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Date:   Sat, 19 May 2018 09:00:08 +0200
From:   Pavel Machek <pavel@ucw.cz>
To:     Linus Torvalds <torvalds@linux-foundation.org>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc:     Josh Poimboeuf <jpoimboe@redhat.com>,
        Alexey Dobriyan <adobriyan@gmail.com>,
        Peter Anvin <h.peter.anvin@intel.com>,
        kernel test robot <xiaolong.ye@intel.com>,
        Ingo Molnar <mingo@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Andrew Lutomirski <luto@kernel.org>,
        Borislav Petkov <bp@alien8.de>,
        Brian Gerst <brgerst@gmail.com>,
        Denys Vlasenko <dvlasenk@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Peter Anvin <hpa@zytor.com>, tipbuild@zytor.com,
        LKP <lkp@01.org>
Subject: "interesting" entry in hibernation code was Re: [lkp-robot]
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Hi!

> Side note: doing some grepping, I find some other sequences that are a bit
> scary, like this:
>=20
> arch/x86/kernel/acpi/wakeup_32.S-.data
> arch/x86/kernel/acpi/wakeup_32.S-ALIGN
> arch/x86/kernel/acpi/wakeup_32.S:ENTRY(saved_magic)     .long   0
> arch/x86/kernel/acpi/wakeup_32.S:ENTRY(saved_eip)       .long   0
>=20
> so apparently people are using ENTRY() for data too (the same pattern
> exists in wakeup_64.S).
>=20
> So we end up having those odd 0x90 bytes (now 0xcc) in the data section as
> "padding" between those two values. Crazy.

Sorry about that. I'm pretty sure intention was simply to use the
variable from C code.. and ENTRY() worked. I was not aware that it has
side effect of padding...

Let me see how this can be improved... (untested).

diff --git a/arch/x86/kernel/acpi/wakeup_32.S b/arch/x86/kernel/acpi/wakeup=
_32.S
index 0c26b1b..d6f477f 100644
--- a/arch/x86/kernel/acpi/wakeup_32.S
+++ b/arch/x86/kernel/acpi/wakeup_32.S
@@ -89,8 +89,8 @@ ret_point:
=20
 .data
 ALIGN
-ENTRY(saved_magic)	.long	0
-ENTRY(saved_eip)	.long	0
+GLOBAL(saved_magic)	.long	0
+saved_eip:	.long	0
=20
 # saved registers
 saved_idt:	.long	0,0


									Pavel
--=20
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blo=
g.html

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