[code_assets] Add arm64e as Architecture #3379

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1. dcharkes

   added

   package:code_assets

   on May 21, 2026
2. dcharkes commented on Jul 8, 2026

   

   dcharkes

   on Jul 8, 2026

   Last edited by dcharkes

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   Arm64e ABI actually has different versions: The hardware has different versions, not all influence the ABI:

   • M1 has PAC
   • M2 has PAC and BTI
   • M5 has Pac, BTI, and EMTE.

   Gemini believes that these are encoded in the cpusubtype in the Mach-O headers:

   Bit Position	Hex Mask (uint32_t)	Meaning
   Bit 31	0x80000000	Versioned ABI Flag: If set to 1, the binary strictly follows a versioned pointer authentication ABI.
   Bit 30	0x40000000	Kernel ABI Flag: If set to 1, the binary is compiled for kernel space signing rules (used for things like .kext files).
   Bits 24 to 27	0x0f000000	The ABI Version Number: A 4-bit integer representing the specific generational ruleset.

   You can compile to that with

   #define __PTRAUTH_INTRINSICS__ 1
   #define __arm64e__ 1
   #define __ptrauth_abi_version__ 0

   https://github.com/lelegard/arm-cpusysregs/blob/main/docs/arm64e-on-macos.md#detecting-arm64-vs-arm64e-compilation-in-the-code

   or in assembly with

   .ptrauth_abi_version 0
   

   I suspect that BTI will then need to set a higher version in bits 24-27. (And then we have a maximum of 16 security ABI version bumps.)

   This means that adding an Architecture.arm64e to the code_assets configuration is not enough. We'll also need to add a ABI version at some point.

   cc @rmacnak-google if you have further insights, let us know.
3. dcharkes commented on Aug 26, 2026

   

   dcharkes

   on Aug 26, 2026

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   Okay, I did some more digging.

   • No PAC: arm64
   • Yes PAC: arm64e version 1.
   • arm64e version 0 was the unstable version while PAC was in development.
   • BTI is backwards compatible and does not change the ABI.
   • EMTE/MIE is also not changing the ABI.
   • Apple has not announced anything for an arm64e version 2.

   So, maybe we just introduce Architecture.arm64e. And if Apple ever introduces a version 2, we can introduce a Architecture.arm64e v2. Simply folding it into the enum rather than having a separate version.
4. dcharkes commented on Aug 26, 2026

   

   dcharkes

   on Aug 26, 2026

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   Note from @rmacnak-google We're conflating architecture and ABI here. An architecture can support multiple ABIs, but in Dart we basically always pick one based on Arch + OS. So we kind of shoe-horn the ABI choice into Architecture here, even though the hardware architecture can run both arm64e and arm64. Anyway, we don't want to do breaking changes. So, we're going to roll with it.

   Also, we don't want the complexity of an extra integer. So, if Apple ever introduces v2 we'll add an Architecture.arm64ev2.
5. dcharkes

   changed the title [-][code_assets] Add `arm64e` as `Architecture`?[/-] [+][code_assets] Add `arm64e` as `Architecture`[/+] on Aug 26, 2026
6. auto-submit

   added a commit that references this issue on Aug 27, 2026

   [code_assets] [native_toolchain_c] Add arm64e (#3589)

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   ff508ae
7. Hassnaa9

   added a commit that references this issue on Sep 7, 2026

   [code_assets] [native_toolchain_c] Add arm64e (dart-lang#3589)

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   e4a923a