| Message ID | 20210310101400.3904724-4-siddhesh@sourceware.org |
|---|---|
| State | New |
| Headers | show |
| Series | Clean up stack-protector-all build | expand |
On 10/03/2021 07:14, Siddhesh Poyarekar via Libc-alpha wrote: > This does not change the emitted code since __libc_start_main does not > return, but is important for formal flags compliance. > > This also cleans up the cosmetic inconsistency in the stack protector > flags in csu, especially the incorrect value of STACK_PROTECTOR_LEVEL. LGTM, thanks. Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org> > --- > Makeconfig | 8 ++++++++ > csu/Makefile | 22 ++++++++++++---------- > elf/Makefile | 4 ---- > 3 files changed, 20 insertions(+), 14 deletions(-) > > diff --git a/Makeconfig b/Makeconfig > index 0a4811b5e5..01f8638c2e 100644 > --- a/Makeconfig > +++ b/Makeconfig > @@ -856,6 +856,14 @@ ifneq ($(stack-protector),) > +stack-protector=$(stack-protector) > endif > > +# Some routines are unsafe to build with stack-protection since they're called > +# before the stack check guard is set up. Provide a way to disable stack > +# protector. The first argument is the extension (.o, .os, .oS) and the second > +# is a list of routines that this path should be applied to. > +define elide-stack-protector > +$(if $(filter $(@F),$(patsubst %,%$(1),$(2))), $(no-stack-protector)) > +endef > + > # This is the program that generates makefile dependencies from C source files. > # The -MP flag tells GCC >= 3.2 (which we now require) to produce dummy > # targets for headers so that removed headers don't break the build. Ok. > diff --git a/csu/Makefile b/csu/Makefile > index e587434be8..3054329cea 100644 > --- a/csu/Makefile > +++ b/csu/Makefile > @@ -45,18 +45,20 @@ install-lib = $(start-installed-name) g$(start-installed-name) $(csu-dummies) > # code is compiled with special flags. > tests = > > -CFLAGS-.o += $(no-stack-protector) > -CFLAGS-.op += $(no-stack-protector) > -CFLAGS-.os += $(no-stack-protector) > - > -# Dummy object not actually used for anything. It is linked into > -# crt1.o nevertheless, which in turn is statically linked into > +# static-reloc.os is a dummy object not actually used for anything. It is > +# linked into crt1.o nevertheless, which in turn is statically linked into > # applications, so that build flags matter. > # See <https://sourceware.org/ml/libc-alpha/2018-07/msg00101.html>. > -# NB: Using $(stack-protector) in this way causes a wrong definition > -# STACK_PROTECTOR_LEVEL due to the preceding $(no-stack-protector), > -# but it does not matter for this source file. > -CFLAGS-static-reloc.os += $(stack-protector) Ok. > +# > +# libc-start.os is safe to be built with stack protector since > +# __libc_start_main is called after stack canary setup is done. > +ssp-safe.os = static-reloc libc-start > + > +CFLAGS-.o += $(call elide-stack-protector,.o,$(routines)) > +CFLAGS-.op += $(call elide-stack-protector,.op,$(routines)) > +CFLAGS-.oS += $(call elide-stack-protector,.oS,$(routines)) > +CFLAGS-.os += $(call elide-stack-protector,.os,$(filter-out \ > + $(ssp-safe.os),$(routines))) > > ifeq (yes,$(build-shared)) > extra-objs += S$(start-installed-name) gmon-start.os Ok. > diff --git a/elf/Makefile b/elf/Makefile > index b06bf6ca20..285d9f2f3c 100644 > --- a/elf/Makefile > +++ b/elf/Makefile > @@ -83,10 +83,6 @@ endif > # Also compile all routines in the static library that are elided from > # the shared libc because they are in libc.a in the same way. > > -define elide-stack-protector > -$(if $(filter $(@F),$(patsubst %,%$(1),$(2))), $(no-stack-protector)) > -endef > - > CFLAGS-.o += $(call elide-stack-protector,.o,$(elide-routines.os)) > CFLAGS-.op += $(call elide-stack-protector,.op,$(elide-routines.os)) > CFLAGS-.os += $(call elide-stack-protector,.os,$(all-rtld-routines)) > Ok.
diff --git a/Makeconfig b/Makeconfig index 0a4811b5e5..01f8638c2e 100644 --- a/Makeconfig +++ b/Makeconfig @@ -856,6 +856,14 @@ ifneq ($(stack-protector),) +stack-protector=$(stack-protector) endif +# Some routines are unsafe to build with stack-protection since they're called +# before the stack check guard is set up. Provide a way to disable stack +# protector. The first argument is the extension (.o, .os, .oS) and the second +# is a list of routines that this path should be applied to. +define elide-stack-protector +$(if $(filter $(@F),$(patsubst %,%$(1),$(2))), $(no-stack-protector)) +endef + # This is the program that generates makefile dependencies from C source files. # The -MP flag tells GCC >= 3.2 (which we now require) to produce dummy # targets for headers so that removed headers don't break the build. diff --git a/csu/Makefile b/csu/Makefile index e587434be8..3054329cea 100644 --- a/csu/Makefile +++ b/csu/Makefile @@ -45,18 +45,20 @@ install-lib = $(start-installed-name) g$(start-installed-name) $(csu-dummies) # code is compiled with special flags. tests = -CFLAGS-.o += $(no-stack-protector) -CFLAGS-.op += $(no-stack-protector) -CFLAGS-.os += $(no-stack-protector) - -# Dummy object not actually used for anything. It is linked into -# crt1.o nevertheless, which in turn is statically linked into +# static-reloc.os is a dummy object not actually used for anything. It is +# linked into crt1.o nevertheless, which in turn is statically linked into # applications, so that build flags matter. # See <https://sourceware.org/ml/libc-alpha/2018-07/msg00101.html>. -# NB: Using $(stack-protector) in this way causes a wrong definition -# STACK_PROTECTOR_LEVEL due to the preceding $(no-stack-protector), -# but it does not matter for this source file. -CFLAGS-static-reloc.os += $(stack-protector) +# +# libc-start.os is safe to be built with stack protector since +# __libc_start_main is called after stack canary setup is done. +ssp-safe.os = static-reloc libc-start + +CFLAGS-.o += $(call elide-stack-protector,.o,$(routines)) +CFLAGS-.op += $(call elide-stack-protector,.op,$(routines)) +CFLAGS-.oS += $(call elide-stack-protector,.oS,$(routines)) +CFLAGS-.os += $(call elide-stack-protector,.os,$(filter-out \ + $(ssp-safe.os),$(routines))) ifeq (yes,$(build-shared)) extra-objs += S$(start-installed-name) gmon-start.os diff --git a/elf/Makefile b/elf/Makefile index b06bf6ca20..285d9f2f3c 100644 --- a/elf/Makefile +++ b/elf/Makefile @@ -83,10 +83,6 @@ endif # Also compile all routines in the static library that are elided from # the shared libc because they are in libc.a in the same way. -define elide-stack-protector -$(if $(filter $(@F),$(patsubst %,%$(1),$(2))), $(no-stack-protector)) -endef - CFLAGS-.o += $(call elide-stack-protector,.o,$(elide-routines.os)) CFLAGS-.op += $(call elide-stack-protector,.op,$(elide-routines.os)) CFLAGS-.os += $(call elide-stack-protector,.os,$(all-rtld-routines))