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From: Luis Machado <>
To: John Baldwin <>,
Subject: Re: [PATCH] [AArch64] Enable pointer authentication support for aarch64 bare metal/kernel mode addresses
Date: Thu, 19 Jan 2023 09:34:22 +0000	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>


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.

  reply	other threads:[~2023-01-19  9:34 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 [this message]
2023-01-19 18:35       ` John Baldwin
2023-02-21  9:11 ` Luis Machado

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