[PATCH v2 06/11] arm64: ptdump: Add hooks on debugfs file operations

[Sebastian Ene <sebastianene@google.com>]

Introduce callbacks invoked when the debugfs entry is accessed from
userspace. This hooks will allow us to allocate and prepare the memory
resources used by ptdump when the debugfs file is opened/closed.

Signed-off-by: Sebastian Ene <sebastianene@google.com>
---
 arch/arm64/include/asm/ptdump.h |  3 +++
 arch/arm64/mm/ptdump.c          |  1 +
 arch/arm64/mm/ptdump_debugfs.c  | 34 ++++++++++++++++++++++++++++++++-
 3 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/ptdump.h b/arch/arm64/include/asm/ptdump.h
index 1f6e0aabf16a..88dcab1dab97 100644
--- a/arch/arm64/include/asm/ptdump.h
+++ b/arch/arm64/include/asm/ptdump.h
@@ -19,7 +19,10 @@ struct ptdump_info {
 	struct mm_struct		*mm;
 	const struct addr_marker	*markers;
 	unsigned long			base_addr;
+	void (*ptdump_prepare_walk)(struct ptdump_info *info);
 	void (*ptdump_walk)(struct seq_file *s, struct ptdump_info *info);
+	void (*ptdump_end_walk)(struct ptdump_info *info);
+	struct mutex			file_lock;
 };
 
 void ptdump_walk(struct seq_file *s, struct ptdump_info *info);
diff --git a/arch/arm64/mm/ptdump.c b/arch/arm64/mm/ptdump.c
index 58a4ea975497..fe239b9af50c 100644
--- a/arch/arm64/mm/ptdump.c
+++ b/arch/arm64/mm/ptdump.c
@@ -24,6 +24,7 @@
 #include <asm/memory.h>
 #include <asm/pgtable-hwdef.h>
 #include <asm/ptdump.h>
+#include <asm/kvm_pkvm.h>
 #include <asm/kvm_pgtable.h>
 
 
diff --git a/arch/arm64/mm/ptdump_debugfs.c b/arch/arm64/mm/ptdump_debugfs.c
index 7564519db1e6..14619452dd8d 100644
--- a/arch/arm64/mm/ptdump_debugfs.c
+++ b/arch/arm64/mm/ptdump_debugfs.c
@@ -15,7 +15,39 @@ static int ptdump_show(struct seq_file *m, void *v)
 	put_online_mems();
 	return 0;
 }
-DEFINE_SHOW_ATTRIBUTE(ptdump);
+
+static int ptdump_open(struct inode *inode, struct file *file)
+{
+	int ret;
+	struct ptdump_info *info = inode->i_private;
+
+	ret = single_open(file, ptdump_show, inode->i_private);
+	if (!ret && info->ptdump_prepare_walk) {
+		mutex_lock(&info->file_lock);
+		info->ptdump_prepare_walk(info);
+	}
+	return ret;
+}
+
+static int ptdump_release(struct inode *inode, struct file *file)
+{
+	struct ptdump_info *info = inode->i_private;
+
+	if (info->ptdump_end_walk) {
+		info->ptdump_end_walk(info);
+		mutex_unlock(&info->file_lock);
+	}
+
+	return single_release(inode, file);
+}
+
+static const struct file_operations ptdump_fops = {
+	.owner		= THIS_MODULE,
+	.open		= ptdump_open,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= ptdump_release,
+};
 
 void __init ptdump_debugfs_register(struct ptdump_info *info, const char *name)
 {
-- 
2.42.0.655.g421f12c284-goog