July 2016 - Darwin-dev - lists.apple.com

Duplicate rpath handling in install_name_tool/otool
by William Woodruff 28 Jul '16

28 Jul '16

Hi Darwin Dev, I'm developing a Mach-O parser in ruby for the Homebrew project [1], and I noticed some potentially unintentional/unintuitive behavior in install_name_tool's handing of rpath additions/modifications/deletions. In particular, as of at least 10.11.5, `install_name_tool -delete_rpath <path>` will only delete the first of two or more duplicate rpath load commands. This is a departure from earlier versions of install_name_tool, which would attempt to delete all duplicate commands (but would fail to update the header's ncmds, leaving the Mach-O in an inconsistent state) [2][3]. While the current behavior is certainly better than the aforementioned corruption, it's also unintuitive - a user who sees that -delete_rpath has completed successfully on a file with duplicated rpaths will (incorrectly) think that the old runtime path is no longer being used. Similarly, it's possible to circumvent install_name_tool's guard against duplicate rpath addition by adding a different rpath, then using `install_name_tool -rpath <new> <existing>`. This doesn't break the binary, but it sets up the conditions above. It's also possible to create duplicate rpaths in a binary by passing -rpath <path> to the compiler/linker multiple times during the compilation process. Can somebody at Apple confirm that this is the intended behavior? Our approach with ruby-macho has been to remove all duplicates of an rpath during deletion [4], and to employ guards on duplication during addition/modification. Thanks, William Woodruff P.S.: rpaths are the most glaring example of this since install_name_tool provides options for adding and removing them (and not just modifying them like dylib_commands). However, I'd be extremely interested to learn whether or not binaries containing other duplicated LCs (dylibs, version infos, etc) are considered "broken" (even when they don't fail the linker/loader/otool). [1]: https://github.com/Homebrew/ruby-macho [2]: https://github.com/Homebrew/ruby-macho/issues/41#issuecomment-235475634 [3]: https://github.com/Homebrew/ruby-macho/issues/41#issuecomment-235683678 [4]: https://github.com/Homebrew/ruby-macho/pull/40 _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.ap… This email sent to site_archiver(a)lists.apple.com

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Re: Timesharing and concurrent users
by Jens Alfke 20 Jul '16

20 Jul '16

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Re: Timesharing and concurrent users
by Peter Teeson 20 Jul '16

20 Jul '16

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Re: Timesharing and concurrent users
by Jeff Kelley 20 Jul '16

20 Jul '16

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Timesharing and concurrent users
by Peter Teeson 20 Jul '16

20 Jul '16

2009 Mac Pro 2 x quadcore CPUs Yosemite 10.10.5 This machine has loads of unused capacity. My wife’s G4 is stuck at Leopard. We share an office and are within arms length of each other. I have 2 PCI video cards, two monitors and a spare keyboard and mouse. Rather than buy a replacement computer for her why not timeshare my capacity? Why not map one HW set (monitor, KB,Mouse) to my account? And the other to my wife’s account (on the Mac Pro.) That way we can concurrently use the system. IOW recover the inherent timesharing capability of Unix. (I come from a timesharing background many years ago,) My questions are: 1. Is it feasible to implement/recover the timesharing capability? For example by allocating specific HW to a specific user? If not why not? Is the dispatcher (GCD?) capable? 2. I see that with two users logged on there are 2 window manager instances, one per account. With Fast User Switching the devices remain the same but with different window managers. 3. Where would I look in the Apple Darwin Open Source to investigate what happens in Fast User Switching? The Mac OS X Internals book only has 1 paragraph on page 119 that is merely descriptive not technical. I've worked on mainframe timesharing OS' so am not afraid. Perhaps it can be done with a kext? Or else build my version of xnu? TIA for you advice which is hereby solicited. respect Peter _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.ap… This email sent to site_archiver(a)lists.apple.com

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Darwin Developers
by Clifford Sekel 06 Jul '16

06 Jul '16

Darwin Dev, I'm working with a group and looking for help with getting some headers and projects released for Darwin use only. These are base lowlevel projects that would allow Darwin OS to stand on it's own ex: libplatform and AHCI even if it's in binary formats like the old days of darwinbuild and source/roots. This would allow us to build other opensource projects such as libdispatch that now requires libplatform source code but is not provided. Both libdispatch source on opensource.apple.com and swift on github require libplatform code to build. We do have a VM only build of a system going based on Darwin 14.5 kernel but due to hw limitations brought on by unreleased code we can only support old ata chipsets found in VM's these days and we're using script to mimic launchd to get us to a single shell prompt as poc that we can get a mini base built we just need help with the release of a few projects. Please let me know if there is anyone I can talk to about what we need from Apple. I'm supporting and working with puredarwin.org we're going to be in the next release of BSDMag too so keep a lookout for that. I can be found on IRC channel below name InSaneDarwin. IRC freenode #puredarwin Thanks Clifford D. Sekel irc InSaneDarwin Email : cds87(a)live.com Linkedin : Public Profile https://www.linkedin.com/in/clifford-sekel-846bb030 _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.ap… This email sent to site_archiver(a)lists.apple.com

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