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Given that this technique is used in production for all current gen Iphones should tell you this isn't vaporware.

by fooker 1y ago

cogman10 1y ago
What technique? There's no technique described in the article. It's just a long article about why this is needed, an announcement of collaboration, and naming the set of instructions.
- OneDeuxTriSeiGo 1y ago
  ARM has an extension called the "Memory Tagging Extension". It works by borrowing 4 bits per 16 byte block of memory to color the allocation. Pointers are given a color "key" inside the pointer during allocation and if that pointer's key isn't the right color as the underlying memory block's during deref, then the hardware throws an MTE segfault. It's a neat system with pretty much no overhead and it's pretty easy to integrate into code as long as your underlying language and libraries are at least semi-intelligent about how they handle pointers and memory allocation (i.e. as long as you aren't doing any long range pointer punting then things "just work"). https://developer.arm.com/-/media/Arm%20Developer%20Community/PDF/Arm_Memory_Tagging_Extension_Whitepaper.pdf https://developer.arm.com/-/media/Arm%20Developer%20Communit...
  - cogman10 1y ago
    Right, but none of this is in the article. MTE is neat and it'll be interesting if AMD64 brings in a similar technique but none of that is actually described in the article.
    - OneDeuxTriSeiGo 1y ago
      Sure but given the description of ChkTag and given the new exceptions and interrupts model they established with FRED, I don't see ChkTag being anything other than an MTE-style lock-and-key color tagging solution. The press article is just saying what the EAG is working on next now that they have shipped FRED, ACE, and AVX10. ChkTag is the current top priority item on the EAG's list and the standard for it should be finalised/released some time in the next few months. What they have done publicly so far is to say that ChkTag will be part of the ISA standard, they just haven't also revealed the details past that.
- fooker 1y ago
  Yes, the article is not self contained. Nothing is self contained, you are expected to look up memory tagging if you want the gory details of how other platforms implement it. If you want technical information about how the x86 ecosystem will implement it, you'll need a time machine (or work at Intel or AMD I guess..)

Given that this technique is used in production for all current gen Iphones should tell you this isn't vaporware.

by fooker 1y ago

Given that this technique is used in production for all current gen Iphones should tell you this isn't vaporware.

What technique? There's no technique described in the article. It's just a long article about why this is needed, an announcement of collaboration, and naming the set of instructions.

OneDeuxTriSeiGo 1y ago
ARM has an extension called the "Memory Tagging Extension". It works by borrowing 4 bits per 16 byte block of memory to color the allocation. Pointers are given a color "key" inside the pointer during allocation and if that pointer's key isn't the right color as the underlying memory block's during deref, then the hardware throws an MTE segfault. It's a neat system with pretty much no overhead and it's pretty easy to integrate into code as long as your underlying language and libraries are at least semi-intelligent about how they handle pointers and memory allocation (i.e. as long as you aren't doing any long range pointer punting then things "just work"). https://developer.arm.com/-/media/Arm%20Developer%20Community/PDF/Arm_Memory_Tagging_Extension_Whitepaper.pdf https://developer.arm.com/-/media/Arm%20Developer%20Communit...
- cogman10 1y ago
  Right, but none of this is in the article. MTE is neat and it'll be interesting if AMD64 brings in a similar technique but none of that is actually described in the article.
  - OneDeuxTriSeiGo 1y ago
    Sure but given the description of ChkTag and given the new exceptions and interrupts model they established with FRED, I don't see ChkTag being anything other than an MTE-style lock-and-key color tagging solution. The press article is just saying what the EAG is working on next now that they have shipped FRED, ACE, and AVX10. ChkTag is the current top priority item on the EAG's list and the standard for it should be finalised/released some time in the next few months. What they have done publicly so far is to say that ChkTag will be part of the ISA standard, they just haven't also revealed the details past that.
fooker 1y ago
Yes, the article is not self contained. Nothing is self contained, you are expected to look up memory tagging if you want the gory details of how other platforms implement it. If you want technical information about how the x86 ecosystem will implement it, you'll need a time machine (or work at Intel or AMD I guess..)