NAME
kmem — perform I/O on kernel memory based on symbol name.
SYNOPSIS
int ioctl(int kmemfd
, int command, void *rks);
DESCRIPTION
When used with a valid file descriptor for
/dev/kmem
(kmemfd),
ioctl
can be used to manipulate kernel memory. The specifics of this manipulation depend on the
command
given as follows:
- MIOC_READKSYM
Read
mirk_buflen
bytes of kernel memory starting at the address for
mirk_symname
into
mirk_buf.
rks
is a pointer to a
mioc_rksym
structure, defined below.
- MIOC_IREADKSYM
Indirect read. Read
sizeof(void *)
bytes of kernel memory starting at the address for
mirk_symname
and use that as the address from which to read
mirk_buflen
bytes of kernel memory into
mirk_buf.
rks
is a pointer to a
mioc_rksym
structure.
- MIOC_WRITEKSYM
Write
mirk_buflen
bytes from
mirk_buf
into kernel memory starting at the address for
mirk_symname.
rks
is a pointer to a
mioc_rksym
structure.
- MIOC_IWRITEKSYM
Indirect write. Read
sizeof(void *)
bytes of kernel memory starting at the address for
mirk_symname
and use that as the kernel memory address into which
mirk_buflen
bytes from
mirk_buf
are written.
rks
is a pointer to a
mioc_rksym
structure.
- MIOC_LOCKSYM
Increase the hold count by one for the dynamically loaded module whose name is given by
rks,
a pointer to a character string, thereby preventing its unloading.
- MIOC_UNLOCKSYM
Decrease the hold count by one for the dynamically loaded module whose name is given by
rks,
a pointer to a character string.
If the count is thereby reduced to 0, the module becomes a candidate for unloading.
The
struct mioc_rksym
definition is:
struct mioc_rksym {
char * mirk_modname; /* limit search for symname
to module modname; if NULL
use standard search order */
char * mirk_symname; /* name of symbol whose address
is the basis for this
operation */
void * mirk_buf; /* buffer into/from which
read/write takes place */
size_t mirk_buflen; /* length (in bytes) of desired
operation */
};
RETURN VALUE
ioctl
returns
0
upon successful completion. If an error occurs, a value of
-1
is returned and
errno
is set to indicate the error.
ERRORS
In addition to the errors described in
ioctl(2),
the
kmem
ioctl
also fails if one or more of the following are true:
- [EINVAL]
modname
does not represent a currently loaded module or this is an
MIOC_UNLOCKSYM
and the hold count is already 0.
- [ENXIO]
kmemfd
open on wrong minor device (i.e., not
/dev/kmem).
- [EBADF]
kmemfd
open for reading and this is an
MIOC_WRITEKSYM.
- [ENOMATCH]
symname
not found.
- [ENAMETOOLONG]
modname
is greater than
MODMAXNAMELEN
characters long, or
symname
is greater that
MAXSYMNMLEN
characters long.
