table of contents
KVM_OPEN(3) | Library Functions Manual | KVM_OPEN(3) |
NAME¶
kvm_open, kvm_openfiles, kvm_close — initialize kernel virtual memory accessLIBRARY¶
Kernel Data Access Library (libkvm, -lkvm)SYNOPSIS¶
#include <fcntl.h>#include <kvm.h> kvm_t *
kvm_open(const char *execfile, const char *corefile, const char *swapfile, int flags, const char *errstr); kvm_t *
kvm_openfiles(const char *execfile, const char *corefile, const 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. The execfile argument is the executable image of the kernel being examined. This file must contain a symbol table. If this argument isNULL
, the currently running system is assumed, as
determined from getbootfile(3).
The corefile argument 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. It can also be
set to a special value /dev/null by utilities like
ps(1) that do not directly access kernel memory.
The swapfile argument is currently unused.
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.
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_getargv(3), kvm_getenvv(3), kvm_geterr(3), kvm_getprocs(3), kvm_nlist(3), kvm_read(3), kvm_write(3), kmem(4), mem(4)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.January 29, 2004 | Debian |