kpatch-build fails: unable to locate patch-hook.o since linux commit 13b25489b6f8

[sumanthkorikkar]

Hi All,

Starting from linux commit 13b25489b6f8 ("kbuild: change working directory to external module directory with M="), the kpatch-build fails

Error log:
meminfo.o: changed function: meminfo_proc_show                                  
make V=1 -C /mnt/linux M=/root/.kpatch/tmp/patch CFLAGS_MODULE=''               
make[1]: Entering directory '/mnt/linux'                                        
make  -C /root/.kpatch/tmp/patch \                                              
-f /mnt/linux/Makefile                                                          
make[2]: Entering directory '/root/.kpatch/tmp/patch'                           
make --no-print-directory -C /root/.kpatch/tmp/patch \                          
-f /mnt/linux/Makefile                                                          
make -f /mnt/linux/scripts/Makefile.build obj=. need-builtin=1 need-modorder=1  
# cmd_mod test-data-new.mod                                                     
  printf '%s\n'   patch-hook.o output.o | awk '!x[$0]++ { print("./"$0) }' > test-data-new.mod
# LDS     kpatch.lds                                                            
  gcc -E -Wp,-MMD,./.kpatch.lds.d -nostdinc -I/mnt/linux/arch/s390/include -I/mnt/linux/arch/s390/include/generated -I/mnt/linux/include -I/mnt/linux/include -I/mnt/linux/arch/s390/include/uapi -I/mnt/linux/arch/s390/include/generated/uapi -I/mnt/linux/include/uapi -I/mnt/linux/include/generated/uapi -include /mnt/linux/include/linux/compiler-version.h -include /mnt/linux/include/linux/kconfig.h -D__KERNEL__ -fmacro-prefix-map=/mnt/linux/=   -P -Us390 -D__ASSEMBLY__ -DLINKER_SCRIPT -o kpatch.lds kpatch.lds.S
make V=1 -C /mnt/linux M=/root/.kpatch/tmp/patch CFLAGS_MODULE='' patch-hook.o  
make -f /mnt/linux/scripts/Makefile.build obj=. need-builtin=1 need-modorder=1 ./patch-hook.o
make[6]: *** No rule to make target 'patch-hook.o'.  Stop. `

Error notes:

- make -C changes the directory to /mnt/linux.
- With linux commit 13b25489b6f8, make inturn switches the working directory to the external module directory /root/.kpatch/tmp/patch.
- $(KPATCH_MAKE) patch-hook.o is called, which inturn changes directory back to /mnt/linux and patch-hook.o is not found

Previous working state:

