powerpc: Add set_memory_{p/np}() and remove set_memory_attr()

set_memory_attr() was implemented by commit 4d1755b6a762 ("powerpc/mm:
implement set_memory_attr()") because the set_memory_xx() couldn't
be used at that time to modify memory "on the fly" as explained it
the commit.

But set_memory_attr() uses set_pte_at() which leads to warnings when
CONFIG_DEBUG_VM is selected, because set_pte_at() is unexpected for
updating existing page table entries.

The check could be bypassed by using __set_pte_at() instead,
as it was the case before commit c988cfd38e48 ("powerpc/32:
use set_memory_attr()") but since commit 9f7853d7609d ("powerpc/mm:
Fix set_memory_*() against concurrent accesses") it is now possible
to use set_memory_xx() functions to update page table entries
"on the fly" because the update is now atomic.

For DEBUG_PAGEALLOC we need to clear and set back _PAGE_PRESENT.
Add set_memory_np() and set_memory_p() for that.

Replace all uses of set_memory_attr() by the relevant set_memory_xx()
and remove set_memory_attr().

Fixes: c988cfd38e48 ("powerpc/32: use set_memory_attr()")
Cc: stable@vger.kernel.org
Reported-by: Maxime Bizon <mbizon@freebox.fr>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Tested-by: Maxime Bizon <mbizon@freebox.fr>
Reviewed-by: Russell Currey <ruscur@russell.cc>
Depends-on: 9f7853d7609d ("powerpc/mm: Fix set_memory_*() against concurrent accesses")
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/cda2b44b55c96f9ac69fa92e68c01084ec9495c5.1640344012.git.christophe.leroy@csgroup.eu

1 files changed, 6 insertions, 33 deletions

diff --git a/arch/powerpc/mm/pageattr.c b/arch/powerpc/mm/pageattr.c
index 8812454e70ff..85753e32a4de 100644
--- a/arch/powerpc/mm/pageattr.c
+++ b/arch/powerpc/mm/pageattr.c
@@ -46,6 +46,12 @@ static int change_page_attr(pte_t *ptep, unsigned long addr, void *data)
 	case SET_MEMORY_X:
 		pte_update_delta(ptep, addr, _PAGE_KERNEL_RO, _PAGE_KERNEL_ROX);
 		break;
+	case SET_MEMORY_NP:
+		pte_update(&init_mm, addr, ptep, _PAGE_PRESENT, 0, 0);
+		break;
+	case SET_MEMORY_P:
+		pte_update(&init_mm, addr, ptep, 0, _PAGE_PRESENT, 0);
+		break;
 	default:
 		WARN_ON_ONCE(1);
 		break;
@@ -90,36 +96,3 @@ int change_memory_attr(unsigned long addr, int numpages, long action)
 	return apply_to_existing_page_range(&init_mm, start, size,
 					    change_page_attr, (void *)action);
 }
-
-/*
- * Set the attributes of a page:
- *
- * This function is used by PPC32 at the end of init to set final kernel memory
- * protection. It includes changing the maping of the page it is executing from
- * and data pages it is using.
- */
-static int set_page_attr(pte_t *ptep, unsigned long addr, void *data)
-{
-	pgprot_t prot = __pgprot((unsigned long)data);
-
-	spin_lock(&init_mm.page_table_lock);
-
-	set_pte_at(&init_mm, addr, ptep, pte_modify(*ptep, prot));
-	flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
-
-	spin_unlock(&init_mm.page_table_lock);
-
-	return 0;
-}
-
-int set_memory_attr(unsigned long addr, int numpages, pgprot_t prot)
-{
-	unsigned long start = ALIGN_DOWN(addr, PAGE_SIZE);
-	unsigned long sz = numpages * PAGE_SIZE;
-
-	if (numpages <= 0)
-		return 0;
-
-	return apply_to_existing_page_range(&init_mm, start, sz, set_page_attr,
-					    (void *)pgprot_val(prot));
-}