[PATCH v4 0/2] bpf: add bpf_probe_write helper & example

From: Sargun Dhillon
Date: Thu Jul 21 2016 - 21:09:24 EST

This patch series contains two patches that add support for a probe_write
helper to BPF programs. This allows them to manipulate user memory during
the course of tracing. The second patch in the series has an example that
uses it, in one the intended ways to divert execution.

Thanks to Alexei Starovoitov, and Daniel Borkmann for review, I've made
changes based on their recommendations.

This helper should be considered experimental, so we print a warning
to dmesg when it is first invoked. Subsequent invocations print the
command and pid

v1->v2: restrict writing to user space, as opposed to globally
v2->v3: Fixed formatting issues
v3->v4: Rename copy_to_user -> bpf_probe_write
Simplify checking of whether or not it's safe to write
Add warnings to dmesg

Sargun Dhillon (2):
bpf: Add bpf_probe_write BPF helper to be called in tracers (kprobes)
samples/bpf: Add example of using bpf_probe_write in bpf kprobes

include/uapi/linux/bpf.h | 12 ++++++++
kernel/bpf/verifier.c | 9 ++++++
kernel/trace/bpf_trace.c | 37 +++++++++++++++++++++++
samples/bpf/Makefile | 4 +++
samples/bpf/bpf_helpers.h | 2 ++
samples/bpf/tracex7_kern.c | 51 +++++++++++++++++++++++++++++++
samples/bpf/tracex7_user.c | 75 ++++++++++++++++++++++++++++++++++++++++++++++
7 files changed, 190 insertions(+)
create mode 100644 samples/bpf/tracex7_kern.c
create mode 100644 samples/bpf/tracex7_user.c