Re: [PATCH v3 1/2] check-uapi: Introduce check-uapi.sh

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On 3/21/2023 2:19 PM, Masahiro Yamada wrote:


I think I pointed out that not all UAPI headers are checked-in.


I applied the following.
This will remove <asm/termios.h>.
So, definitely it is a UAPI breakage, but check_all=true
mode succeeds.


  diff --git a/include/uapi/asm-generic/Kbuild b/include/uapi/asm-generic/Kbuild
  index ebb180aac74e..a9c88b0a8b3b 100644
  --- a/include/uapi/asm-generic/Kbuild
  +++ b/include/uapi/asm-generic/Kbuild
  @@ -31,6 +31,6 @@ mandatory-y += stat.h
   mandatory-y += statfs.h
   mandatory-y += swab.h
   mandatory-y += termbits.h
  -mandatory-y += termios.h
  +#mandatory-y += termios.h
   mandatory-y += types.h
   mandatory-y += unistd.h




Another false positive is a change outside the uapi directories.

For x86, syscall UAPI headers are generated in
arch/x86/entry/syscalls/.


You never know the compatibility of UAPI unless you check
all the headers that 'make headers_install' results in.


Excellent points. We'll make another pass looking exclusively at the "make headers_install" trees for the two refs. That should be more reliable, require less code, and catch issues like these.


I am reluctant to read the whole code,
but I spotted possible bugs.





+
+readonly SUCCESS=0
+readonly FAIL_ABI=1
+readonly FAIL_PREREQ=2
+readonly FAIL_COMPILE=3
+readonly FAIL_ARCH=4
+readonly FAIL=5
+
+# Print to stderr
+eprintf() {
+       # shellcheck disable=SC2059
+       printf "$@" >&2
+}
+
+# Print list of UAPI files to operate on
+get_uapi_files() {
+       local -r check_all="$1"
+       local -r base_ref="$2"
+       local -r ref="$3"

local -r past_ref="$3"



+       local -r file_list="${tmp_dir}/file_list.txt"
+
+       # Return already-processed list if it's available
+       if [ -s "$file_list" ]; then
+               cat "$file_list"
+               return 0
+       fi
+
+       if [ "$check_all" = "true" ]; then
+               # Print all of the UAPI header files at the commit in question
+               # Ignore the headers that we can't test.
+               # shellcheck disable=SC2086,SC2046
+               git ls-tree --full-tree --name-only -r "${base_ref:-HEAD}" -- "${UAPI_DIRS[@]}" \
+                       | grep '.h$' \
+                       | sed -e 's/^/M\t/g' \
+                       | grep -v $({ get_no_header_list "$base_ref"; get_no_export_list; } | xargs -- printf '-e %s ') \
+                       > "$file_list"
+       else
+               if [ -z "$base_ref" ] || [ -z "$ref" ]; then


[ -z "$ref" ] is always false.



+                       # shellcheck disable=SC2086
+                       git diff $GIT_ARGS > "$file_list"


This is a bug.

Think about this situation:

   $base_ref is empty, i.e. workspace
   $ref is not HEAD but a commit in the past.


"git diff" will return the diff
between the cache and the workspace.






+               else
+                       # shellcheck disable=SC2086
+                       git diff "$ref" "$base_ref" $GIT_ARGS > "$file_list"
+               fi


Do you need this if...else...fi block in the first place?


    git diff $ref $base_ref $GIT_ARGS > "$file_list"


will naturally work correctly for all cases.
(do not quote $base_ref, which might be empty)



Great suggestion, that's far more elegant. Thank you!



