Accessing the macOS Dynamic Linker (dyld)

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Created Apr ’24

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The documentation about the Disable Library Validation Entitlement mentioned that the macOS dynamic linker (dyld) provides a detailed error message when the system prevents code from loading due to library validation.

You can find more information here: https://developer.apple.com/documentation/bundleresources/entitlements/com_apple_security_cs_disable-library-validation

I need assistance in locating the dynamic linker (dyld) on macOS Ventura 13.0.

What are the various methods available to locate it?
How can I access or open it for reading?
Additionally, do I need any external tools to facilitate this process?

My ultimate goal is to examine the detailed error message to identify any issues I am encountering with my application.

Additionally, I have found one at /usr/lib/dyld, but it's not human-readable, nor does it have timestamps for whatever is logged. Based on my findings, I should be able to locate dyld at System/Library, but I can't find it there either.

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Answer 1

ssmith_c OP

Apr ’24

You said "My ultimate goal is to examine the detailed error message " The error message will appear in the system log, along with all the other messages from numerous processes on your Mac. You could use the Console app to look at the log, but its filtering is a bit rudimentary.

The only tool you need is the command line tool log. Try man log for starters, then go looking on the Internet for "macOS log predicate example" or something like that. You probably want to look for logs emitted by tccd (the Transparency, Consent and Control daemon) with the text "disable-library-validation" in the message field. You can also cause the problem, then quickly use sudo log collect --last 1m. This will write a .logarchive file into the current directory (it won't overwrite one that is there already), giving you an archive you can poke around in at your leisure. A minute of logs is still a pretty huge database, but it might be a good way to find out what predicate you should be using.

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Answer 2

DTS Engineer OP

Apple

Apr ’24

Additionally, I have found one at /usr/lib/dyld

That is the dynamic linker implementation, not a log file:

% file /usr/lib/dyld
/usr/lib/dyld: Mach-O universal binary with 3 architectures…

I need assistance in locating the dynamic linker (dyld) on macOS Ventura 13.0.

You found it.

As a general rule you don’t invoke the dynamic linker directly. Rather, tools that build executables for Apple platforms build them in a way that invokes the dynamic linker. I just added a short explanation of this to An Apple Library Primer.

The dynamic linker is invoked in two different ways:

When you run an executable
When you load images dynamically, using dlopen

In the second case, call dlerror to learn about errors. See the dlerror man page for details.

When you run an executable, the dynamic linker loads all of the libraries it references, and the libraries they reference, and so on. If something goes wrong in that process, there are two common sources of diagnostics:

A crash report
A message to stdout

To learn more about crash reports, see Diagnosing issues using crash reports and device logs.

To see messages on stdout, run your program from Xcode. Or, if it’s a macOS program, run it from Terminal. For an example of that, see Resolving Trusted Execution Problems (search for MissingLibrary).

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