| Message ID | 20210106200801.31993-2-alobakin@pm.me |
|---|---|
| State | New |
| Headers | show |
| Series | MIPS: vmlinux.lds.S sections fix & cleanup | expand |
On Wed, Jan 06, 2021 at 08:08:19PM +0000, Alexander Lobakin wrote: > Discard GNU attributes at link time as kernel doesn't use it at all. > Solves a dozen of the following ld warnings (one per every file): > > mips-alpine-linux-musl-ld: warning: orphan section `.gnu.attributes' > from `arch/mips/kernel/head.o' being placed in section > `.gnu.attributes' > mips-alpine-linux-musl-ld: warning: orphan section `.gnu.attributes' > from `init/main.o' being placed in section `.gnu.attributes' > > Misc: sort DISCARDS section entries alphabetically. Hmm, I wonder what is causing the appearance of .eh_frame? With help I tracked down all the causes of this on x86, arm, and arm64, so that's why it's not in the asm-generic DISCARDS section. I suspect this could be cleaned up for mips too? Similarly for .gnu.attributes. What is generating that? (Or, more specifically, why is it both being generated AND discarded?) -Kees > > Signed-off-by: Alexander Lobakin <alobakin@pm.me> > --- > arch/mips/kernel/vmlinux.lds.S | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/arch/mips/kernel/vmlinux.lds.S b/arch/mips/kernel/vmlinux.lds.S > index 83e27a181206..5d6563970ab2 100644 > --- a/arch/mips/kernel/vmlinux.lds.S > +++ b/arch/mips/kernel/vmlinux.lds.S > @@ -221,9 +221,10 @@ SECTIONS > /* ABI crap starts here */ > *(.MIPS.abiflags) > *(.MIPS.options) > + *(.eh_frame) > + *(.gnu.attributes) > *(.options) > *(.pdr) > *(.reginfo) > - *(.eh_frame) > } > } > -- > 2.30.0 > >
From: Kees Cook <keescook@chromium.org> Date: Wed, 6 Jan 2021 14:07:07 -0800 > On Wed, Jan 06, 2021 at 08:08:19PM +0000, Alexander Lobakin wrote: >> Discard GNU attributes at link time as kernel doesn't use it at all. >> Solves a dozen of the following ld warnings (one per every file): >> >> mips-alpine-linux-musl-ld: warning: orphan section `.gnu.attributes' >> from `arch/mips/kernel/head.o' being placed in section >> `.gnu.attributes' >> mips-alpine-linux-musl-ld: warning: orphan section `.gnu.attributes' >> from `init/main.o' being placed in section `.gnu.attributes' >> >> Misc: sort DISCARDS section entries alphabetically. > > Hmm, I wonder what is causing the appearance of .eh_frame? With help I > tracked down all the causes of this on x86, arm, and arm64, so that's > why it's not in the asm-generic DISCARDS section. I suspect this could > be cleaned up for mips too? I could take a look and hunt it down. Could you please give some refs on what were the causes and solutions for the mentioned architectures? > Similarly for .gnu.attributes. What is generating that? (Or, more > specifically, why is it both being generated AND discarded?) On my setup, GNU Attributes consist of MIPS FP type (soft) and (if I'm correct) MIPS GNU Hash tables. > -Kees By the way. I've built the kernel with LLVM stack (and found several subjects for more patches) and, besides '.got', also got a fistful of '.data..compoundliteral*' symbols (drivers/mtd/nand/spi/, net/ipv6/ etc). Where should they be placed (rodata, rwdata, ...) or they are anomalies of some kind and should be fixed somehow? >> >> Signed-off-by: Alexander Lobakin <alobakin@pm.me> >> --- >> arch/mips/kernel/vmlinux.lds.S | 3 ++- >> 1 file changed, 2 insertions(+), 1 deletion(-) >> >> diff --git a/arch/mips/kernel/vmlinux.lds.S b/arch/mips/kernel/vmlinux.lds.S >> index 83e27a181206..5d6563970ab2 100644 >> --- a/arch/mips/kernel/vmlinux.lds.S >> +++ b/arch/mips/kernel/vmlinux.lds.S >> @@ -221,9 +221,10 @@ SECTIONS >> /* ABI crap starts here */ >> *(.MIPS.abiflags) >> *(.MIPS.options) >> + *(.eh_frame) >> + *(.gnu.attributes) >> *(.options) >> *(.pdr) >> *(.reginfo) >> - *(.eh_frame) >> } >> } >> -- >> 2.30.0 >> >> > > -- > Kees Cook Thanks, Al
