From f623cad20b092002d627a03451ea256add2e53d0 Mon Sep 17 00:00:00 2001

From: Kazuhito Hagio <k-hagio-ab@nec.com>

Date: Wed, 15 Jun 2022 10:50:13 +0900

Subject: [PATCH 01/28] Fix for "dev" command on Linux 5.11 and later

The following kernel commits eventually removed the bdev_map array in

Linux v5.11 kernel:

  e418de3abcda ("block: switch gendisk lookup to a simple xarray")

  22ae8ce8b892 ("block: simplify bdev/disk lookup in blkdev_get")

Without the patch, the "dev" command fails to dump block device data

with the following error:

  crash> dev

  ...

  dev: blkdevs or all_bdevs: symbols do not exist

To get block device's gendisk, search blockdev_superblock.s_inodes

instead of bdev_map.

Signed-off-by: Kazuhito Hagio <k-hagio-ab@nec.com>

Signed-off-by: Lianbo Jiang <lijiang@redhat.com>

---

 dev.c | 77 +++++++++++++++++++++++++++++++++++++++++++++++++++++++----

 1 file changed, 72 insertions(+), 5 deletions(-)

diff --git a/dev.c b/dev.c

index db97f8aebdc2..75d30bd022a1 100644

--- a/dev.c

+++ b/dev.c

@@ -24,6 +24,7 @@ static void dump_blkdevs_v2(ulong);

 static void dump_blkdevs_v3(ulong);

 static ulong search_cdev_map_probes(char *, int, int, ulong *);

 static ulong search_bdev_map_probes(char *, int, int, ulong *);

+static ulong search_blockdev_inodes(int, ulong *);

 static void do_pci(void); 

 static void do_pci2(void);

 static void do_io(void);

@@ -493,9 +494,10 @@ dump_blkdevs(ulong flags)

                 ulong ops;

         } blkdevs[MAX_DEV], *bp;

-	if (kernel_symbol_exists("major_names") && 

-	    kernel_symbol_exists("bdev_map")) {

-                dump_blkdevs_v3(flags);

+	if (kernel_symbol_exists("major_names") &&

+	    (kernel_symbol_exists("bdev_map") ||

+	     kernel_symbol_exists("blockdev_superblock"))) {

+		dump_blkdevs_v3(flags);

 		return;

 	}

@@ -717,6 +719,7 @@ dump_blkdevs_v3(ulong flags)

 	char buf[BUFSIZE];

 	uint major;

 	ulong gendisk, addr, fops;

+	int use_bdev_map = kernel_symbol_exists("bdev_map");

 	if (!(len = get_array_length("major_names", NULL, 0)))

 		len = MAX_DEV;

@@ -745,8 +748,11 @@ dump_blkdevs_v3(ulong flags)

 		strncpy(buf, blk_major_name_buf +  

 			OFFSET(blk_major_name_name), 16);

-		fops = search_bdev_map_probes(buf, major == i ? major : i, 

-			UNUSED, &gendisk);

+		if (use_bdev_map)

+			fops = search_bdev_map_probes(buf, major == i ? major : i,

+				UNUSED, &gendisk);

+		else /* v5.11 and later */

+			fops = search_blockdev_inodes(major, &gendisk);

 		if (CRASHDEBUG(1))

 			fprintf(fp, "blk_major_name: %lx block major: %d name: %s gendisk: %lx fops: %lx\n", 

@@ -829,6 +835,67 @@ search_bdev_map_probes(char *name, int major, int minor, ulong *gendisk)

 	return fops;

 }

+/* For bdev_inode.  See block/bdev.c */

+#define I_BDEV(inode) (inode - SIZE(block_device))

+

+static ulong

+search_blockdev_inodes(int major, ulong *gendisk)

+{

+	struct list_data list_data, *ld;

+	ulong addr, bd_sb, disk, fops = 0;

+	int i, inode_count, gendisk_major;

+	char *gendisk_buf;

+

+	ld = &list_data;

+	BZERO(ld, sizeof(struct list_data));

+

+	get_symbol_data("blockdev_superblock", sizeof(void *), &bd_sb);

+

+	addr = bd_sb + OFFSET(super_block_s_inodes);

+	if (!readmem(addr, KVADDR, &ld->start, sizeof(ulong),

+	    "blockdev_superblock.s_inodes", QUIET|RETURN_ON_ERROR))

+		return 0;

+

+	if (empty_list(ld->start))

+		return 0;

+

+	ld->flags |= LIST_ALLOCATE;

+	ld->end = bd_sb + OFFSET(super_block_s_inodes);

+	ld->list_head_offset = OFFSET(inode_i_sb_list);

+

+	inode_count = do_list(ld);

+

+	gendisk_buf = GETBUF(SIZE(gendisk));

+

+	for (i = 0; i < inode_count; i++) {

+		addr = I_BDEV(ld->list_ptr[i]) + OFFSET(block_device_bd_disk);

+		if (!readmem(addr, KVADDR, &disk, sizeof(ulong),

+		    "block_device.bd_disk", QUIET|RETURN_ON_ERROR))

+			continue;

+

+		if (!disk)

+			continue;

+

+		if (!readmem(disk, KVADDR, gendisk_buf, SIZE(gendisk),

+		    "gendisk buffer", QUIET|RETURN_ON_ERROR))

+			continue;

+

+		gendisk_major = INT(gendisk_buf + OFFSET(gendisk_major));

+		if (gendisk_major != major)

+			continue;

+

+		fops = ULONG(gendisk_buf + OFFSET(gendisk_fops));

+		if (fops) {

+			*gendisk = disk;

+			break;

+		}

+	}

+

+	FREEBUF(ld->list_ptr);

+	FREEBUF(gendisk_buf);

+	return fops;

+}

+

 void

 dump_dev_table(void)

 {

-- 

2.37.1