+
+               if mismatch_arch_files=$(grep -v "arch/${ARCH}" "$file_list" | grep -o "arch/.*\.h"); then
+                       eprintf "warning - detected changes to following files, but can't check them with %s compiler:\n" "$ARCH"
+                       for f in $mismatch_arch_files; do
+                               eprintf "  - %s\n" "$f"
+                               sed -i -e "\|${f}|d" "$file_list"
+                               printf "warning - could not perform ABI check on %s with %s compiler\n" "$f" "$ARCH" \
+                                       >> "${tmp_dir}/arch_mismatches.error"
+                       done
+                       eprintf "\nFiltering them out and performing partial check on remaining files...\n"
+                       if [ ! -s "$file_list" ]; then
+                               eprintf "error - all files were filtered out, there's nothing to check!\n"
+                               exit "$FAIL_ARCH"
+                       fi
+               fi
+       fi
+
+       if [ ! -s "$file_list" ]; then
+               return 1
+       fi
+
+       cat "$file_list"
+}
+
+# Compile the simple test app
+do_compile() {
+       local -r inc_dir="$1"
+       local -r header="$2"
+       local -r out="$3"
+       printf "int main(void) { return 0; }\n" | \
+               "$CC" -c \
+                 -o "$out" \
+                 -x c \
+                 -O0 \
+                 -std=c90 \
+                 -fno-eliminate-unused-debug-types \
+                 -g \
+                 "-I${inc_dir}" \
+                 -include "$header" \
+                 -
+}
+
+# Print the list of incompatible headers
+get_no_header_list() {
+       local -r ref="${1:-HEAD}"
+       # Start with the usr/include/Makefile to get a list of the headers
+       # that don't compile using this method.
+       {
+               # shellcheck disable=SC2016
+               printf 'all: ; @echo $(no-header-test)\n'
+               cat "usr/include/Makefile"
+       } | SRCARCH="$ARCH" make -f - | tr " " "\n" | grep -v "asm-generic"
+
+       # The makefile also skips all asm-generic files, but prints "asm-generic/%"
+       # which won't match the files in this script, so just print all the asm-generic
+       # headers manually.
+       git ls-tree --full-tree --name-only -r "$ref" -- include/uapi/asm-generic \
+               | grep '.h$' \
+               | cut -d '/' -f 2-
+
+       # Finally, print all the architecture-specific headers that are _not_ for the
+       # ARCH we're targeting
+       git ls-tree --full-tree --name-only -r "$ref" -- arch/*/include/uapi \
+               | grep '.h$' \
+               | grep -v "^arch/${ARCH}"
+}
+
+# Print the list of headers that are not exported for this architecture
+get_no_export_list() {
+       {
+               # shellcheck disable=SC2016
+               printf 'all: ; @echo $(no-export-headers)\n'
+               cat "include/uapi/Kbuild"
+       } | SRCARCH="$ARCH" srctree="$KERNEL_SRC" make -f - | tr " " "\n" | sed '/^[[:space:]]*$/d'
+}
+
+# Save the current git tree state, stashing if needed
+save_tree_state() {
+       printf "Saving current tree state... "
+       current_ref="$(git rev-parse HEAD)"
+       readonly current_ref
+       if ! git diff-index --quiet HEAD; then
+               unstash="true"
+               git stash push --quiet
+       fi
+       printf "OK\n"
+}
+
+# Restore the git tree state, unstashing if needed
+restore_tree_state() {
+       if [ -z "$current_ref" ]; then
+               return 0
+       fi
+
+       printf "Restoring current tree state... "
+       git checkout --quiet "$current_ref"
+       if [ "$unstash" = "true" ]; then
+               git stash pop --quiet
+               unstash="false"
+       fi
+       printf "OK\n"
+}
+
+# Install headers for both git refs
+install_headers() {
+       local -r check_all="$1"
+       local -r base_ref="$2"
+       local -r ref="$3"
+
+       deviated_from_current_tree="false"
+       for inst_ref in "$base_ref" "$ref"; do


Bakeshed1: personally, I would use 'ref' as an iterator.

      for ref in "$base_ref" "$past_ref"; do

I see overall inconsistency between ref vs past_ref.



Right, I will clean that up in v4.




