mbox series

[v4,mips-next,0/7] MIPS: vmlinux.lds.S sections fixes & cleanup

Message ID 20210107123331.354075-1-alobakin@pm.me
Headers show
Series MIPS: vmlinux.lds.S sections fixes & cleanup | expand

Message

Alexander Lobakin Jan. 7, 2021, 12:33 p.m. UTC
This series hunts the problems discovered after manual enabling of
ARCH_WANT_LD_ORPHAN_WARN. Notably:
 - adds the missing PAGE_ALIGNED_DATA() section affecting VDSO
   placement (marked for stable);
 - properly stops .eh_frame section generation.

Compile and runtime tested on MIPS32R2 CPS board with no issues
using two different toolkits:
 - Binutils 2.35.1, GCC 10.2.0;
 - LLVM stack 11.0.0.

Since v3 [2]:
 - fix the third patch as GNU stack emits .rel.dyn into VDSO for
   some reason if .cfi_sections is specified.

Since v2 [1]:
 - stop discarding .eh_frame and just prevent it from generating
   (Kees);
 - drop redundant sections assertions (Fangrui);
 - place GOT table in .text instead of asserting as it's not empty
   when building with LLVM (Nathan);
 - catch compound literals in generic definitions when building with
   LD_DEAD_CODE_DATA_ELIMINATION (Kees);
 - collect two Reviewed-bys (Kees).

Since v1 [0]:
 - catch .got entries too as LLD may produce it (Nathan);
 - check for unwanted sections to be zero-sized instead of
   discarding (Fangrui).

[0] https://lore.kernel.org/linux-mips/20210104121729.46981-1-alobakin@pm.me
[1] https://lore.kernel.org/linux-mips/20210106200713.31840-1-alobakin@pm.me
[2] https://lore.kernel.org/linux-mips/20210107115120.281008-1-alobakin@pm.me

Alexander Lobakin (7):
  MIPS: vmlinux.lds.S: add missing PAGE_ALIGNED_DATA() section
  MIPS: vmlinux.lds.S: add ".gnu.attributes" to DISCARDS
  MIPS: properly stop .eh_frame generation
  MIPS: vmlinux.lds.S: catch bad .rel.dyn at link time
  MIPS: vmlinux.lds.S: explicitly declare .got table
  vmlinux.lds.h: catch compound literals into data and BSS
  MIPS: select ARCH_WANT_LD_ORPHAN_WARN

 arch/mips/Kconfig                 |  1 +
 arch/mips/include/asm/asm.h       | 18 ++++++++++++++++++
 arch/mips/kernel/vmlinux.lds.S    | 15 ++++++++++++++-
 include/asm-generic/vmlinux.lds.h |  6 +++---
 4 files changed, 36 insertions(+), 4 deletions(-)

Comments

Thomas Bogendoerfer Jan. 9, 2021, 11:12 a.m. UTC | #1
On Thu, Jan 07, 2021 at 12:33:38PM +0000, Alexander Lobakin wrote:
> This series hunts the problems discovered after manual enabling of

> ARCH_WANT_LD_ORPHAN_WARN. Notably:

>  - adds the missing PAGE_ALIGNED_DATA() section affecting VDSO

>    placement (marked for stable);

>  - properly stops .eh_frame section generation.

> 

> Compile and runtime tested on MIPS32R2 CPS board with no issues

> using two different toolkits:

>  - Binutils 2.35.1, GCC 10.2.0;

>  - LLVM stack 11.0.0.

> 

> Since v3 [2]:

>  - fix the third patch as GNU stack emits .rel.dyn into VDSO for

>    some reason if .cfi_sections is specified.

> 

> Since v2 [1]:

>  - stop discarding .eh_frame and just prevent it from generating

>    (Kees);

>  - drop redundant sections assertions (Fangrui);

>  - place GOT table in .text instead of asserting as it's not empty

>    when building with LLVM (Nathan);

>  - catch compound literals in generic definitions when building with

>    LD_DEAD_CODE_DATA_ELIMINATION (Kees);

>  - collect two Reviewed-bys (Kees).

> 

> Since v1 [0]:

>  - catch .got entries too as LLD may produce it (Nathan);

>  - check for unwanted sections to be zero-sized instead of

>    discarding (Fangrui).

