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[xen master] automation/eclair_analysis: deviate linker symbols for Rule 18.2

Date: Fri, 13 Sep 2024 06:55:11 +0000

Delivery-date: Fri, 13 Sep 2024 06:55:12 +0000

List-id: "Change log for Mercurial $receive only$" <xen-changelog.lists.xenproject.org>

commit 33888e7aaabc2947aeb6d8b0adcf16c6330b55ba Author: Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx> AuthorDate: Sat Sep 7 15:03:25 2024 +0200 Commit: Stefano Stabellini <stefano.stabellini@xxxxxxx> CommitDate: Wed Sep 11 17:11:09 2024 -0700 automation/eclair_analysis: deviate linker symbols for Rule 18.2 MISRA C Rule 18.2 states: "Subtraction between pointers shall only be applied to pointers that address elements of the same array". Subtractions between pointer where at least one symbol is a symbol defined by the linker are safe and thus deviated, because the compiler cannot exploit the undefined behaviour that would arise from violating the rules in this case. To create an ECLAIR configuration that contains the list of linker-defined symbols, the script "linker-symbols.sh" is used after a build of xen (without static analysis) is performed. The generated file "linker_symbols.ecl" is then used as part of the static analysis configuration. Additional changes to the ECLAIR integration are: - perform a build of xen without static analysis during prepare.sh - run the scripts to generated ECL configuration during the prepare.sh, rather than analysis.sh - export ECLAIR_PROJECT_ROOT earlier, to allow such generation Additionally, the macro page_to_mfn performs a subtraction that is safe, so its uses are deviated. No functional changes. Signed-off-by: Nicola Vetrini <nicola.vetrini@xxxxxxxxxxx> Acked-by: Stefano Stabellini <sstabellini@xxxxxxxxxx> --- automation/eclair_analysis/ECLAIR/analyze.sh | 6 ----- automation/eclair_analysis/ECLAIR/deviations.ecl | 11 ++++++++ .../ECLAIR/generate-linker-symbols.sh | 31 ++++++++++++++++++++++ automation/eclair_analysis/ECLAIR/generate_ecl.sh | 3 +++ automation/eclair_analysis/prepare.sh | 6 ++++- automation/scripts/eclair | 3 +++ docs/misra/deviations.rst | 10 +++++++ 7 files changed, 63 insertions(+), 7 deletions(-) diff --git a/automation/eclair_analysis/ECLAIR/analyze.sh b/automation/eclair_analysis/ECLAIR/analyze.sh index e96456c3c1..1dc63c1bc2 100755 --- a/automation/eclair_analysis/ECLAIR/analyze.sh +++ b/automation/eclair_analysis/ECLAIR/analyze.sh @@ -73,17 +73,11 @@ export ECLAIR_WORKSPACE="${ECLAIR_DATA_DIR}/eclair_workspace" # Identifies the particular build of the project. export ECLAIR_PROJECT_NAME="XEN_${VARIANT}-${SET}" -# All paths mentioned in ECLAIR reports that are below this directory -# will be presented as relative to ECLAIR_PROJECT_ROOT. -export ECLAIR_PROJECT_ROOT="${PWD}" # Erase and recreate the output directory and the data directory. rm -rf "${ECLAIR_OUTPUT_DIR:?}/*" mkdir -p "${ECLAIR_DATA_DIR}" -# Generate additional configuration files -"${SCRIPT_DIR}/generate_ecl.sh" - # Perform the build (from scratch) in an ECLAIR environment. "${ECLAIR_BIN_DIR}eclair_env" \ "-config_file='${SCRIPT_DIR}/analysis.ecl'" \ diff --git a/automation/eclair_analysis/ECLAIR/deviations.ecl b/automation/eclair_analysis/ECLAIR/deviations.ecl index ed80ac7958..9c3ebc9cc7 100644 --- a/automation/eclair_analysis/ECLAIR/deviations.ecl +++ b/automation/eclair_analysis/ECLAIR/deviations.ecl @@ -533,6 +533,17 @@ safe." # Series 18. # +-doc_begin="Subtractions between pointers involving at least one of the linker symbols specified by the regex below +are guaranteed not to be exploited by a compiler that relies on the absence of +C99 Undefined Behaviour 45: Pointers that do not point into, or just beyond, the same array object are subtracted (6.5.6)." +-eval_file=linker_symbols.ecl +-config=MC3R1.R18.2,reports+={safe, "any_area(stmt(operator(sub)&&child(lhs||rhs, skip(__non_syntactic_paren_stmts, ref(linker_symbols)))))"} +-doc_end + +-doc_begin="The following macro performs a subtraction between pointers to obtain the mfn, but