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Hengqi Chen
a475805a81
Add support for `{LDX,STX,ST} | PROBE_MEM32 | {B,H,W,DW}` instructions.
They are similar to PROBE_MEM instructions with the following differences:
* PROBE_MEM32 supports store.
* PROBE_MEM32 relies on the verifier to clear upper 32-bit of the
src/dst register
* PROBE_MEM32 adds 64-bit kern_vm_start address (which is stored in S6
in the prologue). Due to bpf_arena constructions such S6 + reg +
off16 access is guaranteed to be within arena virtual range, so no
address check at run-time.
* S6 is a free callee-saved register, so it is used to store arena_vm_start
* PROBE_MEM32 allows ST and STX. If they fault the store is a nop. When
LDX faults the destination register is zeroed.
To support these on LoongArch, we employ the t2/t3 registers to store the
intermediate results of reg_arena + src/dst reg and use the t2/t3 registers
as the new src/dst reg. This allows us to reuse most of the existing code.
Acked-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Tested-by: Vincent Li <vincent.mc.li@gmail.com>
Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: maoxiaochuan <maoxiaochuan@loongson.cn>
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.