Xen-Devel Archive on lore.kernel.org
 help / color / Atom feed
From: "Jan Beulich" <JBeulich@suse.com>
To: "Andrew Cooper" <andrew.cooper3@citrix.com>,
	"xen-devel" <xen-devel@lists.xenproject.org>
Cc: WeiLiu <wl@xen.org>, Roger Pau Monne <roger.pau@citrix.com>
Subject: Re: [Xen-devel] [PATCH 2/2] x86/traps: widen condition for logging top-of-stack
Date: Tue, 11 Jun 2019 03:46:38 -0600
Message-ID: <5CFF787E0200007800236EA5@prv1-mh.provo.novell.com> (raw)
In-Reply-To: <691e7133-4a75-0ca9-c347-5a37aa59a30f@citrix.com>

>>> On 07.06.19 at 20:01, <andrew.cooper3@citrix.com> wrote:
> On 31/05/2019 10:22, Jan Beulich wrote:
>> Despite -fno-omit-frame-pointer the compiler may omit the frame pointer,
>> often for relatively simple leaf functions. (To give a specific example,
>> the case I've run into this with is _pci_hide_device() and gcc 8.
>> Interestingly the even more simple neighboring iommu_has_feature() does
>> get a frame pointer set up, around just a single instruction. But this
>> may be a result of the size-of-asm() effects discussed elsewhere.)
>>
>> Log the top-of-stack value if it looks valid _or_ if RIP looks invalid.
>>
>> Also annotate non-frame-pointer-based stack trace entries with a
>> question mark, to signal clearly that any one of them may not actually
>> be part of the call stack.
> 
> I very specifically didn't do that before, because it give the false
> impression that when a question mark isn't present, the logging line is
> accurate.
> 
> This is not true for %rbp corruption, asm blocks which don't respect the
> frame pointer ABI (arguably also corruption), any fault raised from
> within an EFI call.

So what do you suggest instead? Somehow we should mark slots
that are more guesses than actually derived.

> Porting Xen to use objtool would be a definite improvement, but cannot
> guard against unexpected %rbp corruption and the EFI case.

I'm not sure about "definite", but I think I see your point. Personally
I continue to believe that programmer (assembly code) and compiler
(C code) attached unwind annotations are the better model.

Jan



_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel

  reply index

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-31  8:59 [PATCH 0/2]: x86/traps: improve show_trace()'s top-of-stack handling Jan Beulich
2019-05-31  8:59 ` [Xen-devel] " Jan Beulich
2019-05-31  9:17 ` [PATCH 1/2] x86/traps: guard top-of-stack reads Jan Beulich
2019-05-31  9:17   ` [Xen-devel] " Jan Beulich
2019-06-07 17:51   ` Andrew Cooper
2019-06-11  9:57     ` Jan Beulich
2019-05-31  9:22 ` [PATCH 2/2] x86/traps: widen condition for logging top-of-stack Jan Beulich
2019-05-31  9:22   ` [Xen-devel] " Jan Beulich
2019-06-07 18:01   ` Andrew Cooper
2019-06-11  9:46     ` Jan Beulich [this message]
2019-06-17  8:10 ` [Xen-devel] [PATCH v2 0/2]: x86/traps: improve show_trace()'s top-of-stack handling Jan Beulich
2019-06-17  8:12   ` [Xen-devel] [PATCH v2 1/2] x86/traps: guard top-of-stack reads Jan Beulich
2019-07-02 17:47     ` Andrew Cooper
2019-07-03  7:10       ` Jan Beulich
2019-06-17  8:13   ` [Xen-devel] [PATCH v2 2/2] x86/traps: widen condition for logging top-of-stack Jan Beulich
2019-07-03 10:21     ` Andrew Cooper
2019-07-03 10:34       ` Jan Beulich
2019-07-03 19:47         ` Andrew Cooper
2019-07-04  9:09           ` Jan Beulich

Reply instructions:

You may reply publically 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=5CFF787E0200007800236EA5@prv1-mh.provo.novell.com \
    --to=jbeulich@suse.com \
    --cc=andrew.cooper3@citrix.com \
    --cc=roger.pau@citrix.com \
    --cc=wl@xen.org \
    --cc=xen-devel@lists.xenproject.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

Xen-Devel Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/xen-devel/0 xen-devel/git/0.git
	git clone --mirror https://lore.kernel.org/xen-devel/1 xen-devel/git/1.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 xen-devel xen-devel/ https://lore.kernel.org/xen-devel \
		xen-devel@lists.xenproject.org xen-devel@archiver.kernel.org
	public-inbox-index xen-devel


Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.xenproject.lists.xen-devel


AGPL code for this site: git clone https://public-inbox.org/ public-inbox