Make libkvm work on live systems and crashdumps with and

without VIMAGE virtualization in the kernel.

If we cannot resolve a symbol try to see if we can find it with
prefix of the virtualized subsystem, currently only "vnet_entry"
by identifying either the vnet of the current process for a
live system or the vnet of proc0 (or of dumptid if compiled
in a non-default way).

The way this is done currently allows us to only touch libkvm
but no single application. Once we are going to virtualize more
subsystems we will have to review this decision for better scaling.

Submitted by:	rwatson (initial version of kvm_vnet.c, lots of ideas)
Reviewed by:	rwatson
Approved by:	re (kib)

1 files changed, 164 insertions, 8 deletions

diff --git a/lib/libkvm/kvm.c b/lib/libkvm/kvm.c
index 8ff8a2b..50f752a 100644
--- a/lib/libkvm/kvm.c
+++ b/lib/libkvm/kvm.c
@@ -41,6 +41,9 @@ static char sccsid[] = "@(#)kvm.c	8.2 (Berkeley) 2/13/94";
 #endif /* LIBC_SCCS and not lint */
 
 #include <sys/param.h>
+
+#define	_WANT_VNET
+
 #include <sys/user.h>
 #include <sys/proc.h>
 #include <sys/ioctl.h>
@@ -48,6 +51,8 @@ static char sccsid[] = "@(#)kvm.c	8.2 (Berkeley) 2/13/94";
 #include <sys/sysctl.h>
 #include <sys/linker.h>
 
+#include <net/vnet.h>
+
 #include <vm/vm.h>
 #include <vm/vm_param.h>
 
@@ -62,6 +67,7 @@ static char sccsid[] = "@(#)kvm.c	8.2 (Berkeley) 2/13/94";
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <strings.h>
 #include <unistd.h>
 
 #include "kvm_private.h"
@@ -299,34 +305,154 @@ kvm_close(kd)
 	return (0);
 }
 
+/*
+ * Walk the list of unresolved symbols, generate a new list and prefix the
+ * symbol names, try again, and merge back what we could resolve.
+ */
+static int
+kvm_fdnlist_prefix(kvm_t *kd, struct nlist *nl, int missing, const char *prefix,
+    uintptr_t (*validate_fn)(kvm_t *, uintptr_t))
+{
+	struct nlist *n, *np, *p;
+	char *cp, *ce;
+	size_t len;
+	int unresolved;
+
+	/*
+	 * Calculate the space we need to malloc for nlist and names.
+	 * We are going to store the name twice for later lookups: once
+	 * with the prefix and once the unmodified name delmited by \0.
+	 */
+	len = 0;
+	unresolved = 0;
+	for (p = nl; p->n_name && p->n_name[0]; ++p) {
+		if (p->n_type != N_UNDF)
+			continue;
+		len += sizeof(struct nlist) + strlen(prefix) +
+		    2 * (strlen(p->n_name) + 1);
+		unresolved++;
+	}
+	if (unresolved == 0)
+		return (unresolved);
+	/* Add space for the terminating nlist entry. */
+	len += sizeof(struct nlist);
+	unresolved++;
+
+	/* Alloc one chunk for (nlist, [names]) and setup pointers. */
+	n = np = malloc(len);
+	bzero(n, len);
+	if (n == NULL)
+		return (missing);
+	cp = ce = (char *)np;
+	cp += unresolved * sizeof(struct nlist);
+	ce += len;
+
+	/* Generate shortened nlist with special prefix. */
+	unresolved = 0;
+	for (p = nl; p->n_name && p->n_name[0]; ++p) {
+		if (p->n_type != N_UNDF)
+			continue;
+		bcopy(p, np, sizeof(struct nlist));
+		/* Save the new\0orig. name so we can later match it again. */
+		len = snprintf(cp, ce - cp, "%s%s%c%s", prefix,
+		    (prefix[0] != '\0' && p->n_name[0] == '_') ?
+			(p->n_name + 1) : p->n_name, '\0', p->n_name);
+		if (len >= ce - cp)
+			continue;
+		np->n_name = cp;
+		cp += len + 1;
+		np++;
+		unresolved++;
+	}
+
+	/* Do lookup on the reduced list. */
+	np = n;
+	unresolved = __fdnlist(kd->nlfd, np);
+
+	/* Check if we could resolve further symbols and update the list. */
+	if (unresolved >= 0 && unresolved < missing) {
+		/* Find the first freshly resolved entry. */
+		for (; np->n_name && np->n_name[0]; np++)
+			if (np->n_type != N_UNDF)
+				break;
+		/*
+		 * The lists are both in the same order,
+		 * so we can walk them in parallel.
+		 */
+		for (p = nl; np->n_name && np->n_name[0] &&
+		    p->n_name && p->n_name[0]; ++p) {
+			if (p->n_type != N_UNDF)
+				continue;
+			/* Skip expanded name and compare to orig. one. */
+			cp = np->n_name + strlen(np->n_name) + 1;
+			if (strcmp(cp, p->n_name))
+				continue;
+			/* Update nlist with new, translated results. */
+			p->n_type = np->n_type;
+			p->n_other = np->n_other;
+			p->n_desc = np->n_desc;
+			if (validate_fn)
+				p->n_value = (*validate_fn)(kd, np->n_value);
+			else
+				p->n_value = np->n_value;
+			missing--;
+			/* Find next freshly resolved entry. */
+			for (np++; np->n_name && np->n_name[0]; np++)
+				if (np->n_type != N_UNDF)
+					break;
+		}
+	}
+	/* We could assert missing = unresolved here. */
+
+	free(n);
+	return (unresolved);
+}
+
 int
-kvm_nlist(kd, nl)
-	kvm_t *kd;
-	struct nlist *nl;
+_kvm_nlist(kvm_t *kd, struct nlist *nl, int initialize)
 {
 	struct nlist *p;
 	int nvalid;
 	struct kld_sym_lookup lookup;
 	int error;
-
+	char *prefix = "", symname[1024]; /* XXX-BZ symbol name length limit? */
 	/*
 	 * If we can't use the kld symbol lookup, revert to the
 	 * slow library call.
 	 */
-	if (!ISALIVE(kd))
-		return (__fdnlist(kd->nlfd, nl));
+	if (!ISALIVE(kd)) {
+		error = __fdnlist(kd->nlfd, nl);
+		if (error <= 0)			/* Hard error or success. */
+			return (error);
+
+		if (_kvm_vnet_initialized(kd, initialize))
+			error = kvm_fdnlist_prefix(kd, nl, error,
+			    VNET_SYMPREFIX, _kvm_vnet_validaddr);
+
+		return (error);
+	}
 