checking file fs/proc/meminfo.c                                                 
Hunk #1 succeeded at 31 (offset 2 lines).                                       
Hunk #2 succeeded at 153 with fuzz 2 (offset 6 lines).                          
patching file fs/proc/meminfo.c                                                 
Hunk #1 succeeded at 31 (offset 2 lines).                                       
Hunk #2 succeeded at 153 with fuzz 2 (offset 6 lines).                          
  CALL    scripts/checksyscalls.sh                                              
  CC      fs/proc/meminfo.o                                                     
  AR      fs/proc/built-in.a                                                    
meminfo.o: changed function: meminfo_proc_show                                  
make V=1 -C /mnt/linux M=/root/.kpatch/tmp/patch CFLAGS_MODULE=''               
make[1]: Entering directory '/mnt/linux'                                        
make --no-print-directory -C /mnt/linux \                                       
-f /mnt/linux/Makefile                                                          
make -f ./scripts/Makefile.build obj=/root/.kpatch/tmp/patch need-builtin=1 need-modorder=1   <<<<< obj=/root/.kpatch/tmp/patch  -> via KBUILD_EXTMOD 
# cmd_mod /root/.kpatch/tmp/patch/test-data-new.mod                             
  printf '%s\n'   patch-hook.o output.o | awk '!x[$0]++ { print("/root/.kpatch/tmp/patch/"$0) }' > /root/.kpatch/tmp/patch/test-data-new.mod
# LDS     /root/.kpatch/tmp/patch/kpatch.lds                                    
  gcc -E -Wp,-MMD,/root/.kpatch/tmp/patch/.kpatch.lds.d -nostdinc -I./arch/s390/include -I./arch/s390/include/generated  -I./include -I./arch/s390/include/uapi -I./arch/s390/include/generated/uapi -I./include/uapi -I./include/generated/uapi -include ./include/linux/compiler-version.h -include ./include/linux/kconfig.h -D__KERNEL__ -fmacro-prefix-map=./=   -P -Us390 -D__ASSEMBLY__ -DLINKER_SCRIPT -o /root/.kpatch/tmp/patch/kpatch.lds /root/.kpatch/tmp/patch/kpatch.lds.S
# CC [M]  /root/.kpatch/tmp/patch/patch-hook.o  <<====
# CC [M]  /root/.kpatch/tmp/patch/patch-hook.o                                  
  gcc -Wp,-MMD,/root/.kpatch/tmp/patch/.patch-hook.o.d -nostdinc -I./arch/s390/include -I./arch/s390/include/generated  -I./include -I./arch/s390/include/uapi -I./arch/s390/include/generated/uapi -I./include/uapi -I./include/generated/uapi -include ./include/linux/compiler-version.h -include ./include/linux/kconfig.h -include ./include/linux/compiler_types.h -D__KERNEL__ -fmacro-prefix-map=./= -std=gnu11 -fshort-wchar -funsigned-char -fno-common -fno-PIE -fno-strict-aliasing -m64 -fPIC -mpacked-stack -mbackchain -msoft-float -march=z13 -mtune=z13 -Wa,-I./arch/s390/include -mindirect-branch=thunk-extern -mfunction-return=thunk-extern -mindirect-branch-table -DCC_USING_EXPOLINE -pipe -Wno-sign-compare -fno-asynchronous-unwind-tables -DCONFIG_AS_CFI_VAL_OFFSET=1 -fno-delete-null-pointer-checks -O2 -fno-allow-store-data-races -fno-stack-protector -ftrivial-auto-var-init=zero -fno-stack-clash-protection -pg -mrecord-mcount -mnop-mcount -mfentry -DCC_USING_NOP_MCOUNT -DCC_USING_FENTRY -fno-inline-functions-called-once -falign-functions=8 -fstrict-flex-arrays=3 -fno-strict-overflow -fno-stack-check -fconserve-stack -Wall -Wundef -Werror=implicit-function-declaration -Werror=implicit-int -Werror=return-type -Werror=strict-prototypes -Wno-format-security -Wno-trigraphs -Wno-frame-address -Wno-address-of-packed-member -Wmissing-declarations -Wmissing-prototypes -Wframe-larger-than=2048 -Wno-main -Wno-dangling-pointer -Wvla -Wno-pointer-sign -Wcast-function-type -Wno-stringop-overflow -Wno-array-bounds -Wno-alloc-size-larger-than -Wimplicit-fallthrough=5 -Werror=date-time -Werror=incompatible-pointer-types -Werror=designated-init -Wenum-conversion -Wextra -Wunused -Wno-unused-but-set-variable -Wno-unused-const-variable -Wno-packed-not-aligned -Wno-format-overflow -Wno-format-truncation -Wno-stringop-truncation -Wno-override-init -Wno-missing-field-initializers -Wno-type-limits -Wno-shift-negative-value -Wno-maybe-uninitialized -Wno-sign-compare -Wno-unused-parameter -g -gdwarf-4 -I/root/kpatch/kmod/patch -mno-pic-data-is-text-relative -fno-section-anchors  -DMODULE -fPIC  -DKBUILD_BASENAME='"patch_hook"' -DKBUILD_MODNAME='"test_data_new"' -D__KBUILD_MODNAME=kmod_test_data_new -c -o /root/.kpatch/tmp/patch/patch-hook.o /root/.kpatch/tmp/patch/patch-hook.c
...

Possible resolution:

- Remove $(KPATCH_MAKE) patch-hook.o in Makefile. This would mean make patch-hook.o cannot be performed directly. 
- Dependencies in Makefile:
  $(KPATCH_NAME)-objs += patch-hook.o output.o
  patch-hook.o: patch-hook.c kpatch-patch-hook.c livepatch-patch-hook.c
- However, If any of the above sources are updated, kpatch module would  be rebuilt anyways.

Possible resolution patch:

diff --git a/kmod/patch/Makefile b/kmod/patch/Makefile
index bb4d49c..c684387 100644
--- a/kmod/patch/Makefile
+++ b/kmod/patch/Makefile
@@ -1,5 +1,5 @@
 KPATCH_BUILD ?= /lib/modules/$(shell uname -r)/build
-KPATCH_MAKE = $(MAKE) -C $(KPATCH_BUILD) M=$(PWD) CFLAGS_MODULE='$(CFLAGS_MODULE)'
+KPATCH_MAKE = $(MAKE) V=1 -C $(KPATCH_BUILD) M=$(PWD) CFLAGS_MODULE='$(CFLAGS_MODULE)'
 LDFLAGS += $(KPATCH_LDFLAGS)
 
 # object files that this Makefile can (re)build on its own
@@ -19,7 +19,6 @@ $(KPATCH_NAME).ko:
 $(obj)/$(KPATCH_NAME).o: $(src)/kpatch.lds
 
 patch-hook.o: patch-hook.c kpatch-patch-hook.c livepatch-patch-hook.c
-       $(KPATCH_MAKE) patch-hook.o
 
 clean:
        $(RM) -Rf .*.o.cmd .*.ko.cmd .tmp_versions $(BUILDABLE_OBJS) *.ko *.mod.c \

