NAME    [Toc]    [Back]

     kvm_open, kvm_openfiles, kvm_close - initialize kernel  virtual memory access

SYNOPSIS    [Toc]    [Back]

     #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    [Toc]    [Back]

     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>).

RETURN VALUES    [Toc]    [Back]

     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    [Toc]    [Back]

     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)

BUGS    [Toc]    [Back]

     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