+               if [ -n "$inst_ref" ]; then
+                       if [ "$deviated_from_current_tree" = "false" ]; then
+                               save_tree_state
+                               trap 'rm -rf "$tmp_dir"; restore_tree_state;' EXIT


Bikeshed2:
Instead of updating the trap back-and-force,
I would create a function.


exit_handler () {
       if [ "$deviated_from_current_tree" = true ]; then
                 restore_tree_state
       fi

       if [ -n "$tmp_dir" ]; then
                 rm -rf "$tmp_dir"
       fi
}

trap exist_handler EXIT



Good idea, will add in v4.





+                               deviated_from_current_tree="true"
+                       fi
+                       # This script ($0) is already loaded into memory at this point,
+                       # so this operation is safe
+                       git checkout --quiet "$(git rev-parse "$inst_ref")"
+               fi
+
+               printf "Installing sanitized UAPI headers from %s... " "${inst_ref:-dirty tree}"
+               make ARCH="$ARCH" INSTALL_HDR_PATH="${tmp_dir}/${inst_ref}/usr" headers_install > /dev/null 2>&1


You can add -j${MAX_THREADS} for faster 'make headers_install'.



Thanks for the tip. Will add in v4.







+               printf "OK\n"
+       done
+
+       restore_tree_state
+       trap 'rm -rf "$tmp_dir"' EXIT
+}
+
+# Check file list for UAPI compatibility
+check_uapi_files() {
+       local -r check_all="$1"
+       local -r base_ref="$2"
+       local -r ref="$3"
+
+       install_headers "$check_all" "$base_ref" "$ref"
+
+       local passed=0;
+       local failed=0;
+       local -a threads=()
+
+       printf "Checking changes to UAPI headers between %s and %s\n" "$ref" "${base_ref:-dirty tree}"
+       while read -r status file; do
+               if [ "${#threads[@]}" -ge "$MAX_THREADS" ]; then
+                       if wait "${threads[0]}"; then
+                               passed=$((passed + 1))
+                       else
+                               failed=$((failed + 1))
+                       fi
+                       threads=("${threads[@]:1}")
+               fi
+
+               check_individual_file "$base_ref" "$ref" "$status" "$file" &
+               threads+=("$!")
+       done < <(get_uapi_files "$check_all" "$base_ref" "$ref")
+
+       for t in "${threads[@]}"; do
+               if wait "$t"; then
+                       passed=$((passed + 1))
+               else
+                       failed=$((failed + 1))
+               fi
+       done
+
+       if [ "$check_all" = "true" ]; then
+               scope=$(printf "UAPI headers compatible with %s" "$ARCH")
+       else
+               scope=$(printf "UAPI headers modified between %s and %s" "$ref" "${base_ref:-dirty tree}")
+       fi
+
+       total="$((passed + failed))"
+       if [ "$failed" -gt 0 ]; then
+               eprintf "error - %d/%d %s appear _not_ to be backwards compatible\n" "$failed" "$total" "$scope"
+       else
+               printf "All %d %s appear to be backwards compatible\n" "$total" "$scope"
+       fi
+
+       if [ "$check_all" = "true" ]; then
+               printf "Note: UAPI headers for architectures other than %s were not checked\n" "$ARCH"
+       fi
+
+       return "$failed"
+}
+
+# Print the path to a given header in the tmp_dir
+get_header() {
+       local -r ref="$1"
+       local -r arch="$2"
+       local -r base="$3"
+
+       if [ -z "$arch" ]; then
+               printf "%s" "${tmp_dir}/${ref}/usr/${base}"
+       else
+               printf "%s" "${tmp_dir}/${ref}/usr/$(printf "%s" "$base" | cut -d '/' -f 3-)"
+       fi
+}
+
+# Check an individual file for UAPI compatibility
+check_individual_file() {
+       local -r base_ref="$1"
+       local -r ref="$2"
+       local -r status="$3"
+       local -r file="$4"
+
+       local -r base=${file/uapi\//}
+       local -r uapi_arch="$(printf "%s" "$file" | grep -o 'arch/.*/uapi' | cut -d '/' -f 2)"
