A first cut at teaching libkvm how to deal with dynamic per-CPU storage

(DPCPU):

A new API, kvm_dpcpu_setcpu(3), selects the active CPU for the purposes
of DPCPU.  Calls to kvm_nlist(3) will automatically translate DPCPU
symbols and return a pointer to the current CPU's version of the data.
Consumers needing to read the same symbol on several CPUs will invoke a
series of setcpu/nlist calls, one per CPU of interest.

This addition makes it possible for tools like netstat(1) to query the
values of DPCPU variables during crashdump analysis, and is based on
similar code handling virtualized global variables.

MFC after:	1 week
Sponsored by:	Juniper Networks, Inc.

1 files changed, 15 insertions, 0 deletions

diff --git a/lib/libkvm/kvm_private.h b/lib/libkvm/kvm_private.h
index cc073db5fe42..69b1658f8e48 100644
--- a/lib/libkvm/kvm_private.h
+++ b/lib/libkvm/kvm_private.h
@@ -68,6 +68,19 @@ struct __kvm {
 	uintptr_t	vnet_stop;	/* stop of kernel's vnet region */
 	uintptr_t	vnet_current;	/* vnet we're working with */
 	uintptr_t	vnet_base;	/* vnet base of current vnet */
+
+	/*
+	 * Dynamic per-CPU kernel memory.  We translate symbols, on-demand,
+	 * to the data associated with dpcpu_curcpu, set with
+	 * kvm_dpcpu_setcpu().
+	 */
+	int		dpcpu_initialized;	/* dpcpu fields set up */
+	uintptr_t	dpcpu_start;	/* start of kernel's dpcpu region */
+	uintptr_t	dpcpu_stop;	/* stop of kernel's dpcpu region */
+	u_int		dpcpu_maxcpus;	/* size of base array */
+	uintptr_t	*dpcpu_off;	/* base array, indexed by CPU ID */
+	u_int		dpcpu_curcpu;	/* CPU we're currently working with */
+	uintptr_t	dpcpu_curoff;	/* dpcpu base of current CPU */
 };
 
 /*
@@ -88,6 +101,8 @@ int	 _kvm_uvatop(kvm_t *, const struct proc *, u_long, u_long *);
 int	 _kvm_vnet_selectpid(kvm_t *, pid_t);
 int	 _kvm_vnet_initialized(kvm_t *, int);
 uintptr_t _kvm_vnet_validaddr(kvm_t *, uintptr_t);
+int	 _kvm_dpcpu_initialized(kvm_t *, int);
+uintptr_t _kvm_dpcpu_validaddr(kvm_t *, uintptr_t);
 
 #if defined(__amd64__) || defined(__i386__) || defined(__arm__)
 void	 _kvm_minidump_freevtop(kvm_t *);