Resolution output:

meminfo.o: changed function: meminfo_proc_show                                  
make V=1 -C /mnt/linux M=/root/.kpatch/tmp/patch CFLAGS_MODULE=''               
make[1]: Entering directory '/mnt/linux'                                        
make  -C /root/.kpatch/tmp/patch \                                              
-f /mnt/linux/Makefile                                                          
make[2]: Entering directory '/root/.kpatch/tmp/patch'                           
make --no-print-directory -C /root/.kpatch/tmp/patch \                          
-f /mnt/linux/Makefile                                                          
make -f /mnt/linux/scripts/Makefile.build obj=. need-builtin=1 need-modorder=1    <<<< obj=.
# cmd_mod test-data-new.mod                                                     
  printf '%s\n'   patch-hook.o output.o | awk '!x[$0]++ { print("./"$0) }' > test-data-new.mod
# LDS     kpatch.lds                                                            
  gcc -E -Wp,-MMD,./.kpatch.lds.d -nostdinc -I/mnt/linux/arch/s390/include -I/mnt/linux/arch/s390/include/generated -I/mnt/linux/include -I/mnt/linux/include -I/mnt/linux/arch/s390/include/uapi -I/mnt/linux/arch/s390/include/generated/uapi -I/mnt/linux/include/uapi -I/mnt/linux/include/generated/uapi -include /mnt/linux/include/linux/compiler-version.h -include /mnt/linux/include/linux/kconfig.h -D__KERNEL__ -fmacro-prefix-map=/mnt/linux/=   -P -Us390 -D__ASSEMBLY__ -DLINKER_SCRIPT -o kpatch.lds kpatch.lds.S
# CC [M]  patch-hook.o  <<<<                                                         
  gcc -Wp,-MMD,./.patch-hook.o.d -nostdinc -I/mnt/linux/arch/s390/include -I/mnt/linux/arch/s390/include/generated -I/mnt/linux/include -I/mnt/linux/include -I/mnt/linux/arch/s390/include/uapi -I/mnt/linux/arch/s390/include/generated/uapi -I/mnt/linux/include/uapi -I/mnt/linux/include/generated/uapi -include /mnt/linux/include/linux/compiler-version.h -include /mnt/linux/include/linux/kconfig.h -include /mnt/linux/include/linux/compiler_types.h -D__KERNEL__ -fmacro-prefix-map=/mnt/linux/= -std=gnu11 -fshort-wchar -funsigned-char -fno-common -fno-PIE -fno-strict-aliasing -m64 -fPIC -mpacked-stack -mbackchain -msoft-float -march=z13 -mtune=z13 -Wa,-I/mnt/linux/arch/s390/include -mindirect-branch=thunk-extern -mfunction-return=thunk-extern -mindirect-branch-table -DCC_USING_EXPOLINE -pipe -Wno-sign-compare -fno-asynchronous-unwind-tables -DCONFIG_AS_CFI_VAL_OFFSET=1 -fno-delete-null-pointer-checks -O2 -fno-allow-store-data-races -fno-stack-protector -ftrivial-auto-var-init=zero -fno-stack-clash-protection -pg -mrecord-mcount -mnop-mcount -mfentry -DCC_USING_NOP_MCOUNT -DCC_USING_FENTRY -fno-inline-functions-called-once -falign-functions=8 -fstrict-flex-arrays=3 -fno-strict-overflow -fno-stack-check -fconserve-stack -Wall -Wundef -Werror=implicit-function-declaration -Werror=implicit-int -Werror=return-type -Werror=strict-prototypes -Wno-format-security -Wno-trigraphs -Wno-frame-address -Wno-address-of-packed-member -Wmissing-declarations -Wmissing-prototypes -Wframe-larger-than=2048 -Wno-main -Wno-dangling-pointer -Wvla -Wno-pointer-sign -Wcast-function-type -Wno-stringop-overflow -Wno-array-bounds -Wno-alloc-size-larger-than -Wimplicit-fallthrough=5 -Werror=date-time -Werror=incompatible-pointer-types -Werror=designated-init -Wenum-conversion -Wextra -Wunused -Wno-unused-but-set-variable -Wno-unused-const-variable -Wno-packed-not-aligned -Wno-format-overflow -Wno-format-truncation -Wno-stringop-truncation -Wno-override-init -Wno-missing-field-initializers -Wno-type-limits -Wno-shift-negative-value -Wno-maybe-uninitialized -Wno-sign-compare -Wno-unused-parameter -g -gdwarf-4 -I/root/kpatch/kmod/patch -mno-pic-data-is-text-relative -fno-section-anchors  -DMODULE -fPIC  -DKBUILD_BASENAME='"patch_hook"' -DKBUILD_MODNAME='"test_data_new"' -D__KBUILD_MODNAME=kmod_test_data_new -c -o patch-hook.o patch-hook.c
...  

Let me know, if this solution is optimal or reasonable. If yes, I will proceed with the patch.

Thank you,
Sumanth