selftests/bpf: Reject graph kptr use after RCU unlockgrafted

Add a sleepable verifier test that loads a graph-node local kptr in an
explicit RCU read-side critical section, then passes its node to
bpf_rbtree_remove() after the section ends.

Before the verifier fix, the stale NON_OWN_REF flag makes the node look like
a live borrowed reference and the program is accepted. After the fix, the
pointer is demoted without NON_OWN_REF and the graph kfunc argument is
rejected.

Also exercise a graph kptr loaded while a spin lock provides implicit RCU
protection. The pointer must be invalidated when the lock is released, which
guards the required ordering between non-owning-reference invalidation and
RCU demotion.

Update the existing fault-protected load test state description. The
post-unlock pointer no longer carries NON_OWN_REF, but remains readable
because the load is rewritten to use BPF_PROBE_MEM.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260904084325.52250-7-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 26 insertions, 0 deletions

diff --git a/arch/powerpc/tools/gcc-check-mprofile-kernel.sh b/arch/powerpc/tools/gcc-check-mprofile-kernel.sh
new file mode 100755
index 000000000..6193b0ed0
--- /dev/null
+++ b/arch/powerpc/tools/gcc-check-mprofile-kernel.sh
@@ -0,0 +1,26 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+set -e
+
+# To debug, uncomment the following line
+# set -x
+
+# -mprofile-kernel is only supported on 64-bit with ELFv2, so this should not
+# be invoked for other targets. Therefore we can pass in -m64 and -mabi
+# explicitly, to take care of toolchains defaulting to other targets.
+
+# Test whether the compile option -mprofile-kernel exists and generates
+# profiling code (ie. a call to _mcount()).
+echo "int func() { return 0; }" | \
+    $* -m64 -mabi=elfv2 -S -x c -O2 -p -mprofile-kernel - -o - \
+    2> /dev/null | grep -q "_mcount"
+
+# Test whether the notrace attribute correctly suppresses calls to _mcount().
+
+echo -e "#include <linux/compiler.h>\nnotrace int func() { return 0; }" | \
+    $* -m64 -mabi=elfv2 -S -x c -O2 -p -mprofile-kernel - -o - \
+    2> /dev/null | grep -q "_mcount" && \
+    exit 1
+
+exit 0