While the run-time testing of FORTIFY_SOURCE is already present in LKDTM, there is no testing of the expected compile-time detections. In preparation for correctly supporting FORTIFY_SOURCE under Clang, adding additional FORTIFY_SOURCE defenses, and making sure FORTIFY_SOURCE doesn't silently regress with GCC, introduce a build-time test suite that checks each expected compile-time failure condition. As this is relatively backwards from standard build rules in the sense that a successful test is actually a compile _failure_, create a wrapper script to check for the correct errors, and wire it up as a dummy dependency to lib/string.o, collecting the results into a log file artifact.
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| 1 | +#!/bin/sh | |
| 2 | +# SPDX-License-Identifier: GPL-2.0-only | |
| 3 | +set -e | |
| 4 | + | |
| 5 | +# Argument 1: Source file to build. | |
| 6 | +IN="$1" | |
| 7 | +shift | |
| 8 | +# Extract just the filename for error messages below. | |
| 9 | +FILE="${IN##*/}" | |
| 10 | +# Extract the function name for error messages below. | |
| 11 | +FUNC="${FILE#*-}" | |
| 12 | +FUNC="${FUNC%%-*}" | |
| 13 | +FUNC="${FUNC%%.*}" | |
| 14 | +# Extract the symbol to test for in build/symbol test below. | |
| 15 | +WANT="__${FILE%%-*}" | |
| 16 | + | |
| 17 | +# Argument 2: Where to write the build log. | |
| 18 | +OUT="$1" | |
| 19 | +shift | |
| 20 | +TMP="${OUT}.tmp" | |
| 21 | + | |
| 22 | +# Argument 3: Path to "nm" tool. | |
| 23 | +NM="$1" | |
| 24 | +shift | |
| 25 | + | |
| 26 | +# Remaining arguments are: $(CC) $(c_flags) | |
| 27 | + | |
| 28 | +# Clean up temporary file at exit. | |
| 29 | +__cleanup() { | |
| 30 | + rm -f "$TMP" | |
| 31 | +} | |
| 32 | +trap __cleanup EXIT | |
| 33 | + | |
| 34 | +# Function names in warnings are wrapped in backticks under UTF-8 locales. | |
| 35 | +# Run the commands with LANG=C so that grep output will not change. | |
| 36 | +export LANG=C | |
| 37 | + | |
| 38 | +status= | |
| 39 | +# Attempt to build a source that is expected to fail with a specific warning. | |
| 40 | +if "$@" -Werror -c "$IN" -o "$OUT".o 2> "$TMP" ; then | |
| 41 | + # If the build succeeds, either the test has failed or the | |
| 42 | + # warning may only happen at link time (Clang). In that case, | |
| 43 | + # make sure the expected symbol is unresolved in the symbol list. | |
| 44 | + # If so, FORTIFY is working for this case. | |
| 45 | + if ! $NM -A "$OUT".o | grep -m1 "\bU ${WANT}$" >>"$TMP" ; then | |
| 46 | + status="warning: unsafe ${FUNC}() usage lacked '$WANT' symbol in $IN" | |
| 47 | + fi | |
| 48 | +else | |
| 49 | + # If the build failed, check for the warning in the stderr (gcc). | |
| 50 | + if ! grep -q -m1 "error: call to .\b${WANT}\b." "$TMP" ; then | |
| 51 | + status="warning: unsafe ${FUNC}() usage lacked '$WANT' warning in $IN" | |
| 52 | + fi | |
| 53 | +fi | |
| 54 | + | |
| 55 | +if [ -n "$status" ]; then | |
| 56 | + # Report on failure results, including compilation warnings. | |
| 57 | + echo "$status" | tee "$OUT" >&2 | |
| 58 | +else | |
| 59 | + # Report on good results, and save any compilation output to log. | |
| 60 | + echo "ok: unsafe ${FUNC}() usage correctly detected with '$WANT' in $IN" >"$OUT" | |
| 61 | +fi | |
| 62 | +cat "$TMP" >>"$OUT" | |