Add support to libkvm for reading vmcores from other architectures.

- Add a kvaddr_type to represent kernel virtual addresses instead of
  unsigned long.
- Add a struct kvm_nlist which is a stripped down version of struct nlist
  that uses kvaddr_t for n_value.
- Add a kvm_native() routine that returns true if an open kvm descriptor
  is for a native kernel and memory image.
- Add a kvm_open2() function similar to kvm_openfiles().  It drops the
  unused 'swapfile' argument and adds a new function pointer argument for
  a symbol resolving function.  Native kernels still use _fdnlist() from
  libc to resolve symbols if a resolver function is not supplied, but cross
  kernels require a resolver.
- Add a kvm_nlist2() function similar to kvm_nlist() except that it uses
  struct kvm_nlist instead of struct nlist.
- Add a kvm_read2() function similar to kvm_read() except that it uses
  kvaddr_t instead of unsigned long for the kernel virtual address.
- Add a new kvm_arch switch of routines needed by a vmcore backend.
  Each backend is responsible for implementing kvm_read2() for a given
  vmcore format.
- Use libelf to read headers from ELF kernels and cores (except for
  powerpc cores).
- Add internal helper routines for the common page offset hash table used
  by the minidump backends.
- Port all of the existing kvm backends to implement a kvm_arch switch and
  to be cross-friendly by using private constants instead of ones that
  vary by platform (e.g. PAGE_SIZE).  Static assertions are present when
  a given backend is compiled natively to ensure the private constants
  match the real ones.
- Enable all of the existing vmcore backends on all platforms.  This means
  that libkvm on any platform should be able to perform KVA translation
  and read data from a vmcore of any platform.

Tested on:	amd64, i386, sparc64 (marius)
Differential Revision:	https://reviews.freebsd.org/D3341

1 files changed, 6 insertions, 0 deletions

diff --git a/lib/libkvm/kvm_getloadavg.c b/lib/libkvm/kvm_getloadavg.c
index ecfc321..b850c02 100644
--- a/lib/libkvm/kvm_getloadavg.c
+++ b/lib/libkvm/kvm_getloadavg.c
@@ -71,6 +71,12 @@ kvm_getloadavg(kvm_t *kd, double loadavg[], int nelem)
 	if (ISALIVE(kd))
 		return (getloadavg(loadavg, nelem));
 
+	if (!kd->arch->ka_native(kd)) {
+		_kvm_err(kd, kd->program,
+		    "cannot read loadavg from non-native core");
+		return (-1);
+	}
+
 	if (kvm_nlist(kd, nl) != 0) {
 		for (p = nl; p->n_type != 0; ++p);
 		_kvm_err(kd, kd->program,