The goal of this patch-set is to reflect attribute bpf_fastcall
for supported helpers and kfuncs in generated header files.
For helpers this requires a tweak for scripts/bpf_doc.py and an update
to uapi/linux/bpf.h doc-comment.
For kfuncs this requires:
- introduction of a new KF_FASTCALL flag;
- modification to pahole to read kfunc flags and generate
DECL_TAG "bpf_fastcall" for marked kfuncs;
- modification to bpftool to scan for DECL_TAG "bpf_fastcall"
presence.
In both cases the following helper macro is defined in the generated
header:
#ifndef __bpf_fastcall
#if __has_attribute(bpf_fastcall)
#define __bpf_fastcall __attribute__((bpf_fastcall))
#else
#define __bpf_fastcall
#endif
#endif
And is used to mark appropriate function prototypes. More information
about bpf_fastcall attribute could be found in [1] and [2].
Modifications to pahole are submitted separately.
[1] LLVM source tree commit:
64e464349bfc ("[BPF] introduce __attribute__((bpf_fastcall))")
[2] Linux kernel tree commit (note: feature was renamed from
no_caller_saved_registers to bpf_fastcall after this commit):
52839f31cece ("Merge branch 'no_caller_saved_registers-attribute-for-helper-calls'")
Eduard Zingerman (4):
bpf: allow specifying bpf_fastcall attribute for BPF helpers
bpf: __bpf_fastcall for bpf_get_smp_processor_id in uapi
bpf: use KF_FASTCALL to mark kfuncs supporting fastcall contract
bpftool: __bpf_fastcall for kfuncs marked with special decl_tag
include/linux/btf.h | 1 +
include/uapi/linux/bpf.h | 2 +
kernel/bpf/helpers.c | 4 +-
kernel/bpf/verifier.c | 5 +-
scripts/bpf_doc.py | 50 ++++++++++++++++-
tools/bpf/bpftool/btf.c | 98 ++++++++++++++++++++++++++++++----
tools/include/uapi/linux/bpf.h | 2 +
7 files changed, 144 insertions(+), 18 deletions(-)
--
2.46.0
