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| author | Paul Chaignon <paul.chaignon@gmail.com> | 2023-11-06 20:21:56 +0100 |
|---|---|---|
| committer | Aleksandr Nogikh <nogikh@google.com> | 2023-11-09 18:26:45 +0000 |
| commit | 77fb079dedee5c8c2fc0c2e3781769b5978ce4fe (patch) | |
| tree | 5c2d6580711463a268b8321a911e7879fbc2c738 /sys/linux/bpf.txt.const | |
| parent | 24206adf8c2510ab24ff5391c676da047e2523d0 (diff) | |
sys/linux: describe call to BPF helper bpf_ringbuf_reserve
Describe a full call to bpf_ringbuf_reserve, using the map type created
in the previous commit. The test corresponds to this simple line:
u64 *e;
e = bpf_ringbuf_reserve(&rb, sizeof(*e), 0);
[...]
return e;
The pointer returned by bpf_ringbuf_reserve is kept in R9. The goal is
to keep it around so we can use it in other instructions later; several
other helpers take a pointer to ringbuf data as argument. There's of
course a risk that some instruction in between will clobber R9, but I
don't know another way. R9 is at least safe for calls (only R1--R5 get
clobbered).
We expect the program loading to fail with EINVAL because we never
release the reference to the ringbuf data. The verifier will therefore
reject the program with:
0: R1=ctx(off=0,imm=0) R10=fp0
0: (18) r0 = 0x0 ; R0_w=0
2: (18) r1 = 0xffff984e4b55da00 ; R1_w=map_ptr(off=0,ks=0,vs=0,imm=0)
4: (b7) r2 = 20 ; R2_w=20
5: (b7) r3 = 0 ; R3_w=0
6: (85) call bpf_ringbuf_reserve#131 ; R0_w=ringbuf_mem_or_null(id=2,ref_obj_id=2,off=0,imm=0) refs=2
7: (bf) r9 = r0 ; R0_w=ringbuf_mem_or_null(id=2,ref_obj_id=2,off=0,imm=0)
R9_w=ringbuf_mem_or_null(id=2,ref_obj_id=2,off=0,imm=0) refs=2
8: (95) exit
Unreleased reference id=2 alloc_insn=6
Signed-off-by: Paul Chaignon <paul.chaignon@gmail.com>
Diffstat (limited to 'sys/linux/bpf.txt.const')
| -rw-r--r-- | sys/linux/bpf.txt.const | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/sys/linux/bpf.txt.const b/sys/linux/bpf.txt.const index 4e55324c0..8091b3944 100644 --- a/sys/linux/bpf.txt.const +++ b/sys/linux/bpf.txt.const @@ -66,6 +66,7 @@ BPF_EXIST = 2 BPF_EXIT0 = 9 BPF_FLOW_DISSECTOR = 17 BPF_FUNC_INFO_SIZE = 8 +BPF_FUNC_ringbuf_reserve = 131 BPF_FUNC_snprintf = 165 BPF_FUNC_tail_call = 12 BPF_FUNC_trace_printk = 6 |