KVM_GETU(3KVM) Kernel VM Library Functions KVM_GETU(3KVM)

NAME

kvm_getu, kvm_getcmd - get the u-area or invocation arguments for a
process

SYNOPSIS

cc [ flag... ] file... -lkvm [ library...]
#include <kvm.h>
#include <sys/param.h>
#include <sys/user.h>
#include <sys/proc.h>

struct user *kvm_getu(kvm_t *kd, struct proc *proc);


int kvm_getcmd(kvm_t *kd, struct proc *proc, struct user *u, char ***arg,
char ***env);

DESCRIPTION

The kvm_getu() function reads the u-area of the process specified by proc
to an area of static storage associated with kd and returns a pointer to
it. Subsequent calls to kvm_getu() will overwrite this static area.


The kd argument is a pointer to a kernel descriptor returned by
kvm_open(3KVM). The proc argument is a pointer to a copy in the current
process's address space of a proc structure, obtained, for instance, by a
prior kvm_nextproc(3KVM) call.


The kvm_getcmd() function constructs a list of string pointers that
represent the command arguments and environment that were used to
initiate the process specified by proc.


The kd argument is a pointer to a kernel descriptor returned by
kvm_open(3KVM). The u argument is a pointer to a copy in the current
process's address space of a user structure, obtained, for instance, by a
prior kvm_getu() call. If arg is not NULL, the command line arguments are
formed into a null-terminated array of string pointers. The address of
the first such pointer is returned in arg. If env is not NULL, the
environment is formed into a null-terminated array of string pointers.
The address of the first of these is returned in env.


The pointers returned in arg and env refer to data allocated by malloc()
and should be freed by a call to free() when no longer needed. See
malloc(3C). Both the string pointers and the strings themselves are
deallocated when freed.


Since the environment and command line arguments might have been modified
by the user process, there is no guarantee that it will be possible to
reconstruct the original command at all. The kvm_getcmd() function will
make the best attempt possible, returning -1 if the user process data is
unrecognizable.

RETURN VALUES

On success, kvm_getu() returns a pointer to a copy of the u-area of the
process specified by proc. On failure, it returns NULL.


The kvm_getcmd() function returns 0 on success and -1 on failure. If -1
is returned, the caller still has the option of using the command line
fragment that is stored in the u-area.

ATTRIBUTES

See attributes(7) for descriptions of the following attributes:


+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | Stable |
+--------------------+-----------------+
|MT-Level | Unsafe |
+--------------------+-----------------+

SEE ALSO

malloc(3C), kvm_kread(3KVM), kvm_nextproc(3KVM), kvm_open(3KVM),
libkvm(3LIB), attributes(7)

NOTES

On systems that support both 32-bit and 64-bit processes, the 64-bit
implementation of libkvm ensures that the arg and env pointer arrays for
kvm_getcmd() are translated to the same form as if they were 64-bit
processes. Applications that wish to access the raw 32-bit stack
directly can use kvm_uread(). See kvm_read(3KVM).

May 2, 2002 KVM_GETU(3KVM)