On Fri, Nov 12, 2021 at 6:02 AM Alexei Starovoitov
<alexei.starovoitov@xxxxxxxxx> wrote:
>
> From: Alexei Starovoitov <ast@xxxxxxxxxx>
>
> v1->v2:
> . Refactor uapi to pass 'struct bpf_core_relo' from LLVM into libbpf and further
> into the kernel instead of bpf_core_apply_relo() bpf helper. Because of this
> change the CO-RE algorithm has an ability to log error and debug events through
> the standard bpf verifer log mechanism which was not possible with helper
> approach.
> . #define RELO_CORE macro was removed and replaced with btf_member_bit_offset() patch.
>
> This set introduces CO-RE support in the kernel.
> There are several reasons to add such support:
> 1. It's a step toward signed BPF programs.
> 2. It allows golang like languages that struggle to adopt libbpf
> to take advantage of CO-RE powers.
> 3. Currently the field accessed by 'ldx [R1 + 10]' insn is recognized
> by the verifier purely based on +10 offset. If R1 points to a union
> the verifier picks one of the fields at this offset.
> With CO-RE the kernel can disambiguate the field access.
>
Great, I tested the same code which was failing with the RFC series,
now there isn't any error.
This is the output with pr_debug() enabled:
root@debian64:~/core# ./core
[ 5.690268] prog '(null)': relo #-2115894237: kind <(null)>
(163299788), spec is
[ 5.690272] prog '(null)': relo #-2115894246: (null) candidate #-2115185528
[ 5.690392] prog '(null)': relo #2: patched insn #208 (LDX/ST/STX)
off 208 -> 208
[ 5.691045] prog '(efault)': relo #-2115894237: kind <(null)>
(163299788), spec is
[ 5.691047] prog '(efault)': relo #-2115894246: (null) candidate
#-2115185528
[ 5.691148] prog '(efault)': relo #3: patched insn #208
(LDX/ST/STX) off 208 -> 208
[ 5.692456] prog '(null)': relo #-2115894237: kind <(null)>
(163302708), spec is
[ 5.692459] prog '(null)': relo #-2115894246: (null) candidate #-2115185668
[ 5.692564] prog '(null)': relo #2: patched insn #104 (LDX/ST/STX)
off 104 -> 104
[ 5.693179] prog '(efault)': relo #-2115894237: kind <(null)>
(163299788), spec is
[ 5.693181] prog '(efault)': relo #-2115894246: (null) candidate
#-2115185528
[ 5.693258] prog '(efault)': relo #3: patched insn #208
(LDX/ST/STX) off 208 -> 208
[ 5.696141] prog '(null)': relo #-2115894237: kind <(null)>
(163302708), spec is
[ 5.696143] prog '(null)': relo #-2115894246: (null) candidate #-2115185668
[ 5.696255] prog '(null)': relo #2: patched insn #104 (LDX/ST/STX)
off 104 -> 104
[ 5.696733] prog '(efault)': relo #-2115894237: kind <(null)>
(163299788), spec is
[ 5.696734] prog '(efault)': relo #-2115894246: (null) candidate
#-2115185528
[ 5.696833] prog '(efault)': relo #3: patched insn #208
(LDX/ST/STX) off 208 -> 208
And the syscall returns success:
bpf(BPF_PROG_TEST_RUN, {test={prog_fd=4, retval=0, data_size_in=0,
data_size_out=0, data_in=NULL, data_out=NULL, repeat=0, duration=0,
ctx_size_in=68, ctx_size_out=0, ctx_in=0x5590b97dd2a0, ctx_out=NULL}},
160) = 0
Regards,
--
per aspera ad upstream
