qemu-devel.nongnu.org archive mirror
 help / color / mirror / Atom feed
From: Richard Henderson <richard.henderson@linaro.org>
To: Peter Maydell <peter.maydell@linaro.org>,
	qemu-arm@nongnu.org, qemu-devel@nongnu.org
Cc: Laurent Vivier <laurent@vivier.eu>
Subject: Re: [PATCH] linux-user/arm: Deliver SIGTRAP for UDF patterns used as breakpoints
Date: Thu, 19 Nov 2020 10:27:07 -0800	[thread overview]
Message-ID: <6fae2e37-525d-5dc9-c9eb-ed482813891b@linaro.org> (raw)
In-Reply-To: <20201117155634.6924-1-peter.maydell@linaro.org>

On 11/17/20 7:56 AM, Peter Maydell wrote:
> The Linux kernel doesn't use the official bkpt insn for breakpoints;
> instead it uses three instructions in the guaranteed-to-UNDEF space,
> and generates SIGTRAP for these rather than the SIGILL that most
> UNDEF insns generate:
> 
> https://elixir.bootlin.com/linux/v5.9.8/source/arch/arm/kernel/ptrace.c#L197
> 
> Make QEMU treat these insns specially too.  The main benefit of this
> is that if you're running a debugger on a guest program that runs
> into a GCC __builtin_trap() or LLVM "trap because execution should
> never reach here" then you'll get the expected signal rather than a
> SIGILL.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
> This is not a "fix" for LP:1904210, but it does bring QEMU's
> behaviour into line with that of the real kernel on that binary.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~


      reply	other threads:[~2020-11-19 18:30 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-17 15:56 [PATCH] linux-user/arm: Deliver SIGTRAP for UDF patterns used as breakpoints Peter Maydell
2020-11-19 18:27 ` Richard Henderson [this message]

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=6fae2e37-525d-5dc9-c9eb-ed482813891b@linaro.org \
    --to=richard.henderson@linaro.org \
    --cc=laurent@vivier.eu \
    --cc=peter.maydell@linaro.org \
    --cc=qemu-arm@nongnu.org \
    --cc=qemu-devel@nongnu.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).