+       local -r base_header=$(get_header "$base_ref" "$uapi_arch" "$base")
+       local -r ref_header=$(get_header "$ref" "$uapi_arch" "$base")
+       local -r installed_base="$(printf "%s" "$base_header" | grep -o "usr/include/.*" | cut -d '/' -f 3-)"
+
+       if [ "$status" = "D" ]; then
+               eprintf "error - UAPI header %s was incorrectly removed\n" "$file" | tee "${base_header}.error"
+               return 1
+       fi
+
+       # shellcheck disable=SC2076
+       if [[ " $(get_no_header_list | xargs) " =~ " $installed_base " ]]; then
+               printf "warning - %s cannot be tested by this script (see usr/include/Makefile)\n" "$file" | tee "${base_header}.error"
+               return 1
+       fi
+
+       # shellcheck disable=SC2076
+       if [[ " $(get_no_export_list | xargs) " =~ " $installed_base " ]]; then
+               printf "warning - %s is not exported by the %s architecture, so cannot be tested\n" "$file" "$ARCH" | tee "${base_header}.error"
+               return 1
+       fi
+
+       for h in "$base_header" "$ref_header"; do
+               if [ ! -f "$h" ]; then
+                       eprintf "error - %s does not exist - cannot compare ABI\n" "$h" | tee "${h}.error"
+                       return 1
+               fi
+       done
+
+       compare_abi "$file" "$base_header" "$ref_header" "$base_ref" "$ref"
+}
+
+# Perform the A/B compilation and compare output ABI
+compare_abi() {
+       local -r file="$1"
+       local -r base_header="$2"
+       local -r ref_header="$3"
+       local -r base_ref="$4"
+       local -r ref="$5"
+       local -r log="${tmp_dir}/log/$(basename "$file").log"
+
+       mkdir -p "$(dirname "$log")"
+
+       if ! do_compile "${tmp_dir}/${base_ref}/usr/include" "$base_header" "${base_header}.bin" 2> "$log"; then
+               eprintf "error - couldn't compile version of UAPI header %s at %s\n" "$file" "$base_ref"
+               cat "$log" >&2
+               exit "$FAIL_COMPILE"
+       fi
+
+       if ! do_compile "${tmp_dir}/${ref}/usr/include" "$ref_header" "${ref_header}.bin" 2> "$log"; then
+               eprintf "error - couldn't compile version of UAPI header %s at %s\n" "$file" "$ref"
+               cat "$log" >&2
+               exit "$FAIL_COMPILE"
+       fi
+
+       "$ABIDIFF" --non-reachable-types "${ref_header}.bin" "${base_header}.bin" > "$log" && ret="$?" || ret="$?"
+       if [ "$ret" -eq 0 ]; then
+               if [ "$VERBOSE" = "true" ]; then
+                       printf "No ABI differences detected in %s from %s -> %s\n" "$file" "$ref" "${base_ref:-dirty tree}"
+               fi
+       else
+               # Bits in abidiff's return code can be used to determine the type of error
+               if [ $(("$ret" & 0x1)) -gt 0 ]; then
+                       eprintf "error - abidiff did not run properly\n"
+                       exit 1
+               fi
+
+               # If the only changes were additions (not modifications to existing APIs), then
+               # there's no problem. Ignore these diffs.
+               if grep "Unreachable types summary" "$log" | grep -q "0 removed" &&
+                  grep "Unreachable types summary" "$log" | grep -q "0 changed"; then
+                       return 0
+               fi
+               {
+                       printf "!!! ABI differences detected in %s from %s -> %s !!!\n\n" "$file" "$ref" "${base_ref:-dirty tree}"
+                       sed  -e '/summary:/d' -e '/changed type/d' -e '/^$/d' -e 's/^/  /g' "$log"
+
+                       if ! cmp "$ref_header" "$base_header" > /dev/null 2>&1; then
+                               printf "\nHeader file diff (after headers_install):\n"
+                               diff -Naur "$ref_header" "$base_header" \
+                                       | sed -e "s|${ref_header}|${ref}/${file}|g" \
+                                             -e "s|${base_header}|${base_ref:-dirty}/${file}|g"
+                               printf "\n"
+                       else
