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/*
 * netsniff-ng - the packet sniffing beast
 * Copyright 2013 Daniel Borkmann.
 * Subject to the GPL, version 2.
 */

#include <pcap.h>
#include <linux/filter.h>

#include "xmalloc.h"
#include "config.h"
#include "bpf.h"
#include "die.h"

void bpf_try_compile(const char *rulefile, struct sock_fprog *bpf, uint32_t link_type)
{
	int i, ret;
	const struct bpf_insn *ins;
	struct sock_filter *out;
	struct bpf_program _bpf;

	ret = pcap_compile_nopcap(65535, link_type, &_bpf, rulefile, 1, 0xffffffff);
	if (ret < 0)
		panic("Cannot compile filter %s\n", rulefile);

	bpf->len = _bpf.bf_len;
	bpf->filter = xrealloc(bpf->filter, 1, bpf->len * sizeof(*out));

	for (i = 0, ins = _bpf.bf_insns, out = bpf->filter; i < bpf->len;
	     ++i, ++ins, ++out) {
		out->code = ins->code;
		out->jt = ins->jt;
		out->jf = ins->jf;
		out->k = ins->k;

		if (out->code == 0x06 && out->k > 0)
			out->k = 0xFFFFFFFF;
	}

	pcap_freecode(&_bpf);

	if (__bpf_validate(bpf) == 0)
		panic("This is not a valid BPF program!\n");
}
> perf_event_open() > - perf_event_alloc() > - account_event() > - account_pmu_sb_event() > - attach_sb_event() > > so at this point the event is being attached but its ->ctx is still > NULL. It seems like ->ctx is set just a bit later in > perf_event_open(), though. > > But before that, __schedule() comes along and creates a stack trace > similar to the one above: > > __schedule() > - __perf_event_task_sched_out() > - perf_iterate_sb() > - perf_iterate_sb_cpu() > - event_filter_match() > - perf_cgroup_match() > - __get_cpu_context() > - (dereference ctx which is NULL) > > So I guess the question is... should the event be attached (= put on > the list) before ->ctx gets set? Or should the cgroup code check for a > NULL ->ctx? The latter seems like the simplest solution. Moving the list-add later creates a bit of a mess. Reported-by: Vegard Nossum <vegard.nossum@gmail.com> Tested-by: Vegard Nossum <vegard.nossum@gmail.com> Tested-by: Vince Weaver <vincent.weaver@maine.edu> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: David Carrillo-Cisneros <davidcc@google.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Kan Liang <kan.liang@intel.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Fixes: f2fb6bef9251 ("perf/core: Optimize side-band event delivery") Link: http://lkml.kernel.org/r/20160804123724.GN6862@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
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