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Adapt libkvm_getswapinfo() to make use of recently committed vm and swap

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sysctls exporting swap information.  When running on a live kernel,
the sysctl's will now be used instead of kvm_read, allowing consumers of
this interface to run without privilege (setgid kmem).  Retain the
ability to run on coredumps, or on a kernel using kmem if explicitly
pointed at one.

A side effect of this change is that kvm_getswapinfo() is faster now in
the general case. If the SWIF_DUMP_TREE flag is given (pstat -ss does
this), the radix tree walker, which still uses kvm_read in any case, is
invoked, and therefore does require privilege.

Submitted by:	Thomas Moestl <tmoestl@gmx.net>
Reviewed by:	freebsd-audit
This commit is contained in:
Robert Watson 2001-02-23 18:49:16 +00:00
parent edfa785a8e
commit ae3a37ad44
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=72950
1 changed files with 258 additions and 64 deletions
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322
lib/libkvm/kvm_getswapinfo.c
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@ -1,5 +1,6 @@
/*
* Copyright (c) 1999, Matthew Dillon. All Rights Reserved.
* Copyright (c) 2001, Thomas Moestl
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided under the terms of the BSD
@ -22,6 +23,7 @@ static const char rcsid[] =
#include <sys/stat.h>
#include <sys/conf.h>
#include <sys/blist.h>
#include <sys/sysctl.h>
#include <err.h>
#include <fcntl.h>
@ -32,6 +34,9 @@ static const char rcsid[] =
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <limits.h>
#include "kvm_private.h"
static struct nlist kvm_swap_nl[] = {
{ "_swapblist" }, /* new radix swap list */
@ -48,11 +53,19 @@ static struct nlist kvm_swap_nl[] = {
static int kvm_swap_nl_cached = 0;
static int nswdev;
static int unswdev;
static int unswdev; /* number of found swap dev's */
static int dmmax;
static void getswapinfo_radix(kvm_t *kd, struct kvm_swap *swap_ary,
int swap_max, int flags);
static int kvm_getswapinfo2(kvm_t *kd, struct kvm_swap *swap_ary,
int swap_max, int flags);
static int kvm_getswapinfo_kvm(kvm_t *, struct kvm_swap *, int, int);
static int kvm_getswapinfo_sysctl(kvm_t *, struct kvm_swap *, int, int);
static int nlist_init(kvm_t *);
static int getsysctl(kvm_t *, char *, void *, int);
static int getsysctl2(kvm_t *, char *, char *, char *, int, void *, int);
#define SVAR(var) __STRING(var) /* to force expansion */
#define KGET(idx, var) \
@ -74,6 +87,17 @@ static void getswapinfo_radix(kvm_t *kd, struct kvm_swap *swap_ary,
return (0); \
}
#define GETSWDEVNAME(dev, str, flags) \
if (dev == NODEV) { \
strlcpy(str, "[NFS swap]", sizeof(str)); \
} else { \
snprintf( \
str, sizeof(str),"%s%s", \
((flags & SWIF_DEV_PREFIX) ? _PATH_DEV : ""), \
devname(dev, S_IFCHR) \
); \
}
int
kvm_getswapinfo(
kvm_t *kd,
@ -81,7 +105,10 @@ kvm_getswapinfo(
int swap_max,
int flags
) {
int ti = 0;
int rv;
#ifdef DEBUG_SWAPINFO
int i;
#endif
/*
* clear cache
@ -91,52 +118,69 @@ kvm_getswapinfo(
return(0);
}
rv = kvm_getswapinfo2(kd, swap_ary, swap_max, flags);
/* This is only called when the tree shall be dumped. It needs kvm. */
if (flags & SWIF_DUMP_TREE) {
#ifdef DEBUG_SWAPINFO
/*
* sanity check: Sizes must be equal - used field must be
* 0 after this. Fill it with total-used before, where
* getswapinfo_radix will subtrat total-used.
* This will of course only work if there is no swap activity
* while we are working, so this code is normally not active.
