1 files changed, 39 insertions, 0 deletions
diff --git a/tools/objtool/tests/generic/test-cold-function.sh b/tools/objtool/tests/generic/test-cold-function.sh
new file mode 100755
index 000000000000..a02652fe5341
--- /dev/null
+++ b/tools/objtool/tests/generic/test-cold-function.sh
@@ -0,0 +1,39 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+#
+# Both halves of a split function belong to the patch; carrying only the hot
+# part leaves the cold path branching into unpatched code.
+
+. "$(dirname "$0")/../lib.sh"
+
+# Clang does not split functions into a cold part at all, so there is nothing
+# for this test to look at there.  A given gcc may or may not split, which is a
+# version property rather than a compiler choice -- that stays a probe below.
+gcc_only "clang does not split functions into a cold part"
+
+setup
+
+split_flag=-freorder-blocks-and-partition
+cc_supports "$split_flag" || split_flag=
+
+build_pair cold_function.c $split_flag
+
+# Find what the compiler called the cold half -- target.cold, target.cold.0,
+# depending on version -- and name it exactly from here on.
+cold_sym="$(in_symbols orig.o | awk '$NF ~ /^target\.cold/ { print $NF; exit }')"
+[ -n "$cold_sym" ] ||
+	probe_skip "compiler did not split the function into a cold part"
+
+run_diff
+
+assert_patched target
+# Match the name field exactly, and require it to be defined.  Had the cold
+# half been left behind, the branch to it would appear as an undefined
+# .klp.sym.vmlinux.target.cold,0 -- a different name, which happens to contain
+# this one.  Asking about a column instead of the name would not tell them
+# apart: readelf prints SHN_LIVEPATCH as "OS [0xff20]" and llvm-readelf as
+# "OS[0xff20]", so the fields either side of the name shift between the two.
+out_symbols | awk -v n="$cold_sym" '$NF == n && $(NF - 1) != "UND"' | grep -q . ||
+	fail "cold half ($cold_sym) was not carried into the patch"
+
+pass "cold half carried into the patch with its parent"