[PATCH v2 1/2] arm64: ptdump: Make note_page_flush() range aware

[Wei-Lin Chang <weilin.chang@arm.com>]

note_page_flush() calls note_page() with addr == 0 and level == -1 to
dump the last row of a ptdump. addr == 0 (1 << 64 wrapped around)
renders a huge region with enormous size for address spaces with
IA bits < 64. For example the stage-2 page tables and the EFI runtime
page table.

More importantly, the last region of the address space and everything
after the address space up to 1 << 64 are merged into one row of
output. If the last region within the address space is valid, it will
appear to remain valid up to 1 << 64 with the same attributes.

Currently only the EFI runtime ptdump is affected by this, but KVM will
soon fix its stage-2 ptdump by using note_page_flush(). Here is an
example of an EFI runtime ptdump (last row):

0x0000008000000000-0x0000000000000000   17179868672G PGD

With this patch:

0x0000008000000000-0x0001000000000000      261632G PGD

To fix this, use ptdump_state.range[] to figure out where the address
space ends, and call note_page() with that.

Fixes: 9d80448ac92b ("efi/arm64: Add debugfs node to dump UEFI runtime page tables")
Signed-off-by: Wei-Lin Chang <weilin.chang@arm.com>
---
 arch/arm64/mm/ptdump.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/mm/ptdump.c b/arch/arm64/mm/ptdump.c
index 1c20144700d7..5b34060ceb96 100644
--- a/arch/arm64/mm/ptdump.c
+++ b/arch/arm64/mm/ptdump.c
@@ -278,9 +278,24 @@ void note_page_pgd(struct ptdump_state *pt_st, unsigned long addr, pgd_t pgd)
 
 void note_page_flush(struct ptdump_state *pt_st)
 {
+	const struct ptdump_range *range = pt_st->range;
+	unsigned long end = 0;
 	pte_t pte_zero = {0};
 
-	note_page(pt_st, 0, -1, pte_val(pte_zero));
+	while (range->start != range->end) {
+		end = range->end;
+		range++;
+	}
+
+	/*
+	 * Address spaces that end at 1 << 64 have range->end == ULONG_MAX,
+	 * but note_page() expects the exclusive end. In this case adjust end
+	 * to the wraparound value 0.
+	 */
+	if (end == ULONG_MAX)
+		end = 0;
+
+	note_page(pt_st, end, -1, pte_val(pte_zero));
 }
 
 static void arm64_ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm)
-- 
2.43.0