> 

> [0] https://lore.kernel.org/linux-mips/20210104121729.46981-1-alobakin@pm.me

> [1] https://lore.kernel.org/linux-mips/20210106200713.31840-1-alobakin@pm.me

> [2] https://lore.kernel.org/linux-mips/20210107115120.281008-1-alobakin@pm.me

> 

> Alexander Lobakin (7):

>   MIPS: vmlinux.lds.S: add missing PAGE_ALIGNED_DATA() section

>   MIPS: vmlinux.lds.S: add ".gnu.attributes" to DISCARDS

>   MIPS: properly stop .eh_frame generation

>   MIPS: vmlinux.lds.S: catch bad .rel.dyn at link time

>   MIPS: vmlinux.lds.S: explicitly declare .got table

>   vmlinux.lds.h: catch compound literals into data and BSS

>   MIPS: select ARCH_WANT_LD_ORPHAN_WARN


this breaks my builds:

  LD      vmlinux.o
  MODPOST vmlinux.symvers
  MODINFO modules.builtin.modinfo
  GEN     modules.builtin
  LD      .tmp_vmlinux.kallsyms1
mips64-linux-gnu-ld: Unexpected run-time relocations (.rel) detected!


$ mips64-linux-gnu-ld --version
GNU ld version 2.27-3.fc24

$ mips64-linux-gnu-gcc --version
mips64-linux-gnu-gcc (GCC) 6.1.1 20160621 (Red Hat Cross 6.1.1-2)

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea.                                                [ RFC1925, 2.3 ]
Alexander Lobakin Jan. 9, 2021, 5:22 p.m. UTC | #2
From: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

Date: Sat, 9 Jan 2021 12:12:59 +0100

> On Thu, Jan 07, 2021 at 12:33:38PM +0000, Alexander Lobakin wrote:

>> This series hunts the problems discovered after manual enabling of

>> ARCH_WANT_LD_ORPHAN_WARN. Notably:

>>  - adds the missing PAGE_ALIGNED_DATA() section affecting VDSO

>>    placement (marked for stable);

>>  - properly stops .eh_frame section generation.

>>

>> Compile and runtime tested on MIPS32R2 CPS board with no issues

>> using two different toolkits:

>>  - Binutils 2.35.1, GCC 10.2.0;

>>  - LLVM stack 11.0.0.

>>

>> Since v3 [2]:

>>  - fix the third patch as GNU stack emits .rel.dyn into VDSO for

>>    some reason if .cfi_sections is specified.

>>

>> Since v2 [1]:

>>  - stop discarding .eh_frame and just prevent it from generating

>>    (Kees);

>>  - drop redundant sections assertions (Fangrui);

>>  - place GOT table in .text instead of asserting as it's not empty

>>    when building with LLVM (Nathan);

>>  - catch compound literals in generic definitions when building with

>>    LD_DEAD_CODE_DATA_ELIMINATION (Kees);

>>  - collect two Reviewed-bys (Kees).

>>

>> Since v1 [0]:

>>  - catch .got entries too as LLD may produce it (Nathan);

>>  - check for unwanted sections to be zero-sized instead of

>>    discarding (Fangrui).

>>

>> [0] https://lore.kernel.org/linux-mips/20210104121729.46981-1-alobakin@pm.me

>> [1] https://lore.kernel.org/linux-mips/20210106200713.31840-1-alobakin@pm.me

>> [2] https://lore.kernel.org/linux-mips/20210107115120.281008-1-alobakin@pm.me

>>

>> Alexander Lobakin (7):

>>   MIPS: vmlinux.lds.S: add missing PAGE_ALIGNED_DATA() section

>>   MIPS: vmlinux.lds.S: add ".gnu.attributes" to DISCARDS

>>   MIPS: properly stop .eh_frame generation

>>   MIPS: vmlinux.lds.S: catch bad .rel.dyn at link time

>>   MIPS: vmlinux.lds.S: explicitly declare .got table

>>   vmlinux.lds.h: catch compound literals into data and BSS

>>   MIPS: select ARCH_WANT_LD_ORPHAN_WARN

>

> this breaks my builds:

>

>   LD      vmlinux.o

>   MODPOST vmlinux.symvers

>   MODINFO modules.builtin.modinfo

>   GEN     modules.builtin

>   LD      .tmp_vmlinux.kallsyms1

> mips64-linux-gnu-ld: Unexpected run-time relocations (.rel) detected!


I think they should be handled as it's done for ARM64 [0]. Will do v5
soon.

[0] https://elixir.bootlin.com/linux/v5.11-rc2/source/arch/arm64/kernel/vmlinux.lds.S#L219

> $ mips64-linux-gnu-ld --version

> GNU ld version 2.27-3.fc24

>

> $ mips64-linux-gnu-gcc --version

> mips64-linux-gnu-gcc (GCC) 6.1.1 20160621 (Red Hat Cross 6.1.1-2)

>

> Thomas.


Thanks,
Alex

> --

> Crap can work. Given enough thrust pigs will fly, but it's not necessarily a

> good idea.                                                [ RFC1925, 2.3 ]