[Crash-utility] [PATCH] 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(a)nec.com>
---
dev.c | 76 +++++++++++++++++++++++++++++++++++++++++++++++++++++++----
1 file changed, 71 insertions(+), 5 deletions(-)
diff --git a/dev.c b/dev.c
index db97f8aebdc2..238dfe0fbe3c 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 +835,66 @@ 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(gendisk_buf);
+ return fops;
+}
+
void
dump_dev_table(void)
{
--
2.31.1