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 <[email protected]>
---
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
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 <[email protected]>
> ---
> 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
From: Kees Cook <[email protected]>
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 <[email protected]>
>> ---
>> 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 6, 2021 at 2:07 PM Kees Cook <[email protected]> wrote:
>
> 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?
On x86, 003602ad5516e59940de42e44c8d8033387bb363 "x86/*/Makefile: Use
-fno-asynchronous-unwind-tables to suppress .eh_frame sections"
noticed that some Makefiles
redefined KBUILD_CFLAGS and dropped -fno-asynchronous-unwind-tables.
Maybe mips has similar issues.
> Similarly for .gnu.attributes. What is generating that? (Or, more
> specifically, why is it both being generated AND discarded?)
>
> -Kees
gcc/config/mips/mips.c
https://github.com/gcc-mirror/gcc/blob/master/gcc/config/mips/mips.c#L9965
.gnu_attribute 4, 0 does not produce .gnu.attributes
(SHT_GNU_ATTRIBUTES) but there are likely code paths that
a non-zero value is used... So .gnu_attributes is likely needed to be excluded.
> >
> > Signed-off-by: Alexander Lobakin <[email protected]>
> > ---
> > 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
--
宋方睿
On Wed, Jan 06, 2021 at 10:36:38PM +0000, Alexander Lobakin wrote:
> From: Kees Cook <[email protected]>
> 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/[email protected]/
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/[email protected]/
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!
--
Kees Cook
From: Kees Cook <[email protected]>
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 <[email protected]>
>> 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/[email protected]/
> 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/[email protected]/
>
> 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