+                               printf "\n%s did not change between %s and %s...\n" "$file" "$ref" "${base_ref:-dirty tree}"
+                               printf "It's possible a change to one of the headers it includes caused this error:\n"
+                               grep '^#include' "$base_header"
+                               printf "\n"
+                       fi
+               } | tee "${base_header}.error" >&2
+               return 1
+       fi
+}
+
+min_version_is_satisfied() {
+       local -r min_version="$1"
+       local -r version_installed="$2"
+
+       printf "%s\n%s\n" "$min_version" "$version_installed" | sort -Vc > /dev/null 2>&1
+}
+
+# Make sure we have the tools we need
+check_deps() {
+       ABIDIFF="${ABIDIFF:-abidiff}"
+       CC="${CC:-gcc}"
+       ARCH="${ARCH:-$(uname -m)}"
+       if [ "$ARCH" = "x86_64" ]; then
+               ARCH="x86"
+       fi
+
+       local -r abidiff_min_version="1.7"
+       local -r libdw_min_version_if_clang="0.171"
+
+       if ! command -v "$ABIDIFF" > /dev/null 2>&1; then
+               eprintf "error - abidiff not found!\n"
+               eprintf "Please install abigail-tools version %s or greater\n" "$abidiff_min_version"
+               eprintf "See: https://sourceware.org/libabigail/manual/libabigail-overview.html\n";
+               exit "$FAIL_PREREQ"
+       fi
+
+       local -r abidiff_version="$("$ABIDIFF" --version | cut -d ' ' -f 2)"
+       if ! min_version_is_satisfied "$abidiff_min_version" "$abidiff_version"; then
+               eprintf "error - abidiff version too old: %s\n" "$abidiff_version"
+               eprintf "Please install abigail-tools version %s or greater\n" "$abidiff_min_version"
+               eprintf "See: https://sourceware.org/libabigail/manual/libabigail-overview.html\n";
+               exit "$FAIL_PREREQ"
+       fi
+
+       if ! command -v "$CC" > /dev/null 2>&1; then
+               eprintf 'error - %s not found\n' "$CC"
+               exit "$FAIL_PREREQ"
+       fi
+
+       if "$CC" --version | grep -q clang; then
+               local -r libdw_version="$(ldconfig -v 2>/dev/null | grep -v SKIPPED | grep -m 1 -o 'libdw-[0-9]\+.[0-9]\+' | cut -c 7-)"
+               if ! min_version_is_satisfied "$libdw_min_version_if_clang" "$libdw_version"; then
+                       eprintf "error - libdw version too old for use with clang: %s\n" "$libdw_version"
+                       eprintf "Please install libdw from elfutils version %s or greater\n" "$libdw_min_version_if_clang"
+                       eprintf "See: https://sourceware.org/elfutils/\n";
+                       exit "$FAIL_PREREQ"
+               fi
+       fi
+
+       if [ ! -d "arch/${ARCH}" ]; then
+               eprintf 'error - ARCH "%s" is not a subdirectory under arch/\n' "$ARCH"
+               eprintf "Please set ARCH to one of:\n%s\n" "$(find arch -maxdepth 1 -mindepth 1 -type d -printf '%f ' | fmt)"
+               exit "$FAIL_PREREQ"
+       fi
+}
+
+run() {
+       local base_ref="$1"
+       local -r check_all="$2"
+       shift 2
+       local -r orig_args="$*"
+       if [ -z "$KERNEL_SRC" ]; then
+               KERNEL_SRC="$(realpath "$(dirname "$0")"/..)"
+       fi
+
+       cd "$KERNEL_SRC"
+
+       abi_error_log="${abi_error_log:-${KERNEL_SRC}/abi_error_log.txt}"
+
+       tmp_dir=$(mktemp -d)
+       trap 'rm -rf "$tmp_dir"' EXIT
+
+       check_deps
+
+       # Set of UAPI directories to check by default
+       UAPI_DIRS=(include/uapi arch/*/include/uapi)
+       GIT_ARGS="--name-status --no-renames --format= --diff-filter=a -- ${UAPI_DIRS[*]/%/\/*.h}"
+
+       if ! git rev-parse --is-inside-work-tree > /dev/null 2>&1; then
+               eprintf "error - this script requires the kernel tree to be initialized with Git\n"
+               exit "$FAIL_PREREQ"
+       fi
+
+       # If there are no dirty UAPI files, use HEAD as base_ref
+       # shellcheck disable=SC2086
+       if [ -z "$base_ref" ] && git diff --exit-code $GIT_ARGS > /dev/null 2>&1; then


