rev-upgrade and checking for +universal dependencies (and build dependencies)

[Saagar Jha]

If you turn SIP off, and patch MacPorts to build an arm64e slice, then you can use trace mode. However your patches will build a broken trace mode for anyone who has SIP enabled, and you will also be very sad if your machine ever boots in that state.

Saagar Jha

> On Jun 18, 2024, at 05:17, René J.V. Bertin <rjvbertin at gmail.com> wrote:
> 
> On Tuesday June 18 2024 05:04:50 Saagar Jha wrote:
> 
>>> With SIP disabled, one can add a kernel boot argument to allow user
>>> space to use Apple's ABI with pointer authentication, which would allow
>>> building a copy of tracelib that works on those binaries.
>>> 
>>> I'm not aware that anybody has successfully done that.
>> 
>> I have. I never chose to upstream it because I figured that nobody cared for that configuration, and it has the unfortunate quality that it cannot be done in a way that degrades gracefully when SIP is off. On systems where SIP is disabled, the loader will look for an arm64e slice or complain loudly. If you include such a slice and SIP is disabled it will be preferentially selected over an arm64 version by the fat binary matching algorithm, and immediately terminate the process upon load. So there’s no good answer here :(
> 
> Something doesn't add up there. Do you mean those problems arise when you turn SIP back ON, or do you mean that you "successfully did that" with SIP turned ON?
> 
> Either way, it was to be foreseen that Apple would start turning their computers into iThings when they came up with their own CPU design; the fact that they're only barely NOT making it impossible to run Linux on them is a telltale sign.
> 
> R.

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