examples: fentry - add comments to illustrate difference with tcprtt #615
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The tcprtt example was added recently, which relies on CO-RE information to work across different kernel versions. fentry, on the other hand, will break if structs change in the running kernel, so document this fact. Replaced unused fields with padding and addressed some nits. Signed-off-by: Timo Beckers <timo@isovalent.com>
mmat11
reviewed
Mar 30, 2022
| * | ||
| * Also note that BTF-enabled programs like fentry, fexit, fmod_ret, tp_btf, | ||
| * lsm, etc. declared using the BPF_PROG macro can read kernel memory without | ||
| * needing to call bpf_probe_read*(). |
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shouldn't this be BPF_CORE_READ*()?
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BPF_CORE_READ and friends emit a CO-RE relocation and call bpf_probe_read_*() behind the scenes, but that's not what is meant here specifically. This comment is just about the memory accesses in the kernel, not the CO-RE part.
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The tcprtt example was added recently, which relies on CO-RE information to work across different kernel versions. fentry, on the other hand, will break if structs change in the running kernel, so document this fact.
Replaced unused fields with padding and addressed some nits.