linux-kernel - [PATCH v5 mips-next 0/9] MIPS: vmlinux.lds.S sections fixes & cleanup

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Date:   Sun, 10 Jan 2021 11:53:50 +0000
From:   Alexander Lobakin <alobakin@...me>
To:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Nathan Chancellor <natechancellor@...il.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Huacai Chen <chenhuacai@...nel.org>,
        Pei Huang <huangpei@...ngson.cn>,
        Kees Cook <keescook@...omium.org>,
        Alexander Lobakin <alobakin@...me>,
        Fangrui Song <maskray@...gle.com>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Corey Minyard <cminyard@...sta.com>,
        linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arch@...r.kernel.org, stable@...r.kernel.org,
        clang-built-linux@...glegroups.com
Subject: [PATCH v5 mips-next 0/9] MIPS: vmlinux.lds.S sections fixes & cleanup

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);
 - stops blind catching of orphan text sections with .text.*
   directive;
 - 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 10.2.1 (with Alpine patches);
 - LLVM stack: 11.0.0 and from latest Git snapshot.

Since v4 [3]:
 - new: drop redundant .text.cps-vec creation and blind inclusion
   of orphan text sections via .text.* directive in vmlinux.lds.S;
 - don't assert SIZEOF(.rel.dyn) as it's reported that it may be not
   empty on certain machines and compilers (Thomas);
 - align GOT table like it's done for ARM64;
 - new: catch UBSAN's "unnamed data" sections in generic definitions
   when building with LD_DEAD_CODE_DATA_ELIMINATION;
 - collect Reviewed-bys (Kees, Nathan).

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
[3] https://lore.kernel.org/linux-mips/20210107123331.354075-1-alobakin@pm.me

Alexander Lobakin (9):
  MIPS: vmlinux.lds.S: add missing PAGE_ALIGNED_DATA() section
  MIPS: CPS: don't create redundant .text.cps-vec section
  MIPS: vmlinux.lds.S: add ".gnu.attributes" to DISCARDS
  MIPS: properly stop .eh_frame generation
  MIPS: vmlinux.lds.S: explicitly catch .rel.dyn symbols
  MIPS: vmlinux.lds.S: explicitly declare .got table
  vmlinux.lds.h: catch compound literals into data and BSS
  vmlinux.lds.h: catch UBSAN's "unnamed data" into data
  MIPS: select ARCH_WANT_LD_ORPHAN_WARN

 arch/mips/Kconfig                 |  1 +
 arch/mips/include/asm/asm.h       | 18 ++++++++++++++++++
 arch/mips/kernel/cps-vec.S        |  1 -
 arch/mips/kernel/vmlinux.lds.S    | 11 +++++++++--
 include/asm-generic/vmlinux.lds.h |  6 +++---
 5 files changed, 31 insertions(+), 6 deletions(-)

-- 
2.30.0