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powerpc: implementation for arch_override_mprotect_pkey()

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arch independent code calls arch_override_mprotect_pkey()
to return a pkey that best matches the requested protection.

This patch provides the implementation.

Signed-off-by: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Ram Pai
2018-01-18 17:50:34 -08:00
committed by Michael Ellerman
parent 013a91b39c
commit 87bbabbed8
3 changed files with 61 additions and 1 deletions
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36
arch/powerpc/mm/pkeys.c
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@@ -322,3 +322,39 @@ int __execute_only_pkey(struct mm_struct *mm)
mm->context.execute_only_pkey = execute_only_pkey;
return execute_only_pkey;
}
static inline bool vma_is_pkey_exec_only(struct vm_area_struct *vma)
{
/* Do this check first since the vm_flags should be hot */
if ((vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)) != VM_EXEC)
return false;
return (vma_pkey(vma) == vma->vm_mm->context.execute_only_pkey);
}
/*
* This should only be called for *plain* mprotect calls.
*/
int __arch_override_mprotect_pkey(struct vm_area_struct *vma, int prot,
int pkey)
{
/*
* If the currently associated pkey is execute-only, but the requested
* protection requires read or write, move it back to the default pkey.
*/
if (vma_is_pkey_exec_only(vma) && (prot & (PROT_READ | PROT_WRITE)))
return 0;
/*
* The requested protection is execute-only. Hence let's use an
* execute-only pkey.
*/
if (prot == PROT_EXEC) {
pkey = execute_only_pkey(vma->vm_mm);
if (pkey > 0)
return pkey;
}
/* Nothing to override. */
return vma_pkey(vma);
}