| Message ID | 20220322173547.677760-1-nathan@kernel.org |
|---|---|
| State | Superseded |
| Headers | show |
| Series | um: Fix filtering '-mno-global-merge' | expand |
On Wed, Mar 23, 2022 at 1:39 AM Nathan Chancellor <nathan@kernel.org> wrote: > > When booting a clang compiled UML kernel, the kernel panics when trying > to run init: > > wait_stub_done : failed to wait for SIGTRAP, pid = 651294, n = 651294, errno = 0, status = 0xb7f > Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b > > After the commit in Fixes, many flags from KBUILD_CFLAGS do not appear > in USER_CFLAGS, likely due to USER_CFLAGS initially being a recursive > variable ("VAR =") then being switched to a simple ("VAR :=") variable. > For example, diffing arch/x86/um/.ptrace_user.o.cmd shows flags such as > '-Os' and '-fno-delete-null-pointer-checks' getting dropped, which both > impact code generation. > > Rework the filtering to use filter-out instead of patsubst, which allows > all the patterns that USER_CFLAGS cares about to be excluded in one > command and ensures all flags from KBUILD_CFLAGS are transferred over to > USER_CFLAGS properly, which resolves the boot issue noted above. > > Fixes: 6580c5c18fb3 ("um: clang: Strip out -mno-global-merge from USER_CFLAGS") > Signed-off-by: Nathan Chancellor <nathan@kernel.org> > --- Thanks. I was able to reproduce the panic here, and this indeed fixes it. Reviewed-by: David Gow <davidgow@google.com> Cheers, -- David > arch/um/Makefile | 6 +----- > 1 file changed, 1 insertion(+), 5 deletions(-) > > diff --git a/arch/um/Makefile b/arch/um/Makefile > index 320b09cd513c..d202f501e9e1 100644 > --- a/arch/um/Makefile > +++ b/arch/um/Makefile > @@ -70,15 +70,11 @@ KBUILD_CFLAGS += $(CFLAGS) $(CFLAGS-y) -D__arch_um__ \ > > KBUILD_AFLAGS += $(ARCH_INCLUDE) > > -USER_CFLAGS = $(patsubst $(KERNEL_DEFINES),,$(patsubst -I%,,$(KBUILD_CFLAGS))) \ > +USER_CFLAGS = $(filter-out $(KERNEL_DEFINES) -I% -mno-global-merge,$(KBUILD_CFLAGS)) \ > $(ARCH_INCLUDE) $(MODE_INCLUDE) $(filter -I%,$(CFLAGS)) \ > -D_FILE_OFFSET_BITS=64 -idirafter $(srctree)/include \ > -idirafter $(objtree)/include -D__KERNEL__ -D__UM_HOST__ > > -ifdef CONFIG_CC_IS_CLANG > -USER_CFLAGS := $(patsubst -mno-global-merge,,$(USER_CFLAGS)) > -endif > - > #This will adjust *FLAGS accordingly to the platform. > include $(srctree)/$(ARCH_DIR)/Makefile-os-$(OS) > > > base-commit: 82017457957a550d7d00dde419435dd74a890887 > -- > 2.35.1 >
On Wed, Mar 23, 2022 at 2:39 AM Nathan Chancellor <nathan@kernel.org> wrote: > > When booting a clang compiled UML kernel, the kernel panics when trying > to run init: > > wait_stub_done : failed to wait for SIGTRAP, pid = 651294, n = 651294, errno = 0, status = 0xb7f > Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b > > After the commit in Fixes, many flags from KBUILD_CFLAGS do not appear > in USER_CFLAGS, likely due to USER_CFLAGS initially being a recursive > variable ("VAR =") then being switched to a simple ("VAR :=") variable. > For example, diffing arch/x86/um/.ptrace_user.o.cmd shows flags such as > '-Os' and '-fno-delete-null-pointer-checks' getting dropped, which both > impact code generation. > > Rework the filtering to use filter-out instead of patsubst, which allows > all the patterns that USER_CFLAGS cares about to be excluded in one > command and ensures all flags from KBUILD_CFLAGS are transferred over to > USER_CFLAGS properly, which resolves the boot issue noted above. > > Fixes: 6580c5c18fb3 ("um: clang: Strip out -mno-global-merge from USER_CFLAGS") > Signed-off-by: Nathan Chancellor <nathan@kernel.org> Can we remove -mno-global-merge entirely? 