 	/*
 	 * We can use the kld lookup syscall.  Go through each nlist entry
 	 * and look it up with a kldsym(2) syscall.
 	 */
 	nvalid = 0;
+again:
 	for (p = nl; p->n_name && p->n_name[0]; ++p) {
+		if (p->n_type != N_UNDF)
+			continue;
+
 		lookup.version = sizeof(lookup);
-		lookup.symname = p->n_name;
 		lookup.symvalue = 0;
 		lookup.symsize = 0;
 
+		error = snprintf(symname, sizeof(symname), "%s%s", prefix,
+		    (prefix[0] != '\0' && p->n_name[0] == '_') ?
+			(p->n_name + 1) : p->n_name);
+		if (error >= sizeof(symname))
+			continue;
+
+		lookup.symname = symname;
 		if (lookup.symname[0] == '_')
 			lookup.symname++;
 
@@ -334,11 +460,28 @@ kvm_nlist(kd, nl)
 			p->n_type = N_TEXT;
 			p->n_other = 0;
 			p->n_desc = 0;
-			p->n_value = lookup.symvalue;
+			if (_kvm_vnet_initialized(kd, initialize) &&
+			    !strcmp(prefix, VNET_SYMPREFIX))
+				p->n_value =
+				    _kvm_vnet_validaddr(kd, lookup.symvalue);
+			else
+				p->n_value = lookup.symvalue;
 			++nvalid;
 			/* lookup.symsize */
 		}
 	}
+
+	/*
+	 * Check the number of entries that weren't found. If they exist,
+	 * try again with a prefix for virtualized symbol names.
+	 */
+	error = ((p - nl) - nvalid);
+	if (error && _kvm_vnet_initialized(kd, initialize) &&
+	    strcmp(prefix, VNET_SYMPREFIX)) {
+		prefix = VNET_SYMPREFIX;
+		goto again;
+	}
+
 	/*
 	 * Return the number of entries that weren't found. If they exist,
 	 * also fill internal error buffer.
@@ -349,6 +492,19 @@ kvm_nlist(kd, nl)
 	return (error);
 }
 
+int
+kvm_nlist(kd, nl)
+	kvm_t *kd;
+	struct nlist *nl;
+{
+
+	/*
+	 * If called via the public interface, permit intialization of
+	 * further virtualized modules on demand.
+	 */
+	return (_kvm_nlist(kd, nl, 1));
+}
+
 ssize_t
 kvm_read(kd, kva, buf, len)
 	kvm_t *kd;