HP 3000 Manuals HP 3000 Manuals
func nmcall
Dynamically calls a procedure/function, passing up to four parameters.
Syntax
nmcall (path) [parm1] [parm2] [parm3] [parm4]
This function is used to perform a dynamic procedure call. It is
implemented by calling the HPGETPROCPLABEL intrinsic to ensure the
desired routine is loaded, and then uses the FCALL routine in the
Pascal/XL compiler to invoke the routine. The called code is invoked at
the same privilege level as the routine that invoked Debug (for example,
the privilege level contained in the PRIV environment variable). DAT
invokes the routine from privilege level 2. This function is not
available from SAT. Four parameters are always passed to the indicated
routine. These values are placed in the argument registers (arg0..arg3).
It is up to the called code to correctly define its parameter list and
interpret the parameters appropriately.
If you are not familiar with the procedure calling conventions as used by
the language compilers, please refer to the Procedure Calling Conventions
Reference Manual (09740-64003).
The value returned by the called routine (if any) in the function return
register (R28), is used as the result of the NMCALL function. Because
this register contains only a 32-bit value, code that returns data larger
than 32 bits should not be invoked. If the called routine does not
return a value, whatever value that happens to be in R28 is used as the
value of this function (for example, the function is undefined).
Formal Declaration
nmcall:s32 (path:str [parm1:sptr=0][parm2:sptr=0] [parm3:sptr=0] [parm4:sptr=0]
Parameters
path The code path specification for the NM
procedure/function to be called. The format of this
parameter is:
file_name/procname
The file_name part specifies the library to be searched
for procname. The file_name part is optional. If it is
not provided, the current list of loaded files for the
process (see the LOADINFO command) will be searched.
Refer to the HPGETPROCPLABEL intrinsic for additional
details, assumptions, and restrictions involving
searching libraries.
NOTE Unlike the other forms of procedure PATH specifications (for
example, the NMADDR function), module names and nested procedures
are not supported by this function.
parm1,2,3,4 These parameters are used to pass values to the routine
being called. They are passed in arg0 (r26), arg1
(r25), arg2 (r24), and arg3 (r23). Each may contain any
value up to 32 bits in length. The called code must
know how to interpret these values. If the called
routine has fewer parameters, the zeros passed in the
remaining argument registers are harmless. If the
called routine has additional parameters, their values
are undefined. Be sure you understand the procedure
calling conventions and the parameter type alignment
restrictions imposed by the various language compilers
before trying to pass complicated parameters.
Examples
$nmdat > wl nmcall("nl.pub.sys/CLOCK")
$d1f3709
$ nmdat > wl nmcall("CLOCK")
$d1f3b00
Call the CLOCK intrinsic which is in the system library. Since that
library is part of every process's loaded file list, the library name is
optional.
Limitations, Restrictions
This function is not supported in SAT.
Debug only is affected by the following restrictions. Currently, you
must have privileged mode (PM) to call this function. Furthermore, only
code that has been running at privilege level 0, 1, or 2 (see the PRIV
environment variable) is able to use this function. This is due to
security problems that would occur due to the internal implementation of
the function.
CAUTION Because the called code runs on the stack above the debugger, it
is possible for the called code to write into the stack space
where the debugger currently exists. It is conceivable that a
process abort or even system abort could result when returning
from the called code due to modification of the debugger's
portion of the stack.