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BOOT_TAG: Make a config(5) option, expose as sysctl and loader tunable

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BOOT_TAG lived shortly in sys/msgbuf.h, but this wasn't necessarily great
for changing it or removing it. Move it into subr_prf.c and add options for
it to opt_printf.h.

One can specify both the BOOT_TAG and BOOT_TAG_SZ (really, size of the
buffer that holds the BOOT_TAG). We expose it as kern.boot_tag and also add
a loader tunable by the same name that we'll fetch upon initialization of
the msgbuf.

This allows for flexibility and also ensures that there's a consistent way
to figure out the boot tag of the running kernel, rather than relying on
headers to be in-sync.

Prodded super-super-lightly by:	imp
This commit is contained in:
Kyle Evans 2018-08-09 17:47:47 +00:00
parent 21aa6e8345
commit 2a4650cc11
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=337545
4 changed files with 29 additions and 4 deletions
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10
sys/conf/NOTES
View File

@ -145,6 +145,16 @@ options INCLUDE_CONFIG_FILE # Include this file in kernel
options BOOTVERBOSE=1
options BOOTHOWTO=RB_MULTIPLE
#
# Compile-time defaults for dmesg boot tagging
#
# Default boot tag; may use 'kern.boot_tag' loader tunable to override. The
# current boot's tag is also exposed via the 'kern.boot_tag' sysctl.
options BOOT_TAG=\"---<<BOOT>>---\"
# Maximum boot tag size the kernel's static buffer should accomodate. Maximum
# size for both BOOT_TAG and the assocated tunable.
options BOOT_TAG_SZ=32
options GEOM_BDE # Disk encryption.
options GEOM_BSD # BSD disklabels (obsolete, gone in 12)
options GEOM_CACHE # Disk cache.

2
sys/conf/options
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@ -811,6 +811,8 @@ TERMINAL_NORM_ATTR opt_teken.h
# options for printf
PRINTF_BUFR_SIZE opt_printf.h
BOOT_TAG opt_printf.h
BOOT_TAG_SZ opt_printf.h
# kbd options
KBD_DISABLE_KEYMAP_LOAD opt_kbd.h

18
sys/kern/subr_prf.c
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@ -124,6 +124,18 @@ static bool msgbufmapped; /* Set when safe to use msgbuf */
int msgbuftrigger;
struct msgbuf *msgbufp;
#ifndef BOOT_TAG_SZ
#define BOOT_TAG_SZ 32
#endif
#ifndef BOOT_TAG
/* Tag used to mark the start of a boot in dmesg */
#define BOOT_TAG "---<<BOOT>>---"
#endif
static char current_boot_tag[BOOT_TAG_SZ + 1] = BOOT_TAG;
SYSCTL_STRING(_kern, OID_AUTO, boot_tag, CTLFLAG_RDTUN | CTLFLAG_NOFETCH,
current_boot_tag, 0, "Tag added to dmesg at start of boot");
static int log_console_output = 1;
SYSCTL_INT(_kern, OID_AUTO, log_console_output, CTLFLAG_RWTUN,
&log_console_output, 0, "Duplicate console output to the syslog");
@ -1025,9 +1037,13 @@ msgbufinit(void *ptr, int size)
size -= sizeof(*msgbufp);
cp = (char *)ptr;
/* Attempt to fetch kern.boot_tag tunable on first mapping */
if (!msgbufmapped)
TUNABLE_STR_FETCH("kern.boot_tag", current_boot_tag,
BOOT_TAG_SZ + 1);
msgbufp = (struct msgbuf *)(cp + size);
msgbuf_reinit(msgbufp, cp, size);
msgbuf_addstr(msgbufp, -1, BOOT_TAG, 0);
msgbuf_addstr(msgbufp, -1, current_boot_tag, 0);
if (msgbufmapped && oldp != msgbufp)
msgbuf_copy(oldp, msgbufp);
msgbufmapped = true;

3
sys/sys/msgbuf.h
View File

@ -60,9 +60,6 @@ struct msgbuf {
/* Subtract sequence numbers. Note that only positive values result. */
#define MSGBUF_SEQSUB(mbp, seq1, seq2) (MSGBUF_SEQNORM((mbp), (seq1) - (seq2)))
/* Tag used to mark the start of a boot in dmesg */
#define BOOT_TAG "---<<BOOT>>---"
#ifdef _KERNEL
extern int msgbufsize;
extern int msgbuftrigger;