Edited the db_show_buffer show command and checked output:
```
db_printf("b_flags = 0x%b, b_xflags=0x%b, b_vflags=0x%b\n",
(u_int)bp->b_flags, PRINT_BUF_FLAGS, (u_int)bp->b_xflags,
PRINT_BUF_XFLAGS, (u_int)bp->b_vflags, PRINT_BUF_VFLAGS);
+ db_printf("b_flags = %#b, b_xflags=%#hhb, b_vflags=%#b\n",
+ bp->b_flags, PRINT_BUF_FLAGS, bp->b_xflags, PRINT_BUF_XFLAGS,
+ bp->b_vflags, PRINT_BUF_VFLAGS);
```
```
# dd if=/dev/zero of=/tmp/foo.dd
~KDB: enter: Break to debugger
[ thread pid 1838 tid 100113 ]
Stopped at kdb_alt_break_internal+0x106: movq $0,kdb_why
db> show lockedbufs
buf at 0xfffffe00f60bd420
b_flags = 0x20000000<vmio>, b_xflags=0x2<clean>, b_vflags=0x0
b_flags = 0x20000000<vmio>, b_xflags=0x2<clean>, b_vflags=0
[...]
```