On Thu, 9 Aug 2018, Kyle Evans wrote:
Log:
kern: Add a BOOT_TAG marker at the beginning of boot dmesg
From the "newly licensed to drive" PR department, add a BOOT_TAG marker (by
default, --<<BOOT>>--, to the beginning of each boot's dmesg. This makes it
easier to do textproc magic to locate the start of each boot and, of
particular interest to some, the dmesg of the current boot.
The PR has a dmesg(8) component as well that I've opted not to include for
the moment- it was the more contentious part of this PR.
bde@ also made the statement that this boot tag should be written with an
ordinary printf, which I've- for the moment- declined to change about this
patch to keep it more transparent to observer of the boot process.
Yes, it should be written with an ordinary printf.
Modified: head/sys/kern/subr_prf.c
==============================================================================
--- head/sys/kern/subr_prf.c Thu Aug 9 01:17:35 2018 (r337517)
+++ head/sys/kern/subr_prf.c Thu Aug 9 01:32:09 2018 (r337518)
@@ -1027,6 +1027,7 @@ msgbufinit(void *ptr, int size)
cp = (char *)ptr;
msgbufp = (struct msgbuf *)(cp + size);
msgbuf_reinit(msgbufp, cp, size);
+ msgbuf_addstr(msgbufp, -1, BOOT_TAG, 0);
if (msgbufmapped && oldp != msgbufp)
msgbuf_copy(oldp, msgbufp);
msgbufmapped = 1;
This seems to be wrong, since it writes the tag for all calls to
msgbufinit(), giving multiple tags for multiple calls, but there should be
only 1 per boot. msgbufinit() should be called multiple times to bootstrap
it. My version does this.
The only obvious bug in (a later version of) the output is a missing newline
for the tag.
My dmesg output on amd64:
X ---<<BOOT>>------<<BOOT>>---Test of early printf to msgbuf
X GDB: debug ports: sio
X KDB: current port: sio
X KDB: debugger backends: ddb gdb
X KDB: current backend: ddb
X Copyright (c) 1992-2018 The FreeBSD Project.
X ...
In -current, all of the lines before the copyright except the tag are broken
by printf() of them to an unmapped msgbuf. (The above output is without -v.
Many more lines are lost with -v.) In my version, msgbufinit() is called
earlier with a small message buffer to hold the early output.
Output across reboots also works right except for the missing newline:
X ---<<BOOT>>------<<BOOT>>---Test of early printf to msgbuf
X GDB: debug ports: sio
X GDB: current port: sio
X KDB: debugger backends: ddb gdb
X KDB: current backend: ddb
X Copyright (c) 1992-2018 The FreeBSD Project.
X ...
X Waiting (max 60 seconds) for system process `vnlru' to stop... done
X Waiting (max 60 seconds) for system process `syncer' to stop...
X Syncing disks, vnodes remaining... 0 0 0 done
X Waiting (max 60 seconds) for system thread `bufdaemon' to stop... done
X Waiting (max 60 seconds) for system thread `bufspacedaemon-0' to stop... done
X Waiting (max 60 seconds) for system thread `bufspacedaemon-1' to stop... done
X Waiting (max 60 seconds) for system thread `bufspacedaemon-2' to stop... done
X Waiting (max 60 seconds) for system thread `bufspacedaemon-3' to stop... done
X Waiting (max 60 seconds) for system thread `bufspacedaemon-4' to stop... done
X Waiting (max 60 seconds) for system thread `bufspacedaemon-5' to stop... done
X Waiting (max 60 seconds) for system thread `bufspacedaemon-6' to stop... done
X All buffers synced.
X ---<<BOOT>>------<<BOOT>>---Test of early printf to msgbuf
X GDB: debug ports: sio
X GDB: current port: sio
X KDB: debugger backends: ddb gdb
X KDB: current backend: ddb
X Copyright (c) 1992-2018 The FreeBSD Project.
X ...
Bruce
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