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powerpc/book3e: Fix set_memory_x() and set_memory_nx()

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set_memory_x() calls pte_mkexec() which sets _PAGE_EXEC.
set_memory_nx() calls pte_exprotec() which clears _PAGE_EXEC.

Book3e has 2 bits, UX and SX, which defines the exec rights
resp. for user (PR=1) and for kernel (PR=0).

_PAGE_EXEC is defined as UX only.

An executable kernel page is set with either _PAGE_KERNEL_RWX
or _PAGE_KERNEL_ROX, which both have SX set and UX cleared.

So set_memory_nx() call for an executable kernel page does
nothing because UX is already cleared.

And set_memory_x() on a non-executable kernel page makes it
executable for the user and keeps it non-executable for kernel.

Also, pte_exec() always returns 'false' on kernel pages, because
it checks _PAGE_EXEC which doesn't include SX, so for instance
the W+X check doesn't work.

To fix this:
  - change tlb_low_64e.S to use _PAGE_BAP_UX instead of _PAGE_USER
  - sets both UX and SX in _PAGE_EXEC so that pte_exec() returns
    true whenever one of the two bits is set and pte_exprotect()
    clears both bits.
  - Define a book3e specific version of pte_mkexec() which sets
    either SX or UX based on UR.

Fixes: 1f9ad21c3b ("powerpc/mm: Implement set_memory() routines")
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/c41100f9c144dc5b62e5a751b810190c6b5d42fd.1635226743.git.christophe.leroy@csgroup.eu
This commit is contained in:
Christophe Leroy
2021-10-26 07:39:25 +02:00
committed by Michael Ellerman
parent b1b93cb7e7
commit b6cb20fdc2
4 changed files with 20 additions and 13 deletions
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5
arch/powerpc/include/asm/nohash/64/pgtable.h
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@@ -118,11 +118,6 @@ static inline pte_t pte_wrprotect(pte_t pte)
return __pte(pte_val(pte) & ~_PAGE_RW);
}
static inline pte_t pte_mkexec(pte_t pte)
{
return __pte(pte_val(pte) | _PAGE_EXEC);
}
#define PMD_BAD_BITS (PTE_TABLE_SIZE-1)
#define PUD_BAD_BITS (PMD_TABLE_SIZE-1)