linux-kernel - [PATCH v3 07/60] arm64: ptdump: Discover start of vmemmap region at runtime

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Message-Id: <20230307140522.2311461-8-ardb@kernel.org>
Date:   Tue,  7 Mar 2023 15:04:29 +0100
From:   Ard Biesheuvel <ardb@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     linux-arm-kernel@...ts.infradead.org,
        Ard Biesheuvel <ardb@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Ryan Roberts <ryan.roberts@....com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Kees Cook <keescook@...omium.org>
Subject: [PATCH v3 07/60] arm64: ptdump: Discover start of vmemmap region at runtime

We will soon reclaim the part of the vmemmap region that covers VA space
that is not addressable by the hardware. To avoid confusion, ensure that
the 'vmemmap start' marker points at the start of the region that is
actually being used for the struct page array, rather than the start of
the region we set aside for it at build time.

Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
---
 arch/arm64/mm/ptdump.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/arm64/mm/ptdump.c b/arch/arm64/mm/ptdump.c
index 910b35f02280cbdb..8f37d6d8b5216473 100644
--- a/arch/arm64/mm/ptdump.c
+++ b/arch/arm64/mm/ptdump.c
@@ -37,6 +37,7 @@ enum address_markers_idx {
 	MODULES_END_NR,
 	VMALLOC_START_NR,
 	VMALLOC_END_NR,
+	VMEMMAP_START_NR,
 };
 
 static struct addr_marker address_markers[] = {
@@ -386,6 +387,10 @@ static int __init ptdump_init(void)
 #endif
 	address_markers[VMALLOC_END_NR].start_address = VMALLOC_END;
 	ptdump_initialize();
+	if (vabits_actual < VA_BITS) {
+		address_markers[VMEMMAP_START_NR].start_address =
+			(unsigned long)virt_to_page(_PAGE_OFFSET(vabits_actual));
+	}
 	ptdump_debugfs_register(&kernel_ptdump_info, "kernel_page_tables");
 	return 0;
 }
-- 
2.39.2