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Re: [PATCH v19 00/10] Compile-time stack metadata validation

Started byIngo Molnar <mingo@kernel.org>
First post2016-03-08 11:40 +0100
Last post2016-03-08 16:20 +0100
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  Re: [PATCH v19 00/10] Compile-time stack metadata validation Ingo Molnar <mingo@kernel.org> - 2016-03-08 11:40 +0100
    Re: [PATCH v19 00/10] Compile-time stack metadata validation Josh Poimboeuf <jpoimboe@redhat.com> - 2016-03-08 13:30 +0100
      Re: [PATCH v19 00/10] Compile-time stack metadata validation Ingo Molnar <mingo@kernel.org> - 2016-03-08 14:50 +0100
        Re: [PATCH v19 00/10] Compile-time stack metadata validation Josh Poimboeuf <jpoimboe@redhat.com> - 2016-03-08 15:30 +0100
          Re: [PATCH v19 00/10] Compile-time stack metadata validation Ingo Molnar <mingo@kernel.org> - 2016-03-08 16:20 +0100

#1352857 — Re: [PATCH v19 00/10] Compile-time stack metadata validation

FromIngo Molnar <mingo@kernel.org>
Date2016-03-08 11:40 +0100
SubjectRe: [PATCH v19 00/10] Compile-time stack metadata validation
Message-ID<randx-84x-53@gated-at.bofh.it>
* Josh Poimboeuf <jpoimboe@redhat.com> wrote:

> This is v19 of the compile-time stack metadata validation patch set.
> 
> It's based on tip:core/objtool.

So I've upgraded my main build box to Fedora 23, to:

  gcc version 5.3.1 20151207 (Red Hat 5.3.1-2) (GCC)
  GNU assembler version 2.25 (x86_64-redhat-linux) using BFD version version 2.25-15.fc23
  GNU ld version 2.25-15.fc23

and I'm now getting a bunch of these warnings:

drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2e7: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2f3: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2ff: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x30b: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x317: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x323: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x32f: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x33b: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x348: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x355: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x362: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x36f: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x37c: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x389: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x396: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2e7: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2f3: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2ff: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x30b: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x317: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x323: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x32f: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x33b: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x348: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x355: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x362: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x36f: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x37c: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x389: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x396: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x19a: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1a6: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1b2: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1be: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1ca: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1d6: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1e2: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1ee: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1ff: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x210: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x221: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x251: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x262: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x273: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x284: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x295: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2a6: frame pointer state mismatch
drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2b7: frame pointer state mismatch

I see nothing particularly weird about rtlwifi_rate_mapping(), except the tons of 
switch statements - maybe GCC does something really clever here?

In any case this needs to be addressed before the merge window. Also, I think we 
should limit the number of objtool warnings to one per function?

Thanks,

	Ingo

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#1352965

FromJosh Poimboeuf <jpoimboe@redhat.com>
Date2016-03-08 13:30 +0100
Message-ID<raoVZ-Mw-33@gated-at.bofh.it>
In reply to#1352857
On Tue, Mar 08, 2016 at 11:37:16AM +0100, Ingo Molnar wrote:
> 
> * Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> 
> > This is v19 of the compile-time stack metadata validation patch set.
> > 
> > It's based on tip:core/objtool.
> 
> So I've upgraded my main build box to Fedora 23, to:
> 
>   gcc version 5.3.1 20151207 (Red Hat 5.3.1-2) (GCC)
>   GNU assembler version 2.25 (x86_64-redhat-linux) using BFD version version 2.25-15.fc23
>   GNU ld version 2.25-15.fc23
> 
> and I'm now getting a bunch of these warnings:
> 
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2e7: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2f3: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2ff: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x30b: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x317: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x323: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x32f: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x33b: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x348: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x355: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x362: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x36f: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x37c: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x389: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x396: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2e7: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2f3: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2ff: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x30b: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x317: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x323: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x32f: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x33b: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x348: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x355: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x362: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x36f: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x37c: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x389: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x396: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x19a: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1a6: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1b2: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1be: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1ca: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1d6: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1e2: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1ee: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1ff: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x210: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x221: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x251: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x262: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x273: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x284: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x295: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2a6: frame pointer state mismatch
> drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2b7: frame pointer state mismatch
> 
> I see nothing particularly weird about rtlwifi_rate_mapping(), except the tons of 
> switch statements - maybe GCC does something really clever here?
> 
> In any case this needs to be addressed before the merge window. Also, I think we 
> should limit the number of objtool warnings to one per function?

