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, 40 insertions, 0 deletions

diff --git a/arch/hexagon/Makefile b/arch/hexagon/Makefile
new file mode 100644
index 000000000..ff172cbe5
--- /dev/null
+++ b/arch/hexagon/Makefile
@@ -0,0 +1,40 @@
+# SPDX-License-Identifier: GPL-2.0
+#  Makefile for the Hexagon arch
+
+KBUILD_DEFCONFIG = comet_defconfig
+
+# Do not use GP-relative jumps
+KBUILD_CFLAGS += -G0
+LDFLAGS_vmlinux += -G0
+
+# Do not use single-byte enums; these will overflow.
+KBUILD_CFLAGS += -fno-short-enums
+
+# We must use long-calls:
+KBUILD_CFLAGS += -mlong-calls
+
+# Modules must use either long-calls, or use pic/plt.
+# Use long-calls for now, it's easier.  And faster.
+# KBUILD_CFLAGS_MODULE += -fPIC
+# KBUILD_LDFLAGS_MODULE += -shared
+KBUILD_CFLAGS_MODULE += -mlong-calls
+
+cflags-y += $(call cc-option,-mv${CONFIG_HEXAGON_ARCH_VERSION})
+aflags-y += $(call cc-option,-mv${CONFIG_HEXAGON_ARCH_VERSION})
+ldflags-y += $(call cc-option,-mv${CONFIG_HEXAGON_ARCH_VERSION})
+
+KBUILD_CFLAGS += $(cflags-y)
+KBUILD_AFLAGS += $(aflags-y)
+KBUILD_LDFLAGS += $(ldflags-y)
+
+# Thread-info register will be r19.  This value is not configureable;
+# it is hard-coded in several files.
+TIR_NAME := r19
+KBUILD_CFLAGS += -ffixed-$(TIR_NAME) -DTHREADINFO_REG=$(TIR_NAME) -D__linux__
+KBUILD_AFLAGS += -DTHREADINFO_REG=$(TIR_NAME)
+
+# Disable HexagonConstExtenders pass for LLVM versions prior to 19.1.0
+# https://github.com/llvm/llvm-project/issues/99714
+ifneq ($(call clang-min-version, 190100),y)
+KBUILD_CFLAGS += -mllvm -hexagon-cext=false
+endif