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Command: kbind | Section: 2 | Source: OpenBSD | File: kbind.2
KBIND(2) FreeBSD System Calls Manual KBIND(2)
NAME
kbind - update protected memory for lazy-binding
SYNOPSIS
#include <sys/unistd.h>
struct __kbind {
void *kb_addr;
size_t kb_size;
};
#define KBIND_BLOCK_MAX 2 /* powerpc and sparc64 need 2 blocks */
#define KBIND_DATA_MAX 24 /* sparc64 needs 6, four-byte words */
int
kbind(const struct __kbind *param, size_t psize, int64_t cookie);
DESCRIPTION
The kbind syscall updates the contents of one or more blocks of the
process's memory with the supplied replacement data. This is used to
efficiently and securely perform lazy-binding.
param points to an array of __kbind structures giving the addresses and
lengths to update. The last __kbind structure is immediately followed in
the same order by the source data for the blocks to copy. psize
specifies the total length of the parameters: both the __kbind structures
and the associated source data. There may be at most KBIND_BLOCK_MAX
__kbind structures and each block may be at most KBIND_DATA_MAX bytes in
size.
kbind updates memory "as if" the thread temporarily made the memory
writable with mprotect(2). If the process does not have write access to
the underlying memory object, kbind will fail without making the
requested change.
kbind is currently intended for use by ld.so(1) only. It is therefore
not provided as a function and two security checks are performed to bind
it (pun intended) to its use in ld.so(1): the first time kbind is used,
the kernel records both the text address of the call and the value of the
cookie argument. If those values differ in a later kbind call, then the
process is killed.
RETURN VALUES
Upon successful completion, the value 0 is returned; otherwise the
value -1 is returned and the global variable errno is set to indicate the
error.
ERRORS
kbind() will fail if:
[ENOMEM] Cannot allocate memory when updating a copy-on-write
page.
[EINVAL] The parameters are inconsistent or exceed kbind
limits.
[EFAULT] Part of the structures or additional data pointed to
by param is outside the process's allocated address
space, or the underlying memory object is not
writable.
SEE ALSO
ld.so(1), mprotect(2)
STANDARDS
The kbind syscall is specific to the OpenBSD dynamic linker and should
not be used in portable applications.
HISTORY
The kbind syscall appeared in OpenBSD 5.8.
FreeBSD 14.1-RELEASE-p8 November 21, 2021 FreeBSD 14.1-RELEASE-p8