selftests/bpf: Test rhtab kptr cancellation semanticsgrafted

Resizable hash-map updates and deletions must not perform full special-field
destruction in their caller context. In particular, a referenced kptr must
remain attached to the allocation until the memory allocator destructor can
release it safely.

Add separate coverage for both affected paths. The update test stores a task
kptr, replaces the ordinary value bytes with BPF_EXIST, and verifies that the
kptr survived. The delete test removes an element and exchanges its kptr
through the still-valid map-value pointer before the allocation is reclaimed.

Both cases observe a NULL kptr when rhtab uses bpf_obj_free_fields(). They
recover and release the reference after rhtab switches to cancellation
semantics.

Signed-off-by: Nuoqi Gui <gnq25@mails.tsinghua.edu.cn>
[ kkd: Split update and delete coverage and rewrote the commit log ]
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260904104203.345917-5-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 17 insertions, 0 deletions

diff --git a/Documentation/firmware_class/hotplug-script b/Documentation/firmware_class/hotplug-script
new file mode 100644
index 000000000..8143a950b
--- /dev/null
+++ b/Documentation/firmware_class/hotplug-script
@@ -0,0 +1,17 @@
+#!/bin/sh
+
+# Simple hotplug script sample:
+# 
+# Both $DEVPATH and $FIRMWARE are already provided in the environment.
+
+HOTPLUG_FW_DIR=/usr/lib/hotplug/firmware/
+
+if [ "$SUBSYSTEM" == "firmware" -a "$ACTION" == "add" ]; then
+  if [ -f $HOTPLUG_FW_DIR/$FIRMWARE ]; then
+    echo 1 > /sys/$DEVPATH/loading
+    cat $HOTPLUG_FW_DIR/$FIRMWARE > /sys/$DEVPATH/data
+    echo 0 > /sys/$DEVPATH/loading
+  else
+    echo -1 > /sys/$DEVPATH/loading
+  fi
+fi