| Message ID | 20200731230820.1742553-24-keescook@chromium.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Warn on orphan section placement | expand |
On Fri, Jul 31, 2020 at 4:18 PM Kees Cook <keescook@chromium.org> wrote: > > In preparation for adding --orphan-handling=warn, explicitly keep the > .ARM.attributes section by expanding the existing ELF_DETAILS macro into > ARM_DETAILS. > > Suggested-by: Nick Desaulniers <ndesaulniers@google.com> > Link: https://lore.kernel.org/lkml/CAKwvOdk-racgq5pxsoGS6Vtifbtrk5fmkmnoLxrQMaOvV0nPWw@mail.gmail.com/ > Signed-off-by: Kees Cook <keescook@chromium.org> > --- > arch/arm/include/asm/vmlinux.lds.h | 4 ++++ > arch/arm/kernel/vmlinux-xip.lds.S | 2 +- > arch/arm/kernel/vmlinux.lds.S | 2 +- > 3 files changed, 6 insertions(+), 2 deletions(-) > > diff --git a/arch/arm/include/asm/vmlinux.lds.h b/arch/arm/include/asm/vmlinux.lds.h > index a08f4301b718..c4af5182ab48 100644 > --- a/arch/arm/include/asm/vmlinux.lds.h > +++ b/arch/arm/include/asm/vmlinux.lds.h > @@ -52,6 +52,10 @@ > ARM_MMU_DISCARD(*(__ex_table)) \ > COMMON_DISCARDS > > +#define ARM_DETAILS \ > + ELF_DETAILS \ > + .ARM.attributes 0 : { *(.ARM.attributes) } I had to look up what the `0` meant: https://sourceware.org/binutils/docs/ld/Output-Section-Attributes.html#Output-Section-Attributes mentions it's an "address" and https://ftp.gnu.org/old-gnu/Manuals/ld-2.9.1/html_chapter/ld_3.html#SEC21 mentions it as "start" (an address). Unless we need those, can we drop them? (Sorry for the resulting churn that would cause). I think the NO_LOAD stuff makes more sense, but I'm curious if the kernel checks for that. > + > #define ARM_STUBS_TEXT \ > *(.gnu.warning) \ > *(.glue_7) \ > diff --git a/arch/arm/kernel/vmlinux-xip.lds.S b/arch/arm/kernel/vmlinux-xip.lds.S > index 904c31fa20ed..57fcbf55f913 100644 > --- a/arch/arm/kernel/vmlinux-xip.lds.S > +++ b/arch/arm/kernel/vmlinux-xip.lds.S > @@ -150,7 +150,7 @@ SECTIONS > _end = .; > > STABS_DEBUG > - ELF_DETAILS > + ARM_DETAILS > } > > /* > diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S > index bb950c896a67..1d3d3b599635 100644 > --- a/arch/arm/kernel/vmlinux.lds.S > +++ b/arch/arm/kernel/vmlinux.lds.S > @@ -149,7 +149,7 @@ SECTIONS > _end = .; > > STABS_DEBUG > - ELF_DETAILS > + ARM_DETAILS > } > > #ifdef CONFIG_STRICT_KERNEL_RWX > -- > 2.25.1 >
On 2020-08-03, 'Nick Desaulniers' via Clang Built Linux wrote: >On Fri, Jul 31, 2020 at 4:18 PM Kees Cook <keescook@chromium.org> wrote: >> >> In preparation for adding --orphan-handling=warn, explicitly keep the >> .ARM.attributes section by expanding the existing ELF_DETAILS macro into >> ARM_DETAILS. >> >> Suggested-by: Nick Desaulniers <ndesaulniers@google.com> >> Link: https://lore.kernel.org/lkml/CAKwvOdk-racgq5pxsoGS6Vtifbtrk5fmkmnoLxrQMaOvV0nPWw@mail.gmail.com/ >> Signed-off-by: Kees Cook <keescook@chromium.org> >> --- >> arch/arm/include/asm/vmlinux.lds.h | 4 ++++ >> arch/arm/kernel/vmlinux-xip.lds.S | 2 +- >> arch/arm/kernel/vmlinux.lds.S | 2 +- >> 3 files changed, 6 insertions(+), 2 deletions(-) >> >> diff --git a/arch/arm/include/asm/vmlinux.lds.h b/arch/arm/include/asm/vmlinux.lds.h >> index a08f4301b718..c4af5182ab48 100644 >> --- a/arch/arm/include/asm/vmlinux.lds.h >> +++ b/arch/arm/include/asm/vmlinux.lds.h >> @@ -52,6 +52,10 @@ >> ARM_MMU_DISCARD(*(__ex_table)) \ >> COMMON_DISCARDS >> >> +#define ARM_DETAILS \ >> + ELF_DETAILS \ >> + .ARM.attributes 0 : { *(.ARM.attributes) } > >I had to look up what the `0` meant: >https://sourceware.org/binutils/docs/ld/Output-Section-Attributes.html#Output-Section-Attributes >mentions it's an "address" and >https://ftp.gnu.org/old-gnu/Manuals/ld-2.9.1/html_chapter/ld_3.html#SEC21 >mentions it as "start" (an address). >Unless we need those, can we drop them? (Sorry for the resulting churn >that would cause). I think the NO_LOAD stuff makes more sense, but >I'm curious if the kernel checks for that. NOLOAD means SHT_NOBITS (usually SHF_ALLOC). .ARM.attributes is a non-SHF_ALLOC section. An explicit 0 (output section address) is good - GNU ld's internal linker scripts (ld --verbose output) use 0 for such non-SHF_ALLOC sections. Without the 0, the section may get a non-zero address, which is not wrong - but probably does not look well. See https://reviews.llvm.org/D85867 for details. Reviewed-by: Fangrui Song <maskray@google.com> >> + >> #define ARM_STUBS_TEXT \ >> *(.gnu.warning) \ >> *(.glue_7) \ >> diff --git a/arch/arm/kernel/vmlinux-xip.lds.S b/arch/arm/kernel/vmlinux-xip.lds.S >> index 904c31fa20ed..57fcbf55f913 100644 >> --- a/arch/arm/kernel/vmlinux-xip.lds.S >> +++ b/arch/arm/kernel/vmlinux-xip.lds.S >> @@ -150,7 +150,7 @@ SECTIONS >> _end = .; >> >> STABS_DEBUG >> - ELF_DETAILS >> + ARM_DETAILS >> } >> >> /* >> diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S >> index bb950c896a67..1d3d3b599635 100644 >> --- a/arch/arm/kernel/vmlinux.lds.S >> +++ b/arch/arm/kernel/vmlinux.lds.S >> @@ -149,7 +149,7 @@ SECTIONS >> _end = .; >> >> STABS_DEBUG >> - ELF_DETAILS >> + ARM_DETAILS >> } >> >> #ifdef CONFIG_STRICT_KERNEL_RWX >> -- >> 2.25.1 >>
diff --git a/arch/arm/include/asm/vmlinux.lds.h b/arch/arm/include/asm/vmlinux.lds.h index a08f4301b718..c4af5182ab48 100644 --- a/arch/arm/include/asm/vmlinux.lds.h +++ b/arch/arm/include/asm/vmlinux.lds.h @@ -52,6 +52,10 @@ ARM_MMU_DISCARD(*(__ex_table)) \ COMMON_DISCARDS +#define ARM_DETAILS \ + ELF_DETAILS \ + .ARM.attributes 0 : { *(.ARM.attributes) } + #define ARM_STUBS_TEXT \ *(.gnu.warning) \ *(.glue_7) \ diff --git a/arch/arm/kernel/vmlinux-xip.lds.S b/arch/arm/kernel/vmlinux-xip.lds.S index 904c31fa20ed..57fcbf55f913 100644 --- a/arch/arm/kernel/vmlinux-xip.lds.S +++ b/arch/arm/kernel/vmlinux-xip.lds.S @@ -150,7 +150,7 @@ SECTIONS _end = .; STABS_DEBUG - ELF_DETAILS + ARM_DETAILS } /* diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S index bb950c896a67..1d3d3b599635 100644 --- a/arch/arm/kernel/vmlinux.lds.S +++ b/arch/arm/kernel/vmlinux.lds.S @@ -149,7 +149,7 @@ SECTIONS _end = .; STABS_DEBUG - ELF_DETAILS + ARM_DETAILS } #ifdef CONFIG_STRICT_KERNEL_RWX
In preparation for adding --orphan-handling=warn, explicitly keep the .ARM.attributes section by expanding the existing ELF_DETAILS macro into ARM_DETAILS. Suggested-by: Nick Desaulniers <ndesaulniers@google.com> Link: https://lore.kernel.org/lkml/CAKwvOdk-racgq5pxsoGS6Vtifbtrk5fmkmnoLxrQMaOvV0nPWw@mail.gmail.com/ Signed-off-by: Kees Cook <keescook@chromium.org> --- arch/arm/include/asm/vmlinux.lds.h | 4 ++++ arch/arm/kernel/vmlinux-xip.lds.S | 2 +- arch/arm/kernel/vmlinux.lds.S | 2 +- 3 files changed, 6 insertions(+), 2 deletions(-)