linux-kernel - [PATCH v2 21/37] powerpc: Implement and use pgprot

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Date:   Mon, 25 Sep 2023 20:31:35 +0200
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>
Cc:     Christophe Leroy <christophe.leroy@...roup.eu>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v2 21/37] powerpc: Implement and use pgprot_nx()

ioremap_page_range() calls pgprot_nx() vmap() and vmap_pfn()
clear execute permission by calling pgprot_nx().

When pgprot_nx() is not defined it falls back to a nop.

Implement it for powerpc then use it in early_ioremap_range().

Then the call to pte_exprotect() can be removed from ioremap_prot().

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 arch/powerpc/include/asm/pgtable.h | 6 ++++++
 arch/powerpc/mm/ioremap.c          | 5 ++---
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
index 966e7c5119f6..2bfb7dd3b49e 100644
--- a/arch/powerpc/include/asm/pgtable.h
+++ b/arch/powerpc/include/asm/pgtable.h
@@ -71,6 +71,12 @@ static inline pgprot_t pte_pgprot(pte_t pte)
 	return __pgprot(pte_flags);
 }
 
+static inline pgprot_t pgprot_nx(pgprot_t prot)
+{
+	return pte_pgprot(pte_exprotect(__pte(pgprot_val(prot))));
+}
+#define pgprot_nx pgprot_nx
+
 #ifndef pmd_page_vaddr
 static inline const void *pmd_page_vaddr(pmd_t pmd)
 {
diff --git a/arch/powerpc/mm/ioremap.c b/arch/powerpc/mm/ioremap.c
index 705e8e8ffde4..d5159f205380 100644
--- a/arch/powerpc/mm/ioremap.c
+++ b/arch/powerpc/mm/ioremap.c
@@ -50,8 +50,7 @@ void __iomem *ioremap_prot(phys_addr_t addr, size_t size, unsigned long flags)
 	if (pte_write(pte))
 		pte = pte_mkdirty(pte);
 
-	/* we don't want to let _PAGE_USER and _PAGE_EXEC leak out */
-	pte = pte_exprotect(pte);
+	/* we don't want to let _PAGE_USER leak out */
 	pte = pte_mkprivileged(pte);
 
 	if (iowa_is_active())
@@ -66,7 +65,7 @@ int early_ioremap_range(unsigned long ea, phys_addr_t pa,
 	unsigned long i;
 
 	for (i = 0; i < size; i += PAGE_SIZE) {
-		int err = map_kernel_page(ea + i, pa + i, prot);
+		int err = map_kernel_page(ea + i, pa + i, pgprot_nx(prot));
 
 		if (WARN_ON_ONCE(err))  /* Should clean up */
 			return err;
-- 
2.41.0