61163efae02040f66a95 was a very old commit, without enough explanation. Shall we remove -mno-global-merge, and do compile-tests. If we are hit by problems for arm/arm64, we can re-add it. > --- > arch/um/Makefile | 6 +----- > 1 file changed, 1 insertion(+), 5 deletions(-) > > diff --git a/arch/um/Makefile b/arch/um/Makefile > index 320b09cd513c..d202f501e9e1 100644 > --- a/arch/um/Makefile > +++ b/arch/um/Makefile > @@ -70,15 +70,11 @@ KBUILD_CFLAGS += $(CFLAGS) $(CFLAGS-y) -D__arch_um__ \ > > KBUILD_AFLAGS += $(ARCH_INCLUDE) > > -USER_CFLAGS = $(patsubst $(KERNEL_DEFINES),,$(patsubst -I%,,$(KBUILD_CFLAGS))) \ > +USER_CFLAGS = $(filter-out $(KERNEL_DEFINES) -I% -mno-global-merge,$(KBUILD_CFLAGS)) \ > $(ARCH_INCLUDE) $(MODE_INCLUDE) $(filter -I%,$(CFLAGS)) \ > -D_FILE_OFFSET_BITS=64 -idirafter $(srctree)/include \ > -idirafter $(objtree)/include -D__KERNEL__ -D__UM_HOST__ > > -ifdef CONFIG_CC_IS_CLANG > -USER_CFLAGS := $(patsubst -mno-global-merge,,$(USER_CFLAGS)) > -endif > - > #This will adjust *FLAGS accordingly to the platform. > include $(srctree)/$(ARCH_DIR)/Makefile-os-$(OS) > > > base-commit: 82017457957a550d7d00dde419435dd74a890887 > -- > 2.35.1 >
On Sat, Mar 26, 2022 at 12:29:55PM +0900, Masahiro Yamada wrote: > On Wed, Mar 23, 2022 at 2:39 AM Nathan Chancellor <nathan@kernel.org> wrote: > > > > When booting a clang compiled UML kernel, the kernel panics when trying > > to run init: > > > > wait_stub_done : failed to wait for SIGTRAP, pid = 651294, n = 651294, errno = 0, status = 0xb7f > > Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b > > > > After the commit in Fixes, many flags from KBUILD_CFLAGS do not appear > > in USER_CFLAGS, likely due to USER_CFLAGS initially being a recursive > > variable ("VAR =") then being switched to a simple ("VAR :=") variable. > > For example, diffing arch/x86/um/.ptrace_user.o.cmd shows flags such as > > '-Os' and '-fno-delete-null-pointer-checks' getting dropped, which both > > impact code generation. > > > > Rework the filtering to use filter-out instead of patsubst, which allows > > all the patterns that USER_CFLAGS cares about to be excluded in one > > command and ensures all flags from KBUILD_CFLAGS are transferred over to > > USER_CFLAGS properly, which resolves the boot issue noted above. > > > > Fixes: 6580c5c18fb3 ("um: clang: Strip out -mno-global-merge from USER_CFLAGS") > > Signed-off-by: Nathan Chancellor <nathan@kernel.org> > > > > Can we remove -mno-global-merge entirely? > > > 61163efae02040f66a95 was a very old commit, > without enough explanation. > > Shall we remove -mno-global-merge, and do compile-tests. > If we are hit by problems for arm/arm64, we can re-add it. Yes, I think that was the conversation that we had on the commit that this fixes: https://lore.kernel.org/r/YiD7R2wRxoWxtVq7@dev-arch.thelio-3990X/ I can test that on my Raspberry Pi 3 and 4 on Monday, although I would like for this patch to be picked up in the meantime so that it is possible to test UML on -next with clang. We can remove -mno-global-merge in a follow up change, if you do not have any objections? Cheers, Nathano
On Sun, Mar 27, 2022 at 5:00 AM Nathan Chancellor <nathan@kernel.org> wrote: > > On Sat, Mar 26, 2022 at 12:29:55PM +0900, Masahiro Yamada wrote: > > On Wed, Mar 23, 2022 at 2:39 AM Nathan Chancellor <nathan@kernel.org> wrote: > > > > > > When booting a clang compiled UML kernel, the kernel panics when trying > > > to run init: > > > > > > wait_stub_done : failed to wait for SIGTRAP, pid = 651294, n = 651294, errno = 0, status = 0xb7f > > > Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b > > > > > > After the commit in Fixes, many flags from KBUILD_CFLAGS