exec_with_loader(2)exec_with_loader(2)NAMEexec_with_loader - Execute a file with a loader
SYNOPSIS
int exec_with_loader(
int flags,
const char *loader,
const char *file,
char * const argv[],
char * const envp[] );
PARAMETERS
Specifies flags to be passed to the loader. Points to a pathname that
identifies a regular, executable, process image file that contains the
loader. This image file must be a nonshared image. Points to a path‐
name that identifies a regular, executable process image file. This
image file must be a call-shared image. Specifies an array of charac‐
ter pointers to null-terminated strings. Specifies an array of charac‐
ter pointers to null-terminated strings, constituting the environment
for the new process.
DESCRIPTION
The exec_with_loader() function replaces the current process image with
a new process image, in a manner similar to what the exec functions do.
Both the loader parameter and the file parameter point to pathnames
that identify regular, executable files called process image files.
Unlike the exec functions, which construct the new process image from
the file identified by the file parameter, exec_with_loader() con‐
structs the new process image from the file identified by the loader
parameter.
Note
Throughout this reference page, the regular, executable, process image
file specified by the loader parameter is referred to as the “program
loader,” and the regular, executable, process image file specified by
the file parameter is referred to as the “file.”
The loader image cannot be linked at the default user addresses. You
must find another place to link it. One acceptable place to link the
loader image is at the address space defined for the loader in the
/usr/shlib/so_locations file.
After the exec_with_loader() function successfully loads the program
loader, it transfers control to the program loader and effectively
passes the file parameter. Under normal usage, the program loader will
then load (that is, merge) the file into the newly constructed process
image, along with any object files upon which the program (that is, the
file) depends. The typical use of exec_with_loader() is to load pro‐
grams that contain unresolved external references, for example, pro‐
grams that require the use of a shared library.
The exec_with_loader() function implements and preserves all of the
semantics of the exec functions, with respect to the file. These
include the handling of the argv and envp parameters, command inter‐
preters, close-on-exec processing, signals, set user ID and set group
ID processing, the process attributes and error returns.
The loader parameter may be null, in which case the exec_with_loader()
function loads the default program loader (/sbin/loader). The
exec_with_loader() function also loads the default program loader under
either of the following sets of conditions, even if the loader parame‐
ter points to a valid program loader: If the set user ID mode bit of
the file is set (see the chmod() function) and the owner ID of the file
is not equal to the effective user ID of the process If the set group
ID mode bit of the file is set and the group ID of the file is not
equal to the effective group ID of the process.
The setting of the user ID or set group ID mode bits on the program
loader have no effect whatsoever.
RETURN VALUES
If the exec_with_loader() function returns to the calling process
image, an error has occurred; the return value is -1, and errno is set
to indicate the error.
ERRORS
If the exec_with_loader() function fails, errno may be set to one of
the following values: Search permission is denied for a directory
listed in either file's path prefix, or either file denies execution
permission, or either file is not a regular file and the implementation
does not support execution of files of its type. Note that the
exec_with_loader() function references two files, one specified by the
loader parameter and one specified by the file parameter. The length
of the loader or file parameters exceeds PATH_MAX, or a pathname compo‐
nent is longer than NAME_MAX and _POSIX_NO_TRUNC is in effect for that
file. One or more components of either file's pathname does not exist,
or the loader or file parameter points to an empty string. Note that
the exec_with_loader() function references two files, one specified by
the loader parameter and one specified by the file parameter. A compo‐
nent of either file's path prefix is not a directory. Note that the
exec_with_loader() function references two files, one specified by the
loader parameter and one specified by the file parameter. The file
specified by the loader parameter has the appropriate access permission
but is not in the proper format. The loader or file parameter is an
invalid address. Too many symbolic links were encountered in pathname
resolution. Insufficient memory is available.
SEE ALSO
Functions: exec(2)exec_with_loader(2)
