linux.git/arch/arm64/kernel/Makefile, branch v5.14

arm64: entry: fix KCOV suppression

2021-07-15T16:37:55+00:00

We suppress KCOV for entry.o rather than entry-common.o. As entry.o is
built from entry.S, this is pointless, and permits instrumentation of
entry-common.o, which is built from entry-common.c.

Fix the Makefile to suppress KCOV for entry-common.o, as we had intended
to begin with. I've verified with objdump that this is working as
expected.

Fixes: bf6fa2c0dda7 ("arm64: entry: don't instrument entry code with KCOV")
Signed-off-by: Mark Rutland 
Cc: Catalin Marinas 
Cc: James Morse 
Cc: Marc Zyngier 
Cc: Will Deacon 
Link: https://lore.kernel.org/r/20210715123049.9990-1-mark.rutland@arm.com
Signed-off-by: Will Deacon

Merge branch 'for-next/insn' into for-next/core

2021-06-24T13:03:24+00:00

Refactoring of our instruction decoding routines and addition of some
missing encodings.

* for-next/insn:
  arm64: insn: avoid circular include dependency
  arm64: insn: move AARCH64_INSN_SIZE into 
  arm64: insn: decouple patching from insn code
  arm64: insn: Add load/store decoding helpers
  arm64: insn: Add some opcodes to instruction decoder
  arm64: insn: Add barrier encodings
  arm64: insn: Add SVE instruction class
  arm64: Move instruction encoder/decoder under lib/
  arm64: Move aarch32 condition check functions
  arm64: Move patching utilities out of instruction encoding/decoding

arm64: idle: don't instrument idle code with KCOV

2021-06-07T10:35:56+00:00

The low-level idle code in arch_cpu_idle() and its callees runs at a
time where where portions of the kernel environment aren't available.
For example, RCU may not be watching, and lockdep state may be
out-of-sync with the hardware. Due to this, it is not sound to
instrument this code.

We generally avoid instrumentation by marking the entry functions as
`noinstr`, but currently this doesn't inhibit KCOV instrumentation.
Prevent this by factoring these functions into a new idle.c so that we
can disable KCOV for the entire compilation unit, as is done for the
core idle code in kernel/sched/idle.c.

We'd like to keep instrumentation of the rest of process.c, and for the
existing code in cpuidle.c, so a new compilation unit is preferable. The
arch_cpu_idle_dead() function in process.c is a cpu hotplug function
that is safe to instrument, so it is left as-is in process.c.

Signed-off-by: Mark Rutland 
Acked-by: Catalin Marinas 
Acked-by: Marc Zyngier 
Cc: James Morse 
Cc: Will Deacon 
Link: https://lore.kernel.org/r/20210607094624.34689-21-mark.rutland@arm.com
Signed-off-by: Will Deacon

arm64: entry: don't instrument entry code with KCOV

2021-06-07T10:35:56+00:00

The code in entry-common.c runs at exception entry and return
boundaries, where portions of the kernel environment aren't available.
For example, RCU may not be watching, and lockdep state may be
out-of-sync with the hardware. Due to this, it is not sound to
instrument this code.

We generally avoid instrumentation by marking the entry functions as
`noinstr`, but currently this doesn't inhibit KCOV instrumentation.
Prevent this by disabling KCOV for the entire compilation unit.

Signed-off-by: Mark Rutland 
Acked-by: Catalin Marinas 
Acked-by: Marc Zyngier 
Cc: James Morse 
Cc: Will Deacon 
Link: https://lore.kernel.org/r/20210607094624.34689-20-mark.rutland@arm.com
Signed-off-by: Will Deacon

arm64: Move instruction encoder/decoder under lib/

2021-05-27T16:38:30+00:00

Aarch64 instruction set encoding and decoding logic can prove useful
for some features/tools both part of the kernel and outside the kernel.

Isolate the function dealing only with encoding/decoding instructions,
with minimal dependency on kernel utilities in order to be able to reuse
that code.