This is a bug in objtool's handling of switch statement jump tables.  In
fact, the 0-day bot warned me about this bug yesterday, but I
misinterpreted it:

  https://lkml.kernel.org/r/201603060006.yNZ9xTcs%fengguang.wu@intel.com

I'll fix it up today.  I'll also limit the warnings to one per function.

BTW, I was only able to recreate this particular issue after updating to
today's tip/master.  It was triggered by a new config option:
CONFIG_UBSAN_SANITIZE_ALL.

-- 
Josh

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#1353054

FromIngo Molnar <mingo@kernel.org>
Date2016-03-08 14:50 +0100
Message-ID<raqbo-1xM-19@gated-at.bofh.it>
In reply to#1352965
* Josh Poimboeuf <jpoimboe@redhat.com> wrote:

> On Tue, Mar 08, 2016 at 11:37:16AM +0100, Ingo Molnar wrote:
> > 
> > * Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> > 
> > > This is v19 of the compile-time stack metadata validation patch set.
> > > 
> > > It's based on tip:core/objtool.
> > 
> > So I've upgraded my main build box to Fedora 23, to:
> > 
> >   gcc version 5.3.1 20151207 (Red Hat 5.3.1-2) (GCC)
> >   GNU assembler version 2.25 (x86_64-redhat-linux) using BFD version version 2.25-15.fc23
> >   GNU ld version 2.25-15.fc23
> > 
> > and I'm now getting a bunch of these warnings:
> > 
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2e7: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2f3: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2ff: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x30b: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x317: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x323: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x32f: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x33b: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x348: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x355: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x362: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x36f: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x37c: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x389: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x396: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2e7: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2f3: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2ff: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x30b: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x317: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x323: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x32f: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x33b: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x348: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x355: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x362: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x36f: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x37c: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x389: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x396: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x19a: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1a6: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1b2: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1be: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1ca: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1d6: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1e2: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1ee: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1ff: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x210: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x221: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x251: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x262: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x273: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x284: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x295: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2a6: frame pointer state mismatch
> > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2b7: frame pointer state mismatch
> > 
> > I see nothing particularly weird about rtlwifi_rate_mapping(), except the tons of 
> > switch statements - maybe GCC does something really clever here?
> > 
> > In any case this needs to be addressed before the merge window. Also, I think we 
> > should limit the number of objtool warnings to one per function?
> 
> This is a bug in objtool's handling of switch statement jump tables.  In
> fact, the 0-day bot warned me about this bug yesterday, but I
> misinterpreted it:
> 
>   https://lkml.kernel.org/r/201603060006.yNZ9xTcs%fengguang.wu@intel.com
> 
> I'll fix it up today.  I'll also limit the warnings to one per function.
> 
> BTW, I was only able to recreate this particular issue after updating to
> today's tip/master.  It was triggered by a new config option:
> CONFIG_UBSAN_SANITIZE_ALL.

ah, makes sense! I also upgraded to the latestest Fedora and misinterpreted the 
warning.

Btw., I like it how in other cases you didn't try to work the warning around in 
objtool, but improved the C code itself. We can consider this warning as a 
'unnecessarily complex switch statement' warning.

For example in this case I think we could use something like the patch below, 
because in reality the various cases are linear ranges. Totally untested.

Thanks,

	Ingo

 drivers/net/wireless/realtek/rtlwifi/base.c | 196 ++--------------------------
 1 file changed, 12 insertions(+), 184 deletions(-)

diff --git a/drivers/net/wireless/realtek/rtlwifi/base.c b/drivers/net/wireless/realtek/rtlwifi/base.c
index 0517a4f2d3f2..a8c4e5b5bebd 100644
--- a/drivers/net/wireless/realtek/rtlwifi/base.c
+++ b/drivers/net/wireless/realtek/rtlwifi/base.c
@@ -890,201 +890,29 @@ int rtlwifi_rate_mapping(struct ieee80211_hw *hw, bool isht, bool isvht,
 	int rate_idx;
 
