| Message ID | 20201020011406.1818918-1-natechancellor@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] arm64: vdso32: Allow ld.lld to properly link the VDSO | expand |
On Mon, Oct 19, 2020 at 06:14:07PM -0700, Nathan Chancellor wrote: > As it stands now, the vdso32 Makefile hardcodes the linker to ld.bfd > using -fuse-ld=bfd with $(CC). This was taken from the arm vDSO > Makefile, as the comment notes, done in commit d2b30cd4b722 ("ARM: > 8384/1: VDSO: force use of BFD linker"). > > Commit fe00e50b2db8 ("ARM: 8858/1: vdso: use $(LD) instead of $(CC) to > link VDSO") changed that Makefile to use $(LD) directly instead of > through $(CC), which matches how the rest of the kernel operates. Since > then, LD=ld.lld means that the arm vDSO will be linked with ld.lld, > which has shown no problems so far. > > Allow ld.lld to link this vDSO as we do the regular arm vDSO. To do > this, we need to do a few things: > > * Add a LD_COMPAT variable, which defaults to $(CROSS_COMPILE_COMPAT)ld > with gcc and $(LD) if LLVM is 1, which will be ld.lld, or > $(CROSS_COMPILE_COMPAT)ld if not, which matches the logic of the main > Makefile. It is overrideable for further customization and avoiding > breakage. > > * Eliminate cc32-ldoption, which matches commit 055efab3120b ("kbuild: > drop support for cc-ldoption"). > > With those, we can use $(LD_COMPAT) in cmd_ldvdso and change the flags > from compiler linker flags to linker flags directly. We eliminate > -mfloat-abi=soft because it is not handled by the linker. > > Link: https://github.com/ClangBuiltLinux/linux/issues/1033 > Reported-by: Nick Desaulniers <ndesaulniers@google.com> > Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> > Tested-by: Nick Desaulniers <ndesaulniers@google.com> > Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com> > Signed-off-by: Nathan Chancellor <natechancellor@gmail.com> > --- Cheers, I'll try to remember to queue this at -rc1 but please feel free to resend then to remind me :) Will
On Mon, 19 Oct 2020 18:14:07 -0700, Nathan Chancellor wrote: > As it stands now, the vdso32 Makefile hardcodes the linker to ld.bfd > using -fuse-ld=bfd with $(CC). This was taken from the arm vDSO > Makefile, as the comment notes, done in commit d2b30cd4b722 ("ARM: > 8384/1: VDSO: force use of BFD linker"). > > Commit fe00e50b2db8 ("ARM: 8858/1: vdso: use $(LD) instead of $(CC) to > link VDSO") changed that Makefile to use $(LD) directly instead of > through $(CC), which matches how the rest of the kernel operates. Since > then, LD=ld.lld means that the arm vDSO will be linked with ld.lld, > which has shown no problems so far. > > [...] Applied to arm64 (for-next/fixes), thanks! [1/1] arm64: vdso32: Allow ld.lld to properly link the VDSO https://git.kernel.org/arm64/c/0fa97e9403c7 Cheers,
diff --git a/arch/arm64/kernel/vdso32/Makefile b/arch/arm64/kernel/vdso32/Makefile index 7f96a1a9f68c..79280c53b9a6 100644 --- a/arch/arm64/kernel/vdso32/Makefile +++ b/arch/arm64/kernel/vdso32/Makefile @@ -22,16 +22,21 @@ endif CC_COMPAT ?= $(CC) CC_COMPAT += $(CC_COMPAT_CLANG_FLAGS) + +ifneq ($(LLVM),) +LD_COMPAT ?= $(LD) +else +LD_COMPAT ?= $(CROSS_COMPILE_COMPAT)ld +endif else CC_COMPAT ?= $(CROSS_COMPILE_COMPAT)gcc +LD_COMPAT ?