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, 50 insertions, 0 deletions

diff --git a/arch/powerpc/boot/zImage.coff.lds.S b/arch/powerpc/boot/zImage.coff.lds.S
new file mode 100644
index 000000000..117951295
--- /dev/null
+++ b/arch/powerpc/boot/zImage.coff.lds.S
@@ -0,0 +1,50 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+OUTPUT_ARCH(powerpc:common)
+ENTRY(_zimage_start_opd)
+EXTERN(_zimage_start_opd)
+SECTIONS
+{
+  .text      :
+  {
+    _start = .;
+    *(.text)
+    *(.fixup)
+    _etext = .;
+  }
+  . = ALIGN(4096);
+  .data    :
+  {
+    *(.rodata*)
+    *(.data*)
+    *(__builtin_*)
+    *(.sdata*)
+    *(.got2)
+
+    _dtb_start = .;
+    *(.kernel:dtb)
+    _dtb_end = .;
+
+    _vmlinux_start =  .;
+    *(.kernel:vmlinux.strip)
+    _vmlinux_end =  .;
+
+    _initrd_start =  .;
+    *(.kernel:initrd)
+    _initrd_end =  .;
+  }
+
+  . = ALIGN(4096);
+  _edata  =  .;
+  __bss_start = .;
+  .bss       :
+  {
+   *(.sbss)
+   *(.bss)
+  }
+  _end = . ;
+
+  /DISCARD/ :
+  {
+    *(.comment)
+  }
+}