petdance/scratch — Issue #258: API to tell which opcode group an opcode is in
Author: petdance
Created: 2011-11-01 05:30:29+00:00
State: open
Labels: core, Pri-major, rfc, Sev-medium

I am currently hacking on PL/Parrot and one of the very important features that we need is disallowing certain operations, most notably file I/O. The motivation for this is that you do not want a stored procedure written in PIR to be able to modify the database via disk operations.

I talked with chromatic in #parrot about needing some security subsystem features and he agreed that we need an API for telling if an opcode is in a particular opcode group. This is talked about in PDD18 if you want to get the full background.

For instance, take the open opcode:
{{{
inline op open(out PMC, in STR, in STR) :filesys_open {
/* etc... */
}
}}}

It is defined to be in the "filesys_open" opcode group. Currently there is no way to tell if a certain opcode is in a given group. The information does not seem to make it into op_info_t, but it is in lib/Parrot/OpLib/core.pm . I propose a public C API that will consist of at least these three functions:

{{{ Parrot_sec_opcode_is_in_group(string opcode_name, string group_name) }}}

This function would take an opcode name and opcode group name as argument and return true if the opcode is in the group, false otherwise.

{{{ Parrot_sec_opcodes_in_group(string opcode_group) }}}

This function takes a string argument of an opcode group name and returns a ResizableStringArray containing all opcodes in that group.

{{{ Parrot_sec_groups_containing_opcode(string opcode_name) }}}

This function takes a string argument of an opcode name and returns a ResizableStringArray listing all groups that contain the given opcode name.

Once an API in C is available to accomplish these things, then it should be straight forward to access this information from PIR.

Trac ID #1500