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Date: Tue, 8 Mar 2016 14:44:57 +0100
From: Ingo Molnar <mingo@...nel.org>
To: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
linux-kernel@...r.kernel.org, live-patching@...r.kernel.org,
Michal Marek <mmarek@...e.cz>,
Peter Zijlstra <peterz@...radead.org>,
Andy Lutomirski <luto@...nel.org>,
Borislav Petkov <bp@...en8.de>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Andi Kleen <andi@...stfloor.org>,
Pedro Alves <palves@...hat.com>,
Namhyung Kim <namhyung@...il.com>,
Bernd Petrovitsch <bernd@...rovitsch.priv.at>,
Chris J Arges <chris.j.arges@...onical.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Jiri Slaby <jslaby@...e.cz>,
Arnaldo Carvalho de Melo <acme@...nel.org>
Subject: Re: [PATCH v19 00/10] Compile-time stack metadata validation
* Josh Poimboeuf <jpoimboe@...hat.com> wrote:
> On Tue, Mar 08, 2016 at 11:37:16AM +0100, Ingo Molnar wrote:
> >
> > * Josh Poimboeuf <jpoimboe@...hat.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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