Namhyung Kim ee2a098851 bpf: Adjust BPF stack helper functions to accommodate skip > 0 ... Let's say that the caller has storage for num_elem stack frames. Then, the BPF stack helper functions walk the stack for only num_elem frames. This means that if skip > 0, one keeps only 'num_elem - skip' frames. This is because it sets init_nr in the perf_callchain_entry to the end of the buffer to save num_elem entries only. I believe it was because the perf callchain code unwound the stack frames until it reached the global max size (sysctl_perf_event_max_stack). However it now has perf_callchain_entry_ctx.max_stack to limit the iteration locally. This simplifies the code to handle init_nr in the BPF callstack entries and removes the confusion with the perf_event's __PERF_SAMPLE_CALLCHAIN_EARLY which sets init_nr to 0. Also change the comment on bpf_get_stack() in the header file to be more explicit what the return value means. Fixes: c195651e56 ("bpf: add bpf_get_stack helper") Signed-off-by: Namhyung Kim <namhyung@kernel.org> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Yonghong Song <yhs@fb.com> Link: https://lore.kernel.org/bpf/30a7b5d5-6726-1cc2-eaee-8da2828a9a9c@oracle.com Link: https://lore.kernel.org/bpf/20220314182042.71025-1-namhyung@kernel.org Based-on-patch-by: Eugene Loh <eugene.loh@oracle.com>		2022-03-20 19:16:23 -07:00
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bpf	bpf: Adjust BPF stack helper functions to accommodate skip > 0	2022-03-20 19:16:23 -07:00
cgroup	Merge branch 'for-5.17-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup	2022-02-22 16:14:35 -08:00
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trace	bpf: Add cookie support to programs attached with kprobe multi link	2022-03-17 20:17:19 -07:00
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user_namespace.c	ucounts: Fix systemd LimitNPROC with private users regression	2022-02-25 10:40:14 -06:00
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