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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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2
arch/powerpc/include/asm/nohash/32/pgtable.h
View file

@ -193,10 +193,12 @@ static inline pte_t pte_wrprotect(pte_t pte)
}
#endif
#ifndef pte_mkexec
static inline pte_t pte_mkexec(pte_t pte)
{
return __pte(pte_val(pte) | _PAGE_EXEC);
}
#endif
#define pmd_none(pmd) (!pmd_val(pmd))
#define pmd_bad(pmd) (pmd_val(pmd) & _PMD_BAD)

5
arch/powerpc/include/asm/nohash/64/pgtable.h
View file

@ -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)

18
arch/powerpc/include/asm/nohash/pte-book3e.h
View file

@ -48,7 +48,7 @@
#define _PAGE_WRITETHRU 0x800000 /* W: cache write-through */
/* "Higher level" linux bit combinations */
#define _PAGE_EXEC _PAGE_BAP_UX /* .. and was cache cleaned */
#define _PAGE_EXEC (_PAGE_BAP_SX | _PAGE_BAP_UX) /* .. and was cache cleaned */
#define _PAGE_RW (_PAGE_BAP_SW | _PAGE_BAP_UW) /* User write permission */
#define _PAGE_KERNEL_RW (_PAGE_BAP_SW | _PAGE_BAP_SR | _PAGE_DIRTY)
#define _PAGE_KERNEL_RO (_PAGE_BAP_SR)
@ -93,11 +93,11 @@
/* Permission masks used to generate the __P and __S table */
#define PAGE_NONE __pgprot(_PAGE_BASE)
#define PAGE_SHARED __pgprot(_PAGE_BASE | _PAGE_USER | _PAGE_RW)
#define PAGE_SHARED_X __pgprot(_PAGE_BASE | _PAGE_USER | _PAGE_RW | _PAGE_EXEC)
#define PAGE_SHARED_X __pgprot(_PAGE_BASE | _PAGE_USER | _PAGE_RW | _PAGE_BAP_UX)
#define PAGE_COPY __pgprot(_PAGE_BASE | _PAGE_USER)
#define PAGE_COPY_X __pgprot(_PAGE_BASE | _PAGE_USER | _PAGE_EXEC)
#define PAGE_COPY_X __pgprot(_PAGE_BASE | _PAGE_USER | _PAGE_BAP_UX)
#define PAGE_READONLY __pgprot(_PAGE_BASE | _PAGE_USER)
#define PAGE_READONLY_X __pgprot(_PAGE_BASE | _PAGE_USER | _PAGE_EXEC)
#define PAGE_READONLY_X __pgprot(_PAGE_BASE | _PAGE_USER | _PAGE_BAP_UX)
#ifndef __ASSEMBLY__
static inline pte_t pte_mkprivileged(pte_t pte)
@ -113,6 +113,16 @@ static inline pte_t pte_mkuser(pte_t pte)
}
#define pte_mkuser pte_mkuser
static inline pte_t pte_mkexec(pte_t pte)
{
if (pte_val(pte) & _PAGE_BAP_UR)
return __pte((pte_val(pte) & ~_PAGE_BAP_SX) | _PAGE_BAP_UX);
else
return __pte((pte_val(pte) & ~_PAGE_BAP_UX) | _PAGE_BAP_SX);
}
#define pte_mkexec pte_mkexec
#endif /* __ASSEMBLY__ */
#endif /* __KERNEL__ */

8
arch/powerpc/mm/nohash/tlb_low_64e.S
View file

@ -222,7 +222,7 @@ tlb_miss_kernel_bolted:
tlb_miss_fault_bolted:
/* We need to check if it was an instruction miss */
andi. r10,r11,_PAGE_EXEC|_PAGE_BAP_SX
andi. r10,r11,_PAGE_BAP_UX|_PAGE_BAP_SX
bne itlb_miss_fault_bolted
dtlb_miss_fault_bolted:
tlb_epilog_bolted
@ -239,7 +239,7 @@ itlb_miss_fault_bolted:
srdi r15,r16,60 /* get region */
bne- itlb_miss_fault_bolted
li r11,_PAGE_PRESENT|_PAGE_EXEC /* Base perm */
li r11,_PAGE_PRESENT|_PAGE_BAP_UX /* Base perm */
/* We do the user/kernel test for the PID here along with the RW test
*/
@ -614,7 +614,7 @@ itlb_miss_fault_e6500:
/* We do the user/kernel test for the PID here along with the RW test
*/
li r11,_PAGE_PRESENT|_PAGE_EXEC /* Base perm */
li r11,_PAGE_PRESENT|_PAGE_BAP_UX /* Base perm */
oris r11,r11,_PAGE_ACCESSED@h
cmpldi cr0,r15,0 /* Check for user region */
@ -734,7 +734,7 @@ normal_tlb_miss_done:
normal_tlb_miss_access_fault:
/* We need to check if it was an instruction miss */
andi. r10,r11,_PAGE_EXEC
andi. r10,r11,_PAGE_BAP_UX
bne 1f
ld r14,EX_TLB_DEAR(r12)
ld r15,EX_TLB_ESR(r12)