TweetFollow Us on Twitter

Oct 96 Tips
Volume Number:12
Issue Number:10
Column Tag:Tips & Tidbits

Tips & Tidbits

by MacTech Staff

Headache Free PCI Driver Development

I have been involved in the development of a couple of PCI driver for the new PowerPC Macintoshes and would like to share a back and time saver.

Unlike your standard system extensions that you can disable by holding down the shift key, you cannot disable PCI driver extensions from loading. This can cause problems if you have tweaked some driver code that causes you to crash and thereby forcing you to bend over your machine and extract the PCI card from the slot, reboot, fix the bug, shutdown, reinstall the PCI card, ... you get the picture. Now Apple may have a way of doing this that I don’t know yet, but in case my hunch is correct, here is a surefire way of disabling the loading of your driver.

A little PowerPC shared library knowledge is required here, so here is a $.05 lesson. When a shared library is being prepared for execution by the code fragment manager, it first calls the initalization routine (if one has been specified) of the shared library. The prototype for that function is:

OSErr CFMInit( CFragInitBlockPtr initBlkPtr );

If the shared library returns anything other than noErr (0) to the code fragment manager, then the execution of the library is terminated and nothing gets loaded. This is the hook we will use to provide the mechanism for disabling a driver on startup.

Here is an example initialization routine:

extern “C” OSErr CFMInitialize( CFragInitBlockPtr /*initBlkPtr*/ ) 
{
 DriverGlobal *globals = GetDriverGlobals();
 OSErr  err = 0x1234;

    // Initialize global data.

 ...

    // Test for on demand disabling...

 if( Button() ) 
 {
 DebugStr( “\p In CFMInitialize...Mouse button down.” );       
 if( err == 0x1234 ) err = noErr; 
 } 
 else err = noErr;

return( err );

}

If the mouse button is held down after MacsBug is loaded (NOTE! Wait until MacsBug is loaded because it uses a similar mechanism to disable loading,) then we will drop into the debugger.

I have set ‘err’ to 0x1234 because it is easy to spot in the register list, which is where the compiler will most likely store it before assigning it to R3 which is will hold the return value. What we do now is set the register holding 0x1234 to something different. This can be done with the following command within MacsBug:

r30 = FFFF

Where r30 is the register holding 0x1234 (NOTE! This will most likely be different on you Mac). When you type Command-G to get out of the debugger, the lines just after the DebugStr will be executed. If you didn’t modify ‘err’ then it will still be 0x1234 and we need to set it to noErr to ensure the shared library gets loaded. Otherwise we fall thru and the shared library will not be loaded. You can then fix your bug, replace the driver in the System Folder, and restart.

Now if for some reason the compiler has stored the ‘err’ value onto the stack then you will need to step through the code, one line at a time, (Command-S will do this) until you get to the ‘blr’ instruction. It will look something like this:

0442FF1Cblr
|4E800020

At this instruction simply execute the command:

r3 = FFFF

...and Command-G to go.

Now you may ask why not just disable the driver if the mouse button is down. You could do that, but you may have multiple drivers that use the same disabling sequence and that would cause all of them to become disabled, plus you can verify which driver is acting up.

- Chris Rudolph

chris_rudolph@claris.com

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Bookends 13.0.6 - Reference management a...
Bookends is a full-featured bibliography/reference and information-management system for students and professionals. Bookends uses the cloud to sync reference libraries on all the Macs you use.... Read more
macOS 10.13.3 Supplemental Update 1.0 -...
macOS High Sierra Supplemental Update includes security improvements to Safari and WebKit to mitigate the effects of Spectre. Version 1.0: Update fixes an issue where using certain character... Read more
ffWorks 1.0.6 - Convert multimedia files...
ffWorks (was iFFmpeg), focused on simplicity, brings a fresh approach to the use of FFmpeg, allowing you to create ultra-high-quality movies without the need to write a single line of code on the... Read more
Adobe Acrobat 18.011.20035 - Powerful PD...
Acrobat DC is available only as a part of Adobe Creative Cloud, and can only be installed and/or updated through Adobe's Creative Cloud app. Adobe Acrobat DC with Adobe Document Cloud services is... Read more
Adobe Acrobat Reader 18.011.20035 - View...
Adobe Acrobat Reader allows users to view PDF documents. You may not know what a PDF file is, but you've probably come across one at some point. PDF files are used by companies and even the IRS to... Read more
EtreCheck 4.0.3 - For troubleshooting yo...
EtreCheck is an app that displays the important details of your system configuration and allow you to copy that information to the Clipboard. It is meant to be used with Apple Support Communities to... Read more
Yummy FTP Pro 2.0 - $29.99
Yummy FTP Pro is an advanced Mac file transfer app which provides a full-featured professional toolkit combined with blazing speeds and impeccable reliability, so whether you want to transfer a few... Read more
Opera 51.0.2830.34 - High-performance We...
Opera is a fast and secure browser trusted by millions of users. With the intuitive interface, Speed Dial and visual bookmarks for organizing favorite sites, news feature with fresh, relevant content... Read more
Apple iOS 11.2.6 - The latest version of...
iOS 11 sets a new standard for what is already the world’s most advanced mobile operating system. It makes iPhone better than before. It makes iPad more capable than ever. And now it opens up both to... Read more
Google Chrome 64.0.3282.167 - Modern and...
Google Chrome is a Web browser by Google, created to be a modern platform for Web pages and applications. It utilizes very fast loading of Web pages and has a V8 engine, which is a custom built... Read more

