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Groups > comp.lang.c > #164676
| Message-ID | <adfbci-2qe.ln1@wilbur.25thandClement.com> (permalink) |
|---|---|
| From | William Ahern <william@25thandClement.com> |
| Subject | Re: Here come the 128-bit pointers |
| Newsgroups | comp.lang.c |
| References | <RZBHJ.39378$gX.11188@fx40.iad> <sso8kg$82t$1@dont-email.me> <ssochk$t26$1@dont-email.me> <sspgoj$s5l$1@dont-email.me> |
| Date | 2022-01-27 13:28 -0800 |
Bonita Montero <Bonita.Montero@gmail.com> wrote: > Am 25.01.2022 um 09:31 schrieb BGB: >> On 1/25/2022 1:25 AM, Bonita Montero wrote: >>> Am 24.01.2022 um 19:12 schrieb Scott Lurndal: >>> >>>> https://www.theregister.com/2022/01/21/arm_morello_testing/ >>>> https://www.arm.com/architecture/cpu/morello >>>> https://developer.arm.com/documentation/ddi0606/latest >>> >>> Where are the 128 bit pointers in Morello ? >> >> A quick skim implies that it works like: >> 64-bit pointers, no special protection; >> 129-bit pointers (with 128-bit storage), capability addressing, ... >> >> So, implicitly, it involves: >> Extra big pointers; >> Extra wonkiness for saving/reloading pointers; >> Registers that are internally significantly wider than what it visible >> in the rest of the ISA; >> ... >> >> A quick skim makes me suspect that this will have few drawbacks: >> More expensive for a hardware implementation (vs normal ARM64); >> Unlikely to be widely adopted, as using it would adversely impact >> existing C codebases (which tend to assume pointers are either 32 or 64 >> bits, and the ability to freely cast to and from integer types and >> manipulate them at the bit level, ...). >> >> >> Ideally, one would want a solution which is both "pretty much invisible" >> (code should not need to know or care) and "nearly free" (does not >> significantly impact performance, memory usage, or the relative >> implementation cost). >> >> ... > > Where's the docuemntation for Morello supporting 128 bit pointers ? Aside from the AAELF64 ABI link elsethread, more information can be found at the CHERI project: https://www.cl.cam.ac.uk/research/security/ctsrd/cheri/ AFAIU, ARM Morello implements the ISA as specified by CHERI. The CHERI project developed the general model, ISA extensions for various existing hardware architectures, an example ABI for common POSIX C environments, and sponsored software implementations, including an entire port of FreeBSD-- compiler, kernel, and userspace--to the new ISA and ABI. This 2019 paper details the extension for typical POSIX C ABIs: "CheriABI: Enforcing Valid Pointer Provenance and Minimizing Pointer Privilege in the POSIX C Run-time Environment", https://www.cl.cam.ac.uk/research/security/ctsrd/pdfs/201904-asplos-cheriabi.pdf Regarding pointer width, see section 2, page 4: "In implementation, CHERI extends 64-bit addresses with metadata in both the in-register and in-memory representations, increasing the in-memory size of pointers to 128 bits, plus an out-of-band tag bit."