does not lead to undefined behaviour." +-config=MC3R1.R18.2,reports+={safe, "any_area(any_loc(any_exp(macro(^page_to_mfn$))))"} +-doc_end + -doc_begin="Flexible array members are deliberately used and XEN developers are aware of the dangers related to them: unexpected result when the structure is given as argument to a sizeof() operator and the truncation in assignment between structures." -config=MC3R1.R18.7,reports+={deliberate, "any()"} diff --git a/automation/eclair_analysis/ECLAIR/generate-linker-symbols.sh b/automation/eclair_analysis/ECLAIR/generate-linker-symbols.sh new file mode 100755 index 0000000000..19943ba98d --- /dev/null +++ b/automation/eclair_analysis/ECLAIR/generate-linker-symbols.sh @@ -0,0 +1,31 @@ +#!/bin/bash + +set -e + +script_name="$(basename "$0")" +script_dir="$( + cd "$(dirname "$0")" + echo "${PWD}" +)" + +fatal() { + echo "${script_name}: $*" >&2 + exit 1 +} + +arch="" +if [ "${XEN_TARGET_ARCH}" == "x86_64" ]; then + arch=x86 +elif [ "${XEN_TARGET_ARCH}" == "arm64" ]; then + arch=arm +else + fatal "Unknown configuration: $1" +fi + +outfile=${script_dir}/linker_symbols.ecl + +( + echo -n "-decl_selector+={linker_symbols, \"^(" >"${outfile}" + "${script_dir}/../linker-symbols.sh" "${arch}" | sort -u | tr '\n' '|' | sed '$ s/|//' >>"${outfile}" + echo -n ")$\"}" >>"${outfile}" +) diff --git a/automation/eclair_analysis/ECLAIR/generate_ecl.sh b/automation/eclair_analysis/ECLAIR/generate_ecl.sh index 66766b23ab..b955783904 100755 --- a/automation/eclair_analysis/ECLAIR/generate_ecl.sh +++ b/automation/eclair_analysis/ECLAIR/generate_ecl.sh @@ -17,3 +17,6 @@ accepted_rst="${ECLAIR_PROJECT_ROOT}/docs/misra/rules.rst" # Generate accepted guidelines "${script_dir}/accepted_guidelines.sh" "${accepted_rst}" + +# Generate the list of linker-defined symbols (must be run after a Xen build) +"${script_dir}/generate-linker-symbols.sh" diff --git a/automation/eclair_analysis/prepare.sh b/automation/eclair_analysis/prepare.sh index 47b2a2f32a..3a646414a3 100755 --- a/automation/eclair_analysis/prepare.sh +++ b/automation/eclair_analysis/prepare.sh @@ -39,10 +39,14 @@ fi cp "${CONFIG_FILE}" xen/.config make clean find . -type f -name "*.safparse" -print -delete + "${script_dir}/build.sh" "$1" + # Generate additional configuration files + "${script_dir}/ECLAIR/generate_ecl.sh" + make clean cd xen make -f "${script_dir}/Makefile.prepare" prepare # Translate the /* SAF-n-safe */ comments into ECLAIR CBTs scripts/xen-analysis.py --run-eclair --no-build --no-clean # Translate function-properties.json into ECLAIR properties - python3 ${script_dir}/propertyparser.py + python3 "${script_dir}/propertyparser.py" ) diff --git a/automation/scripts/eclair b/automation/scripts/eclair index 3ec760bab8..0a2353c20a 100755 --- a/automation/scripts/eclair +++ b/automation/scripts/eclair @@ -3,6 +3,9 @@ ECLAIR_ANALYSIS_DIR=automation/eclair_analysis ECLAIR_DIR="${ECLAIR_ANALYSIS_DIR}/ECLAIR" ECLAIR_OUTPUT_DIR=$(realpath "${ECLAIR_OUTPUT_DIR}") +# All paths mentioned in ECLAIR reports that are below this directory +# will be presented as relative to ECLAIR_PROJECT_ROOT. +export ECLAIR_PROJECT_ROOT="${PWD}" "${ECLAIR_ANALYSIS_DIR}/prepare.sh" "${VARIANT}" diff --git a/docs/misra/deviations.rst b/docs/misra/deviations.rst index 74bb815bf0..247e69e7f1 100644 --- a/docs/misra/deviations.rst +++ b/docs/misra/deviations.rst @@ -501,6 +501,16 @@ Deviations related to MISRA C:2012 Rules: - __builtin_memset() - cpumask_check() + * - R18.2 + - Subtractions between pointers where at least one of the operand is a + pointer to a symbol defined by the linker are safe. + - Tagged as `safe` for ECLAIR. + + * - R18.2 + - Subtraction between pointers encapsulated by macro page_to_mfn + are safe. + - Tagged as `safe` for ECLAIR. + * - R20.4 - The override of the keyword \"inline\" in xen/compiler.h is present so that section contents checks pass when the compiler chooses not to -- generated by git-patchbot for /home/xen/git/xen.git#master

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