[PATCH v3 0/9] Warn on orphan section placement

Kees Cook keescook at chromium.org
Tue Jun 23 21:49:31 EDT 2020

- merge series back together (I tried to make it separable, but no luck)
- remove unwanted sections in libstub
- remove unwanted .eh_frame sections for both .c and .S
- handle sections seen during allnoconfig builds
- handle synthetic and double-quoted sections reported by Clang
- add reviewed-bys
v2: https://lore.kernel.org/lkml/20200622205815.2988115-1-keescook@chromium.org/
v1: https://lore.kernel.org/lkml/20200228002244.15240-1-keescook@chromium.org/

A recent bug[1] was solved for builds linked with ld.lld, and tracking
it down took way longer than it needed to (a year). Ultimately, it
boiled down to differences between ld.bfd and ld.lld's handling of
orphan sections. Similarly, the recent FGKASLR series brough up orphan
section handling too[2]. In both cases, it would have been nice if the
linker was running with --orphan-handling=warn so that surprise sections
wouldn't silently get mapped into the kernel image at locations up to the
whim of the linker's orphan handling logic. Instead, all desired sections
should be explicitly identified in the linker script (to be either kept or
discarded) with any orphans throwing a warning. The powerpc architecture
actually already does this, so this series extends coverage to x86, arm,
and arm64.

All three architectures depend on the first two commits (to
vmlinux.lds.h), and x86 and arm64 depend on the third patch (to
libstub). As such, I'd like to land this series as a whole. Given that
two thirds of it is in the arm universe, perhaps this can land via the
arm64 tree? If x86 -tip is preferred, that works too. Or I could just
carry this myself in -next. In all cases, I would really appreciate
reviews/acks/etc. :)



This series is here:

[1] https://github.com/ClangBuiltLinux/linux/issues/282
[2] https://lore.kernel.org/lkml/202002242122.AA4D1B8@keescook/

Kees Cook (9):
  vmlinux.lds.h: Add .gnu.version* to DISCARDS
  vmlinux.lds.h: Add .symtab, .strtab, and .shstrtab to STABS_DEBUG
  efi/libstub: Remove .note.gnu.property
  x86/build: Warn on orphan section placement
  x86/boot: Warn on orphan section placement
  arm/build: Warn on orphan section placement
  arm/boot: Warn on orphan section placement
  arm64/build: Use common DISCARDS in linker script
  arm64/build: Warn on orphan section placement

 arch/arm/Makefile                             |  4 ++++
 arch/arm/boot/compressed/Makefile             |  2 ++
 arch/arm/boot/compressed/vmlinux.lds.S        | 17 ++++++--------
 .../arm/{kernel => include/asm}/vmlinux.lds.h | 22 ++++++++++++++-----
 arch/arm/kernel/vmlinux-xip.lds.S             |  5 ++---
 arch/arm/kernel/vmlinux.lds.S                 |  5 ++---
 arch/arm64/Makefile                           |  9 +++++++-
 arch/arm64/kernel/smccc-call.S                |  2 --
 arch/arm64/kernel/vmlinux.lds.S               | 16 ++++++++++----
 arch/arm64/mm/mmu.c                           |  2 +-
 arch/x86/Makefile                             |  4 ++++
 arch/x86/boot/compressed/Makefile             |  3 ++-
 arch/x86/boot/compressed/vmlinux.lds.S        | 11 ++++++++++
 arch/x86/include/asm/asm.h                    |  6 ++++-
 arch/x86/kernel/vmlinux.lds.S                 |  6 +++++
 drivers/firmware/efi/libstub/Makefile         |  3 +++
 include/asm-generic/vmlinux.lds.h             |  7 +++++-
 17 files changed, 92 insertions(+), 32 deletions(-)
 rename arch/arm/{kernel => include/asm}/vmlinux.lds.h (92%)


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