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powerpc: Implement user_access_save() and user_access_restore()

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Implement user_access_save() and user_access_restore()

On 8xx and radix:
  - On save, get the value of the associated special register then
    prevent user access.
  - On restore, set back the saved value to the associated special
    register.

On book3s/32:
  - On save, get the value stored in current->thread.kuap and prevent
    user access.
  - On restore, regenerate address range from the stored value and
    reopen read/write access for that range.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/54f2f74938006b33c55a416674807b42ef222068.1579866752.git.christophe.leroy@c-s.fr
This commit is contained in:
Christophe Leroy
2020-01-24 11:54:45 +00:00
committed by Michael Ellerman
parent 5cd623333e
commit 3d7dfd632f
5 changed files with 63 additions and 3 deletions
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5
arch/powerpc/include/asm/uaccess.h
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@@ -465,9 +465,8 @@ static __must_check inline bool user_access_begin(const void __user *ptr, size_t
}
#define user_access_begin user_access_begin
#define user_access_end prevent_current_access_user
static inline unsigned long user_access_save(void) { return 0UL; }
static inline void user_access_restore(unsigned long flags) { }
#define user_access_save prevent_user_access_return
#define user_access_restore restore_user_access
#define unsafe_op_wrap(op, err) do { if (unlikely(op)) goto err; } while (0)
#define unsafe_get_user(x, p, e) unsafe_op_wrap(__get_user_allowed(x, p), e)