freebsd-skq/lib/libkvm/kvm.c
will ea532c48b8 libkvm: Improve physical address lookup scaling.
Instead of using a hash table to convert physical page addresses to offsets
in the sparse page array, cache the number of bits set for each 4MB chunk of
physical pages.  Upon lookup, find the nearest cached population count, then
add/subtract the number of bits from that point to the page's PTE bit.
Then multiply by page size and add to the sparse page map's base offset.

This replaces O(n) worst-case lookup with O(1) (plus a small number of bits
to scan in the bitmap).  Also, for a 128GB system, a typical kernel core of
about 8GB will now only require ~4.5MB of RAM for this approach instead of
~48MB as with the hash table.

More concretely, /usr/sbin/crashinfo against the same core improves from a
max RSS of 188MB and wall time of 43.72s (33.25 user 2.94 sys) to 135MB and
9.43s (2.58 user 1.47 sys).  Running "thread apply all bt" in kgdb has a
similar RSS improvement, and wall time drops from 4.44s to 1.93s.

Reviewed by:	jhb
Sponsored by:	Backtrace I/O
2016-07-18 01:55:25 +00:00

441 lines
10 KiB
C

/*-
* Copyright (c) 1989, 1992, 1993
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software developed by the Computer Systems
* Engineering group at Lawrence Berkeley Laboratory under DARPA contract
* BG 91-66 and contributed to Berkeley.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#if defined(LIBC_SCCS) && !defined(lint)
#if 0
static char sccsid[] = "@(#)kvm.c 8.2 (Berkeley) 2/13/94";
#endif
#endif /* LIBC_SCCS and not lint */
#include <sys/param.h>
#include <sys/fnv_hash.h>
#define _WANT_VNET
#include <sys/user.h>
#include <sys/linker.h>
#include <sys/pcpu.h>
#include <sys/stat.h>
#include <net/vnet.h>
#include <fcntl.h>
#include <kvm.h>
#include <limits.h>
#include <paths.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "kvm_private.h"
SET_DECLARE(kvm_arch, struct kvm_arch);
char *
kvm_geterr(kvm_t *kd)
{
return (kd->errbuf);
}
static int
_kvm_read_kernel_ehdr(kvm_t *kd)
{
Elf *elf;
if (elf_version(EV_CURRENT) == EV_NONE) {
_kvm_err(kd, kd->program, "Unsupported libelf");
return (-1);
}
elf = elf_begin(kd->nlfd, ELF_C_READ, NULL);
if (elf == NULL) {
_kvm_err(kd, kd->program, "%s", elf_errmsg(0));
return (-1);
}
if (elf_kind(elf) != ELF_K_ELF) {
_kvm_err(kd, kd->program, "kernel is not an ELF file");
return (-1);
}
if (gelf_getehdr(elf, &kd->nlehdr) == NULL) {
_kvm_err(kd, kd->program, "%s", elf_errmsg(0));
elf_end(elf);
return (-1);
}
elf_end(elf);
switch (kd->nlehdr.e_ident[EI_DATA]) {
case ELFDATA2LSB:
case ELFDATA2MSB:
return (0);
default:
_kvm_err(kd, kd->program,
"unsupported ELF data encoding for kernel");
return (-1);
}
}
static kvm_t *
_kvm_open(kvm_t *kd, const char *uf, const char *mf, int flag, char *errout)
{
struct kvm_arch **parch;
struct stat st;
kd->vmfd = -1;
kd->pmfd = -1;
kd->nlfd = -1;
kd->vmst = NULL;
kd->procbase = NULL;
kd->argspc = NULL;
kd->argv = NULL;
if (uf == NULL)
uf = getbootfile();
else if (strlen(uf) >= MAXPATHLEN) {
_kvm_err(kd, kd->program, "exec file name too long");
goto failed;
}
