Date: Sun, 21 Nov 1999 01:14:03 -0500 (EST) From: vns@delta.odessa.ua To: FreeBSD-gnats-submit@freebsd.org Subject: kern/15014: DDB can't find symbol for address in kernel loadable modules. Message-ID: <199911210614.BAA00543@mindspring.com>
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>Number: 15014
>Category: kern
>Synopsis: DDB can't find symbol for address in kernel loadable modules.
>Confidential: no
>Severity: non-critical
>Priority: medium
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Sat Nov 20 22:20:00 PST 1999
>Closed-Date:
>Last-Modified:
>Originator: Vladimir N. Silyaev
>Release: FreeBSD 4.0-CURRENT i386
>Organization:
>Environment:
FreeBSD 4.0-CURRENT i386
ELF kernel
ELF KLD
>Description:
DDB can't locate names to stack frame, when frames include pointer
from kernel loadable module
>How-To-Repeat:
- Build kernel with DDB support.
- Load linux KLD (launch linux command).
Throw to DDB, then
db> b linux_open
db> c
Run any linux command, for example:
> /compat/linux/bin/bash
Breakpoint at linux_open: pushl %ebp
db> trace
_end(c4324280,c45f3f80,28051dc6,3,28054a10) at 0xc06ef344
syscall(2f,2f,2f,28054a10,3) at syscall+0x119
Xint0x80_syscall() at Xint0x80_syscall+0x26
db> c
>Fix:
Apply the following patch.
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
--- /sys/kern/link_elf.c.orig Fri Oct 29 18:12:02 1999
+++ /sys/kern/link_elf.c Sat Nov 20 17:51:16 1999
@@ -958,17 +958,19 @@
const Elf_Sym* es;
const Elf_Sym* best = 0;
int i;
+ u_long st_value;
for (i = 0, es = ef->ddbsymtab; i < ef->ddbsymcnt; i++, es++) {
if (es->st_name == 0)
continue;
- if (off >= es->st_value) {
- if (off - es->st_value < diff) {
- diff = off - es->st_value;
+ st_value = es->st_value + (u_long)ef->address;
+ if (off >= st_value) {
+ if (off - st_value < diff) {
+ diff = off - st_value;
best = es;
if (diff == 0)
break;
- } else if (off - es->st_value == diff) {
+ } else if (off - st_value == diff) {
best = es;
}
}
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
After applying this patch, in the same circumstance, trace will be printing:
db> trace
linux_open(c4324280,c45f3f80,28051dc6,3,28054a10) at linux_open
syscall(2f,2f,2f,28054a10,3) at syscall+0x119
Xint0x80_syscall() at Xint0x80_syscall+0x26
P.S. It's looks like that the /sys/kern/link_aout.c have the same kind
of problem.
>Release-Note:
>Audit-Trail:
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