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Re: [PATCH 0/3 v3] [AArch64] Support tagged pointer
- From: Simon Marchi <simon dot marchi at polymtl dot ca>
- To: Omair Javaid <omair dot javaid at linaro dot org>
- Cc: Yao Qi <qiyaoltc at gmail dot com>, GDB Patches <gdb-patches at sourceware dot org>, Pedro Alves <palves at redhat dot com>
- Date: Tue, 10 Apr 2018 22:46:17 -0400
- Subject: Re: [PATCH 0/3 v3] [AArch64] Support tagged pointer
- References: <1512727471-30745-1-git-send-email-yao.qi@linaro.org> <CAH=s-PP6BcsW_RCZivdm1DCkxVz6E94dtFGBBtHWnDcF6EO7YQ@mail.gmail.com> <CANW4E-1SQ5Ye-kVm45x0A_8EFK6919E62NFLSHHceLnWDsJLng@mail.gmail.com> <CANW4E-1-165=L2_xtQJVEohPZ-xL5i25ftB-2znghdXWa_Nffg@mail.gmail.com>
On 2018-04-10 20:36, Omair Javaid wrote:
This patch has broken kernel debugging using kgdb and openOCD.
Tagged address should only be considered while debugging only
user-space
programs on linux.
I still need to understand the full background behind this patch but
can
we pull it out of 8.1 release to make sure kernel debugging works?
Just found out that patch series posted here
https://sourceware.org/ml/gdb-patches/2017-12/msg00160.html does change
aarch64-linux-tdep only.
But the committed version here
https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=commit;h=a738ea1d41daeec0cccb4ab6671f4f6d53bd9e18
is
applying it to aarch64-tdep
I think it was because of Pedro's suggestion in this reply:
https://sourceware.org/ml/gdb-patches/2017-12/msg00179.html
although there was now acknowledgement from Yao, so I can only guess.
As Pedro said, it's the hardware that ignores these top bits. But it
first has to be configured to do so, so we can't assume that all aarch64
code behaves like this. So far we only know that the Linux userspace
threads work like that, so I think it would make sense to move it to
aarch64-linux-tdep.c. Did you confirm that it indeed fixes your
problem?
I could see a fix for this getting into the 8.1 branch (not reverting
the patch though).
Simon