hi,
adding new helpers to access traced function arguments that
came out of the trampoline batch changes [1].
Get n-th argument of the traced function:
long bpf_get_func_arg(void *ctx, u32 n, u64 *value)
Get return value of the traced function:
long bpf_get_func_ret(void *ctx, u64 *value)
Get arguments count of the traced funtion:
long bpf_get_func_arg_cnt(void *ctx)
changes from original post [1]:
- change helpers names to get_func_*
- change helpers to return error values instead of
direct values
- replaced stack_size usage with specific offset
variables in arch_prepare_bpf_trampoline
- add comment on stack layout
- add more tests
- allow bpf_get_func_ret in FENTRY programs
- use BPF_LSH instead of BPF_MUL
thanks,
jirka
[1] https://lore.kernel.org/bpf/20211118112455.475349-1-jolsa@xxxxxxxxxx/
---
Jiri Olsa (3):
bpf, x64: Replace some stack_size usage with offset variables
bpf: Add get_func_[arg|ret|arg_cnt] helpers
selftests/bpf: Add tests for get_func_[arg|ret|arg_cnt] helpers
arch/x86/net/bpf_jit_comp.c | 55 +++++++++++++++++++++++++++++++++------------
include/uapi/linux/bpf.h | 28 +++++++++++++++++++++++
kernel/bpf/verifier.c | 73 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++--
kernel/trace/bpf_trace.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++-
tools/include/uapi/linux/bpf.h | 28 +++++++++++++++++++++++
tools/testing/selftests/bpf/prog_tests/get_func_args_test.c | 38 +++++++++++++++++++++++++++++++
tools/testing/selftests/bpf/progs/get_func_args_test.c | 112 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
7 files changed, 375 insertions(+), 17 deletions(-)
create mode 100644 tools/testing/selftests/bpf/prog_tests/get_func_args_test.c
create mode 100644 tools/testing/selftests/bpf/progs/get_func_args_test.c
