NAME
kvm_open,
kvm_openfiles, kvm_close
— initialize kernel virtual
memory access
SYNOPSIS
#include <fcntl.h>
#include <kvm.h>
kvm_t *
kvm_open(const
char *execfile, const
char *corefile, char
*swapfile, int
flags, const char
*errstr);
kvm_t *
kvm_openfiles(const
char *execfile, const
char *corefile, char
*swapfile, int
flags, char
*errbuf);
int
kvm_close(kvm_t
*kd);
DESCRIPTION
The functions
kvm_open()
and kvm_openfiles() return a descriptor used to
access kernel virtual memory via the
kvm(3) library routines. Both active kernels and crash dumps are
accessible through this interface.
execfile is the executable image of the
kernel being examined. This file must contain a symbol table. If this
argument is NULL, the currently running system is
assumed, which is indicated by _PATH_KSYMS, if it
exists, otherwise _PATH_UNIX is used. Both are
defined in <paths.h>.
corefile is the kernel memory device file.
It can be either /dev/mem or a crash dump core
generated by
savecore(8). If corefile is
NULL, the default indicated by
_PATH_MEM from
<paths.h> is used.
swapfile should indicate the swap device. If
NULL, no swap device will be used.
The flags argument indicates read/write
access as in open(2) and applies only to the core file. Only
O_RDONLY, O_WRONLY, and
O_RDWR are permitted. A special value
KVM_NO_FILES can be specified which will cause no
files to be opened and the handle can only be used on live kernels on a
limited subset of all kvm operations.
There are two open routines which differ only with respect to the error mechanism. One provides backward compatibility with the SunOS kvm library, while the other provides an improved error reporting framework.
The
kvm_open()
function is the Sun kvm compatible open call. Here, the
errstr argument indicates how errors should be
handled. If it is NULL, no errors are reported and
the application cannot know the specific nature of the failed kvm call. If
it is not NULL, errors are printed to stderr with
errstr prepended to the message, as in
perror(3). Normally, the name of the program is used here. The string
is assumed to persist at least until the corresponding
kvm_close()
call.
The
kvm_openfiles()
function provides BSD style error reporting. Here,
error messages are not printed out by the library. Instead, the application
obtains the error message corresponding to the most recent kvm library call
using
kvm_geterr()
(see kvm_geterr(3)). The results are undefined if the most recent
kvm call did not produce an error. Since
kvm_geterr() requires a kvm descriptor, but the open
routines return NULL on failure,
kvm_geterr() cannot be used to get the error message
if open fails. Thus, kvm_openfiles() will place any
error message in the errbuf argument. This buffer
should be _POSIX2_LINE_MAX characters large (from
<limits.h>).
RETURN VALUES
The kvm_open() and
kvm_openfiles() functions both return a descriptor
to be used in all subsequent kvm library calls. The library is fully
re-entrant. On failure, NULL is returned, in which
case kvm_openfiles() writes the error message into
errbuf.
The kvm_close() function returns 0 on
success and -1 on failure.
SEE ALSO
open(2), kvm(3), kvm_geterr(3), kvm_getprocs(3), kvm_nlist(3), kvm_read(3)
BUGS
There should not be two open calls. The ill-defined error semantics of the Sun library and the desire to have a backward-compatible library for BSD left little choice.