Re: [Crash-utility] Viewing module symbols using crash

Durga Prasad wrote: Accessing data in kernel modules can be spotty at best, but the embedded gdb module should typically be able to pick up structure definitions in modules. For example, these two structures are defined in ./fs/ext3/xattr.c like so: struct ext3_xattr_info { int name_index; const char *name; const void *value; size_t value_len; }; struct ext3_xattr_search { struct ext3_xattr_entry *first; void *base; void *end; struct ext3_xattr_entry *here; int not_found; }; Without the ext3 module debuginfo, crash (gdb) doesn't know what they are: # crash -s crash> struct ext3_xattr_search struct: invalid data structure reference: ext3_xattr_search crash> struct ext3_xattr_info struct: invalid data structure reference: ext3_xattr_info crash> Until after adding the module debuginfo data: crash> mod -s ext3 MODULE NAME SIZE OBJECT FILE ffffffff8806be00 ext3 168017 /lib/modules/2.6.18-102.el5.perfmon2/kernel/fs/ext3/ext3.ko crash> struct ext3_xattr_search struct ext3_xattr_search { struct ext3_xattr_entry *first; void *base; void *end; struct ext3_xattr_entry *here; int not_found; } SIZE: 40 crash> struct ext3_xattr_info struct ext3_xattr_info { int name_index; const char *name; const void *value; size_t value_len; } SIZE: 32 crash> Then you may be able to "p" individual instances of the structures if there are symbolic/static declaration of them. Otherwise you can always cast the address of the structure to the structure type, as in: crash> struct ext3_xattr_info <address> If you cannot get the structure declaration after using "mod -[sS]", then you'll have to get primitive, and just dump the data at the relevant address with "rd". For SLES I'm guessing that you could use the post-built (CONFIG_DEBUG_INFO) kernel, but also add the System.map file of the live kernel to the command line, as in: $ crash /boot/System.map vmlinux-post-built-with-debuginfo Crash will use the debuginfo data from the vmlinux file, but then go in and back-patch all the vmlinux file's minimal_symbols with the correct symbol values from the System.map file. But Bernhard Walle (bwalle(a)suse.de) can answer that part of your question. He's active on this list, but I've added him to the cc: list to make sure he sees this. Dave Anderson