Latest Forum Discussions

See All

Check out these 5 games that are a lot l...
So you're in love with Minecraft, but you're looking for something else to play as well? You've come to the right place then, because this list is all about games that are a bit like Minecraft. Some of them, more than others. [Read more] | Read more »
Our top 5 characters from casual RPG Cre...
Creature Quest definitely lives up to its name with a host of collectible creatures based on fantasy tales and world mythologies. To celebrate Creature Quest’s first birthday, we’re going to lay out what we think are the five best characters in the... | Read more »
Around the Empire: What have you missed...
Did you know that Steel Media has a whole swathe of other sites dedicated to all aspects of mobile gaming? Sure you'll get the very best iPhone news, reviews, and opinions right here at 148Apps, but we don't want you missing out on a single piece... | Read more »
All the best games on sale for iPhone an...
Oh hi there, and welcome to our round-up of the best games that are currently on sale for iPhone and iPad. You thought I didn't see you there, did you, skulking behind the bushes? Trust me though, the bushes aren't where the best deals are. The... | Read more »
The Battle of Polytopia Guide - How to H...
A new update just released for The Battle of Polytopia (formerly Super Tribes), which introduces online multiplayer. For all the fans of Midjiwan’s lite take on Civilization, this is certainly welcome news, but playing online isn’t as easy and... | Read more »
Here are the very best mobile games to p...
It's Valentine's Day! Did you get loads of cards and chocolates and other tacky, simple expressions of human affection? Did you send out tat because you find it almost impossible to express emotion unless there's a section dedicated to it at your... | Read more »
Florence (Games)
Florence 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: Florence is an interactive storybook from the award-winning lead designer of Monument Valley about the heart-racing highs and... | Read more »
Purrfect Date (Games)
Purrfect Date 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: Cats are a lil’ like marmite. Either you absolutely head-over-heels love’ em, or… nahhh, who are we kidding?! Everyone... | Read more »
More monsters to collect and evolve in C...
A laid-back mix of RPG and TCG, Creature Quest is all about building your deck, evolving your creatures and winning in battle. It’s the creation of VC Mobile, set up by Might and Magic producer Jon Van Caneghem. There are elements of that classic... | Read more »
Check out this awesome hands-on with the...
Well, PlayerUnknown's Battlegrounds has come out on mobile. This isn't a clone, this isn't a riff on the battleroyale mechanics of the game, it's the official mobile port by Tencent. But there's a little bit of a hitch. [Read more] | Read more »

Price Scanner via MacPrices.net

Apple refurbished Mac minis in stock again st...
Apple has restocked Certified Refurbished Mac minis starting at $419. Apple’s one-year warranty is included with each mini, and shipping is free: – 1.4GHz Mac mini: $419 $80 off MSRP – 2.6GHz Mac... Read more
Tuesday MacBook Deals: $250 off 15″ 2.9GHz Ma...
Adorama has the Silver 15″ 2.9GHz Apple MacBook Pro on sale today for $250 off MSRP. Shipping is free, and Adorama charges sales tax for residents in NY & NJ only: – 15″ 2.9GHz Silver MacBook Pro... Read more
Save up to $350 with these Apple Certified Re...
Apple has a full line of Certified Refurbished iMacs available for up to $350 off original MSRP. Apple’s one-year warranty is standard, and shipping is free. The following models are available: – 27... Read more
B&H offers $200 discount on Silver 15″ Ma...
B&H Photo has Silver 15″ Apple MacBook Pros on sale for $200 off MSRP. Shipping is free, and B&H charges sales tax for NY & NJ residents only: – 15″ 2.8GHz Touch Bar MacBook Pro Silver (... Read more
12″ Apple iPad Pro Sale of the Year! Models u...
B&H Photo has 12″ #iPad Pros on sale for up to $150 off MSRP. Shipping is free, and B&H charges sales tax in NY & NJ only: – 12″ 64GB WiFi iPad Pro: $719 $80 off MSRP – 12″ 256GB WiFi... Read more
Deals on 32GB 9″ iPads: Up to $50 off MSRP, s...
B&H Photo has 2017 9.7″ 32GB iPads on sale for $299 including free shipping plus NY & NJ sales tax only. Their price is $30 off MSRP, and it’s currently the lowest price available for these... Read more
15″ 2.2GHz Retina MacBook Pro available for o...
Apple has Certified Refurbished 15″ 2.2GHz Retina MacBook Pros available for $1699. That’s $300 off MSRP for this model, and it’s the lowest price available for a 15″ MacBook Pro currently offered by... Read more
13″ 3.1GHz/256GB Silver Touch Bar MacBook Pro...
Amazon has the Silver 13″ 3.1GHz/256GB Touch Bar MacBook Pro (MPXX2LL/A) on sale for $1649.99 including free shipping. Their price is $150 off MSRP, and it’s the lowest price available for a new 13″... Read more
Saturday Sale: Amazon offers 13″ 1.8GHz/256GB...
Amazon has the 13″ 1.8GHz/256B Apple MacBook Air on sale today for $250 off MSRP including free shipping: – 13″ 1.8GHz/256GB MacBook Air (MQD42LL/A): $949.99, $250 off MSRP Their price is the lowest... Read more
Roundup of Apple Certified Refurbished 12″ Ma...
Apple has Certified Refurbished 2017 12″ Retina MacBooks available for $200-$240 off the cost of new models. Apple will include a standard one-year warranty with each MacBook, and shipping is free.... Read more

Jobs Board

*Apple* Store Leader - Retail District Manag...
Job Description:Job SummaryAs more and more people discover Apple , they visit our retail stores seeking ways to incorporate our products into their lives. It's your Read more
*Apple* Retail - Multiple Positions - Apple,...
Job Description:SalesSpecialist - Retail Customer Service and SalesTransform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Retail - Multiple Positions - Apple,...
Job Description:SalesSpecialist - Retail Customer Service and SalesTransform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Retail - Multiple Positions - Apple,...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.