Go to main content

man pages section 3: Extended Library Functions, Volume 2

Exit Print View

Updated: Thursday, June 13, 2019
 
 

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
Committed
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).