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bpf, docs: Better document the regular load and store instructions

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Add a separate section and a little intro blurb for the regular load and
store instructions.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20220131183638.3934982-3-hch@lst.de
This commit is contained in:
Christoph Hellwig 2022-01-31 19:36:35 +01:00 committed by Alexei Starovoitov
parent dd33fb571f
commit 63d8c242b9
1 changed files with 12 additions and 5 deletions
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17
Documentation/bpf/instruction-set.rst
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@ -215,23 +215,30 @@ The mode modifier is one of:
BPF_IMM 0x00 used for 64-bit mov
BPF_ABS 0x20 legacy BPF packet access
BPF_IND 0x40 legacy BPF packet access
BPF_MEM 0x60 all normal load and store operations
BPF_MEM 0x60 regular load and store operations
BPF_ATOMIC 0xc0 atomic operations
============= ===== ====================================
BPF_MEM | <size> | BPF_STX means::
Regular load and store operations
---------------------------------
The ``BPF_MEM`` mode modifier is used to encode regular load and store
instructions that transfer data between a register and memory.
``BPF_MEM | <size> | BPF_STX`` means::
*(size *) (dst_reg + off) = src_reg
BPF_MEM | <size> | BPF_ST means::
``BPF_MEM | <size> | BPF_ST`` means::
*(size *) (dst_reg + off) = imm32
BPF_MEM | <size> | BPF_LDX means::
``BPF_MEM | <size> | BPF_LDX`` means::
dst_reg = *(size *) (src_reg + off)
Where size is one of: BPF_B or BPF_H or BPF_W or BPF_DW.
Where size is one of: ``BPF_B``, ``BPF_H``, ``BPF_W``, or ``BPF_DW``.
Atomic operations
-----------------