Re: [Crash-utility] [PATCH] Fix for "dev" command on Linux 5.11 and later

Date: Wed, 15 Jun 2022 01:50:13 +0000 From: HAGIO KAZUHITO(?????) <k-hagio-ab(a)nec.com&gt; To: &quot;lijiang(a)redhat.com&quot; <lijiang(a)redhat.com&gt;, &quot;crash-utility(a)redhat.com&quot; <crash-utility(a)redhat.com&gt; Subject: [Crash-utility] [PATCH] Fix for "dev" command on Linux 5.11 and later Message-ID: <1655257808-3245-1-git-send-email-k-hagio-ab(a)nec.com&gt; Content-Type: text/plain; charset="iso-2022-jp" 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&gt; --- 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_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)) +

+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; + } + } +

+ return fops; +} + void dump_dev_table(void) { -- 2.31.1