[PATCH] kbuild: escape single backslashes in macro make-cmd

Konstantin Khlebnikov
2014-07-26T16:36:10Z

This already has been fixed in commit c353acba28fb3fa1fd05fd
("kbuild: make: fix if_changed when command contains backslashes")
but escaping still isn't perfect and triggers false-positive rebuilds.

For x86 problem happens every time, because rules in arch/x86/realmode/rm/
and arch/x86/boot/ contains commands like sed -n -e 's/foo\(.*\)/\1/p'.
Backslash in \1 isn't escaped and turns into ascii symbol with code 1.
Macro if_changed detects command change and rebuilds target again and again.

Backslash escaping conflicts with other passes because it's used for escaping
other symbols. To avoid that current macro handles only double backslashes.
Obviously this doesn't work for \1 like above.

This patch reorders passes. It doubles all backslashes before escaping # and '

Visible effect in rebuilding x86/defconfig without changes, before patch:

blind@zurg:~/src/linux$ make V=2
CHK include/config/kernel.release
CHK include/generated/uapi/linux/version.h
CHK include/generated/utsrelease.h
CALL scripts/checksyscalls.sh - due to target missing
CHK include/generated/compile.h
PASYMS arch/x86/realmode/rm/pasyms.h - due to command line change
LDS arch/x86/realmode/rm/realmode.lds - due to: arch/x86/realmode/rm/pasyms.h
LD arch/x86/realmode/rm/realmode.elf - due to: arch/x86/realmode/rm/realmode.lds
RELOCS arch/x86/realmode/rm/realmode.relocs - due to: arch/x86/realmode/rm/realmode.elf
OBJCOPY arch/x86/realmode/rm/realmode.bin - due to: arch/x86/realmode/rm/realmode.elf arch/x86/realmode/rm/realmode.relocs
AS arch/x86/realmode/rmpiggy.o - due to: arch/x86/realmode/rm/realmode.bin
LD arch/x86/realmode/built-in.o - due to: arch/x86/realmode/rmpiggy.o
LD arch/x86/built-in.o - due to: arch/x86/realmode/built-in.o
LINK vmlinux - due to: arch/x86/built-in.o
LD vmlinux.o
MODPOST vmlinux.o - due to vmlinux.o not in $(targets)
GEN .version
CHK include/generated/compile.h
UPD include/generated/compile.h
CC init/version.o - due to: include/generated/compile.h
LD init/built-in.o - due to: init/version.o
KSYM .tmp_kallsyms1.o
KSYM .tmp_kallsyms2.o
LD vmlinux
SORTEX vmlinux
SYSMAP System.map
VOFFSET arch/x86/boot/voffset.h - due to: vmlinux
OBJCOPY arch/x86/boot/compressed/vmlinux.bin - due to: vmlinux
GZIP arch/x86/boot/compressed/vmlinux.bin.gz - due to: arch/x86/boot/compressed/vmlinux.bin
MKPIGGY arch/x86/boot/compressed/piggy.S - due to: arch/x86/boot/compressed/vmlinux.bin.gz
AS arch/x86/boot/compressed/piggy.o - due to: arch/x86/boot/compressed/piggy.S
LD arch/x86/boot/compressed/vmlinux - due to: arch/x86/boot/compressed/piggy.o
ZOFFSET arch/x86/boot/zoffset.h - due to: arch/x86/boot/compressed/vmlinux
AS arch/x86/boot/header.o - due to: arch/x86/boot/voffset.h arch/x86/boot/zoffset.h
CC arch/x86/boot/version.o - due to: include/generated/compile.h
LD arch/x86/boot/setup.elf - due to: arch/x86/boot/header.o arch/x86/boot/version.o
OBJCOPY arch/x86/boot/setup.bin - due to: arch/x86/boot/setup.elf
OBJCOPY arch/x86/boot/vmlinux.bin - due to: arch/x86/boot/compressed/vmlinux
BUILD arch/x86/boot/bzImage - due to: arch/x86/boot/setup.bin arch/x86/boot/vmlinux.bin
Setup is 15676 bytes (padded to 15872 bytes).
System is 5569 kB
CRC c06bbc0c
Kernel: arch/x86/boot/bzImage is ready (#4)
Building modules, stage 2.
MODPOST 12 modules - due to target is PHONY

After:

blind@zurg:~/src/linux$ make V=2
CHK include/config/kernel.release
CHK include/generated/uapi/linux/version.h
CHK include/generated/utsrelease.h
CALL scripts/checksyscalls.sh - due to target missing
CHK include/generated/compile.h
Kernel: arch/x86/boot/bzImage is ready (#5)
Building modules, stage 2.
MODPOST 12 modules - due to target is PHONY

Signed-off-by: Konstantin Khlebnikov <koct9i@gmail.com>
---
scripts/Kbuild.include | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
index 122f95c..edd0b0d 100644
--- a/scripts/Kbuild.include
+++ b/scripts/Kbuild.include
@@ -219,7 +219,7 @@ endif
# >$< substitution to preserve $ when reloading .cmd file
# note: when using inline perl scripts [perl -e '...$$t=1;...']
# in $(cmd_xxx) double $$ your perl vars
-make-cmd = $(subst \\,\\\\,$(subst \#,\\\#,$(subst $$,$$$$,$(call escsq,$(cmd_$(1))))))
+make-cmd = $(call escsq,$(subst \#,\\\#,$(subst \,\\,$(subst $$,$$$$,$(cmd_$(1))))))

# Find any prerequisites that is newer than target or that does not exist.
# PHONY targets skipped in both cases.