linux-kernel - [PATCH v2] arm64: ptdump: Support userspace page tables

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Message-ID: <20211014081441.7982-1-vincent.whitchurch@axis.com>
Date:   Thu, 14 Oct 2021 10:14:41 +0200
From:   Vincent Whitchurch <vincent.whitchurch@...s.com>
To:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>
CC:     <kernel@...s.com>,
        Vincent Whitchurch <vincent.whitchurch@...s.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH v2] arm64: ptdump: Support userspace page tables

The kernel_page_tables debugfs file can be used to examine the page
table entries for mappings in kernel space but there is currently no
easy way to check userspace mappings.  /proc/*/pagemap provides some
information but it does not include architecture-specific details such
as the memory type (Normal, Device etc).

Add a user_page_tables debugfs file to dump out the userspace page
tables for the current process.  This is enabled by the same config
options as kernel_page_tables.

Signed-off-by: Vincent Whitchurch <vincent.whitchurch@...s.com>
---

Notes:
    v2: Reworded commit message.

 arch/arm64/mm/ptdump.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/mm/ptdump.c b/arch/arm64/mm/ptdump.c
index 1c403536c9bb..91a62f07eae2 100644
--- a/arch/arm64/mm/ptdump.c
+++ b/arch/arm64/mm/ptdump.c
@@ -309,6 +309,7 @@ static void note_page(struct ptdump_state *pt_st, unsigned long addr, int level,
 
 void ptdump_walk(struct seq_file *s, struct ptdump_info *info)
 {
+	struct mm_struct *mm = info->mm ?: current->mm;
 	unsigned long end = ~0UL;
 	struct pg_state st;
 
@@ -328,7 +329,7 @@ void ptdump_walk(struct seq_file *s, struct ptdump_info *info)
 		}
 	};
 
-	ptdump_walk_pgd(&st.ptdump, info->mm, NULL);
+	ptdump_walk_pgd(&st.ptdump, mm, NULL);
 }
 
 static void __init ptdump_initialize(void)
@@ -347,6 +348,16 @@ static struct ptdump_info kernel_ptdump_info = {
 	.base_addr	= PAGE_OFFSET,
 };
 
+static struct addr_marker user_address_markers[] = {
+	{ 0,				"Userspace memory start" },
+	{ 0 /* TASK_SIZE_64 */,		"Userspace memory end" },
+	{ -1,				NULL },
+};
+
+static struct ptdump_info user_ptdump_info = {
+	.markers	= user_address_markers,
+};
+
 void ptdump_check_wx(void)
 {
 	struct pg_state st = {
@@ -381,8 +392,10 @@ static int __init ptdump_init(void)
 #if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
 	address_markers[KASAN_START_NR].start_address = KASAN_SHADOW_START;
 #endif
+	user_address_markers[1].start_address = TASK_SIZE_64;
 	ptdump_initialize();
 	ptdump_debugfs_register(&kernel_ptdump_info, "kernel_page_tables");
+	ptdump_debugfs_register(&user_ptdump_info, "user_page_tables");
 	return 0;
 }
 device_initcall(ptdump_init);
-- 
2.28.0