2012-04-20 13:45:54 +00:00
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menu "Kernel hacking"
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source "lib/Kconfig.debug"
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2016-10-27 16:27:31 +00:00
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config ARM64_PTDUMP_CORE
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def_bool n
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config ARM64_PTDUMP_DEBUGFS
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2014-11-26 00:28:39 +00:00
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bool "Export kernel pagetable layout to userspace via debugfs"
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depends on DEBUG_KERNEL
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2016-10-27 16:27:31 +00:00
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select ARM64_PTDUMP_CORE
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2014-11-26 00:28:39 +00:00
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select DEBUG_FS
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help
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Say Y here if you want to show the kernel pagetable layout in a
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debugfs file. This information is only useful for kernel developers
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who are working in architecture specific areas of the kernel.
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It is probably not a good idea to enable this feature in a production
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kernel.
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arm64: enable CONFIG_SET_MODULE_RONX by default
The SET_MODULE_RONX protections are effectively the same as the
DEBUG_RODATA protections we enabled by default back in commit
57efac2f7108e325 ("arm64: enable CONFIG_DEBUG_RODATA by default"). It
seems unusual to have one but not the other.
As evidenced by the help text, the rationale appears to be that
SET_MODULE_RONX interacts poorly with tracing and patching, but both of
these make use of the insn framework, which takes SET_MODULE_RONX into
account. Any remaining issues are bugs which should be fixed regardless
of the default state of the option.
This patch enables DEBUG_SET_MODULE_RONX by default, and replaces the
help text with a new wording derived from the DEBUG_RODATA help text,
which better describes the functionality. Previously, the DEBUG_RODATA
entry was inconsistently indented with spaces, which are replaced with
tabs as with the other Kconfig entries.
Additionally, the wording of recommended defaults is made consistent for
all options. These are placed in a new paragraph, unquoted, as a full
sentence (with a period/full stop) as this appears to be the most common
form per $(git grep 'in doubt').
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Laura Abbott <labbott@fedoraproject.org>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
2016-05-13 11:20:36 +00:00
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If in doubt, say N.
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2014-11-26 00:28:39 +00:00
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2013-01-17 12:31:45 +00:00
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config PID_IN_CONTEXTIDR
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bool "Write the current PID to the CONTEXTIDR register"
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help
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Enabling this option causes the kernel to write the current PID to
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the CONTEXTIDR register, at the expense of some additional
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instructions during context switch. Say Y here only if you are
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planning to use hardware trace tools with this kernel.
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2014-06-24 15:51:37 +00:00
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config ARM64_RANDOMIZE_TEXT_OFFSET
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bool "Randomize TEXT_OFFSET at build time"
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help
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Say Y here if you want the image load offset (AKA TEXT_OFFSET)
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of the kernel to be randomized at build-time. When selected,
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this option will cause TEXT_OFFSET to be randomized upon any
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build of the kernel, and the offset will be reflected in the
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text_offset field of the resulting Image. This can be used to
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fuzz-test bootloaders which respect text_offset.
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This option is intended for bootloader and/or kernel testing
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only. Bootloaders must make no assumptions regarding the value
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of TEXT_OFFSET and platforms must not require a specific
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value.
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2016-10-27 16:27:34 +00:00
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config DEBUG_WX
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bool "Warn on W+X mappings at boot"
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select ARM64_PTDUMP_CORE
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---help---
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Generate a warning if any W+X mappings are found at boot.
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This is useful for discovering cases where the kernel is leaving
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W+X mappings after applying NX, as such mappings are a security risk.
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This check also includes UXN, which should be set on all kernel
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mappings.
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Look for a message in dmesg output like this:
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arm64/mm: Checked W+X mappings: passed, no W+X pages found.
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or like this, if the check failed:
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arm64/mm: Checked W+X mappings: FAILED, <N> W+X pages found.
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Note that even if the check fails, your kernel is possibly
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still fine, as W+X mappings are not a security hole in
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themselves, what they do is that they make the exploitation
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of other unfixed kernel bugs easier.
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There is no runtime or memory usage effect of this option
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once the kernel has booted up - it's a one time check.
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If in doubt, say "Y".
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2015-01-22 01:36:06 +00:00
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config DEBUG_ALIGN_RODATA
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arm64: simplify kernel segment mapping granularity
The mapping of the kernel consist of four segments, each of which is mapped
with different permission attributes and/or lifetimes. To optimize the TLB
and translation table footprint, we define various opaque constants in the
linker script that resolve to different aligment values depending on the
page size and whether CONFIG_DEBUG_ALIGN_RODATA is set.
Considering that
- a 4 KB granule kernel benefits from a 64 KB segment alignment (due to
the fact that it allows the use of the contiguous bit),
- the minimum alignment of the .data segment is THREAD_SIZE already, not
PAGE_SIZE (i.e., we already have padding between _data and the start of
the .data payload in many cases),
- 2 MB is a suitable alignment value on all granule sizes, either for
mapping directly (level 2 on 4 KB), or via the contiguous bit (level 3 on
16 KB and 64 KB),
- anything beyond 2 MB exceeds the minimum alignment mandated by the boot
protocol, and can only be mapped efficiently if the physical alignment
happens to be the same,
we can simplify this by standardizing on 64 KB (or 2 MB) explicitly, i.e.,
regardless of granule size, all segments are aligned either to 64 KB, or to
2 MB if CONFIG_DEBUG_ALIGN_RODATA=y. This also means we can drop the Kconfig
dependency of CONFIG_DEBUG_ALIGN_RODATA on CONFIG_ARM64_4K_PAGES.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
2016-03-30 15:43:09 +00:00
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depends on DEBUG_RODATA
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2015-01-22 01:36:06 +00:00
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bool "Align linker sections up to SECTION_SIZE"
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help
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If this option is enabled, sections that may potentially be marked as
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read only or non-executable will be aligned up to the section size of
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the kernel. This prevents sections from being split into pages and
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avoids a potential TLB penalty. The downside is an increase in
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alignment and potentially wasted space. Turn on this option if
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performance is more important than memory pressure.
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arm64: enable CONFIG_SET_MODULE_RONX by default
The SET_MODULE_RONX protections are effectively the same as the
DEBUG_RODATA protections we enabled by default back in commit
57efac2f7108e325 ("arm64: enable CONFIG_DEBUG_RODATA by default"). It
seems unusual to have one but not the other.
As evidenced by the help text, the rationale appears to be that
SET_MODULE_RONX interacts poorly with tracing and patching, but both of
these make use of the insn framework, which takes SET_MODULE_RONX into
account. Any remaining issues are bugs which should be fixed regardless
of the default state of the option.
This patch enables DEBUG_SET_MODULE_RONX by default, and replaces the
help text with a new wording derived from the DEBUG_RODATA help text,
which better describes the functionality. Previously, the DEBUG_RODATA
entry was inconsistently indented with spaces, which are replaced with
tabs as with the other Kconfig entries.
Additionally, the wording of recommended defaults is made consistent for
all options. These are placed in a new paragraph, unquoted, as a full
sentence (with a period/full stop) as this appears to be the most common
form per $(git grep 'in doubt').
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Laura Abbott <labbott@fedoraproject.org>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
2016-05-13 11:20:36 +00:00
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If in doubt, say N.
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2015-01-22 01:36:06 +00:00
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2015-03-30 20:13:41 +00:00
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source "drivers/hwtracing/coresight/Kconfig"
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2015-03-30 20:13:36 +00:00
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2012-04-20 13:45:54 +00:00
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endmenu
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