[RFC Patch v2 11/16] kexec: Add /proc/kimage interface for kimage tracking

[Cong Wang <xiyou.wangcong@gmail.com>]

From: Cong Wang <cwang@multikernel.io>

Add a dedicated /proc/kimage file to provide read-only access to
all loaded kernel images in the system, for both regular kexec kernel
images and multikernel images.

The interface displays kernel images in a tabular format showing:
- Type: kexec type (default, crash, multikernel)
- Start Address: entry point in hexadecimal format
- Segments: number of memory segments

This interface is particularly useful for inspecting kimages, debugging
kexec, and verifying that kernel images are loaded correctly.

Signed-off-by: Cong Wang <cwang@multikernel.io>
---
 kernel/kexec_core.c | 63 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 63 insertions(+)

diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index ed5c97b4531e..7db755e64dd6 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -13,6 +13,8 @@
 #include <linux/slab.h>
 #include <linux/fs.h>
 #include <linux/kexec.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
 #include <linux/mutex.h>
 #include <linux/list.h>
 #include <linux/highmem.h>
@@ -1214,6 +1216,52 @@ struct kimage *kexec_image;
 struct kimage *kexec_crash_image;
 static int kexec_load_disabled;
 
+/*
+ * Proc interface for /proc/kimage
+ */
+static int kimage_proc_show(struct seq_file *m, void *v)
+{
+	struct kimage *image;
+	const char *type_names[] = {
+		[KEXEC_TYPE_DEFAULT] = "default",
+		[KEXEC_TYPE_CRASH] = "crash",
+		[KEXEC_TYPE_MULTIKERNEL] = "multikernel"
+	};
+
+	seq_printf(m, "MK_ID  Type        Start Address   Segments\n");
+	seq_printf(m, "-----  ----------  --------------  --------\n");
+
+	kimage_list_lock();
+	if (list_empty(&kexec_image_list)) {
+		seq_printf(m, "No kimages loaded\n");
+	} else {
+		list_for_each_entry(image, &kexec_image_list, list) {
+			const char *type_name = "unknown";
+
+			if (image->type < ARRAY_SIZE(type_names) && type_names[image->type])
+				type_name = type_names[image->type];
+
+			seq_printf(m, "%5d  %-10s  0x%012lx  %8lu\n",
+				   image->mk_id, type_name, image->start, image->nr_segments);
+		}
+	}
+	kimage_list_unlock();
+
+	return 0;
+}
+
+static int kimage_proc_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, kimage_proc_show, NULL);
+}
+
+static const struct proc_ops kimage_proc_ops = {
+	.proc_open	= kimage_proc_open,
+	.proc_read	= seq_read,
+	.proc_lseek	= seq_lseek,
+	.proc_release	= single_release,
+};
+
 #ifdef CONFIG_SYSCTL
 static int kexec_limit_handler(const struct ctl_table *table, int write,
 			       void *buffer, size_t *lenp, loff_t *ppos)
@@ -1285,6 +1333,21 @@ static int __init kexec_core_sysctl_init(void)
 late_initcall(kexec_core_sysctl_init);
 #endif
 
+static int __init kimage_proc_init(void)
+{
+	struct proc_dir_entry *entry;
+
+	entry = proc_create("kimage", 0444, NULL, &kimage_proc_ops);
+	if (!entry) {
+		pr_err("Failed to create /proc/kimage\n");
+		return -ENOMEM;
+	}
+
+	pr_debug("Created /proc/kimage interface\n");
+	return 0;
+}
+late_initcall(kimage_proc_init);
+
 bool kexec_load_permitted(int kexec_image_type)
 {
 	struct kexec_load_limit *limit;
-- 
2.34.1