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PAE support for kvm(3)
Hi list,
Attached is the patch required to add PAE support in kvm(3). Except for
one "major" nit (see below), it seems to be functional: I can sync a
kernel, with or without PAE enabled, and all libkvm binaries (vmstat(1),
netstat(1), ...) still work on the core files.
I am facing an interesting limitation there: some weeks ago, I added a
symbol, i386_use_pae. This variable is also exposed through a sysctl(7):
"machdep.pae".
Goal was to easily provide an indication whether a kernel is currently
using PAE mode or not, and also query its value through kvm_nlist(3) (to
select the proper kvatop function, depending on the mode).
However, I have some kind of "chicken-egg" situation there: getting
i386_use_pae value needs a go through KREAD/kvm_read, but these
functions cannot work properly until the correct kvatop function has
been selected. Downside is, this depends on i386_use_pae value...
At this late hour, I cannot think of a quick and clean solution. Adding
an element to the cpu_kcore_hdr_t will break all core dumps from before
the change (the offset of the memory segments, "memsegs", will differ);
that would need compat code to cope with that. Another possibility is to
set the last bit in pdppaddr to indicate PAE activation, but, this seems
like a dirty hack (I don't think that PDPpaddr will ever go that high
though).
Any advice for that one? Thanks in advance!
--
Jean-Yves Migeon
jeanyves.migeon%free.fr@localhost
Index: lib/libkvm/Makefile
===================================================================
RCS file: /cvsroot/src/lib/libkvm/Makefile,v
retrieving revision 1.45
diff -u -p -r1.45 Makefile
--- lib/libkvm/Makefile 25 Oct 2008 23:59:42 -0000 1.45
+++ lib/libkvm/Makefile 1 Oct 2010 00:03:55 -0000
@@ -7,9 +7,6 @@ USE_SHLIBDIR= yes
LIB= kvm
CPPFLAGS+=-DLIBC_SCCS -I${NETBSDSRCDIR}/sys
-.if ${MACHINE_ARCH} == "i386"
-LINTFLAGS+=-w
-.endif
SRCS= kvm.c kvm_file.c kvm_getloadavg.c kvm_proc.c
@@ -31,6 +28,11 @@ SRCS+= kvm_${MACHINE_CPU}.c
@false
.endif
+.if ${MACHINE_ARCH} == "i386"
+LINTFLAGS+=-w
+SRCS+= kvm_i386pae.c # Hook PAE support in the i386 build
+.endif
+
# Additional modules needed for m68k
.if (${MACHINE_ARCH} == "m68k" || ${MACHINE_CPU} == "m68k")
SRCS+= kvm_m68k_cmn.c kvm_sun2.c kvm_sun3.c kvm_sun3x.c
Index: lib/libkvm/kvm_i386.c
===================================================================
RCS file: /cvsroot/src/lib/libkvm/kvm_i386.c,v
retrieving revision 1.28
diff -u -p -r1.28 kvm_i386.c
--- lib/libkvm/kvm_i386.c 20 Sep 2010 23:23:16 -0000 1.28
+++ lib/libkvm/kvm_i386.c 1 Oct 2010 00:03:55 -0000
@@ -74,6 +74,16 @@ __RCSID("$NetBSD: kvm_i386.c,v 1.28 2010
#define ptob(x) ((caddr_t)((x) << PGSHIFT)) /* XXX */
#endif
+/*
+ * Indicates whether PAE is in use for the kernel image
+ * 0: native i386 virtual memory mappings
+ * 1: i386 PAE mappings
+ */
+static int i386_use_pae;
+
+int _kvm_kvatop_i386(kvm_t *, vaddr_t, paddr_t *);
+int _kvm_kvatop_i386pae(kvm_t *, vaddr_t, paddr_t *);
+
void
_kvm_freevtop(kvm_t *kd)
{
@@ -87,6 +97,23 @@ _kvm_freevtop(kvm_t *kd)
int
_kvm_initvtop(kvm_t *kd)
{
+ struct nlist nl[2];
+
+ nl[0].n_name = "i386_use_pae";
+ nl[1].n_name = NULL;
+
+ if (kvm_nlist(kd, nl) != 0) {
+ /* Support kernels from before the PAE era */
+ _kvm_err(kd, 0, "could not read i386 virtual memory mode -- "
+ "assuming i386 native");
+ i386_use_pae = 0;
+ return 0;
+ }
+
+ if (KREAD(kd, nl[0].n_value, &i386_use_pae)) {
+ _kvm_err(kd, kd->program, "can't read i386_use_pae");
+ return -1;
+ }
return 0;
}
@@ -97,17 +124,36 @@ _kvm_initvtop(kvm_t *kd)
int
_kvm_kvatop(kvm_t *kd, vaddr_t va, paddr_t *pa)
{
- cpu_kcore_hdr_t *cpu_kh;
- u_long page_off;
- pd_entry_t pde;
- pt_entry_t pte;
- paddr_t pde_pa, pte_pa;
if (ISALIVE(kd)) {
_kvm_err(kd, 0, "vatop called in live kernel!");
return 0;
}
+ switch (i386_use_pae) {
+ default:
+ case 0:
+ return _kvm_kvatop_i386(kd, va, pa);
+ case 1:
+ return _kvm_kvatop_i386pae(kd, va, pa);
+ }
+
+}
+
+/*
+ * Used to translate a virtual address to a physical address for systems
+ * with PAE mode disabled. Only two levels of virtual memory pages are
+ * dereferenced (L2 PDEs, then L1 PTEs).
