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

     kvm_open, kvm_openfiles, kvm_close	-- initialize kernel virtual memory

     Kernel Data Access	Library	(libkvm, -lkvm)

     #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);

     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 ac-
     tive kernels and crash dumps are accessible through this interface.

     The execfile argument is the executable image of the kernel being exam-
     ined.  This file must contain a symbol table.  If this argument is	NULL,
     the currently running system is assumed, as determined from

     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 permit-

     There are two open	routines which differ only with	respect	to the error
     mechanism.	 One provides backward compatibility with the SunOS kvm	li-
     brary, 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 na-
     ture 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 applica-
     tion obtains the error message corresponding to the most recent kvm li-
     brary call	using kvm_geterr() (see	kvm_geterr(3)).	 The results are unde-
     fined 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

     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-en-
     trant.  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), kmem(4),	mem(4)

     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			       January 29, 2004				   BSD


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