arm64: Rework valid_user_regs

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commit dbd4d7ca56 upstream.

We validate pstate using PSR_MODE32_BIT, which is part of the
user-provided pstate (and cannot be trusted). Also, we conflate
validation of AArch32 and AArch64 pstate values, making the code
difficult to reason about.

Instead, validate the pstate value based on the associated task. The
task may or may not be current (e.g. when using ptrace), so this must be
passed explicitly by callers. To avoid circular header dependencies via
sched.h, is_compat_task is pulled out of asm/ptrace.h.

To make the code possible to reason about, the AArch64 and AArch32
validation is split into separate functions. Software must respect the
RES0 policy for SPSR bits, and thus the kernel mirrors the hardware
policy (RAZ/WI) for bits as-yet unallocated. When these acquire an
architected meaning writes may be permitted (potentially with additional
validation).

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Cc: Dave Martin <dave.martin@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
[ rebased for v3.16
  v3.16 does not support SETEND, support for this was added by
  2d888f48e0 ("arm64: Emulate SETEND for AArch32 tasks") in v3.20
  This backport forces the kernel endianness on userspace.

  Added a DBG_SPSR_SS define hidden by #ifdefs to avoid conflicts with
  other backports.
]
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

...

This commit is contained in:

Mark Rutland 2016-03-01 14:18:50 +00:00 • committed by Ben Hutchings

parent ff7079dbcd

commit 34cb9ae07f

4 changed files with 89 additions and 34 deletions

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34

arch/arm64/include/asm/ptrace.h

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83

arch/arm64/kernel/ptrace.c

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4

arch/arm64/kernel/signal.c

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2

arch/arm64/kernel/signal32.c

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