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Linux kernel source tree
8afd3170d5
Support BPF load-acquire (BPF_LOAD_ACQ) and store-release (BPF_STORE_REL) instructions in the riscv64 JIT compiler. For example, consider the following 64-bit load-acquire (assuming little-endian): db 10 00 00 00 01 00 00 r1 = load_acquire((u64 *)(r1 + 0x0)) 95 00 00 00 00 00 00 00 exit opcode (0xdb): BPF_ATOMIC | BPF_DW | BPF_STX imm (0x00000100): BPF_LOAD_ACQ The JIT compiler will emit an LD instruction followed by a FENCE R,RW instruction for the above, e.g.: ld x7,0(x6) fence r,rw Similarly, consider the following 16-bit store-release: cb 21 00 00 10 01 00 00 store_release((u16 *)(r1 + 0x0), w2) 95 00 00 00 00 00 00 00 exit opcode (0xcb): BPF_ATOMIC | BPF_H | BPF_STX imm (0x00000110): BPF_STORE_REL A FENCE RW,W instruction followed by an SH instruction will be emitted, e.g.: fence rw,w sh x2,0(x4) 8-bit and 16-bit load-acquires are zero-extending (cf., LBU, LHU). The verifier always rejects misaligned load-acquires/store-releases (even if BPF_F_ANY_ALIGNMENT is set), so the emitted load and store instructions are guaranteed to be single-copy atomic. Introduce primitives to emit the relevant (and the most common/used in the kernel) fences, i.e. fences with R -> RW, RW -> W and RW -> RW. Rename emit_atomic() to emit_atomic_rmw() to make it clear that it only handles RMW atomics, and replace its is64 parameter to allow to perform the required checks on the opsize (BPF_SIZE(code)). Acked-by: Björn Töpel <bjorn@kernel.org> Tested-by: Björn Töpel <bjorn@rivosinc.com> # QEMU/RVA23 Signed-off-by: Andrea Parri <parri.andrea@gmail.com> Co-developed-by: Peilin Ye <yepeilin@google.com> Signed-off-by: Peilin Ye <yepeilin@google.com> Reviewed-by: Pu Lehui <pulehui@huawei.com> Link: https://lore.kernel.org/r/3059c560e537ad43ed19055d2ebbd970c698095a.1746588351.git.yepeilin@google.com Signed-off-by: Alexei Starovoitov <ast@kernel.org> |
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| README | ||
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 reStructuredText 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.