[PATCH bpf-next v6 0/3] Add 12-argument support for RV64 bpf trampoline

Pu Lehui
2024-07-02T12:18:04Z

This patch adds 12 function arguments support for riscv64 bpf
trampoline. The current bpf trampoline supports <= sizeof(u64) bytes
scalar arguments [0] and <= 16 bytes struct arguments [1]. Therefore, we
focus on the situation where scalars are at most XLEN bits and
aggregates whose total size does not exceed 2×XLEN bits in the riscv
calling convention [2].

Link: https://elixir.bootlin.com/linux/v6.8/source/kernel/bpf/btf.c#L6184 [0]
Link: https://elixir.bootlin.com/linux/v6.8/source/kernel/bpf/btf.c#L6769 [1]
Link: https://github.com/riscv-non-isa/riscv-elf-psabi-doc/releases/download/draft-20230929-e5c800e661a53efe3c2678d71a306323b60eb13b/riscv-abi.pdf [2]

v6:
- Remove unnecessary skel detach ops as it will be covered by skel destroy ops.

v5: https://lore.kernel.org/all/20240702013730.1082285-1-pulehui@huaweicloud.com/
- Remove unnecessary copyright.

v4: https://lore.kernel.org/all/20240622022129.3844473-1-pulehui@huaweicloud.com/
- Separate many args test logic from tracing_struct. (Daniel)

v3: https://lore.kernel.org/all/20240403072818.1462811-1-pulehui@huaweicloud.com/
- Variable and macro name alignment:
nr_reg_args: number of args in reg
nr_stack_args: number of args on stack
RV_MAX_REG_ARGS: macro for riscv max args in reg

v2: https://lore.kernel.org/all/20240403041710.1416369-1-pulehui@huaweicloud.com/
- Add tracing_struct to DENYLIST.aarch64 while aarch64 does not yet support
bpf trampoline with more than 8 args.
- Change the macro RV_MAX_ARG_REGS to RV_MAX_ARGS_REG to synchronize with
the variable definition below.
- Add some comments for stk_arg_off and magic number of skip slots for loading
args on stack.

v1: https://lore.kernel.org/all/20240331092405.822571-1-pulehui@huaweicloud.com/

Pu Lehui (3):
riscv, bpf: Add 12-argument support for RV64 bpf trampoline
selftests/bpf: Factor out many args tests from tracing_struct
selftests/bpf: Add testcase where 7th argment is struct

arch/riscv/net/bpf_jit_comp64.c | 66 +++++++++----
tools/testing/selftests/bpf/DENYLIST.aarch64 | 1 +
.../selftests/bpf/bpf_testmod/bpf_testmod.c | 19 ++++
.../selftests/bpf/prog_tests/tracing_struct.c | 44 ++++++++-
.../selftests/bpf/progs/tracing_struct.c | 54 -----------
.../bpf/progs/tracing_struct_many_args.c | 95 +++++++++++++++++++
6 files changed, 202 insertions(+), 77 deletions(-)
create mode 100644 tools/testing/selftests/bpf/progs/tracing_struct_many_args.c

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2.34.1