On Wed, Jan 06, 2021 at 10:36:38PM +0000, Alexander Lobakin wrote: > From: Kees Cook <keescook@chromium.org> > Date: Wed, 6 Jan 2021 14:07:07 -0800 > > > On Wed, Jan 06, 2021 at 08:08:19PM +0000, Alexander Lobakin wrote: > >> Discard GNU attributes at link time as kernel doesn't use it at all. > >> Solves a dozen of the following ld warnings (one per every file): > >> > >> mips-alpine-linux-musl-ld: warning: orphan section `.gnu.attributes' > >> from `arch/mips/kernel/head.o' being placed in section > >> `.gnu.attributes' > >> mips-alpine-linux-musl-ld: warning: orphan section `.gnu.attributes' > >> from `init/main.o' being placed in section `.gnu.attributes' > >> > >> Misc: sort DISCARDS section entries alphabetically. > > > > Hmm, I wonder what is causing the appearance of .eh_frame? With help I > > tracked down all the causes of this on x86, arm, and arm64, so that's > > why it's not in the asm-generic DISCARDS section. I suspect this could > > be cleaned up for mips too? > > I could take a look and hunt it down. Could you please give some refs on > what were the causes and solutions for the mentioned architectures? Sure! Here are the ones I could find again: 34b4a5c54c42 ("arm64/kernel: Remove needless Call Frame Information annotations") 6e0a66d10c5b ("arm64/build: Remove .eh_frame* sections due to unwind tables") d1c0272bc1c0 ("x86/boot/compressed: Remove, discard, or assert for unwanted sections") > > Similarly for .gnu.attributes. What is generating that? (Or, more > > specifically, why is it both being generated AND discarded?) > > On my setup, GNU Attributes consist of MIPS FP type (soft) and > (if I'm correct) MIPS GNU Hash tables. Ah, right, the soft-float markings sound correct to discard, IIUC. > By the way. I've built the kernel with LLVM stack (and found several > subjects for more patches) and, besides '.got', also got a fistful > of '.data..compoundliteral*' symbols (drivers/mtd/nand/spi/, > net/ipv6/ etc). Where should they be placed (rodata, rwdata, ...) > or they are anomalies of some kind and should be fixed somehow? Ah yeah, I've seen this before: https://lore.kernel.org/lkml/202010051345.2Q0cvqdM-lkp@intel.com/ https://lore.kernel.org/lkml/CAKwvOd=s53vUELe311VSjxt2_eQd+RGNCf__n+cV+R=PQ_CdXQ@mail.gmail.com/ And it looks like LTO trips over it too: https://lore.kernel.org/lkml/20201211184633.3213045-3-samitolvanen@google.com/ So I think the correct solution is to follow Sami's patch and add it to vmlinux.lds.h: -#define DATA_MAIN .data .data.[0-9a-zA-Z_]* .data..LPBX* +#define DATA_MAIN .data .data.[0-9a-zA-Z_]* .data..L* .data..compoundliteral* ... -#define RODATA_MAIN .rodata .rodata.[0-9a-zA-Z_]* -#define BSS_MAIN .bss .bss.[0-9a-zA-Z_]* +#define RODATA_MAIN .rodata .rodata.[0-9a-zA-Z_]* .rodata..L* +#define BSS_MAIN .bss .bss.[0-9a-zA-Z_]* .bss..compoundliteral* Can you include a patch for this in your series? Thanks!
