linux-kernel - [PATCH 2/8] perf tests lib: Add perf_has

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Date:   Thu, 23 Nov 2023 09:58:42 +0200
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Jiri Olsa <jolsa@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        James Clark <james.clark@....com>,
        German Gomez <german.gomez@....com>,
        Leo Yan <leo.yan@...aro.org>, linux-kernel@...r.kernel.org,
        linux-perf-users@...r.kernel.org
Subject: [PATCH 2/8] perf tests lib: Add perf_has_symbol.sh

Some shell tests depend on finding symbols for perf itself, and fail if
perf has been stripped and no debug object is available. Add helper
functions to check if perf has a needed symbol. This is preparation for
amending the tests themselves to be skipped if a needed symbol is not
found.

The functions make use of the "Symbols" test which reads and checks symbols
from a dso, perf itself by default. Note the "Symbols" test will find
symbols using the same method as other perf tests, including, for example,
looking in the buildid cache.

An alternative would be to prevent the needed symbols from being stripped,
which seems to work with gcc's externally_visible attribute, but that
attribute is not supported by clang.

Another alternative would be to use option -Wl,-E (which is already used
when perf is built with perl support) which causes the linker to add all
(global) symbols to the dynamic symbol table. Then the required symbols
need only be made global in scope to avoid being strippable. However that
goes beyond what is needed.

Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
---
 tools/perf/tests/shell/lib/perf_has_symbol.sh | 21 +++++++++++++++++++
 1 file changed, 21 insertions(+)
 create mode 100644 tools/perf/tests/shell/lib/perf_has_symbol.sh

diff --git a/tools/perf/tests/shell/lib/perf_has_symbol.sh b/tools/perf/tests/shell/lib/perf_has_symbol.sh
new file mode 100644
index 000000000000..5d59c32ae3e7
--- /dev/null
+++ b/tools/perf/tests/shell/lib/perf_has_symbol.sh
@@ -0,0 +1,21 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+
+perf_has_symbol()
+{
+	if perf test -vv "Symbols" 2>&1 | grep "[[:space:]]$1$"; then
+		echo "perf does have symbol '$1'"
+		return 0
+	fi
+	echo "perf does not have symbol '$1'"
+	return 1
+}
+
+skip_test_missing_symbol()
+{
+	if ! perf_has_symbol "$1" ; then
+		echo "perf is missing symbols - skipping test"
+		exit 2
+	fi
+	return 0
+}
-- 
2.34.1