selftests/bpf: Add a test for objects stuck in free_by_rcu_ttracegrafted

Delete all elements of BPF_F_NO_PREALLOC hash map in one batch. The first
free_bulk() starts RCU tasks trace GP and the rest of the elements are
freed while it's in flight. Wait for call_rcu_ttrace_in_progress to clear
in bpf_mem_cache of every cpu and check that free_by_rcu_ttrace and
waiting_for_gp_ttrace lists are empty.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20260930095920.601738-4-alexei.starovoitov@gmail.com
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>

1 files changed, 21 insertions, 0 deletions

diff --git a/scripts/tools-support-relr.sh b/scripts/tools-support-relr.sh
new file mode 100755
index 000000000..4c121946e
--- /dev/null
+++ b/scripts/tools-support-relr.sh
@@ -0,0 +1,21 @@
+#!/bin/sh -eu
+# SPDX-License-Identifier: GPL-2.0
+
+tmp_file=$(mktemp)
+trap "rm -f $tmp_file.o $tmp_file $tmp_file.bin" EXIT
+
+cat << "END" | $CC -c -x c - -o $tmp_file.o >/dev/null 2>&1
+void *p = &p;
+END
+
+# ld.lld before 15 did not support -z pack-relative-relocs.
+if ! $LD $tmp_file.o -shared -Bsymbolic --pack-dyn-relocs=relr -o $tmp_file 2>/dev/null; then
+	$LD $tmp_file.o -shared -Bsymbolic -z pack-relative-relocs -o $tmp_file 2>&1 |
+		grep -q pack-relative-relocs && exit 1
+fi
+
+# Despite printing an error message, GNU nm still exits with exit code 0 if it
+# sees a relr section. So we need to check that nothing is printed to stderr.
+test -z "$($NM $tmp_file 2>&1 >/dev/null)"
+
+$OBJCOPY -O binary $tmp_file $tmp_file.bin