> Acked-by: Marc Zyngier <maz@kernel.org> Link: https://lore.kernel.org/r/20220127162127.2391947-4-james.morse@arm.com Signed-off-by: Will Deacon <will@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.