<Ermine>
Does anybody do non-trivial segmentation these days? Seems like everybody uses flat memory and paging, but SDM makes an emphasis on multi-segment stuff to enforce code/data protection. But paging can do the very same thing
<kazinsal>
nope
<kazinsal>
closest I know is that OpenBSD/i386 uses it to enforce W^X on non-PAE systems
<kazinsal>
but honestly I don't even know if that's going to be supported for much longer. kind of a gnarly hack
<gorgonical>
Having gcc14 as the system default compiler is such a hassle. So many things are broken now because of default upgrades to -W
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<zid>
nobody did it when it still worked, and it doesn't work in long mode
<dostoyevsky2>
gorgonical: isn't that a problem with every new gcc/clang version?
<gorgonical>
yes
<geist>
fix dem warnins!
<gorgonical>
but it seems that gcc14 has finally pulled the leash in and made the most common mistakes errors
<gorgonical>
which is better ideologically, but makes my life hard
<dostoyevsky2>
examples?
<gorgonical>
I am using buildroot to build a research environment, and so I have a buildroot version that's targeted about 18 months. Many of the versions tagged are before gcc14 fixes were applied
<dostoyevsky2>
> One of them is a new warning, -Wnrvo, which warns about missed optimization opportunities
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<dostoyevsky2>
Wasn't there also something like a -Werror-but-only-basics
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<bslsk05>
developer.arm.com: Documentation – Arm Developer
<heat>
you can only address up to 2^51 bytes before you literally run out of bits *in the PTE*
<heat>
you'd find that the difference between the amount of arm64 MMIO regions and x86 PC MMIO regions is residual really, particularly when talking about gigabytes or terabytes or petabytes of memory
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<Bitweasil>
Hm. ARMv8 also has the tension between "physical address size" and "tags and other stuff it crams in the PTEs."
<Bitweasil>
Going to 128 bit would free up those constraints and give you more or less infinite room for pointer authentication, tagging, and all that other stuff they cram into the same few bits.
<zid>
what we should do
<zid>
is shove 6 bits in that's an index into a TABLE OF DESCRIPTORS
<zid>
you could call them 'memory segments'
<Bitweasil>
Can they have some weird hidden attributes you can't really see? :D
<pog>
can they??
<pog>
you better belive they will
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<Bitweasil>
Also, geist, do you know what that 128 bit format is called?
<Bitweasil>
... I guess they're just calling it 128-bit translation tables for now.
<Ermine>
geist: you may want to update pre-built gcc link in lk's readme
<geist>
oh did the link go stale?
<geist>
or is it just old? I should update it
<Ermine>
I mean, it points to 13.x when there's 14.1