+ */
+int
+_kvm_kvatop_i386(kvm_t *kd, vaddr_t va, paddr_t *pa)
+{
+ cpu_kcore_hdr_t *cpu_kh;
+ u_long page_off;
+ pd_entry_t pde;
+ pt_entry_t pte;
+ paddr_t pde_pa, pte_pa;
+
cpu_kh = kd->cpu_data;
page_off = va & PGOFSET;
--- /dev/null 2010-10-01 02:32:35.000000000 +0200
+++ lib/libkvm/kvm_i386pae.c 2010-09-26 16:05:38.000000000 +0200
@@ -0,0 +1,131 @@
+/* $NetBSD$ */
+
+/*
+ * Copyright (c) 2010 Jean-Yves Migeon.
+ *
+ * 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.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. 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 FOUNDATION 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>
+__RCSID("$NetBSD$");
+
+/*
+ * This will expose PAE functions, macros, definitions and constants.
+ * Note: this affects all virtual memory related functions. Only their
+ * PAE versions can be used below.
+ */
+#define PAE
+
+#include <sys/param.h>
+#include <sys/user.h>
+#include <sys/stat.h>
+#include <sys/kcore.h>
+#include <sys/types.h>
+
+#include <stdlib.h>
+#include <unistd.h>
+#include <nlist.h>
+#include <kvm.h>
+
+#include <uvm/uvm_extern.h>
+
+#include <limits.h>
+#include <db.h>
+
+#include "kvm_private.h"
+
+#include <i386/kcore.h>
+#include <i386/pmap.h>
+#include <i386/pte.h>
+#include <i386/vmparam.h>
+
+int _kvm_kvatop_i386pae(kvm_t *, vaddr_t, paddr_t *);
+
+/*
+ * Used to translate a virtual address to a physical address for systems
+ * running under PAE mode. Three levels of virtual memory pages are handled
+ * here: the per-CPU L3 page, the 4 L2 PDs and the PTs.
+ */
+int
+_kvm_kvatop_i386pae(kvm_t *kd, vaddr_t va, paddr_t *pa)
+{
+ cpu_kcore_hdr_t *cpu_kh;
+ u_long page_off;
+ pd_entry_t pde;
+ pt_entry_t pte;
+ paddr_t pde_pa, pte_pa;
+
+ cpu_kh = kd->cpu_data;
+ page_off = va & PGOFSET;
+
+ /*
+ * Find and read the PDE. Ignore the L3, as it is only a per-CPU
+ * page, not needed for kernel VA => PA translations.
+ * Remember that the 4 L2 pages are contiguous, so it is safe
+ * to increment pdppaddr to compute the address of the PDE.
+ */
+ pde_pa = cpu_kh->pdppaddr + (pl2_pi(va) * sizeof(pd_entry_t));
+
+ if (_kvm_pread(kd, kd->pmfd, (void *)&pde, sizeof(pde),
+ _kvm_pa2off(kd, pde_pa)) != sizeof(pde)) {
+ _kvm_syserr(kd, 0, "could not read PDE");
+ goto lose;
+ }
+
+ /*
+ * Find and read the page table entry.
+ */
+ if ((pde & PG_V) == 0) {
+ _kvm_err(kd, 0, "invalid translation (invalid PDE)");
+ goto lose;
+ }
+ if ((pde & PG_PS) != 0) {
+ /*
+ * This is a 2MB page.
+ */
+ page_off = va & ((vaddr_t)~PG_LGFRAME);
+ *pa = (pde & PG_LGFRAME) + page_off;
+ return (int)(NBPD_L2 - page_off);
+ }
+
+ pte_pa = (pde & PG_FRAME) + (pl1_pi(va) * sizeof(pt_entry_t));
+ if (_kvm_pread(kd, kd->pmfd, (void *) &pte, sizeof(pte),
+ _kvm_pa2off(kd, pte_pa)) != sizeof(pte)) {
+ _kvm_syserr(kd, 0, "could not read PTE");
+ goto lose;
+ }
+
+ /*
+ * Validate the PTE and return the physical address.
+ */
+ if ((pte & PG_V) == 0) {
+ _kvm_err(kd, 0, "invalid translation (invalid PTE)");
+ goto lose;
+ }
+ *pa = (pte & PG_FRAME) + page_off;
+ return (int)(NBPG - page_off);
+
+lose:
+ *pa = (paddr_t)~0L;
+ return 0;
+
+}
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