I think this behavior is difficult to understand.

I think it is clearer to do 'git diff' for the entire tree
when you determine the base_ref.



Okay. With the model of only looking at "make headers_install" output, I imagine this bit will change anyway.




+               base_ref="HEAD"
+       fi
+
+       if [ -z "$past_ref" ]; then
+               if [ -n "$base_ref" ]; then
+                       past_ref="${base_ref}^1"
+               else
+                       past_ref="HEAD"
+               fi
+       fi



So, past_ref is set to either ${base_ref}^1 or HEAD here.


No quotes are needed for HEAD.

    past_ref=HEAD

is enough.



+
+       if [ -n "$past_ref" ] && ! git rev-parse --verify "$past_ref" > /dev/null 2>&1; then


[ -n "$past_ref" ] is always true since past_ref is set to something.



Good point, must have missed this in an earlier refactor. Will fix in v4.







+               printf 'error - invalid git reference "%s"\n' "$past_ref"
+               exit "$FAIL_PREREQ"
+       fi
+
+       if [ -n "$base_ref" ]; then
+               if ! git merge-base --is-ancestor "$past_ref" "$base_ref" > /dev/null 2>&1; then
+                       printf 'error - "%s" is not an ancestor of base ref "%s"\n' "$past_ref" "$base_ref"
+                       exit "$FAIL_PREREQ"
+               fi
+       fi
+
+       if [ "$check_all" != "true" ] && ! get_uapi_files "$check_all" "$base_ref" "$past_ref" > /dev/null; then
+               printf "No changes to UAPI headers were applied between %s and %s\n" "$past_ref" "$base_ref"
+               exit "$SUCCESS"
+       fi
+
+       if ! check_uapi_files "$check_all" "$base_ref" "$past_ref"; then
+               eprintf "error - UAPI header ABI check failed\n"
+               {
+                       printf 'Generated by "%s %s" from git ref %s\n\n' "$0" "$orig_args" "$(git rev-parse "HEAD")"
+                       find "$tmp_dir" -type f -name '*.error' -exec cat {} +
+               } > "$abi_error_log"
+               eprintf "Failure summary saved to %s\n" "$abi_error_log"
+               exit "$FAIL_ABI"
+       fi
+}
+
+main() {
+       MAX_THREADS=$(nproc)
+       VERBOSE="false"
+       local base_ref=""
+       local check_all="true"
+       local quiet="false"
+       while getopts "hb:p:mj:l:qv" opt; do
+               case $opt in
+               h)
+                       print_usage
+                       exit "$SUCCESS"
+                       ;;
+               b)
+                       base_ref="$OPTARG"
+                       ;;
+               p)
+                       past_ref="$OPTARG"
+                       ;;
+               m)
+                       check_all="false"
+                       ;;
+               j)
+                       MAX_THREADS="$OPTARG"
+                       ;;
+               l)
+                       abi_error_log="$OPTARG"
+                       ;;
+               q)
+                       quiet="true"
+                       ;;
+               v)
+                       VERBOSE="true"
+                       ;;
+               *)
+                       exit "$FAIL_PREREQ"
+               esac
+       done
+
+       if [ "$quiet" = "true" ]; then
+               run "$base_ref" "$check_all" "$@" > /dev/null
+       else
+               run "$base_ref" "$check_all" "$@"
+       fi
+}
+
+main "$@"
--
2.17.1



--
Best Regards
Masahiro Yamada

Thanks for the review!



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