*/
for (i = 0; i < unswdev; i++) {
swap_ary[i].ksw_used = swap_ary[i].ksw_total -
swap_ary[i].ksw_used;
}
#endif
getswapinfo_radix(kd, swap_ary, swap_max, flags);
#ifdef DEBUG_SWAPINFO
for (i = 0; i < unswdev; i++) {
if (swap_ary[i].ksw_used != 0) {
fprintf(stderr, "kvm_getswapinfo: swap size "
"mismatch (%d blocks)!\n",
swap_ary[i].ksw_used
);
}
}
/* This is fast enough now, so just do it again. */
rv = kvm_getswapinfo2(kd, swap_ary, swap_max, flags);
#endif
}
return rv;
}
static int
kvm_getswapinfo2(
kvm_t *kd,
struct kvm_swap *swap_ary,
int swap_max,
int flags
) {
if (ISALIVE(kd)) {
return kvm_getswapinfo_sysctl(kd, swap_ary, swap_max, flags);
} else {
return kvm_getswapinfo_kvm(kd, swap_ary, swap_max, flags);
}
}
int
kvm_getswapinfo_kvm(
kvm_t *kd,
struct kvm_swap *swap_ary,
int swap_max,
int flags
) {
int ti = 0;
/*
* namelist
*/
if (kvm_swap_nl_cached == 0) {
struct swdevt *sw;
if (kvm_nlist(kd, kvm_swap_nl) < 0)
return(-1);
/*
* required entries
*/
if (
kvm_swap_nl[NL_SWDEVT].n_value == 0 ||
kvm_swap_nl[NL_NSWDEV].n_value == 0 ||
kvm_swap_nl[NL_DMMAX].n_value == 0 ||
kvm_swap_nl[NL_SWAPBLIST].n_type == 0
) {
return(-1);
}
/*
* get globals, type of swap
*/
KGET(NL_NSWDEV, nswdev);
KGET(NL_DMMAX, dmmax);
/*
* figure out how many actual swap devices are enabled
*/
KGET(NL_SWDEVT, sw);
for (unswdev = nswdev - 1; unswdev >= 0; --unswdev) {
struct swdevt swinfo;
KGET2(&sw[unswdev], &swinfo, sizeof(swinfo), "swinfo");
if (swinfo.sw_nblks)
break;
}
++unswdev;
kvm_swap_nl_cached = 1;
}
if (!nlist_init(kd))
return (-1);
{
struct swdevt *sw;
@ -174,33 +218,19 @@ kvm_getswapinfo(
if (i < ti) {
swap_ary[i].ksw_total = ttl;
swap_ary[i].ksw_used = ttl;
swap_ary[i].ksw_used = swinfo.sw_used;
swap_ary[i].ksw_flags = swinfo.sw_flags;
if (swinfo.sw_dev == NODEV) {
snprintf(
swap_ary[i].ksw_devname,
sizeof(swap_ary[i].ksw_devname),
"%s",
"[NFS swap]"
);
} else {
snprintf(
swap_ary[i].ksw_devname,
sizeof(swap_ary[i].ksw_devname),
"%s%s",
((flags & SWIF_DEV_PREFIX) ? _PATH_DEV : ""),
devname(swinfo.sw_dev, S_IFCHR)
);
}
GETSWDEVNAME(swinfo.sw_dev,
swap_ary[i].ksw_devname, flags
);
}
if (ti >= 0) {
swap_ary[ti].ksw_total += ttl;
swap_ary[ti].ksw_used += ttl;
swap_ary[ti].ksw_used += swinfo.sw_used;
}
}
}
getswapinfo_radix(kd, swap_ary, swap_max, flags);
return(ti);
}
@ -226,7 +256,9 @@ scanradix(
int flags
) {
blmeta_t meta;
#ifdef DEBUG_SWAPINFO
int ti = (unswdev >= swap_max) ? swap_max - 1 : unswdev;
#endif
KGET2(scan, &meta, sizeof(meta), "blmeta_t");
@ -248,7 +280,9 @@ scanradix(
/*
* Leaf bitmap
*/
#ifdef DEBUG_SWAPINFO
int i;
#endif
if (flags & SWIF_DUMP_TREE) {
printf("%*.*s(0x%06x,%d) Bitmap %08x big=%d\n",
@ -260,6 +294,7 @@ scanradix(
);
}
#ifdef DEBUG_SWAPINFO
/*
* If not all allocated, count.