= $(CROSS_COMPILE_COMPAT)ld endif cc32-option = $(call try-run,\ $(CC_COMPAT) $(1) -c -x c /dev/null -o "$$TMP",$(1),$(2)) cc32-disable-warning = $(call try-run,\ $(CC_COMPAT) -W$(strip $(1)) -c -x c /dev/null -o "$$TMP",-Wno-$(strip $(1))) -cc32-ldoption = $(call try-run,\ - $(CC_COMPAT) $(1) -nostdlib -x c /dev/null -o "$$TMP",$(1),$(2)) cc32-as-instr = $(call try-run,\ printf "%b\n" "$(1)" | $(CC_COMPAT) $(VDSO_AFLAGS) -c -x assembler -o "$$TMP" -,$(2),$(3)) @@ -122,14 +127,10 @@ dmbinstr := $(call cc32-as-instr,dmb ishld,-DCONFIG_AS_DMB_ISHLD=1) VDSO_CFLAGS += $(dmbinstr) VDSO_AFLAGS += $(dmbinstr) -VDSO_LDFLAGS := $(VDSO_CPPFLAGS) # From arm vDSO Makefile -VDSO_LDFLAGS += -Wl,-Bsymbolic -Wl,--no-undefined -Wl,-soname=linux-vdso.so.1 -VDSO_LDFLAGS += -Wl,-z,max-page-size=4096 -Wl,-z,common-page-size=4096 -VDSO_LDFLAGS += -nostdlib -shared -mfloat-abi=soft -VDSO_LDFLAGS += -Wl,--hash-style=sysv -VDSO_LDFLAGS += -Wl,--build-id=sha1 -VDSO_LDFLAGS += $(call cc32-ldoption,-fuse-ld=bfd) +VDSO_LDFLAGS += -Bsymbolic --no-undefined -soname=linux-vdso.so.1 +VDSO_LDFLAGS += -z max-page-size=4096 -z common-page-size=4096 +VDSO_LDFLAGS += -nostdlib -shared --hash-style=sysv --build-id=sha1 # Borrow vdsomunge.c from the arm vDSO @@ -189,8 +190,8 @@ quiet_cmd_vdsold_and_vdso_check = LD32 $@ cmd_vdsold_and_vdso_check = $(cmd_vdsold); $(cmd_vdso_check) quiet_cmd_vdsold = LD32 $@ - cmd_vdsold = $(CC_COMPAT) -Wp,-MD,$(depfile) $(VDSO_LDFLAGS) \ - -Wl,-T $(filter %.lds,$^) $(filter %.o,$^) -o $@ + cmd_vdsold = $(LD_COMPAT) $(VDSO_LDFLAGS) \ + -T $(filter %.lds,$^) $(filter %.o,$^) -o $@ quiet_cmd_vdsocc = CC32 $@ cmd_vdsocc = $(CC_COMPAT) -Wp,-MD,$(depfile) $(VDSO_CFLAGS) -c -o $@ $< quiet_cmd_vdsocc_gettimeofday = CC32 $@
As it stands now, the vdso32 Makefile hardcodes the linker to ld.bfd using -fuse-ld=bfd with $(CC). This was taken from the arm vDSO Makefile, as the comment notes, done in commit d2b30cd4b722 ("ARM: 8384/1: VDSO: force use of BFD linker"). Commit fe00e50b2db8 ("ARM: 8858/1: vdso: use $(LD) instead of $(CC) to link VDSO") changed that Makefile to use $(LD) directly instead of through $(CC), which matches how the rest of the kernel operates. Since then, LD=ld.lld means that the arm vDSO will be linked with ld.lld, which has shown no problems so far. Allow ld.lld to link this vDSO as we do the regular arm vDSO. To do this, we need to do a few things: * Add a LD_COMPAT variable, which defaults to $(CROSS_COMPILE_COMPAT)ld with gcc and $(LD) if LLVM is 1, which will be ld.lld, or $(CROSS_COMPILE_COMPAT)ld if not, which matches the logic of the main Makefile. It is overrideable for further customization and avoiding breakage. * Eliminate cc32-ldoption, which matches commit 055efab3120b ("kbuild: drop support for cc-ldoption"). With those, we can use $(LD_COMPAT) in cmd_ldvdso and change the flags from compiler linker flags to linker flags directly. We eliminate -mfloat-abi=soft because it is not handled by the linker. Link: https://github.com/ClangBuiltLinux/linux/issues/1033 Reported-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> Tested-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com> --- v1 -> v2: * Change ifeq ($(LLVM),1) to ifneq ($(LLVM),) to match the main Makefile per Vincenzo. * Carry forward Nick and Vincenzo's tags. arch/arm64/kernel/vdso32/Makefile | 23 ++++++++++++----------- 1 file changed, 12 insertions(+), 11 deletions(-) base-commit: 0fa21cf4489fe11737d56f8056dda1ba0257bd8d