On 07/10/2019 08:00 PM, Javier Honduvilla Coto wrote: > Hi all, > > This patch adds the bpf_descendant_of helper which accepts a PID and > returns 1 if the PID of the process currently being executed is a > descendant of it or if it's itself. Returns 0 otherwise. The passed > PID should be the one as seen from the "global" pid namespace as the > processes' PIDs in the hierarchy are resolved using the context of said > initial namespace. > > This is very useful in tracing programs when we want to filter by a > given PID and all the children it might spawn. The current workarounds > most people implement for this purpose have issues: > > - Attaching to process spawning syscalls and dynamically add those PIDs > to some bpf map that would be used to filter is cumbersome and > potentially racy. > - Unrolling some loop to perform what this helper is doing consumes lots > of instructions. That and the impossibility to jump backwards makes it > really hard to be correct in really large process chains. > > > Let me know what do you think! > > Thanks, > > --- > Changes in V6: > - Small style fix > - Clarify in the docs that we are resolving PIDs using the global, > initial PID namespace, and the provided *pid* argument should be global, too > - Changed the way we assert on the helper return value > > Changes in V5: > - Addressed code review feedback > - Renamed from progenyof => descendant_of as suggested by Jon Haslam > and Brendan Gregg > > Changes in V4: > - Rebased on latest bpf-next after merge window > > Changes in V3: > - Removed RCU read (un)locking as BPF programs alredy run in RCU > locked > context > - progenyof(0) now returns 1, which, semantically makes more sense > - Added new test case for PID 0 and changed sentinel value for errors > - Rebase on latest bpf-next/master > - Used my work email as somehow I accidentally used my personal one > in v2 > > Changes in V2: > - Adding missing docs in include/uapi/linux/bpf.h >
bpf-next is currently closed due to merge window, please resubmit once it reopens. Thanks, Daniel
