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powerpc/mm: Move page fault VMA access checks to a helper 

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Benjamin Herrenschmidt 2017-07-19 14:49:43 +10:00 committed by Michael Ellerman
parent d2e0d2c51a
commit bd0d63f809
1 changed files with 33 additions and 24 deletions
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57
arch/powerpc/mm/fault.c
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@ -222,6 +222,37 @@ static bool bad_kernel_fault(bool is_exec, unsigned long error_code,
return is_exec || (address >= TASK_SIZE); return is_exec || (address >= TASK_SIZE);
} }
static bool access_error(bool is_write, bool is_exec,
struct vm_area_struct *vma)
{
/*
* Allow execution from readable areas if the MMU does not
* provide separate controls over reading and executing.
*
* Note: That code used to not be enabled for 4xx/BookE.
* It is now as I/D cache coherency for these is done at
* set_pte_at() time and I see no reason why the test
* below wouldn't be valid on those processors. This -may-
* break programs compiled with a really old ABI though.
*/
if (is_exec) {
return !(vma->vm_flags & VM_EXEC) &&
(cpu_has_feature(CPU_FTR_NOEXECUTE) ||
!(vma->vm_flags & (VM_READ | VM_WRITE)));
}
if (is_write) {
if (unlikely(!(vma->vm_flags & VM_WRITE)))
return true;
return false;
}
if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))))
return true;
return false;
}
#ifdef CONFIG_PPC_SMLPAR #ifdef CONFIG_PPC_SMLPAR
static inline void cmo_account_page_fault(void) static inline void cmo_account_page_fault(void)
{ {
@ -461,30 +492,8 @@ static int __do_page_fault(struct pt_regs *regs, unsigned long address,
return bad_area(regs, address); return bad_area(regs, address);
good_area: good_area:
if (is_exec) { if (unlikely(access_error(is_write, is_exec, vma)))
/* return bad_area(regs, address);
* Allow execution from readable areas if the MMU does not
* provide separate controls over reading and executing.
*
* Note: That code used to not be enabled for 4xx/BookE.
* It is now as I/D cache coherency for these is done at
* set_pte_at() time and I see no reason why the test
* below wouldn't be valid on those processors. This -may-
* break programs compiled with a really old ABI though.
*/
if (unlikely(!(vma->vm_flags & VM_EXEC) &&
(cpu_has_feature(CPU_FTR_NOEXECUTE) ||
!(vma->vm_flags & (VM_READ | VM_WRITE)))))
return bad_area(regs, address);
/* a write */
} else if (is_write) {
if (unlikely(!(vma->vm_flags & VM_WRITE)))
return bad_area(regs, address);
/* a read */
} else {
if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))))
return bad_area(regs, address);
}
/* /*
* If for any reason at all we couldn't handle the fault, * If for any reason at all we couldn't handle the fault,