if (flag & ~O_RDWR) {
_kvm_err(kd, kd->program, "bad flags arg");
goto failed;
}
if (mf == NULL)
mf = _PATH_MEM;
if ((kd->pmfd = open(mf, flag | O_CLOEXEC, 0)) < 0) {
_kvm_syserr(kd, kd->program, "%s", mf);
goto failed;
}
if (fstat(kd->pmfd, &st) < 0) {
_kvm_syserr(kd, kd->program, "%s", mf);
goto failed;
}
if (S_ISREG(st.st_mode) && st.st_size <= 0) {
errno = EINVAL;
_kvm_syserr(kd, kd->program, "empty file");
goto failed;
}
if (S_ISCHR(st.st_mode)) {
/*
* If this is a character special device, then check that
* it's /dev/mem. If so, open kmem too. (Maybe we should
* make it work for either /dev/mem or /dev/kmem -- in either
* case you're working with a live kernel.)
*/
if (strcmp(mf, _PATH_DEVNULL) == 0) {
kd->vmfd = open(_PATH_DEVNULL, O_RDONLY | O_CLOEXEC);
return (kd);
} else if (strcmp(mf, _PATH_MEM) == 0) {
if ((kd->vmfd = open(_PATH_KMEM, flag | O_CLOEXEC)) <
0) {
_kvm_syserr(kd, kd->program, "%s", _PATH_KMEM);
goto failed;
}
return (kd);
}
}
/*
* This is a crash dump.
* Open the namelist fd and determine the architecture.
*/
if ((kd->nlfd = open(uf, O_RDONLY | O_CLOEXEC, 0)) < 0) {
_kvm_syserr(kd, kd->program, "%s", uf);
goto failed;
}
if (_kvm_read_kernel_ehdr(kd) < 0)
goto failed;
if (strncmp(mf, _PATH_FWMEM, strlen(_PATH_FWMEM)) == 0)
kd->rawdump = 1;
SET_FOREACH(parch, kvm_arch) {
if ((*parch)->ka_probe(kd)) {
kd->arch = *parch;
break;
}
}
if (kd->arch == NULL) {
_kvm_err(kd, kd->program, "unsupported architecture");
goto failed;
}
/*
* Non-native kernels require a symbol resolver.
*/
if (!kd->arch->ka_native(kd) && kd->resolve_symbol == NULL) {
_kvm_err(kd, kd->program,
"non-native kernel requires a symbol resolver");
goto failed;
}
/*
* Initialize the virtual address translation machinery.
*/
if (kd->arch->ka_initvtop(kd) < 0)
goto failed;
return (kd);
failed:
/*
* Copy out the error if doing sane error semantics.
*/
if (errout != NULL)
strlcpy(errout, kd->errbuf, _POSIX2_LINE_MAX);
(void)kvm_close(kd);
return (0);
}
kvm_t *
kvm_openfiles(const char *uf, const char *mf, const char *sf __unused, int flag,
char *errout)
{
kvm_t *kd;
if ((kd = calloc(1, sizeof(*kd))) == NULL) {
if (errout != NULL)
(void)strlcpy(errout, strerror(errno),
_POSIX2_LINE_MAX);
return (0);
}
return (_kvm_open(kd, uf, mf, flag, errout));
}
kvm_t *
kvm_open(const char *uf, const char *mf, const char *sf __unused, int flag,
const char *errstr)
{
kvm_t *kd;
if ((kd = calloc(1, sizeof(*kd))) == NULL) {
if (errstr != NULL)
(void)fprintf(stderr, "%s: %s\n",
errstr, strerror(errno));
return (0);
}
kd->program = errstr;
return (_kvm_open(kd, uf, mf, flag, NULL));
}
kvm_t *
kvm_open2(const char *uf, const char *mf, int flag, char *errout,
int (*resolver)(const char *, kvaddr_t *))
{
kvm_t *kd;
if ((kd = calloc(1, sizeof(*kd))) == NULL) {
if (errout != NULL)
(void)strlcpy(errout, strerror(errno),
_POSIX2_LINE_MAX);
return (0);
}
kd->resolve_symbol = resolver;
return (_kvm_open(kd, uf, mf, flag, errout));
}
int
kvm_close(kvm_t *kd)
{
int error = 0;
if (kd->vmst != NULL)
kd->arch->ka_freevtop(kd);
if (kd->pmfd >= 0)
error |= close(kd->pmfd);
if (kd->vmfd >= 0)
