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arm64: add better page protections to arm64

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Add page protections for arm64 similar to those in arm.
This is for security reasons to prevent certain classes
of exploits. The current method:

- Map all memory as either RWX or RW. We round to the nearest
  section to avoid creating page tables before everything is mapped
- Once everything is mapped, if either end of the RWX section should
  not be X, we split the PMD and remap as necessary
- When initmem is to be freed, we change the permissions back to
  RW (using stop machine if necessary to flush the TLB)
- If CONFIG_DEBUG_RODATA is set, the read only sections are set
  read only.

Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: Kees Cook <keescook@chromium.org>
Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Laura Abbott 2015-01-21 17:36:06 -08:00 • committed by Catalin Marinas
commit da141706ae
6 changed files with 233 additions and 26 deletions
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