From: Kees Cook <keescook@chromium.org> Date: Wed, 6 Jan 2021 15:26:18 -0800 > On Wed, Jan 06, 2021 at 10:36:38PM +0000, Alexander Lobakin wrote: >> From: Kees Cook <keescook@chromium.org> >> Date: Wed, 6 Jan 2021 14:07:07 -0800 >> >>> On Wed, Jan 06, 2021 at 08:08:19PM +0000, Alexander Lobakin wrote: >>>> Discard GNU attributes at link time as kernel doesn't use it at all. >>>> Solves a dozen of the following ld warnings (one per every file): >>>> >>>> mips-alpine-linux-musl-ld: warning: orphan section `.gnu.attributes' >>>> from `arch/mips/kernel/head.o' being placed in section >>>> `.gnu.attributes' >>>> mips-alpine-linux-musl-ld: warning: orphan section `.gnu.attributes' >>>> from `init/main.o' being placed in section `.gnu.attributes' >>>> >>>> Misc: sort DISCARDS section entries alphabetically. >>> >>> Hmm, I wonder what is causing the appearance of .eh_frame? With help I >>> tracked down all the causes of this on x86, arm, and arm64, so that's >>> why it's not in the asm-generic DISCARDS section. I suspect this could >>> be cleaned up for mips too? >> >> I could take a look and hunt it down. Could you please give some refs on >> what were the causes and solutions for the mentioned architectures? > > Sure! Here are the ones I could find again: > > 34b4a5c54c42 ("arm64/kernel: Remove needless Call Frame Information annotations") > 6e0a66d10c5b ("arm64/build: Remove .eh_frame* sections due to unwind tables") > d1c0272bc1c0 ("x86/boot/compressed: Remove, discard, or assert for unwanted sections") > >>> Similarly for .gnu.attributes. What is generating that? (Or, more >>> specifically, why is it both being generated AND discarded?) >> >> On my setup, GNU Attributes consist of MIPS FP type (soft) and >> (if I'm correct) MIPS GNU Hash tables. > > Ah, right, the soft-float markings sound correct to discard, IIUC. > >> By the way. I've built the kernel with LLVM stack (and found several >> subjects for more patches) and, besides '.got', also got a fistful >> of '.data..compoundliteral*' symbols (drivers/mtd/nand/spi/, >> net/ipv6/ etc). Where should they be placed (rodata, rwdata, ...) >> or they are anomalies of some kind and should be fixed somehow? > > Ah yeah, I've seen this before: > https://lore.kernel.org/lkml/202010051345.2Q0cvqdM-lkp@intel.com/ > https://lore.kernel.org/lkml/CAKwvOd=s53vUELe311VSjxt2_eQd+RGNCf__n+cV+R=PQ_CdXQ@mail.gmail.com/ > > And it looks like LTO trips over it too: > https://lore.kernel.org/lkml/20201211184633.3213045-3-samitolvanen@google.com/ > > So I think the correct solution is to follow Sami's patch and add it to > vmlinux.lds.h: > > -#define DATA_MAIN .data .data.[0-9a-zA-Z_]* .data..LPBX* > +#define DATA_MAIN .data .data.[0-9a-zA-Z_]* .data..L* .data..compoundliteral* > ... > -#define RODATA_MAIN .rodata .rodata.[0-9a-zA-Z_]* > -#define BSS_MAIN .bss .bss.[0-9a-zA-Z_]* > +#define RODATA_MAIN .rodata .rodata.[0-9a-zA-Z_]* .rodata..L* > +#define BSS_MAIN .bss .bss.[0-9a-zA-Z_]* .bss..compoundliteral* > > Can you include a patch for this in your series? > > Thanks! Thanks for the help! Hope now I caught them all properly in v3. > -- > Kees Cook Al
diff --git a/arch/mips/kernel/vmlinux.lds.S b/arch/mips/kernel/vmlinux.lds.S index 83e27a181206..5d6563970ab2 100644 --- a/arch/mips/kernel/vmlinux.lds.S +++ b/arch/mips/kernel/vmlinux.lds.S @@ -221,9 +221,10 @@ SECTIONS /* ABI crap starts here */ *(.MIPS.abiflags) *(.MIPS.options) + *(.eh_frame) + *(.gnu.attributes) *(.options) *(.pdr) *(.reginfo) - *(.eh_frame) } }
Discard GNU attributes at link time as kernel doesn't use it at all. Solves a dozen of the following ld warnings (one per every file): mips-alpine-linux-musl-ld: warning: orphan section `.gnu.attributes' from `arch/mips/kernel/head.o' being placed in section `.gnu.attributes' mips-alpine-linux-musl-ld: warning: orphan section `.gnu.attributes' from `init/main.o' being placed in section `.gnu.attributes' Misc: sort DISCARDS section entries alphabetically. Signed-off-by: Alexander Lobakin <alobakin@pm.me> --- arch/mips/kernel/vmlinux.lds.S | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)