Code was only moved, no code should have been added, removed nor
modifier.

Signed-off-by: Julien Thierry 
Link: https://lore.kernel.org/r/20210303170536.1838032-5-jthierry@redhat.com
Signed-off-by: Will Deacon

arm64: Move patching utilities out of instruction encoding/decoding

2021-05-27T16:37:25+00:00

Files insn.[c|h] containt some functions used for instruction patching.
In order to reuse the instruction encoder/decoder, move the patching
utilities to their own file.

Signed-off-by: Julien Thierry 
Link: https://lore.kernel.org/r/20210303170536.1838032-2-jthierry@redhat.com
[will: Include patching.h in insn.h to fix header mess; add __ASSEMBLY__ guards]
Signed-off-by: Will Deacon 

Signed-off-by: Will Deacon

arm64: entry: Enable random_kstack_offset support

2021-04-08T12:12:19+00:00

Allow for a randomized stack offset on a per-syscall basis, with roughly
5 bits of entropy. (And include AAPCS rationale AAPCS thanks to Mark
Rutland.)

In order to avoid unconditional stack canaries on syscall entry (due to
the use of alloca()), also disable stack protector to avoid triggering
needless checks and slowing down the entry path. As there is no general
way to control stack protector coverage with a function attribute[1],
this must be disabled at the compilation unit level. This isn't a problem
here, though, since stack protector was not triggered before: examining
the resulting syscall.o, there are no changes in canary coverage (none
before, none now).

[1] a working __attribute__((no_stack_protector)) has been added to GCC
and Clang but has not been released in any version yet:
https://gcc.gnu.org/git/gitweb.cgi?p=gcc.git;h=346b302d09c1e6db56d9fe69048acb32fbb97845
https://reviews.llvm.org/rG4fbf84c1732fca596ad1d6e96015e19760eb8a9b

Signed-off-by: Kees Cook 
Signed-off-by: Thomas Gleixner 
Acked-by: Will Deacon 
Link: https://lore.kernel.org/r/20210401232347.2791257-6-keescook@chromium.org

Merge branch 'for-next/vdso' into for-next/core

2021-02-12T15:17:42+00:00

vDSO build improvements.

* for-next/vdso:
  arm64: Support running gen_vdso_offsets.sh with BSD userland.
  arm64: do not descend to vdso directories twice

arm64: cpufeature: Add an early command-line cpufeature override facility

2021-02-09T13:50:52+00:00

In order to be able to override CPU features at boot time,
let's add a command line parser that matches options of the
form "cpureg.feature=value", and store the corresponding
value into the override val/mask pair.

No features are currently defined, so no expected change in
functionality.

Signed-off-by: Marc Zyngier 
Acked-by: David Brazdil 
Reviewed-by: Catalin Marinas 
Link: https://lore.kernel.org/r/20210208095732.3267263-14-maz@kernel.org
Signed-off-by: Will Deacon

arm64: do not descend to vdso directories twice

2021-01-20T12:18:46+00:00

arm64 descends into each vdso directory twice; first in vdso_prepare,
second during the ordinary build process.

PPC mimicked it and uncovered a problem [1]. In the first descend,
Kbuild directly visits the vdso directories, therefore it does not
inherit subdir-ccflags-y from upper directories.

This means the command line parameters may differ between the two.
If it happens, the offset values in the generated headers might be
different from real offsets of vdso.so in the kernel.

This potential danger should be avoided. The vdso directories are
built in the vdso_prepare stage, so the second descend is unneeded.

[1]: https://lore.kernel.org/linux-kbuild/CAK7LNARAkJ3_-4gX0VA2UkapbOftuzfSTVMBbgbw=HD8n7N+7w@mail.gmail.com/T/#ma10dcb961fda13f36d42d58fa6cb2da988b7e73a

Signed-off-by: Masahiro Yamada 
Link: https://lore.kernel.org/r/20201218024540.1102650-1-masahiroy@kernel.org
Signed-off-by: Will Deacon