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A script that used by GDB to load the symbols from Linux kernel modules
- From: Hui Zhu <teawater at gmail dot com>
- To: linux-kernel at vger dot kernel dot org, gdb at sourceware dot org
- Date: Wed, 17 Aug 2011 13:45:27 +0800
- Subject: A script that used by GDB to load the symbols from Linux kernel modules
Hi,
When use GDB to debug or trace your kernel with KGDB, QEMU debug
interface or KGTP. You must get some trouble with LKM symbols. For
example:
(gdb) target remote localhost:12345
Remote debugging using localhost:12345
native_safe_halt () at
/home/teawater/big/kernel/linux-2.6/arch/x86/include/asm/irqflags.h:50
50 }
(gdb) b e100_poll
Function "e100_poll" not defined.
Make breakpoint pending on future shared library load? (y or [n])
This is because GDB didn't get the LKM symbols. You can do it with
your hand. But if you have a lot of LKMs, it will need some time.
Now, GDB support python script. The attachment is a script to load
all symbols from Linux kernel modules to GDB.
For example:
(gdb) target remote localhost:12345
Remote debugging using localhost:12345
native_safe_halt () at
/home/teawater/big/kernel/linux-2.6/arch/x86/include/asm/irqflags.h:50
50 }
(gdb) so ~/kernel/svn/branches/teawater/getmod.py
(gdb) b e100_poll
Breakpoint 1 at 0xc889db40: file
/home/teawater/big/kernel/linux-2.6/drivers/net/e100.c, line 2165.
This script will include in KGTP(https://code.google.com/p/kgtp/) source.
Thanks,
Hui
#!/usr/bin/python
# This script is used by GDB to load the symbols from Linux kernel modules
# GPL
# Copyright(C) Hui Zhu (teawater@gmail.com), 2011
#Set special mod_search_dir
#set $mod_search_dir="dir"
#Clear special mod_search_dir
#set $mod_search_dir=(void)1
import gdb;
import os;
def format_file(name):
tmp = "";
for c in name:
if c == "_":
c = "-";
tmp += c;
return tmp;
#Get the mod_search_dir
mod_search_dir = gdb.parse_and_eval("$mod_search_dir");
if mod_search_dir.type.code == gdb.TYPE_CODE_ARRAY:
mod_search_dir = str(mod_search_dir);
mod_search_dir = mod_search_dir[1:len(mod_search_dir)];
mod_search_dir = mod_search_dir[0:mod_name.index("\"")];
else:
mod_search_dir = str(gdb.execute("info files", False, True));
mod_search_dir = mod_search_dir[mod_search_dir.index("Symbols from \"")+len("Symbols from \""):len(mod_search_dir)];
mod_search_dir = mod_search_dir[0:mod_search_dir.index("\"")];
mod_search_dir = mod_search_dir[0:mod_search_dir.rindex("/")];
print "Search modules from "+mod_search_dir+"\n";
mod_list_offset = long(gdb.parse_and_eval("((size_t) &(((struct module *)0)->list))"));
mod_list = long(gdb.parse_and_eval("(&modules)"));
mod_list_current = mod_list;
while 1:
mod_list_current = long(gdb.parse_and_eval("((struct list_head *) "+str(mod_list_current)+")->next"));
#check if need break the loop
if mod_list == mod_list_current:
break;
mod = mod_list_current - mod_list_offset;
#get mod_name
mod_name = str(gdb.parse_and_eval("((struct module *)"+str(mod)+")->name"));
mod_name = mod_name[mod_name.index("\"")+1:len(mod_name)];
mod_name = mod_name[0:mod_name.index("\"")];
mod_name += ".ko"
mod_name = format_file(mod_name);
#get mod_dir_name
mod_dir_name = "";
for root, dirs, files in os.walk(mod_search_dir):
for afile in files:
tmp_file = format_file(afile);
if tmp_file == mod_name:
mod_dir_name = os.path.join(root,afile);
break;
if mod_dir_name != "":
break;
command = " ";
#Add module_core to command
command += str(gdb.parse_and_eval("((struct module *)"+str(mod)+")->module_core"));
#Add each sect_attrs->attrs to command
#get nsections
nsections = int(gdb.parse_and_eval("((struct module *)"+str(mod)+")->sect_attrs->nsections"));
sect_attrs = long(gdb.parse_and_eval("(u64)((struct module *)"+str(mod)+")->sect_attrs"));
for i in range(0, nsections):
command += " -s";
tmp = str(gdb.parse_and_eval("((struct module_sect_attrs *)"+str(sect_attrs)+")->attrs["+str(i)+"].name"));
tmp = tmp[tmp.index("\"")+1:len(tmp)];
tmp = tmp[0:tmp.index("\"")];
command += " "+tmp;
tmp = str(gdb.parse_and_eval("((struct module_sect_attrs *)"+str(sect_attrs)+")->attrs["+str(i)+"].address"));
command += " "+tmp;
if mod_dir_name == "":
print "Can find out",mod_name,"from directory.";
print "Please use following command load the symbols from it:"
print "add-symbol-file some_dir/"+mod_name+command;
else:
#print "add-symbol-file "+mod_dir_name+command;
gdb.execute("add-symbol-file "+mod_dir_name+command, False, False);