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From: Christophe Leroy <>
To: Benjamin Herrenschmidt <>,
	Paul Mackerras <>,
	Michael Ellerman <>
Subject: [PATCH] powerpc/ptdump: fix W+X verification
Date: Tue, 14 Jan 2020 08:13:09 +0000 (UTC)
Message-ID: <> (raw)

Verification cannot rely on simple bit checking because on some
platforms PAGE_RW is 0, checking that a page is not W means
checking that PAGE_RO is set instead of checking that PAGE_RW
is not set.

Use pte helpers instead of checking bits.

Signed-off-by: Christophe Leroy <>
Fixes: 453d87f6a8ae ("powerpc/mm: Warn if W+X pages found on boot")
 arch/powerpc/mm/ptdump/ptdump.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/mm/ptdump/ptdump.c b/arch/powerpc/mm/ptdump/ptdump.c
index 4af0d5d9589e..206156255247 100644
--- a/arch/powerpc/mm/ptdump/ptdump.c
+++ b/arch/powerpc/mm/ptdump/ptdump.c
@@ -175,10 +175,12 @@ static void dump_addr(struct pg_state *st, unsigned long addr)
 static void note_prot_wx(struct pg_state *st, unsigned long addr)
+	pte_t pte = __pte(st->current_flags);
 	if (!IS_ENABLED(CONFIG_PPC_DEBUG_WX) || !st->check_wx)
-	if (!((st->current_flags & pgprot_val(PAGE_KERNEL_X)) == pgprot_val(PAGE_KERNEL_X)))
+	if (!pte_write(pte) || !pte_exec(pte))
 	WARN_ONCE(1, "powerpc/mm: Found insecure W+X mapping at address %p/%pS\n",

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Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-14  8:13 Christophe Leroy [this message]
2020-01-29  5:17 ` Michael Ellerman

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