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NetBSD 6.1.5 - man page for kvm_openfiles (netbsd section 3)

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KVM_OPEN(3)			   BSD Library Functions Manual 		      KVM_OPEN(3)

NAME
     kvm_open, kvm_openfiles, kvm_close -- initialize kernel virtual memory access

LIBRARY
     Kernel Data Access Library (libkvm, -lkvm)

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 vir-
     tual memory via the kvm(3) library routines.  Both active kernels and crash dumps are acces-
     sible 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; in this
     case, the functions will attempt to use the ksyms(4) device indicated by _PATH_KSYMS in
     <paths.h>; if that fails, then they will use the file indicated by the sysctl(3) variable
     machdep.booted_kernel, or (if the sysctl information is not available) the default kernel
     path indicated by _PATH_UNIX 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.  The only permitted flags from open(2) are O_RDONLY, O_WRONLY, and O_RDWR.

     As a special case, a flags argument of KVM_NO_FILES will initialize the kvm(3) library for
     use on active kernels only using sysctl(3) for retrieving kernel data and ignores the
     execfile, corefile and swapfile arguments.  Only a small subset of the kvm(3) library func-
     tions are available using this method.  These are currently kvm_getproc2(3), kvm_getargv2(3)
     and kvm_getenvv2(3).

     There are two open routines which differ only with respect to the error mechanism.  One pro-
     vides 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).  Nor-
     mally, 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 corre-
     sponding 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 sub-
     sequent 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_getkernelname(3),
     kvm_getprocs(3), kvm_nlist(3), kvm_read(3), kvm_write(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.

BSD					September 14, 2011				      BSD
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