BPF trampoline is the critical infrastructure of the BPF subsystem,
acting as a mediator between kernel functions and BPF programs. Numerous
important features, such as using BPF program for zero overhead kernel
introspection, rely on this key component.
The related tests have passed, including the following technical points:
1. fentry
2. fmod_ret
3. fexit
The following related testcases passed on LoongArch:
sudo ./test_progs -a fentry_test/fentry
sudo ./test_progs -a fexit_test/fexit
sudo ./test_progs -a fentry_fexit
sudo ./test_progs -a modify_return
sudo ./test_progs -a fexit_sleep
sudo ./test_progs -a test_overhead
sudo ./test_progs -a trampoline_count
This issue was first reported by Geliang Tang in June 2024 while
debugging MPTCP BPF selftests on a LoongArch machine (see commit
eef0532e900c "selftests/bpf: Null checks for links in bpf_tcp_ca").
Geliang, Huacai, and Tiezhu then worked together to drive the
implementation of this feature, encouraging broader collaboration among
Chinese kernel engineers.
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202507100034.wXofj6VX-lkp@intel.com/
Reported-by: Geliang Tang <geliang@kernel.org>
Tested-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Tested-by: Vincent Li <vincent.mc.li@gmail.com>
Co-developed-by: George Guo <guodongtai@kylinos.cn>
Signed-off-by: George Guo <guodongtai@kylinos.cn>
Signed-off-by: Chenghao Duan <duanchenghao@kylinos.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: maoxiaochuan <maoxiaochuan@loongson.cn>
This commit adds support for BPF dynamic code modification on the
LoongArch architecture:
1. Add bpf_arch_text_copy() for instruction block copying.
2. Add bpf_arch_text_poke() for runtime instruction patching.
3. Add bpf_arch_text_invalidate() for code invalidation.
On LoongArch, since symbol addresses in the direct mapping region can't
be reached via relative jump instructions from the paged mapping region,
we use the move_imm+jirl instruction pair as absolute jump instructions.
These require 2-5 instructions, so we reserve 5 NOP instructions in the
program as placeholders for function jumps.
The larch_insn_text_copy() function is solely used for BPF. And the use
of larch_insn_text_copy() requires PAGE_SIZE alignment. Currently, only
the size of the BPF trampoline is page-aligned.
Co-developed-by: George Guo <guodongtai@kylinos.cn>
Signed-off-by: George Guo <guodongtai@kylinos.cn>
Signed-off-by: Chenghao Duan <duanchenghao@kylinos.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: maoxiaochuan <maoxiaochuan@loongson.cn>
1. Rename the existing validate_code() to validate_ctx()
2. Factor out the code validation handling into a new helper
validate_code()
Then:
* validate_code() is used to check the validity of code.
* validate_ctx() is used to check both code validity and table entry
correctness.
The new validate_code() will be used in subsequent changes.
Reviewed-by: Hengqi Chen <hengqi.chen@gmail.com>
Co-developed-by: George Guo <guodongtai@kylinos.cn>
Signed-off-by: George Guo <guodongtai@kylinos.cn>
Signed-off-by: Chenghao Duan <duanchenghao@kylinos.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: maoxiaochuan <maoxiaochuan@loongson.cn>
Chenghao Duan