kvm_open, kvm_openfiles, kvm_close - initialize kernel virtual memory access
#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);
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,
_PATH_DRUM from
<paths.h> is 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>).
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.
open(2), kvm(3), kvm_getargv(3), kvm_getenvv(3),
kvm_geterr(3),
kvm_getprocs(3), kvm_nlist(3), kvm_read(3), kvm_write(3)
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.
OpenBSD 3.6 April 19, 1994
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