*/
@ -280,6 +315,7 @@ scanradix(
}
}
}
#endif
} else if (meta.u.bmu_avail == radix) {
/*
* Meta node if all free
@ -291,6 +327,7 @@ scanradix(
radix
);
}
#ifdef DEBUG_SWAPINFO
/*
* Note: both dmmax and radix are powers of 2. However, dmmax
* may be larger then radix so use a smaller increment if
@ -312,6 +349,7 @@ scanradix(
swap_ary[ti].ksw_used -= tinc;
}
}
#endif
} else if (meta.u.bmu_avail == 0) {
/*
* Meta node if all used
@ -378,6 +416,11 @@ getswapinfo_radix(kvm_t *kd, struct kvm_swap *swap_ary, int swap_max, int flags)
struct blist *swapblist = NULL;
struct blist blcopy = { 0 };
if (!nlist_init(kd)) {
fprintf(stderr, "radix tree: nlist_init failed!\n");
return;
}
KGET(NL_SWAPBLIST, swapblist);
if (swapblist == NULL) {
@ -412,3 +455,154 @@ getswapinfo_radix(kvm_t *kd, struct kvm_swap *swap_ary, int swap_max, int flags)
flags
);
}
#define GETSYSCTL(kd, name, var) \
getsysctl(kd, name, &(var), sizeof(var))
#define GETSYSCTL2(kd, pref, suff, buf, var) \
getsysctl2(kd, pref, suff, buf, sizeof(buf), &(var), \
sizeof(var))
int
kvm_getswapinfo_sysctl(
kvm_t *kd,
struct kvm_swap *swap_ary,
int swap_max,
int flags
) {
int ti = 0;
udev_t dev;
char node[15];
char buf[20];
int used, ttl, i;
if (!GETSYSCTL(kd, "vm.nswapdev", unswdev))
return -1;
ti = unswdev;
if (ti >= swap_max)
ti = swap_max - 1;
if (ti >= 0)
bzero(swap_ary, sizeof(struct kvm_swap) * (ti + 1));
if (!GETSYSCTL(kd, "vm.dmmax", dmmax))
return -1;
for (i = 0; i < unswdev; ++i) {
if (snprintf(node, sizeof(node), "vm.swapdev%d.", i) >=
sizeof(node)) {
_kvm_err(kd, kd->program, "XXX: node buffer too small");
return -1;
}
if (!GETSYSCTL2(kd, node, "nblks", buf, ttl))
return -1;
if (!GETSYSCTL2(kd, node, "used", buf, used))
return -1;
ttl -= dmmax;
if (i < ti) {
if (!GETSYSCTL2(kd, node, "dev", buf, dev))
return -1;
if (!GETSYSCTL2(kd, node, "flags", buf,
swap_ary[i].ksw_flags))
return -1;
swap_ary[i].ksw_total = ttl;
swap_ary[i].ksw_used = used;
GETSWDEVNAME(dev, swap_ary[i].ksw_devname, flags);
}
if (ti >= 0) {
swap_ary[ti].ksw_total += ttl;
swap_ary[ti].ksw_used += used;
}
}
return(ti);
}
static int
nlist_init (
kvm_t *kd
) {
struct swdevt *sw;
if (kvm_swap_nl_cached)
return (1);
if (kvm_nlist(kd, kvm_swap_nl) < 0)
return (0);
/*
* required entries
*/
if (
kvm_swap_nl[NL_SWDEVT].n_value == 0 ||
kvm_swap_nl[NL_NSWDEV].n_value == 0 ||
kvm_swap_nl[NL_DMMAX].n_value == 0 ||
kvm_swap_nl[NL_SWAPBLIST].n_type == 0
) {
return (0);
}
/*
* get globals, type of swap
*/
KGET(NL_NSWDEV, nswdev);
KGET(NL_DMMAX, dmmax);
/*
* figure out how many actual swap devices are enabled
*/
KGET(NL_SWDEVT, sw);
for (unswdev = nswdev - 1; unswdev >= 0; --unswdev) {
struct swdevt swinfo;
KGET2(&sw[unswdev], &swinfo, sizeof(swinfo), "swinfo");
if (swinfo.sw_nblks)
break;
}
++unswdev;
kvm_swap_nl_cached = 1;
return (1);
}
static int
getsysctl (
kvm_t *kd,
char *name,
void *ptr,
int len
) {
int nlen = len;
if (sysctlbyname(name, ptr, &nlen, NULL, 0) == -1) {
_kvm_err(kd, kd->program, "cannot read sysctl %s", name);
return (0);
}
if (nlen != len) {
_kvm_err(kd, kd->program, "sysctl %s has unexpected size", name);
return (0);
}
return (1);
}
static int
getsysctl2 (
kvm_t *kd,
char *pref,
char *suff,
char *buf,
int buflen,
void *ptr,
int len
) {
if (strlcpy(buf, pref, buflen) >= buflen) {
_kvm_err(kd, kd->program, "getsysctl2: string buffer too small");
return (0);
}
if (strlcat(buf, suff, buflen) >= buflen) {
_kvm_err(kd, kd->program, "getsysctl2: string buffer too small");
return (0);
}
return getsysctl(kd, buf, ptr, len);
}