From 04b8cb0945b4bf679c71dc2351e0d3c25481e3c6 Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Mon, 20 May 2024 21:42:09 +0900 Subject: kbuild: avoid unneeded kallsyms step 3 Since commit 951bcae6c5a0 ("kallsyms: Avoid weak references for kallsyms symbols"), the kallsyms step 3 always occurs. You can compare the build logs. [Before 951bcae6c5a0] $ git checkout 951bcae6c5a0^ $ make defconfig all [ snip ] LD .tmp_vmlinux.kallsyms1 NM .tmp_vmlinux.kallsyms1.syms KSYMS .tmp_vmlinux.kallsyms1.S AS .tmp_vmlinux.kallsyms1.S LD .tmp_vmlinux.kallsyms2 NM .tmp_vmlinux.kallsyms2.syms KSYMS .tmp_vmlinux.kallsyms2.S AS .tmp_vmlinux.kallsyms2.S LD vmlinux [After 951bcae6c5a0] $ git checkout 951bcae6c5a0 $ make defconfig all [ snip ] LD .tmp_vmlinux.kallsyms1 NM .tmp_vmlinux.kallsyms1.syms KSYMS .tmp_vmlinux.kallsyms1.S AS .tmp_vmlinux.kallsyms1.S LD .tmp_vmlinux.kallsyms2 NM .tmp_vmlinux.kallsyms2.syms KSYMS .tmp_vmlinux.kallsyms2.S AS .tmp_vmlinux.kallsyms2.S LD .tmp_vmlinux.kallsyms3 # should not happen NM .tmp_vmlinux.kallsyms3.syms # should not happen KSYMS .tmp_vmlinux.kallsyms3.S # should not happen AS .tmp_vmlinux.kallsyms3.S # should not happen LD vmlinux The resulting vmlinux is correct, but it always requires an additional linking step. The symbols produced by kallsyms are excluded from kallsyms itself because they were previously missing in step 1. With those symbols excluded, the symbol lists matched between step 1 and step 2, eliminating the need for step 3. Now, this has a negative effect. Since 951bcae6c5a0, the PROVIDE() directives provide the fallback definitions, which are not trimmed from the sysbol list in step 1 because ${kallsymso_prev} is empty at this point. In step 2, ${kallsymso_prev} is set, and the kallsyms_* symbols are trimmed from the symbol list. Due to the table size difference between step 1 and step 2 (the former is larger due to the presence of kallsyms_*), step 3 is triggered. Now that the kallsyms_* symbols are always linked, let's stop omitting them from kallsyms. This avoids unnecessary step 3. Fixes: 951bcae6c5a0 ("kallsyms: Avoid weak references for kallsyms symbols") Signed-off-by: Masahiro Yamada --- scripts/mksysmap | 11 +---------- 1 file changed, 1 insertion(+), 10 deletions(-) (limited to 'scripts/mksysmap') diff --git a/scripts/mksysmap b/scripts/mksysmap index 57ff5656d566..e46bafe333bd 100755 --- a/scripts/mksysmap +++ b/scripts/mksysmap @@ -4,7 +4,7 @@ # tools to retrieve the actual addresses of symbols in the kernel. # # Usage -# mksysmap vmlinux System.map [exclude] +# mksysmap vmlinux System.map ##### @@ -92,13 +92,4 @@ ${NM} -n ${1} | sed >${2} -e " # ppc stub /\.long_branch\./d /\.plt_branch\./d - -# --------------------------------------------------------------------------- -# Ignored kallsyms symbols -# -# If the 3rd parameter exists, symbols from it will be omitted from the output. -# This makes kallsyms have the identical symbol lists in the step 1 and 2. -# Without this, the step2 would get new symbols generated by scripts/kallsyms.c -# when CONFIG_KALLSYMS_ALL is enabled. That might require one more pass. -$(if [ $# -ge 3 ]; then ${NM} ${3} | sed -n '/ U /!s:.* \([^ ]*\)$:/ \1$/d:p'; fi) " -- cgit v1.2.3 From b18b047002b7d3b19d9fb905c1bd2a214016c153 Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Mon, 20 May 2024 21:42:10 +0900 Subject: kbuild: change scripts/mksysmap into sed script The previous commit removed the subshell execution from scripts/mksysmap, which is now simple enough to become a sed script. Signed-off-by: Masahiro Yamada --- scripts/mksysmap | 19 ++++++------------- 1 file changed, 6 insertions(+), 13 deletions(-) (limited to 'scripts/mksysmap') diff --git a/scripts/mksysmap b/scripts/mksysmap index e46bafe333bd..c12723a04655 100755 --- a/scripts/mksysmap +++ b/scripts/mksysmap @@ -1,22 +1,16 @@ -#!/bin/sh -x -# Based on the vmlinux file create the System.map file +#!/bin/sed -f +# SPDX-License-Identifier: GPL-2.0-only +# +# sed script to filter out symbols that are not needed for System.map, +# or not suitable for kallsyms. The input should be 'nm -n '. +# # System.map is used by module-init tools and some debugging # tools to retrieve the actual addresses of symbols in the kernel. # -# Usage -# mksysmap vmlinux System.map - - -##### -# Generate System.map (actual filename passed as second argument) -# The following refers to the symbol type as per nm(1). - # readprofile starts reading symbols when _stext is found, and # continue until it finds a symbol which is not either of 'T', 't', # 'W' or 'w'. # - -${NM} -n ${1} | sed >${2} -e " # --------------------------------------------------------------------------- # Ignored symbol types # @@ -92,4 +86,3 @@ ${NM} -n ${1} | sed >${2} -e " # ppc stub /\.long_branch\./d /\.plt_branch\./d -" -- cgit v1.2.3