From: Borislav Petkov <bp@alien8.de>
To: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: X86 ML <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Oleg Nesterov <oleg@redhat.com>,
Andy Lutomirski <luto@amacapital.net>
Subject: Re: [PATCH] x86/xsave: Robustify and merge macros
Date: Fri, 3 Apr 2015 19:06:25 +0200 [thread overview]
Message-ID: <20150403170625.GJ3418@pd.tnic> (raw)
In-Reply-To: <20150403154055.GF14902@chrystal.uk.oracle.com>
On Fri, Apr 03, 2015 at 05:40:55PM +0200, Quentin Casasnovas wrote:
> So yeah I still think we're not properly padding, if you take my earlier
> example where repl2 = 5 bytes, repl1 = 4 bytes and orin_insn = 3.
>
> I'll let you re-read my original mail and come back to me to tell me what'd
> I really miss! :)
Dammit, dammit, dammit!
And I thought this aspect was taken care of. I went into the old
branches where I had done this and there I have:
+#define OLDINSTR_2(oldinstr, num1, num2) \
+ __OLDINSTR(oldinstr, num1) \
+ ".skip -(((" alt_rlen(num2) ")-(" alt_rlen(num1) ")) > 0) * " \
+ "((" alt_rlen(num2) ")-(" alt_rlen(num1) ")),0x90\n" \
+ alt_end_marker ":\n"
+
without the size of the orig_insn factored in into the padding.
And that would work for your example because it would add 1+1 bytes
padding.
Basically, the idea was:
.skip len(repl1) - len(orig), 0x90
.skip len(repl2) - len(repl1), 0x90
BUT!, for some reason I changed it to what's there now and I can't
remember why anymore.
IOW, this should fix your example but I need to think about it on a
clear head first, to try to remember what was the problem with that
original approach:
---
diff --git a/arch/x86/include/asm/alternative-asm.h b/arch/x86/include/asm/alternative-asm.h
index 524bddce0b76..708838260f7c 100644
--- a/arch/x86/include/asm/alternative-asm.h
+++ b/arch/x86/include/asm/alternative-asm.h
@@ -50,7 +50,7 @@
\oldinstr
141:
.skip -(((144f-143f)-(141b-140b)) > 0) * ((144f-143f)-(141b-140b)),0x90
- .skip -(((145f-144f)-(144f-143f)-(141b-140b)) > 0) * ((145f-144f)-(144f-143f)-(141b-140b)),0x90
+ .skip -(((145f-144f)-(144f-143f)) > 0) * ((145f-144f)-(144f-143f)),0x90
142:
.pushsection .altinstructions,"a"
diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index 5aef6a97d80e..2b8cc1dd7dbf 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -101,8 +101,8 @@ static inline int alternatives_text_reserved(void *start, void *end)
*/
#define OLDINSTR_2(oldinstr, num1, num2) \
__OLDINSTR(oldinstr, num1) \
- ".skip -(((" alt_rlen(num2) ")-(" alt_rlen(num1) ")-(662b-661b)) > 0) * " \
- "((" alt_rlen(num2) ")-(" alt_rlen(num1) ")-(662b-661b)),0x90\n" \
+ ".skip -(((" alt_rlen(num2) ")-(" alt_rlen(num1) ")) > 0) * " \
+ "((" alt_rlen(num2) ")-(" alt_rlen(num1) ")),0x90\n" \
alt_end_marker ":\n"
#define ALTINSTR_ENTRY(feature, num) \
---
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
--
next prev parent reply other threads:[~2015-04-03 17:08 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-02 13:11 [PATCH] x86/xsave: Robustify and merge macros Borislav Petkov
2015-04-02 15:52 ` Quentin Casasnovas
2015-04-02 16:12 ` Borislav Petkov
2015-04-02 16:33 ` Quentin Casasnovas
2015-04-02 16:45 ` Borislav Petkov
2015-04-03 14:06 ` Quentin Casasnovas
2015-04-03 14:14 ` Quentin Casasnovas
2015-04-03 15:23 ` Borislav Petkov
2015-04-03 15:40 ` Quentin Casasnovas
2015-04-03 17:06 ` Borislav Petkov [this message]
2015-04-03 17:33 ` Quentin Casasnovas
2015-04-03 17:48 ` Borislav Petkov
2015-04-03 20:42 ` Quentin Casasnovas
2015-04-04 7:34 ` Borislav Petkov
2015-04-04 8:36 ` Quentin Casasnovas
2015-04-04 9:25 ` Borislav Petkov
2015-04-04 10:11 ` Quentin Casasnovas
2015-04-04 10:29 ` Borislav Petkov
2015-04-04 13:32 ` Borislav Petkov
2015-04-04 13:34 ` [PATCH] x86/alternatives: Fix ALTERNATIVE_2 padding generation properly Borislav Petkov
2015-04-07 9:27 ` Quentin Casasnovas
2015-04-07 9:40 ` [tip:x86/asm] " tip-bot for Borislav Petkov
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