On Wed, Apr 06, 2016 at 06:43:25PM -0700, Alexei Starovoitov wrote: > introduce BPF_PROG_TYPE_TRACEPOINT program type and allow it to be attached > to the perf tracepoint handler, which will copy the arguments into > the per-cpu buffer and pass it to the bpf program as its first argument. > The layout of the fields can be discovered by doing > 'cat /sys/kernel/debug/tracing/events/sched/sched_switch/format' > prior to the compilation of the program with exception that first 8 bytes > are reserved and not accessible to the program. This area is used to store > the pointer to 'struct pt_regs' which some of the bpf helpers will use: > +---------+ > | 8 bytes | hidden 'struct pt_regs *' (inaccessible to bpf program) > +---------+ > | N bytes | static tracepoint fields defined in tracepoint/format (bpf > readonly) > +---------+ > | dynamic | __dynamic_array bytes of tracepoint (inaccessible to bpf yet) > +---------+ > > Not that all of the fields are already dumped to user space via perf ring > buffer > and broken application access it directly without consulting > tracepoint/format. > Same rule applies here: static tracepoint fields should only be accessed > in a format defined in tracepoint/format. The order of fields and > field sizes are not an ABI. > > Signed-off-by: Alexei Starovoitov <a...@kernel.org>
Acked-by: Peter Zijlstra (Intel) <pet...@infradead.org>
