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Owen Rafferty 033a52d033 kbuild: rewrite check-local-export in sh/awk

Remove the bash build dependency for those who otherwise do not
have it installed. This also provides a significant speedup:

$ make defconfig
$ make yes2modconfig

...

$ find  .  -name "*.o" | grep -v vmlinux | wc
     3169      3169     89615
$ export NM=nm
$ time sh -c 'find . -name "*.o" | grep -v vmlinux | xargs -n1
./scripts/check-local-export'

Without patch:
    0m15.90s real     0m12.17s user     0m05.28s system

With patch:
dash + nawk
    0m02.16s real     0m02.92s user     0m00.34s system

dash + busybox awk
    0m02.36s real     0m03.36s user     0m00.34s system

dash + gawk
    0m02.07s real     0m03.26s user     0m00.32s system

bash + gawk
    0m03.55s real     0m05.00s user     0m00.54s system

Signed-off-by: Owen Rafferty <owen@owenrafferty.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

2022-09-29 04:40:15 +09:00

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#!/bin/sh

SPDX-License-Identifier: GPL-2.0-only

Copyright (C) 2022 Masahiro Yamada masahiroy@kernel.org

Copyright (C) 2022 Owen Rafferty owen@owenrafferty.com

Exit with error if a local exported symbol is found.

EXPORT_SYMBOL should be used for global symbols.

set -e pid=

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 simpler:

{ ${NM} --quiet ${1} || kill 0; } |

{ ${NM} ${1} 2>/dev/null || { echo "${0}: ${NM} failed" >&2; kill $pid; } } | ${AWK} -v "file=${1}" ' BEGIN { i = 0 }

Skip the line if the number of fields is less than 3.

case 1)

For undefined symbols, the first field (value) is empty.

The outout looks like this:

" U _printk"

It is unneeded to record undefined symbols.

case 2)

For Clang LTO, llvm-nm outputs a line with type t but empty name:

"---------------- t"

!length($3) { next }

save (name, type) in the associative array

{ symbol_types[$3]=$2 }

append the exported symbol to the array

($3 ~ /^_ksymtab/) { export_symbols[i] = $3 sub(/^_ksymtab/, "", export_symbols[i]) i++ }

END { exit_code = 0 for (j = 0; j < i; ++j) { name = export_symbols[j] # nm(3) says "If lowercase, the symbol is usually local" if (symbol_types[name] ~ /[a-z]/) { printf "%s: error: local symbol %s was exported\n", file, name | "cat 1>&2" exit_code = 1 } }

exit exit_code

exit $?

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