error |= close(kd->vmfd);
if (kd->nlfd >= 0)
error |= close(kd->nlfd);
if (kd->procbase != 0)
free((void *)kd->procbase);
if (kd->argbuf != 0)
free((void *) kd->argbuf);
if (kd->argspc != 0)
free((void *) kd->argspc);
if (kd->argv != 0)
free((void *)kd->argv);
if (kd->pt_map != NULL)
free(kd->pt_map);
free((void *)kd);
return (0);
}
int
kvm_nlist2(kvm_t *kd, struct kvm_nlist *nl)
{
/*
* If called via the public interface, permit initialization of
* further virtualized modules on demand.
*/
return (_kvm_nlist(kd, nl, 1));
}
int
kvm_nlist(kvm_t *kd, struct nlist *nl)
{
struct kvm_nlist *kl;
int count, i, nfail;
/*
* Avoid reporting truncated addresses by failing for non-native
* cores.
*/
if (!kvm_native(kd)) {
_kvm_err(kd, kd->program, "kvm_nlist of non-native vmcore");
return (-1);
}
for (count = 0; nl[count].n_name != NULL && nl[count].n_name[0] != '\0';
count++)
;
if (count == 0)
return (0);
kl = calloc(count + 1, sizeof(*kl));
for (i = 0; i < count; i++)
kl[i].n_name = nl[i].n_name;
nfail = kvm_nlist2(kd, kl);
for (i = 0; i < count; i++) {
nl[i].n_type = kl[i].n_type;
nl[i].n_other = 0;
nl[i].n_desc = 0;
nl[i].n_value = kl[i].n_value;
}
return (nfail);
}
ssize_t
kvm_read(kvm_t *kd, u_long kva, void *buf, size_t len)
{
return (kvm_read2(kd, kva, buf, len));
}
ssize_t
kvm_read2(kvm_t *kd, kvaddr_t kva, void *buf, size_t len)
{
int cc;
ssize_t cr;
off_t pa;
char *cp;
if (ISALIVE(kd)) {
/*
* We're using /dev/kmem. Just read straight from the
* device and let the active kernel do the address translation.
*/
errno = 0;
if (lseek(kd->vmfd, (off_t)kva, 0) == -1 && errno != 0) {
_kvm_err(kd, 0, "invalid address (0x%jx)",
(uintmax_t)kva);
return (-1);
}
cr = read(kd->vmfd, buf, len);
if (cr < 0) {
_kvm_syserr(kd, 0, "kvm_read");
return (-1);
} else if (cr < (ssize_t)len)
_kvm_err(kd, kd->program, "short read");
return (cr);
}
cp = buf;
while (len > 0) {
cc = kd->arch->ka_kvatop(kd, kva, &pa);
if (cc == 0)
return (-1);
if (cc > (ssize_t)len)
cc = len;
errno = 0;
if (lseek(kd->pmfd, pa, 0) == -1 && errno != 0) {
_kvm_syserr(kd, 0, _PATH_MEM);
break;
}
cr = read(kd->pmfd, cp, cc);
if (cr < 0) {
_kvm_syserr(kd, kd->program, "kvm_read");
break;
}
/*
* If ka_kvatop returns a bogus value or our core file is
* truncated, we might wind up seeking beyond the end of the
* core file in which case the read will return 0 (EOF).
*/
if (cr == 0)
break;
cp += cr;
kva += cr;
len -= cr;
}
return (cp - (char *)buf);
}
ssize_t
kvm_write(kvm_t *kd, u_long kva, const void *buf, size_t len)
{
int cc;
if (ISALIVE(kd)) {
/*
* Just like kvm_read, only we write.
*/
errno = 0;
if (lseek(kd->vmfd, (off_t)kva, 0) == -1 && errno != 0) {
_kvm_err(kd, 0, "invalid address (%lx)", kva);
return (-1);
}
cc = write(kd->vmfd, buf, len);
if (cc < 0) {
_kvm_syserr(kd, 0, "kvm_write");
return (-1);
} else if ((size_t)cc < len)
_kvm_err(kd, kd->program, "short write");
return (cc);
} else {
_kvm_err(kd, kd->program,
"kvm_write not implemented for dead kernels");
return (-1);
}
/* NOTREACHED */
}
int
kvm_native(kvm_t *kd)
{
if (ISALIVE(kd))
return (1);
return (kd->arch->ka_native(kd));
}