necessarily produce a valid result if
the program is enabled for interruptions
or operating ina multiprocessing
configuration. This could be the case,
for example, in a multiprocessing
configuration if anotherCPU executed
INVALIDATEPAGE TABLE ENTRY, followed by
a reassignment of the page.
SETPSW KEY FROM ADDRESS, which is
changed by DAS to be semiprivileged,
provides the semiprivileged program with
the capability of changing thePSW key,
under control of thePSW-key mask, and
thus permits the program to access
different data areas protected by
different keys.
Increased flexibility in key handling is
controlled by a 16-bitPSW-key mask in
controlregister 3. The PSW-key mask
permits the semiprivileged program to
operate with more than one key withouthaving authorization to all keys. This
mask controlsthe semiprivileged-program use of keys in MOVE TO PRIMARY, MOVE TO SECONDARY, MOVE WITH KEY, and SET PSW KEY FROM ADDRESS. Each bit position
corresponds toa key value. The bit in
the mask must be onein order for the
corresponding key to be used.Program-Problem Analysis
Toaid program-problem analysis, the
option is provided of havinga trace
entry made implicitly for three DAS
instructions. When tracing is
activated, a trace entry is made each
timePROGRAM CALL, PROGRAM TRANSFER, or
SETSECONDARY ASN is executed.
As a further analysis aid,PROGRAM CALL and PROGRAM TRANSFER are also recognized
forPER purposes as successful branching
events. Additionally, for these two
instructions, the space-switch-event
control bit is provided both in control
register 1 and in the second-table entry
used duringASN translation. When
either bit is one, a program inter
ruption for a space-switch event occurs
at the completion of the instruction.
The effect is to provide for an inter
ruption whena primary-space switch
occurs, allowing recognition that a
space has been entered, left, or both.
DASAUTHORIZATION MECHANISMS The DAS authorization mechanisms which
are described in this section permit the
control program to establish the degree
of function which is provided to a
particular semiprivileged program. (A
summary of the authorization mechanisms
is given in the figure "Summary of DAS
Authorization Mechanisms.") The DAS
authorization mechanismsare intended
for use by programs considered to be
semiprivileged, that is, programs whichare executed in the problem state but
which may be authorized to use addi
tional capabilities. With these
authorization controls, a hierarchy of
programs may be established, with
programsat a higher level having a
greater degree of privilege or authority
than programs at a lower level. The
range of functions available at each
level, and the ability to transfer
control from a lower to a higher level,
are specified in tables which are
managed by the control program.
ProgrammingNote The DAS authorization mechanisms are
defined such that if zeros are placed in
the previously unassigned control
register positions, a problem program
attempting to use the semiprivileged
instructions causes a privileged
operation or special-operation exception
to be recognized.
Mode Reguirements
Most of the DAS instructions can be
executed only with DAT on.PROGRAM CALL and PROGRAM TRANSFER are valid only in
the primary-space mode. When a DAS
instruction is executed in an invalid
translation mode, a special-operation
exception is recognized.PROGRAM TRANSFER specifies a new value
for the problem-state bit in the PSW.
If a program in the problem state
attempts to executePROGRAM TRANSFER and
set the supervisor state, a privileged
operation exception is recognized.
Extraction-AuthorityControl The extraction-authority-control bit is
located in bit position 4 of control
registerO. In the problem state, bit 4
must be one to allow completion of these
instructions:EXTRACT PRIMARY ASN EXTRACT SECONDARY ASN INSERT ADDRESS SPACE CONTROL INSERT PSW KEY INSERT VIRTUAL STORAGE KEY Otherwise, a privileged-operation excep
tion is recognized. The extraction
authority-control bit is not examined in
the supervisor state.Chapter 5. Program Execution 5-17
the program is enabled for interruptions
or operating in
configuration. This could be the case,
for example, in a multiprocessing
configuration if another
INVALIDATE
a reassignment of the page.
SET
changed by DAS to be semiprivileged,
provides the semiprivileged program with
the capability of changing the
under control of the
thus permits the program to access
different data areas protected by
different keys.
Increased flexibility in key handling is
controlled by a 16-bit
control
permits the semiprivileged program to
operate with more than one key without
mask controls
corresponds to
the mask must be one
corresponding key to be used.
To
option is provided of having
entry made implicitly for three DAS
instructions. When tracing is
activated, a trace entry is made each
time
SET
As a further analysis aid,
for
events. Additionally, for these two
instructions, the space-switch-event
control bit is provided both in control
register 1 and in the second-table entry
used during
either bit is one, a program inter
ruption for a space-switch event occurs
at the completion of the instruction.
The effect is to provide for an inter
ruption when
occurs, allowing recognition that a
space has been entered, left, or both.
DAS
are described in this section permit the
control program to establish the degree
of function which is provided to a
particular semiprivileged program. (A
summary of the authorization mechanisms
is given in the figure "Summary of DAS
Authorization Mechanisms.") The DAS
authorization mechanisms
for use by programs considered to be
semiprivileged, that is, programs which
which may be authorized to use addi
tional capabilities. With these
authorization controls, a hierarchy of
programs may be established, with
programs
greater degree of privilege or authority
than programs at a lower level. The
range of functions available at each
level, and the ability to transfer
control from a lower to a higher level,
are specified in tables which are
managed by the control program.
Programming
defined such that if zeros are placed in
the previously unassigned control
register positions, a problem program
attempting to use the semiprivileged
instructions causes a privileged
operation or special-operation exception
to be recognized.
Mode Reguirements
Most of the DAS instructions can be
executed only with DAT on.
the primary-space mode. When a DAS
instruction is executed in an invalid
translation mode, a special-operation
exception is recognized.
for the problem-state bit in the PSW.
If a program in the problem state
attempts to execute
set the supervisor state, a privileged
operation exception is recognized.
Extraction-Authority
located in bit position 4 of control
register
must be one to allow completion of these
instructions:
tion is recognized. The extraction
authority-control bit is not examined in
the supervisor state.