 	if (isvht) {
-		switch (desc_rate) {
-		case DESC_RATEVHT1SS_MCS0:
-			rate_idx = 0;
-			break;
-		case DESC_RATEVHT1SS_MCS1:
-			rate_idx = 1;
-			break;
-		case DESC_RATEVHT1SS_MCS2:
-			rate_idx = 2;
-			break;
-		case DESC_RATEVHT1SS_MCS3:
-			rate_idx = 3;
-			break;
-		case DESC_RATEVHT1SS_MCS4:
-			rate_idx = 4;
-			break;
-		case DESC_RATEVHT1SS_MCS5:
-			rate_idx = 5;
-			break;
-		case DESC_RATEVHT1SS_MCS6:
-			rate_idx = 6;
-			break;
-		case DESC_RATEVHT1SS_MCS7:
-			rate_idx = 7;
-			break;
-		case DESC_RATEVHT1SS_MCS8:
-			rate_idx = 8;
-			break;
-		case DESC_RATEVHT1SS_MCS9:
-			rate_idx = 9;
-			break;
-		case DESC_RATEVHT2SS_MCS0:
-			rate_idx = 0;
-			break;
-		case DESC_RATEVHT2SS_MCS1:
-			rate_idx = 1;
-			break;
-		case DESC_RATEVHT2SS_MCS2:
-			rate_idx = 2;
-			break;
-		case DESC_RATEVHT2SS_MCS3:
-			rate_idx = 3;
-			break;
-		case DESC_RATEVHT2SS_MCS4:
-			rate_idx = 4;
-			break;
-		case DESC_RATEVHT2SS_MCS5:
-			rate_idx = 5;
-			break;
-		case DESC_RATEVHT2SS_MCS6:
-			rate_idx = 6;
-			break;
-		case DESC_RATEVHT2SS_MCS7:
-			rate_idx = 7;
-			break;
-		case DESC_RATEVHT2SS_MCS8:
-			rate_idx = 8;
-			break;
-		case DESC_RATEVHT2SS_MCS9:
-			rate_idx = 9;
-			break;
-		default:
+		if (desc_rate >= DESC_RATEVHT1SS_MCS0 && desc_rate <= DESC_RATEVHT2SS_MCS9)
+			rate_idx = desc_rate-DESC_RATEVHT1SS_MCS0;
+		else
 			rate_idx = 0;
-			break;
-		}
 		return rate_idx;
 	}
 	if (false == isht) {
 		if (IEEE80211_BAND_2GHZ == hw->conf.chandef.chan->band) {
-			switch (desc_rate) {
-			case DESC_RATE1M:
-				rate_idx = 0;
-				break;
-			case DESC_RATE2M:
-				rate_idx = 1;
-				break;
-			case DESC_RATE5_5M:
-				rate_idx = 2;
-				break;
-			case DESC_RATE11M:
-				rate_idx = 3;
-				break;
-			case DESC_RATE6M:
-				rate_idx = 4;
-				break;
-			case DESC_RATE9M:
-				rate_idx = 5;
-				break;
-			case DESC_RATE12M:
-				rate_idx = 6;
-				break;
-			case DESC_RATE18M:
-				rate_idx = 7;
-				break;
-			case DESC_RATE24M:
-				rate_idx = 8;
-				break;
-			case DESC_RATE36M:
-				rate_idx = 9;
-				break;
-			case DESC_RATE48M:
-				rate_idx = 10;
-				break;
-			case DESC_RATE54M:
-				rate_idx = 11;
-				break;
-			default:
+			if (desc_rate <= DESC_RATE54M)
+				rate_idx = desc_rate;
+			else
 				rate_idx = 0;
-				break;
-			}
 		} else {
-			switch (desc_rate) {
-			case DESC_RATE6M:
-				rate_idx = 0;
-				break;
-			case DESC_RATE9M:
-				rate_idx = 1;
-				break;
-			case DESC_RATE12M:
-				rate_idx = 2;
-				break;
-			case DESC_RATE18M:
-				rate_idx = 3;
-				break;
-			case DESC_RATE24M:
-				rate_idx = 4;
-				break;
-			case DESC_RATE36M:
-				rate_idx = 5;
-				break;
-			case DESC_RATE48M:
-				rate_idx = 6;
-				break;
-			case DESC_RATE54M:
-				rate_idx = 7;
-				break;
-			default:
+			if (desc_rate >= DESC_RATE6M && desc_rate <= DESC_RATE54M)
+				rate_idx = desc_rate-DESC_RATE6M;
+			else
 				rate_idx = 0;
-				break;
-			}
 		}
 	} else {
-		switch (desc_rate) {
-		case DESC_RATEMCS0:
-			rate_idx = 0;
-			break;
-		case DESC_RATEMCS1:
-			rate_idx = 1;
-			break;
-		case DESC_RATEMCS2:
-			rate_idx = 2;
-			break;
-		case DESC_RATEMCS3:
-			rate_idx = 3;
-			break;
-		case DESC_RATEMCS4:
-			rate_idx = 4;
-			break;
-		case DESC_RATEMCS5:
-			rate_idx = 5;
-			break;
-		case DESC_RATEMCS6:
-			rate_idx = 6;
-			break;
-		case DESC_RATEMCS7:
-			rate_idx = 7;
-			break;
-		case DESC_RATEMCS8:
-			rate_idx = 8;
-			break;
-		case DESC_RATEMCS9:
-			rate_idx = 9;
-			break;
-		case DESC_RATEMCS10:
-			rate_idx = 10;
-			break;
-		case DESC_RATEMCS11:
-			rate_idx = 11;
-			break;
-		case DESC_RATEMCS12:
-			rate_idx = 12;
-			break;
-		case DESC_RATEMCS13:
-			rate_idx = 13;
-			break;
-		case DESC_RATEMCS14:
-			rate_idx = 14;
-			break;
-		case DESC_RATEMCS15:
-			rate_idx = 15;
-			break;
-		default:
+		if (desc_rate >= DESC_RATEMCS0 && desc_rate <= DESC_RATEMCS15)
+			rate_idx = desc_rate-DESC_RATEMCS0;
+		else
 			rate_idx = 0;
-			break;
-		}
 	}
 	return rate_idx;
 }

