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From: Christophe Leroy <christophe.leroy@c-s.fr>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Paul Mackerras <paulus@samba.org>,
	Michael Ellerman <mpe@ellerman.id.au>
Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: [PATCH 2/5] powerpc/ptdump: fix walk_pagetables() address mismatch
Date: Wed, 14 Aug 2019 12:36:10 +0000 (UTC)
Message-ID: <5aa2ac513295f594cce8ddb1c649f61947bd063d.1565786091.git.christophe.leroy@c-s.fr> (raw)
In-Reply-To: <eb4d626514e22f85814830012642329018ef6af9.1565786091.git.christophe.leroy@c-s.fr>

walk_pagetables() always walk the entire pgdir from address 0
but considers PAGE_OFFSET or KERN_VIRT_START as the starting
address of the walk, resulting in a possible mismatch in the
displayed addresses.

Ex: on PPC32, when KERN_VIRT_START was locally defined as
PAGE_OFFSET, ptdump displayed 0x80000000
instead of 0xc0000000 for the first kernel page,
because 0xc0000000 + 0xc0000000 = 0x80000000

Start the walk at st->start_address instead of starting at 0.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
 arch/powerpc/mm/ptdump/ptdump.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/mm/ptdump/ptdump.c b/arch/powerpc/mm/ptdump/ptdump.c
index 3ad64fc11419..74ff2bff4ea0 100644
--- a/arch/powerpc/mm/ptdump/ptdump.c
+++ b/arch/powerpc/mm/ptdump/ptdump.c
@@ -299,17 +299,15 @@ static void walk_pud(struct pg_state *st, pgd_t *pgd, unsigned long start)
 
 static void walk_pagetables(struct pg_state *st)
 {
-	pgd_t *pgd = pgd_offset_k(0UL);
 	unsigned int i;
-	unsigned long addr;
-
-	addr = st->start_address;
+	unsigned long addr = st->start_address & PGDIR_MASK;
+	pgd_t *pgd = pgd_offset_k(addr);
 
 	/*
 	 * Traverse the linux pagetable structure and dump pages that are in
 	 * the hash pagetable.
 	 */
-	for (i = 0; i < PTRS_PER_PGD; i++, pgd++, addr += PGDIR_SIZE) {
+	for (i = pgd_index(addr); i < PTRS_PER_PGD; i++, pgd++, addr += PGDIR_SIZE) {
 		if (!pgd_none(*pgd) && !pgd_is_leaf(*pgd))
 			/* pgd exists */
 			walk_pud(st, pgd, addr);
-- 
2.13.3


  reply index

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-14 12:36 [PATCH 1/5] powerpc/ptdump: fix addresses display on PPC32 Christophe Leroy
2019-08-14 12:36 ` Christophe Leroy [this message]
2019-08-14 12:36 ` [PATCH 3/5] powerpc/ptdump: drop dummy KERN_VIRT_START " Christophe Leroy
2019-08-14 12:36 ` [PATCH 4/5] powerpc/ptdump: get out of note_prot_wx() when CONFIG_PPC_DEBUG_WX is not selected Christophe Leroy
2019-08-14 12:36 ` [PATCH 5/5] powerpc/ptdump: drop non vital #ifdefs Christophe Leroy
2019-08-14 12:51 ` [PATCH 1/5] powerpc/ptdump: fix addresses display on PPC32 Christophe Leroy
2019-08-22 13:09 ` Michael Ellerman

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