From: will.deacon@arm.com (Will Deacon)
To: linux-arm-kernel@lists.infradead.org
Subject: ARM: hw_breakpoint mismatch breakpoint behaves unexpectedly like a match breakpoint on ARM_DEBUG_ARCH_V7_ECP14
Date: Tue, 22 Jan 2013 09:31:02 +0000 [thread overview]
Message-ID: <20130122093102.GC12295@mudshark.cambridge.arm.com> (raw)
In-Reply-To: <CAPfQmKJaYf6M4iHKuNcHgYZi5R8M7fXdXta34Q=1C0cHKimkyQ@mail.gmail.com>
On Tue, Jan 22, 2013 at 04:28:35AM +0000, Valentin Pistol wrote:
> Hi Will,
Hi Valentin,
> I am trying to single-step each instruction in a target process by
> using the hardware breakpoints with the mismatch set (bit 22) and I am
> experiencing unexpected behavior: with mismatch set it behaves as a
> match breakpoint.
> I checked that my Debug Arch ARM_DEBUG_ARCH_V7_ECP14 has mismatch
> breakpoint support.
> The BCR (0x4001e5) value and DSCR (0x3070002) seem to be correct
> according to the manual, so I am confused what is causing the odd
> behavior.
[...]
> I should note that I am able to set a match breakpoint using the
> ptrace interface, have it trigger a SIGTRAP and capture it in my own
> user space handler. When attempting to use mismatch instead, the
> behavior appears to be same as a match breakpoint: breaks on the
> specified PC value.
The ptrace interface doesn't support mismatch breakpoints, and ignores those
bits in the user request, hence why you see a normal breakpoint being
created. Note that mismatch breakpoints are used internally for stepping
over breakpoints set by perf.
If you wanted to add single-step using mismatch breakpoints, I think we'd be
better off re-introducing the SINGLESTEP ptrace request for ARM to use
hw_breakpoints.
Will
next prev parent reply other threads:[~2013-01-22 9:31 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-22 4:28 ARM: hw_breakpoint mismatch breakpoint behaves unexpectedly like a match breakpoint on ARM_DEBUG_ARCH_V7_ECP14 Valentin Pistol
2013-01-22 9:31 ` Will Deacon [this message]
2013-01-22 17:11 ` Valentin Pistol
2013-01-23 14:50 ` Will Deacon
2013-01-23 17:35 ` Valentin Pistol
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20130122093102.GC12295@mudshark.cambridge.arm.com \
--to=will.deacon@arm.com \
--cc=linux-arm-kernel@lists.infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).