do not appear > > > in USER_CFLAGS, likely due to USER_CFLAGS initially being a recursive > > > variable ("VAR =") then being switched to a simple ("VAR :=") variable. > > > For example, diffing arch/x86/um/.ptrace_user.o.cmd shows flags such as > > > '-Os' and '-fno-delete-null-pointer-checks' getting dropped, which both > > > impact code generation. > > > > > > Rework the filtering to use filter-out instead of patsubst, which allows > > > all the patterns that USER_CFLAGS cares about to be excluded in one > > > command and ensures all flags from KBUILD_CFLAGS are transferred over to > > > USER_CFLAGS properly, which resolves the boot issue noted above. > > > > > > Fixes: 6580c5c18fb3 ("um: clang: Strip out -mno-global-merge from USER_CFLAGS") > > > Signed-off-by: Nathan Chancellor <nathan@kernel.org> > > > > > > > > Can we remove -mno-global-merge entirely? > > > > > > 61163efae02040f66a95 was a very old commit, > > without enough explanation. > > > > Shall we remove -mno-global-merge, and do compile-tests. > > If we are hit by problems for arm/arm64, we can re-add it. > > Yes, I think that was the conversation that we had on the commit that > this fixes: > > https://lore.kernel.org/r/YiD7R2wRxoWxtVq7@dev-arch.thelio-3990X/ > > I can test that on my Raspberry Pi 3 and 4 on Monday, although I would > like for this patch to be picked up in the meantime so that it is > possible to test UML on -next with clang. We can remove > -mno-global-merge in a follow up change, if you do not have any > objections? > > Cheers, > Nathano This patch is unneeded now because I picked up the alternative: https://lore.kernel.org/all/CAK7LNAS6C6Uj9cCQ0o=bYF1F-EVD=VgdR8YYx-1PJc9toX_HZA@mail.gmail.com/
diff --git a/arch/um/Makefile b/arch/um/Makefile index 320b09cd513c..d202f501e9e1 100644 --- a/arch/um/Makefile +++ b/arch/um/Makefile @@ -70,15 +70,11 @@ KBUILD_CFLAGS += $(CFLAGS) $(CFLAGS-y) -D__arch_um__ \ KBUILD_AFLAGS += $(ARCH_INCLUDE) -USER_CFLAGS = $(patsubst $(KERNEL_DEFINES),,$(patsubst -I%,,$(KBUILD_CFLAGS))) \ +USER_CFLAGS = $(filter-out $(KERNEL_DEFINES) -I% -mno-global-merge,$(KBUILD_CFLAGS)) \ $(ARCH_INCLUDE) $(MODE_INCLUDE) $(filter -I%,$(CFLAGS)) \ -D_FILE_OFFSET_BITS=64 -idirafter $(srctree)/include \ -idirafter $(objtree)/include -D__KERNEL__ -D__UM_HOST__ -ifdef CONFIG_CC_IS_CLANG -USER_CFLAGS := $(patsubst -mno-global-merge,,$(USER_CFLAGS)) -endif - #This will adjust *FLAGS accordingly to the platform. include $(srctree)/$(ARCH_DIR)/Makefile-os-$(OS)
When booting a clang compiled UML kernel, the kernel panics when trying to run init: wait_stub_done : failed to wait for SIGTRAP, pid = 651294, n = 651294, errno = 0, status = 0xb7f Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b After the commit in Fixes, many flags from KBUILD_CFLAGS do not appear in USER_CFLAGS, likely due to USER_CFLAGS initially being a recursive variable ("VAR =") then being switched to a simple ("VAR :=") variable. For example, diffing arch/x86/um/.ptrace_user.o.cmd shows flags such as '-Os' and '-fno-delete-null-pointer-checks' getting dropped, which both impact code generation. Rework the filtering to use filter-out instead of patsubst, which allows all the patterns that USER_CFLAGS cares about to be excluded in one command and ensures all flags from KBUILD_CFLAGS are transferred over to USER_CFLAGS properly, which resolves the boot issue noted above. Fixes: 6580c5c18fb3 ("um: clang: Strip out -mno-global-merge from USER_CFLAGS") Signed-off-by: Nathan Chancellor <nathan@kernel.org> --- arch/um/Makefile | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-) base-commit: 82017457957a550d7d00dde419435dd74a890887