Date: Fri, 08 Feb 2002 07:38:53 +1100 (EST) From: Peter Jeremy <peter.jeremy@alcatel.com.au> To: FreeBSD-gnats-submit@freebsd.org Subject: gnu/34709: [patch] Inaccurate GDB documentation Message-ID: <200202072038.g17Kcrt79668@gsmx07.alcatel.com.au>
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>Number: 34709
>Category: gnu
>Synopsis: [patch] Inaccurate GDB documentation
>Confidential: no
>Severity: non-critical
>Priority: low
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: doc-bug
>Submitter-Id: current-users
>Arrival-Date: Thu Feb 07 12:40:01 PST 2002
>Closed-Date:
>Last-Modified:
>Originator: Peter Jeremy
>Release: FreeBSD 4.4-STABLE i386
>Organization:
Alcatel Australia
>Environment:
System: FreeBSD aalp03.alcatel.com.au 4.4-STABLE FreeBSD 4.4-STABLE #0: Wed Dec 19 03:14:51 EST 2001 root@aalp03.alcatel.com.au:/usr/obj/usr/src/sys/wansim i386
>Description:
The GDB .info documentation states (node "Patching"):
`set write on'
`set write off'
If you specify `set write on', GDB opens executable and core files
for both reading and writing; if you specify `set write off' (the
default), GDB opens them read-only.
When in kgdb mode, the "set write" command has no effect. Instead
the command line option "-wcore" must be used. This option is not
documented in the .info file. Whilst it is documented in the
man page, GNU man pages are generally not reliable.
>How-To-Repeat:
aalp03# gdb -k /kernel /dev/mem
GNU gdb 4.18
...
#0 0xc0159bf0 in mi_switch ()
(kgdb) set write on
(kgdb) exec-file /kernel
(kgdb) core-file /dev/mem
IdlePTD 3457024
initial pcb at 724e000
panic messages:
---
---
#0 0xc0159bf0 in mi_switch ()
(kgdb) x/4x sched_yield+16
0xc01fffa4 <sched_yield+16>: 0x00004eb8 0x5dec8900 0x00768dc3 0x8be58955
(kgdb) print {int}0xc01fffa4 = 0x00004eb8
kvm_write:write failed
(kgdb)
>Fix:
The .info file should be updated to correctly document GDB
behaviour. The following patch is untested.
Index: gdb.texinfo
===================================================================
RCS file: /usr/ncvs/src/contrib/gdb/gdb/doc/gdb.texinfo,v
retrieving revision 1.3
diff -u -r1.3 gdb.texinfo
--- gdb.texinfo 2 May 1999 11:25:25 -0000 1.3
+++ gdb.texinfo 7 Feb 2002 20:36:58 -0000
@@ -1266,6 +1266,15 @@
a signal to display the source code for the frame.
@end ifclear
+@item -kernel
+@itemx -k
+Use gdb in kernel debugging mode.
+The prompt is set to @samp{kgdb}.
+
+@item -wcore
+This option may only be used in kernel debugging mode while debugging
+a ``live'' kernel and makes the corefile @file{/dev/mem} writable.
+
@ifset SERIAL
@ifclear HPPA
@item -b @var{bps}
@@ -7865,6 +7874,9 @@
@end ifclear
files for both reading and writing; if you specify @samp{set write
off} (the default), @value{GDBN} opens them read-only.
+Note that this command has no effect in kernel debugging mode.
+To write to @file{/dev/mem}, you must specift @samp{-wcore} on the
+command line.
If you have already loaded a file, you must load it again (using the
@code{exec-file}
>Release-Note:
>Audit-Trail:
>Unformatted:
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