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KVM_READ(3)           DragonFly Library Functions Manual           KVM_READ(3)


NAME

     kvm_read, kvm_readstr, kvm_write -- read or write kernel virtual memory


LIBRARY

     Kernel Data Access Library (libkvm, -lkvm)


SYNOPSIS

     #include <sys/types.h>
     #include <kvm.h>

     ssize_t
     kvm_read(kvm_t *kd, unsigned long addr, void *buf, size_t nbytes);

     char *
     kvm_readstr(kvm_t *kd, unsigned long addr, char *buf, size_t *len);

     ssize_t
     kvm_write(kvm_t *kd, unsigned long addr, const void *buf, size_t nbytes);


DESCRIPTION

     The kvm_read(), kvm_readstr() and kvm_write() functions are used to read
     and write kernel virtual memory (or a crash dump file). See kvm_open(3)
     or kvm_openfiles(3) for information regarding opening kernel virtual mem-
     ory and crash dumps.

     The kvm_read() function transfers nbytes bytes of data from the kernel
     space address addr to buf.  Conversely, kvm_write() transfers data from
     buf to addr.  Unlike their SunOS counterparts, these functions cannot be
     used to read or write process address spaces.

     The kvm_readstr() function exists for convenience to read NUL terminated
     strings from the kernel address space.  If buf is NULL, kvm_readstr()
     will allocate a sufficiently large buffer, which needs to be deallocated
     via free(3) by the caller.  If len is not NULL, kvm_readstr() will inter-
     pret the value it is pointing to as the size of buf and will store the
     size of the complete string at addr.  Note that if only buf is too small
     to hold the complete string, kvm_readstr() will return NULL but set len
     to the size needed.


RETURN VALUES

     For kvm_read() and kvm_write() the number of bytes actually transferred
     is returned, if the request was successful.  Otherwise, -1 is returned.

     For kvm_readstr() NULL is returned on failure.  Upon success, the address
     of the string is returned, which will be buf if this was supplied.


SEE ALSO

     kvm(3), kvm_close(3), kvm_getargv(3), kvm_getenvv(3), kvm_geterr(3),
     kvm_getprocs(3), kvm_nlist(3), kvm_open(3), kvm_openfiles(3)

DragonFly 3.5                   January 8, 2006                  DragonFly 3.5

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