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#1353094

FromJosh Poimboeuf <jpoimboe@redhat.com>
Date2016-03-08 15:30 +0100
Message-ID<raqO6-21z-5@gated-at.bofh.it>
In reply to#1353054
On Tue, Mar 08, 2016 at 02:44:57PM +0100, Ingo Molnar wrote:
> 
> * Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> 
> > On Tue, Mar 08, 2016 at 11:37:16AM +0100, Ingo Molnar wrote:
> > > 
> > > * Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> > > 
> > > > This is v19 of the compile-time stack metadata validation patch set.
> > > > 
> > > > It's based on tip:core/objtool.
> > > 
> > > So I've upgraded my main build box to Fedora 23, to:
> > > 
> > >   gcc version 5.3.1 20151207 (Red Hat 5.3.1-2) (GCC)
> > >   GNU assembler version 2.25 (x86_64-redhat-linux) using BFD version version 2.25-15.fc23
> > >   GNU ld version 2.25-15.fc23
> > > 
> > > and I'm now getting a bunch of these warnings:
> > > 
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2e7: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2f3: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2ff: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x30b: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x317: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x323: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x32f: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x33b: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x348: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x355: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x362: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x36f: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x37c: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x389: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x396: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2e7: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2f3: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2ff: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x30b: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x317: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x323: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x32f: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x33b: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x348: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x355: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x362: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x36f: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x37c: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x389: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x396: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x19a: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1a6: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1b2: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1be: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1ca: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1d6: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1e2: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1ee: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1ff: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x210: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x221: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x251: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x262: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x273: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x284: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x295: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2a6: frame pointer state mismatch
> > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2b7: frame pointer state mismatch
> > > 
> > > I see nothing particularly weird about rtlwifi_rate_mapping(), except the tons of 
> > > switch statements - maybe GCC does something really clever here?
> > > 
> > > In any case this needs to be addressed before the merge window. Also, I think we 
> > > should limit the number of objtool warnings to one per function?
> > 
> > This is a bug in objtool's handling of switch statement jump tables.  In
> > fact, the 0-day bot warned me about this bug yesterday, but I
> > misinterpreted it:
> > 
> >   https://lkml.kernel.org/r/201603060006.yNZ9xTcs%fengguang.wu@intel.com
> > 
> > I'll fix it up today.  I'll also limit the warnings to one per function.
> > 
> > BTW, I was only able to recreate this particular issue after updating to
> > today's tip/master.  It was triggered by a new config option:
> > CONFIG_UBSAN_SANITIZE_ALL.
> 
> ah, makes sense! I also upgraded to the latestest Fedora and misinterpreted the 
> warning.
> 
> Btw., I like it how in other cases you didn't try to work the warning around in 
> objtool, but improved the C code itself. We can consider this warning as a 
> 'unnecessarily complex switch statement' warning.

