linux/arch/arm64/Kconfig.debug
Ard Biesheuvel 57efac2f71 arm64: enable CONFIG_DEBUG_RODATA by default
In spite of its name, CONFIG_DEBUG_RODATA is an important hardening feature
for production kernels, and distros all enable it by default in their
kernel configs. However, since enabling it used to result in more granular,
and thus less efficient kernel mappings, it is not enabled by default for
performance reasons.

However, since commit 2f39b5f91e ("arm64: mm: Mark .rodata as RO"), the
various kernel segments (.text, .rodata, .init and .data) are already
mapped individually, and the only effect of setting CONFIG_DEBUG_RODATA is
that the existing .text and .rodata mappings are updated late in the boot
sequence to have their read-only attributes set, which means that any
performance concerns related to enabling CONFIG_DEBUG_RODATA are no longer
valid.

So from now on, make CONFIG_DEBUG_RODATA default to 'y'

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2016-03-03 18:14:17 +00:00

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menu "Kernel hacking"
source "lib/Kconfig.debug"
config ARM64_PTDUMP
bool "Export kernel pagetable layout to userspace via debugfs"
depends on DEBUG_KERNEL
select DEBUG_FS
help
Say Y here if you want to show the kernel pagetable layout in a
debugfs file. This information is only useful for kernel developers
who are working in architecture specific areas of the kernel.
It is probably not a good idea to enable this feature in a production
kernel.
If in doubt, say "N"
config PID_IN_CONTEXTIDR
bool "Write the current PID to the CONTEXTIDR register"
help
Enabling this option causes the kernel to write the current PID to
the CONTEXTIDR register, at the expense of some additional
instructions during context switch. Say Y here only if you are
planning to use hardware trace tools with this kernel.
config ARM64_RANDOMIZE_TEXT_OFFSET
bool "Randomize TEXT_OFFSET at build time"
help
Say Y here if you want the image load offset (AKA TEXT_OFFSET)
of the kernel to be randomized at build-time. When selected,
this option will cause TEXT_OFFSET to be randomized upon any
build of the kernel, and the offset will be reflected in the
text_offset field of the resulting Image. This can be used to
fuzz-test bootloaders which respect text_offset.
This option is intended for bootloader and/or kernel testing
only. Bootloaders must make no assumptions regarding the value
of TEXT_OFFSET and platforms must not require a specific
value.
config DEBUG_SET_MODULE_RONX
bool "Set loadable kernel module data as NX and text as RO"
depends on MODULES
help
This option helps catch unintended modifications to loadable
kernel module's text and read-only data. It also prevents execution
of module data. Such protection may interfere with run-time code
patching and dynamic kernel tracing - and they might also protect
against certain classes of kernel exploits.
If in doubt, say "N".
config DEBUG_RODATA
bool "Make kernel text and rodata read-only"
default y
help
If this is set, kernel text and rodata will be made read-only. This
is to help catch accidental or malicious attempts to change the
kernel's executable code.
If in doubt, say Y
config DEBUG_ALIGN_RODATA
depends on DEBUG_RODATA && ARM64_4K_PAGES
bool "Align linker sections up to SECTION_SIZE"
help
If this option is enabled, sections that may potentially be marked as
read only or non-executable will be aligned up to the section size of
the kernel. This prevents sections from being split into pages and
avoids a potential TLB penalty. The downside is an increase in
alignment and potentially wasted space. Turn on this option if
performance is more important than memory pressure.
If in doubt, say N
source "drivers/hwtracing/coresight/Kconfig"
endmenu