Re: git: 706f4a81a812 - main - exec: Introduce the PROC_PS_STRINGS() macro

From: John Baldwin <jhb_at_FreeBSD.org>
Date: Tue, 18 Jan 2022 15:31:47 UTC 
On 1/17/22 1:13 PM, Mark Johnston wrote:
> The branch main has been updated by markj:
> 
> URL: https://cgit.FreeBSD.org/src/commit/?id=706f4a81a81250a326ea25914e7effe1768f1a37
> 
> commit 706f4a81a81250a326ea25914e7effe1768f1a37
> Author:     Mark Johnston <markj@FreeBSD.org>
> AuthorDate: 2022-01-17 16:42:28 +0000
> Commit:     Mark Johnston <markj@FreeBSD.org>
> CommitDate: 2022-01-17 21:11:54 +0000
> 
>      exec: Introduce the PROC_PS_STRINGS() macro
>      
>      Rather than fetching the ps_strings address directly from a process'
>      sysentvec, use this macro.  With stack address randomization the
>      ps_strings address is no longer fixed.
>      
>      Reviewed by:    kib
>      MFC after:      2 weeks
>      Sponsored by:   The FreeBSD Foundation
>      Differential Revision:  https://reviews.freebsd.org/D33704

FWIW, in CheriBSD we have a 'p_psstrings' member in struct proc that is a pointer
to the ps_strings structure in user space that is set by the ABI during exec.
CHERI removes the need for ASLR, but due to alignment requirements of capabilities
the stack is not a fixed location as its address can vary based on the size.

-- 
John Baldwin