So the bug is that when there's more than one switch statement in a
function, objtool interprets all the switch jump tables as a single
table.  If the targets of one jump table assume a stack frame and the
targets of another one don't, you'll see frame pointer warnings like
those above.

It *is* interesting that both functions which triggered this bug --
rtlwifi_rate_mapping() and cik_tiling_mode_table_init() -- are cases
where the code is way too complex and can be simplified.

But, unless we want to institute an "only one switch statement allowed
per function" policy, I think I should still fix the bug.  Because I
don't really have the clout to tell people "you need to clean up your
code because my tool is buggy." :-)

-- 
Josh

[toc] | [prev] | [next] | [standalone]

#1353133

FromIngo Molnar <mingo@kernel.org>
Date2016-03-08 16:20 +0100
Message-ID<rarAu-2yX-11@gated-at.bofh.it>
In reply to#1353094
* Josh Poimboeuf <jpoimboe@redhat.com> wrote:

> On Tue, Mar 08, 2016 at 02:44:57PM +0100, Ingo Molnar wrote:
> > 
> > * Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> > 
> > > On Tue, Mar 08, 2016 at 11:37:16AM +0100, Ingo Molnar wrote:
> > > > 
> > > > * Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> > > > 
> > > > > This is v19 of the compile-time stack metadata validation patch set.
> > > > > 
> > > > > It's based on tip:core/objtool.
> > > > 
> > > > So I've upgraded my main build box to Fedora 23, to:
> > > > 
> > > >   gcc version 5.3.1 20151207 (Red Hat 5.3.1-2) (GCC)
> > > >   GNU assembler version 2.25 (x86_64-redhat-linux) using BFD version version 2.25-15.fc23
> > > >   GNU ld version 2.25-15.fc23
> > > > 
> > > > and I'm now getting a bunch of these warnings:
> > > > 
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2e7: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2f3: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2ff: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x30b: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x317: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x323: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x32f: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x33b: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x348: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x355: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x362: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x36f: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x37c: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x389: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x396: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2e7: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2f3: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2ff: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x30b: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x317: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x323: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x32f: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x33b: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x348: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x355: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x362: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x36f: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x37c: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x389: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x396: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x19a: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1a6: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1b2: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1be: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1ca: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1d6: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1e2: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1ee: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x1ff: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x210: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x221: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x251: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x262: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x273: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x284: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x295: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2a6: frame pointer state mismatch
> > > > drivers/net/wireless/realtek/rtlwifi/base.o: warning: objtool: rtlwifi_rate_mapping()+0x2b7: frame pointer state mismatch
> > > > 
> > > > I see nothing particularly weird about rtlwifi_rate_mapping(), except the tons of 
> > > > switch statements - maybe GCC does something really clever here?
> > > > 
> > > > In any case this needs to be addressed before the merge window. Also, I think we 
> > > > should limit the number of objtool warnings to one per function?
> > > 
> > > This is a bug in objtool's handling of switch statement jump tables.  In
> > > fact, the 0-day bot warned me about this bug yesterday, but I
> > > misinterpreted it:
> > > 
> > >   https://lkml.kernel.org/r/201603060006.yNZ9xTcs%fengguang.wu@intel.com
> > > 
> > > I'll fix it up today.  I'll also limit the warnings to one per function.
> > > 
> > > BTW, I was only able to recreate this particular issue after updating to
> > > today's tip/master.  It was triggered by a new config option:
> > > CONFIG_UBSAN_SANITIZE_ALL.
> > 
> > ah, makes sense! I also upgraded to the latestest Fedora and misinterpreted the 
> > warning.
> > 
> > Btw., I like it how in other cases you didn't try to work the warning around in 
> > objtool, but improved the C code itself. We can consider this warning as a 
> > 'unnecessarily complex switch statement' warning.
> 
> So the bug is that when there's more than one switch statement in a
> function, objtool interprets all the switch jump tables as a single
> table.  If the targets of one jump table assume a stack frame and the
> targets of another one don't, you'll see frame pointer warnings like
> those above.
> 
> It *is* interesting that both functions which triggered this bug --
> rtlwifi_rate_mapping() and cik_tiling_mode_table_init() -- are cases
> where the code is way too complex and can be simplified.
> 
> But, unless we want to institute an "only one switch statement allowed
> per function" policy, I think I should still fix the bug.

Yeah, agreed!

Thanks,

	Ingo

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