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From: John Baldwin <>
To: Luis Machado <>,
Subject: Re: [PATCH] [AArch64] Enable pointer authentication support for aarch64 bare metal/kernel mode addresses
Date: Thu, 19 Jan 2023 10:35:32 -0800	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On 1/19/23 1:34 AM, Luis Machado wrote:
> Hi,
> On 1/18/23 18:39, John Baldwin wrote:
>> On 1/5/23 5:16 AM, Luis Machado wrote:
>>> Hi John,
>>> Any thoughts on this patch from BSD's side?
>> Sorry, I missed the cc earlier.  FreeBSD does have support for the userland
>> registers that I haven't yet added for userland PAC and this seems to make
>> that easier as I will just need to add the registers to the tdesc when
>> present/supported.  However, one question I have is what does this do if the
>> registers aren't available and kernel addresses are used?  I have this use
>> case for existing FreeBSD/aarch64 kernel debugging.  The default version of
>> the gdbarch hook seems to always assume TBI and strip the upper bits, but
>> for kernel addresses what I kind of need is to sign-extend addresses based
>> on bit 55.  I do have a separate gdbarch for kernels vs userland programs
>> so it might just be I need a custom version of this gdbarch hook for the kernel
>> gdbarch?>
> The default behavior in the absence of the PAC registers for the kernel addresses is to
> assume TBI, remove the top bits and sign-extend based on bit 55.
> This is done by aarch64_remove_top_bits.
> I suppose that would work for you then.

That sounds perfect then, thanks!

John Baldwin

  reply	other threads:[~2023-01-19 18:35 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-12-16 10:57 Luis Machado
2022-12-20  3:20 ` Thiago Jung Bauermann
2022-12-20  9:17   ` Luis Machado
2023-01-05 13:16 ` Luis Machado
2023-01-18 18:39   ` John Baldwin
2023-01-19  9:34     ` Luis Machado
2023-01-19 18:35       ` John Baldwin [this message]
2023-02-21  9:11 ` Luis Machado

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