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Re: [PATCH] [AArch64 Linux] Get rid of top byte from tagged address

From: Ramana Radhakrishnan <ramana dot radhakrishnan at foss dot arm dot com>
To: Yao Qi <qiyaoltc at gmail dot com>, gdb-patches at sourceware dot org
Date: Thu, 19 Oct 2017 10:50:53 +0100
Subject: Re: [PATCH] [AArch64 Linux] Get rid of top byte from tagged address
Authentication-results: sourceware.org; auth=none
References: <1508400527-20718-1-git-send-email-yao.qi@linaro.org>

On 10/19/17 9:08 AM, Yao Qi wrote:

ARMv8 supports tagged address, that is, the top one byte in address
is ignored.  It is always enabled on aarch64-linux.  The patch clear
the top byte of the virtual address, at the point before GDB/GDBserver
pass the address to /proc or ptrace syscall.  The top byte of address is
still retained in the rest of GDB, because these bits can be used by
different applications in different ways.  That is reason I didn't
implement gdbarch method addr_bits_remove to get rid of them.


I think you also want to point people at ...

https://www.kernel.org/doc/Documentation/arm64/tagged-pointers.txt

regards
Ramana

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References:
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  - From: Yao Qi

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