[aaelf64-morello] ELF markers to identify Morello purecap binaries #101
Conversation
amilendra
commented
May 21, 2021
amilendra
commented
- Assign e_flags bit 16 (0x00010000) to identify CHERI purecap binaries.
- Add platform agnostic CHERI Note Section to specify abi variant.
1) Assign e_flags bit 16 (0x00010000) to identify CHERI purecap binaries. 2) Add platform agnostic CHERI Note Section to specify abi variant.
aaelf64-morello/aaelf64-morello.rst
Outdated
| .. _Morello-specific e_flags: | ||
|
|
||
| .. class:: aaelf64-morello-elf-flags | ||
|
|
||
| .. table:: Morello-specific e_flags | ||
|
|
||
| +---------------------------------+--------------------------------------------------------------+ | ||
| | Value | Meaning | | ||
| +---------------------------------+--------------------------------------------------------------+ | ||
| | :code:`EF_AARCH64_MORELLO_EXT` | The ELF file contains uses an ABI where all pointers are | | ||
| | (:code:`0x00010000`) | implemented using capabilities (Pure-capability ABI) | | ||
| +---------------------------------+--------------------------------------------------------------+ | ||
|
|
||
| Sections | ||
| -------- | ||
|
|
||
| Special Sections | ||
| ^^^^^^^^^^^^^^^^ | ||
|
|
||
| A Morello toolchain can emit ELF Note sections in accordance to [CHERI_ELF_]. |
There was a problem hiding this comment.
Should Morello prove successful, do you want to reserve the ability to reuse this flag to be its real non-prototype successor? As it stands this bit will forever be wasted once the Morello program comes to an end.
There was a problem hiding this comment.
i.e. should this really be EF_AARCH64_CHERI_PURECAP?
There was a problem hiding this comment.
That is my only concern as well and the reason I had originally suggested an ELF note with a name of "Morello" as it could be easily jettisoned in the future. Checking e_flags bits is of course vastly simpler to deal with than looking for an ELF note, so if the bit is potentially forward looking I'm happy with having a flag in e_flags.
There was a problem hiding this comment.
It is difficult to make predictions at this stage. We can either reuse or rename the flag for a future architecture.
However we don't have any strong opinions on the name so will go with the more generic EF_AARCH64_CHERI_PURECAP.
Change-Id: Ic9e6f3bde6d3862b8a955f740d82db1e280a352e
