dortania/OpenCore-Legacy-Patcher

AirPlay to Mac with macOS 12.1 and iMac14,x

Open

#783 opened on Dec 9, 2021

View on GitHub
 (4 comments) (0 reactions) (0 assignees)Python (9,760 stars) (977 forks)batch import
back-endhelp wanted

Description

With the first beta of macOS 12.1, FeatureUnlock.kext started having patching issues with with regards to enabling AirPlay to Mac support on pre-Skylake machines.

Upon further inspection, we found the issue to be our iMac patch set:

static const uint8_t kSideCarAirPlayiMacOriginal[] = {
    // iMac13,1 iMac13,2 iMac13,3 iMac14,1 iMac14,2 iMac14,3 iMac14,4 iMac15,1 iMac16,1 iMac16,2
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x33, 0x2C, 0x31, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x33, 0x2C, 0x32, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x33, 0x2C, 0x33, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x34, 0x2C, 0x31, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x34, 0x2C, 0x32, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x34, 0x2C, 0x33, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x34, 0x2C, 0x34, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x35, 0x2C, 0x31, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x36, 0x2C, 0x31, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x36, 0x2C, 0x32, 0x00,
};

Specifically the early iMac14,x family:

    // iMac14,1 iMac14,2 iMac14,3 iMac14,4
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x34, 0x2C, 0x31, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x34, 0x2C, 0x32, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x34, 0x2C, 0x33, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x34, 0x2C, 0x34, 0x00,

The cause of this issue is due to the page size limitation of cs_validate_page, as patching data on the edge of the array can result in issues when sections of the dyld grow or shrink.

Work-Arounds

Currently with OCLP 0.3.2, I've added a new build of FeatureUnlock that splits the iMac patch set into 3 portions:

static const uint8_t kSideCarAirPlayiMacPart1Original[] = {
    // iMac13,1 iMac13,2 iMac13,3
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x33, 0x2C, 0x31, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x33, 0x2C, 0x32, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x33, 0x2C, 0x33, 0x00,
};

static const uint8_t kSideCarAirPlayiMacPart2Original[] = {
    // iMac14,1 iMac14,2 iMac14,3 iMac14,4
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x34, 0x2C, 0x31, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x34, 0x2C, 0x32, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x34, 0x2C, 0x33, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x34, 0x2C, 0x34, 0x00,
};

static const uint8_t kSideCarAirPlayiMacPart3Original[] = {
    // iMac15,1 iMac16,1 iMac16,2
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x35, 0x2C, 0x31, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x36, 0x2C, 0x31, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x36, 0x2C, 0x32, 0x00,
};

This means that whenever we receive a patch failure for iMac14,x, only that model family is affected. Unfortunately this still means iMac14,x users will not have AirPlay to Mac on 12.1 and newer.

Additionally we have attempted to patch out the model check in AirPlaySupport.framework within the dyld, but have been unsuccessful.

Additional Testing


// Good 12.1 Beta 1 (21C5021h):
// iMac13,1 iMac13,2 iMac13,3 iMac14,1 iMac14,
    0x69, 0x4E, 0x61, 0x63, 0x31, 0x33, 0x2C, 0x31, 0x00,
    0x69, 0x4E, 0x61, 0x63, 0x31, 0x33, 0x2C, 0x32, 0x00,
    0x69, 0x4E, 0x61, 0x63, 0x31, 0x33, 0x2C, 0x33, 0x00,
    0x69, 0x4E, 0x61, 0x63, 0x31, 0x34, 0x2C, 0x31, 0x00,
    0x69, 0x4E, 0x61, 0x63, 0x31, 0x34, 0x2C,

// Good 12.1 Beta 2 (21C5031d):
// iMac13,1 iMac13,2 iMac13,3 iMac14,1 iMac14,2 iMac14,3
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x33, 0x2C, 0x31, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x33, 0x2C, 0x32, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x33, 0x2C, 0x33, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x34, 0x2C, 0x31, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x34, 0x2C, 0x32, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x34, 0x2C, 0x33,

// Good 12.1 Beta 3 (21C5039b):
// iMac13,1 iMac13,2 iMac13,3 iMac14,1 iMac14,2 iMac14,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x33, 0x2C, 0x31, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x33, 0x2C, 0x32, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x33, 0x2C, 0x33, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x34, 0x2C, 0x31, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x34, 0x2C, 0x32, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x34, 0x2C,

   
// Good 12.1 RC 1:
// iMac13,1 iMac13,2 iMac13,3 iMac14,1 iMac14,2 iMac14,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x33, 0x2C, 0x31, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x33, 0x2C, 0x32, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x33, 0x2C, 0x33, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x34, 0x2C, 0x31, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x34, 0x2C, 0x32, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x34, 0x2C,

-----------------------------------------------------------

// Bad 12.1 Beta 1 (21C5021h):
// iMac13,1 iMac13,2 iMac13,3 iMac14,1 iMac14,2
    0x69, 0x4E, 0x61, 0x63, 0x31, 0x33, 0x2C, 0x31, 0x00,
    0x69, 0x4E, 0x61, 0x63, 0x31, 0x33, 0x2C, 0x32, 0x00,
    0x69, 0x4E, 0x61, 0x63, 0x31, 0x33, 0x2C, 0x33, 0x00,
    0x69, 0x4E, 0x61, 0x63, 0x31, 0x34, 0x2C, 0x31, 0x00,
    0x69, 0x4E, 0x61, 0x63, 0x31, 0x34, 0x2C, 0x32,

// Bad 12.1 Beta 2 (21C5031d):
// iMac13,1 iMac13,2 iMac13,3 iMac14,1 iMac14,2 iMac14,3 
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x33, 0x2C, 0x31, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x33, 0x2C, 0x32, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x33, 0x2C, 0x33, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x34, 0x2C, 0x31, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x34, 0x2C, 0x32, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x34, 0x2C, 0x33, 0x00,

// Bad 12.1 Beta 3 (21C5039b):
// iMac13,1 iMac13,2 iMac13,3 iMac14,1 iMac14,2 iMac14,3
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x33, 0x2C, 0x31, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x33, 0x2C, 0x32, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x33, 0x2C, 0x33, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x34, 0x2C, 0x31, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x34, 0x2C, 0x32, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x34, 0x2C, 0x33,

// Bad 12.1 RC 1:
// iMac13,1 iMac13,2 iMac13,3 iMac14,1 iMac14,2 iMac14,3
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x33, 0x2C, 0x31, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x33, 0x2C, 0x32, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x33, 0x2C, 0x33, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x34, 0x2C, 0x31, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x34, 0x2C, 0x32, 0x00,
    0x69, 0x4D, 0x61, 0x63, 0x31, 0x34, 0x2C, 0x33,

Contributor guide

Tech stack
cpython
Domain
tooling
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
5
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
over 1 week
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Basic knowledge of kernel patchingFamiliarity with dyldAbility to read C byte arraysUnderstanding of FeatureUnlock kext
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
15
Research direction
Investigate the cs validate page page size limitation that causes patching failures for iMac14,x models. Review the current split patch workaround and explore alternative approaches to patch the model check in AirPlaySupport.framework within dyld. Examine the byte array patch sets and the dyld behavior across macOS 12.1 betas and RC.