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kvm_close (3)

>> kvm_close (3) ( FreeBSD man: Библиотечные вызовы )

BSD mandoc

NAME



kvm_open

 
kvm_openfiles

 
kvm_close

 - initialize kernel virtual memory access

LIBRARY

Lb libkvm

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 Fa execfile argument 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, as determined from getbootfile(3).

The Fa corefile argument is the kernel memory device file. It can be either /dev/mem or a crash dump core generated by savecore(8). If Fa corefile is NULL the default indicated by _PATH_MEM from #include <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 Fa swapfile argument is currently unused.

The Fa 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 Fa 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 Fa 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_geterr3). 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 Fa 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 Fa errbuf .

The kvm_close ();
function returns 0 on success and -1 on failure.

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.

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Created 1996-2024 by Maxim Chirkov
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