linux-kernel - [PATCH 06/11] arm64: ptdump: Register a debugfs entry for the host stage-2 page-tables

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Date:   Wed, 27 Sep 2023 11:25:12 +0000
From:   Sebastian Ene <sebastianene@...gle.com>
To:     linux-kernel@...r.kernel.org
Cc:     kernel-team@...roid.com, will@...nel.org, ryan.roberts@....com,
        mark.rutland@....com, maz@...nel.org, vdonnefort@...gle.com,
        Sebastian Ene <sebastianene@...gle.com>
Subject: [PATCH 06/11] arm64: ptdump: Register a debugfs entry for the host
 stage-2 page-tables

Initialize the structures used to keep the state of the stage-2 ptdump
walker. To satisfy the ptdump API for parsing no VMA regions, initialize
a memory structure. Since we are going to parse a snapshot of the host
stage-2 paget-tables we don't rely on the locking from the memory
structure.

Signed-off-by: Sebastian Ene <sebastianene@...gle.com>
---
 arch/arm64/kvm/Kconfig | 12 ++++++++++++
 arch/arm64/mm/ptdump.c | 26 ++++++++++++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig
index 83c1e09be42e..2974bb5c4838 100644
--- a/arch/arm64/kvm/Kconfig
+++ b/arch/arm64/kvm/Kconfig
@@ -71,4 +71,16 @@ config PROTECTED_NVHE_STACKTRACE
 
 	  If unsure, or not using protected nVHE (pKVM), say N.
 
+config NVHE_EL2_PTDUMP_DEBUGFS
+	bool "Present the stage-2 pagetables to debugfs"
+	depends on NVHE_EL2_DEBUG && PTDUMP_DEBUGFS
+	help
+	  Say Y here if you want to show the pKVM host stage-2 kernel pagetable
+	  layout in a debugfs file. This information is only useful for kernel developers
+	  who are working in architecture specific areas of the kernel.
+	  It is probably not a good idea to enable this feature in a production
+	  kernel.
+
+	  If in doubt, say N.
+
 endif # VIRTUALIZATION
diff --git a/arch/arm64/mm/ptdump.c b/arch/arm64/mm/ptdump.c
index 8c4f06ca622a..25c0640e82aa 100644
--- a/arch/arm64/mm/ptdump.c
+++ b/arch/arm64/mm/ptdump.c
@@ -469,6 +469,21 @@ void ptdump_check_wx(void)
 		pr_info("Checked W+X mappings: passed, no W+X pages found\n");
 }
 
+#ifdef CONFIG_NVHE_EL2_PTDUMP_DEBUGFS
+static struct ptdump_info stage2_kernel_ptdump_info;
+static struct addr_marker ipa_address_markers[] = {
+	{ 0,	"IPA start"},
+	{ -1,	"IPA end"},
+	{ -1,	NULL},
+};
+
+/* Initialize a memory structure used by ptdump to walk the no-VMA region */
+static struct mm_struct ipa_init_mm = {
+	.mm_mt		= MTREE_INIT_EXT(mm_mt, MM_MT_FLAGS,
+					 ipa_init_mm.mmap_lock),
+};
+#endif /* CONFIG_NVHE_EL2_PTDUMP_DEBUGFS */
+
 static int __init ptdump_init(void)
 {
 	address_markers[PAGE_END_NR].start_address = PAGE_END;
@@ -477,6 +492,17 @@ static int __init ptdump_init(void)
 #endif
 	ptdump_initialize();
 	ptdump_debugfs_register(&kernel_ptdump_info, "kernel_page_tables");
+
+#ifdef CONFIG_NVHE_EL2_PTDUMP_DEBUGFS
+	stage2_kernel_ptdump_info = (struct ptdump_info) {
+		.markers	= ipa_address_markers,
+		.mm		= &ipa_init_mm,
+	};
+
+	init_rwsem(&ipa_init_mm.mmap_lock);
+	ptdump_debugfs_register(&stage2_kernel_ptdump_info,
+				"host_stage2_kernel_page_tables");
+#endif
 	return 0;
 }
 device_initcall(ptdump_init);
-- 
2.42.0.515.g380fc7ccd1-goog