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bpf: permit multiple bpf attachments for a single perf event

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This patch enables multiple bpf attachments for a
kprobe/uprobe/tracepoint single trace event.
Each trace_event keeps a list of attached perf events.
When an event happens, all attached bpf programs will
be executed based on the order of attachment.

A global bpf_event_mutex lock is introduced to protect
prog_array attaching and detaching. An alternative will
be introduce a mutex lock in every trace_event_call
structure, but it takes a lot of extra memory.
So a global bpf_event_mutex lock is a good compromise.

The bpf prog detachment involves allocation of memory.
If the allocation fails, a dummy do-nothing program
will replace to-be-detached program in-place.

Signed-off-by: Yonghong Song <yhs@fb.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Yonghong Song 2017-10-23 23:53:08 -07:00 • committed by David S. Miller
parent 0b4c6841fe
commit e87c6bc385
9 changed files with 255 additions and 56 deletions
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6
include/trace/perf.h
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@ -34,7 +34,6 @@ perf_trace_##call(void *__data, proto) \
struct trace_event_call *event_call = __data; \
struct trace_event_data_offsets_##call __maybe_unused __data_offsets;\
struct trace_event_raw_##call *entry; \
struct bpf_prog *prog = event_call->prog; \
struct pt_regs *__regs; \
u64 __count = 1; \
struct task_struct *__task = NULL; \
@ -46,8 +45,9 @@ perf_trace_##call(void *__data, proto) \
__data_size = trace_event_get_offsets_##call(&__data_offsets, args); \
\
head = this_cpu_ptr(event_call->perf_events); \
if (!prog && __builtin_constant_p(!__task) && !__task && \
hlist_empty(head)) \
if (!bpf_prog_array_valid(event_call) && \
__builtin_constant_p(!__task) && !__task && \
hlist_empty(head)) \
return; \
\
__entry_size = ALIGN(__data_size + sizeof(*entry) + sizeof(u32),\