SystemSupportforCustom SpeculationPolicies - - PowerPoint PPT Presentation

System
Support
for
Custom Speculation
Policies

Benjamin
Wester,
Peter
M.
Chen University
of
Michigan SOSP
2009




App

Overview

Benjamin
Wester
‐
University
of
Michigan 2

Speculation Infrastructure

Mechanism App App Policy Policy

Speculation
Policy

Default

• Predict
system
calls
• Allow
no

uncommitted
output

• Commit
identical
results
• Roll
back
after
any
change

Custom

• Predict
arbitrary
operations
• Allow
harmless

uncommitted
output

• Commit
equivalent
results
• Correction
appropriate
to

error

3 Benjamin
Wester
‐
University
of
Michigan

Interface

Process

spec_fork()

Controlling
process Speculative
process try
to
establish
x

if (x) commit()

[else
rollback()]

4 Benjamin
Wester
‐
University
of
Michigan

allow_fd_output()

assume
x

Arbitrary operations Set output policy {allow, taint, defer, block} Define equivalence Error correction

Uses

• Predicting
user
actions

– Bash
shell

• Authentication
• User‐level
network
services

More?

5 Benjamin
Wester
‐
University
of
Michigan