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Here come the 128-bit pointers scott@slp53.sl.home (Scott Lurndal) - 2022-01-24 18:12 +0000
Re: Here come the 128-bit pointers Dan Purgert <dan@djph.net> - 2022-01-24 18:31 +0000
Re: Here come the 128-bit pointers BGB <cr88192@gmail.com> - 2022-01-24 15:41 -0600
Re: Here come the 128-bit pointers Bonita Montero <Bonita.Montero@gmail.com> - 2022-01-25 08:25 +0100
Re: Here come the 128-bit pointers BGB <cr88192@gmail.com> - 2022-01-25 02:31 -0600
Re: Here come the 128-bit pointers Öö Tiib <ootiib@hot.ee> - 2022-01-25 02:04 -0800
Re: Here come the 128-bit pointers scott@slp53.sl.home (Scott Lurndal) - 2022-01-25 14:48 +0000
Re: Here come the 128-bit pointers BGB <cr88192@gmail.com> - 2022-01-25 11:54 -0600
Re: Here come the 128-bit pointers scott@slp53.sl.home (Scott Lurndal) - 2022-01-25 18:23 +0000
Re: Here come the 128-bit pointers BGB <cr88192@gmail.com> - 2022-01-25 14:17 -0600
Re: Here come the 128-bit pointers David Brown <david.brown@hesbynett.no> - 2022-01-26 09:36 +0100
Re: Here come the 128-bit pointers Theo <theom+news@chiark.greenend.org.uk> - 2022-01-28 22:12 +0000
Re: Here come the 128-bit pointers Bonita Montero <Bonita.Montero@gmail.com> - 2022-01-25 19:49 +0100
Re: Here come the 128-bit pointers BGB <cr88192@gmail.com> - 2022-01-25 15:59 -0600
Re: Here come the 128-bit pointers scott@slp53.sl.home (Scott Lurndal) - 2022-01-25 22:25 +0000
Re: Here come the 128-bit pointers Bonita Montero <Bonita.Montero@gmail.com> - 2022-01-26 09:43 +0100
Re: Here come the 128-bit pointers scott@slp53.sl.home (Scott Lurndal) - 2022-01-26 15:53 +0000
Re: Here come the 128-bit pointers Bonita Montero <Bonita.Montero@gmail.com> - 2022-01-26 17:25 +0100
Re: Here come the 128-bit pointers Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2022-01-26 08:34 -0800
Re: Here come the 128-bit pointers Bonita Montero <Bonita.Montero@gmail.com> - 2022-01-26 17:57 +0100
Re: Here come the 128-bit pointers Bart <bc@freeuk.com> - 2022-01-26 17:10 +0000
Re: Here come the 128-bit pointers scott@slp53.sl.home (Scott Lurndal) - 2022-01-26 17:27 +0000
Re: Here come the 128-bit pointers Bart <bc@freeuk.com> - 2022-01-26 17:41 +0000
Re: Here come the 128-bit pointers scott@slp53.sl.home (Scott Lurndal) - 2022-01-26 18:05 +0000
Re: Here come the 128-bit pointers Bart <bc@freeuk.com> - 2022-01-26 18:23 +0000
Re: Here come the 128-bit pointers BGB <cr88192@gmail.com> - 2022-01-26 14:42 -0600
Re: Here come the 128-bit pointers BGB <cr88192@gmail.com> - 2022-01-26 14:30 -0600
Re: Here come the 128-bit pointers Mateusz Viste <mateusz@xyz.invalid> - 2022-01-26 19:36 +0100
Re: Here come the 128-bit pointers scott@slp53.sl.home (Scott Lurndal) - 2022-01-26 18:52 +0000
Re: Here come the 128-bit pointers tth <tth@none.invalid> - 2022-01-26 21:01 +0100
Re: Here come the 128-bit pointers Bart <bc@freeuk.com> - 2022-01-26 20:18 +0000
Re: Here come the 128-bit pointers BGB <cr88192@gmail.com> - 2022-01-26 15:35 -0600
Re: Here come the 128-bit pointers scott@slp53.sl.home (Scott Lurndal) - 2022-01-26 21:50 +0000
Re: Here come the 128-bit pointers BGB <cr88192@gmail.com> - 2022-01-26 20:34 -0600
Re: Here come the 128-bit pointers Bart <bc@freeuk.com> - 2022-01-27 12:11 +0000
Re: Here come the 128-bit pointers BGB <cr88192@gmail.com> - 2022-01-27 13:40 -0600
Re: Here come the 128-bit pointers William Ahern <william@25thandClement.com> - 2022-01-27 13:28 -0800
Re: Here come the 128-bit pointers Theo Markettos <theom+news@chiark.greenend.org.uk> - 2022-01-28 23:18 +0000
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