[PATCH v4 00/17] Warn on orphan section placement

Kees Cook
2020-06-29T19:12:49Z

v4:
- explicitly add .ARM.attributes
- split up arm64 changes into separate patches
- split up arm changes into separate patches
- work around Clang section generation bug in -mbranch-protection
- work around Clang section generation bug in KASAN and KCSAN
- split "common" ELF sections out of STABS_DEBUG
- changed relative position of .comment
- add reviews/acks
v3: https://lore.kernel.org/lkml/20200624014940.1204448-1-keescook@chromium.org/
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 four commits (to
vmlinux.lds.h), and arm64 depends on the 5th and 6th patches (to ctype,
and efi/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. :)

Thanks!

-Kees

https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git/log/?h=linker/orphans/warn/v4

Kees Cook (17):
vmlinux.lds.h: Add .gnu.version* to DISCARDS
vmlinux.lds.h: Avoid KASAN and KCSAN's unwanted sections
vmlinux.lds.h: Split ELF_DETAILS from STABS_DEBUG
vmlinux.lds.h: Add .symtab, .strtab, and .shstrtab to ELF_DETAILS
ctype: Work around Clang -mbranch-protection=none bug
efi/libstub: Disable -mbranch-protection
arm64/build: Use common DISCARDS in linker script
arm64/mm: Remove needless section quotes
arm64/build: Remove .eh_frame* sections due to unwind tables
arm64/kernel: Remove needless Call Frame Information annotations
arm64/build: Warn on orphan section placement
arm/build: Refactor linker script headers
arm/build: Explicitly keep .ARM.attributes sections
arm/build: Warn on orphan section placement
arm/boot: Warn on orphan section placement
x86/build: Warn on orphan section placement
x86/boot: Warn on orphan section placement

arch/alpha/kernel/vmlinux.lds.S | 1 +
arch/arc/kernel/vmlinux.lds.S | 1 +
arch/arm/boot/compressed/Makefile | 2 ++
arch/arm/boot/compressed/vmlinux.lds.S | 18 +++++-----
.../arm/{kernel => include/asm}/vmlinux.lds.h | 25 ++++++++++---
arch/arm/kernel/vmlinux-xip.lds.S | 6 ++--
arch/arm/kernel/vmlinux.lds.S | 6 ++--
arch/arm64/Makefile | 9 ++++-
arch/arm64/kernel/smccc-call.S | 2 --
arch/arm64/kernel/vmlinux.lds.S | 17 ++++++---
arch/arm64/mm/mmu.c | 2 +-
arch/csky/kernel/vmlinux.lds.S | 1 +
arch/hexagon/kernel/vmlinux.lds.S | 1 +
arch/ia64/kernel/vmlinux.lds.S | 1 +
arch/mips/kernel/vmlinux.lds.S | 1 +
arch/nds32/kernel/vmlinux.lds.S | 1 +
arch/nios2/kernel/vmlinux.lds.S | 1 +
arch/openrisc/kernel/vmlinux.lds.S | 1 +
arch/parisc/boot/compressed/vmlinux.lds.S | 1 +
arch/parisc/kernel/vmlinux.lds.S | 1 +
arch/powerpc/kernel/vmlinux.lds.S | 2 +-
arch/riscv/kernel/vmlinux.lds.S | 1 +
arch/s390/kernel/vmlinux.lds.S | 1 +
arch/sh/kernel/vmlinux.lds.S | 1 +
arch/sparc/kernel/vmlinux.lds.S | 1 +
arch/um/kernel/dyn.lds.S | 2 +-
arch/um/kernel/uml.lds.S | 2 +-
arch/unicore32/kernel/vmlinux.lds.S | 1 +
arch/x86/Makefile | 8 ++++-
arch/x86/boot/compressed/Makefile | 3 +-
arch/x86/boot/compressed/vmlinux.lds.S | 12 +++++++
arch/x86/include/asm/asm.h | 6 +++-
arch/x86/kernel/vmlinux.lds.S | 7 ++++
drivers/firmware/efi/libstub/Makefile | 3 +-
include/asm-generic/vmlinux.lds.h | 35 +++++++++++++++++--
lib/ctype.c | 10 ++++++
36 files changed, 154 insertions(+), 39 deletions(-)
rename arch/arm/{kernel => include/asm}/vmlinux.lds.h (88%)

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2.25.1