From da4288b95baa1c7c9aa8a476f58b37eb238745b0 Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Wed, 8 Jun 2022 10:11:00 +0900 Subject: [PATCH] scripts/check-local-export: avoid 'wait $!' for process substitution Bash 4.4, released in 2016, supports 'wait $!' to check the exit status of a process substitution, but it seems too new. Some people using older bash versions (on CentOS 7, Ubuntu 16.04, etc.) reported an error like this: ./scripts/check-local-export: line 54: wait: pid 17328 is not a child of this shell I used the process substitution to avoid a pipeline, which executes each command in a subshell. If the while-loop is executed in the subshell context, variable changes within are lost after the subshell terminates. Fortunately, Bash 4.2, released in 2011, supports the 'lastpipe' option, which makes the last element of a pipeline run in the current shell process. Switch to the pipeline with 'lastpipe' solution, and also set 'pipefail' to catch errors from ${NM}. Add the bash requirement to Documentation/process/changes.rst. Fixes: 31cb50b5590f ("kbuild: check static EXPORT_SYMBOL* by script instead of modpost") Reported-by: Tetsuo Handa Reported-by: Michael Ellerman Reported-by: Wang Yugui Tested-by: Tetsuo Handa Tested-by: Jon Hunter Acked-by: Nick Desaulniers Tested-by: Sedat Dilek # LLVM-14 (x86-64) Signed-off-by: Masahiro Yamada --- Documentation/process/changes.rst | 12 ++++++++++++ scripts/check-local-export | 36 +++++++++++++++++++++--------------- 2 files changed, 33 insertions(+), 15 deletions(-) diff --git a/Documentation/process/changes.rst b/Documentation/process/changes.rst index 34415ae..19c286c 100644 --- a/Documentation/process/changes.rst +++ b/Documentation/process/changes.rst @@ -32,6 +32,7 @@ you probably needn't concern yourself with pcmciautils. GNU C 5.1 gcc --version Clang/LLVM (optional) 11.0.0 clang --version GNU make 3.81 make --version +bash 4.2 bash --version binutils 2.23 ld -v flex 2.5.35 flex --version bison 2.0 bison --version @@ -84,6 +85,12 @@ Make You will need GNU make 3.81 or later to build the kernel. +Bash +---- + +Some bash scripts are used for the kernel build. +Bash 4.2 or newer is needed. + Binutils -------- @@ -362,6 +369,11 @@ Make - +Bash +---- + +- + Binutils -------- diff --git a/scripts/check-local-export b/scripts/check-local-export index da745e2..6ccc2f4 100755 --- a/scripts/check-local-export +++ b/scripts/check-local-export @@ -8,11 +8,31 @@ set -e +# catch errors from ${NM} +set -o pipefail + +# Run the last element of a pipeline in the current shell. +# Without this, the while-loop would be executed in a subshell, and +# the changes made to 'symbol_types' and 'export_symbols' would be lost. +shopt -s lastpipe + declare -A symbol_types declare -a export_symbols exit_code=0 +# If there is no symbol in the object, ${NM} (both GNU nm and llvm-nm) shows +# 'no symbols' diagnostic (but exits with 0). It is harmless and hidden by +# '2>/dev/null'. However, it suppresses real error messages as well. Add a +# hand-crafted error message here. +# +# TODO: +# Use --quiet instead of 2>/dev/null when we upgrade the minimum version of +# binutils to 2.37, llvm to 13.0.0. +# Then, the following line will be really simple: +# ${NM} --quiet ${1} | + +{ ${NM} ${1} 2>/dev/null || { echo "${0}: ${NM} failed" >&2; false; } } | while read value type name do # Skip the line if the number of fields is less than 3. @@ -37,21 +57,7 @@ do if [[ ${name} == __ksymtab_* ]]; then export_symbols+=(${name#__ksymtab_}) fi - - # If there is no symbol in the object, ${NM} (both GNU nm and llvm-nm) - # shows 'no symbols' diagnostic (but exits with 0). It is harmless and - # hidden by '2>/dev/null'. However, it suppresses real error messages - # as well. Add a hand-crafted error message here. - # - # Use --quiet instead of 2>/dev/null when we upgrade the minimum version - # of binutils to 2.37, llvm to 13.0.0. - # - # Then, the following line will be really simple: - # done < <(${NM} --quiet ${1}) -done < <(${NM} ${1} 2>/dev/null || { echo "${0}: ${NM} failed" >&2; false; } ) - -# Catch error in the process substitution -wait $! +done for name in "${export_symbols[@]}" do -- 2.7.4