linux-kernel - [patch 01/38] x86/paravirt: Ensure proper alignment

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Message-ID: <20220716230952.727288644@linutronix.de>
Date:   Sun, 17 Jul 2022 01:17:11 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org, Linus Torvalds <torvalds@...ux-foundation.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Andrew Cooper <Andrew.Cooper3@...rix.com>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Johannes Wikner <kwikner@...z.ch>,
        Alyssa Milburn <alyssa.milburn@...ux.intel.com>,
        Jann Horn <jannh@...gle.com>, "H.J. Lu" <hjl.tools@...il.com>,
        Joao Moreira <joao.moreira@...el.com>,
        Joseph Nuzman <joseph.nuzman@...el.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Juergen Gross <jgross@...e.com>
Subject: [patch 01/38] x86/paravirt: Ensure proper alignment

The entries in the .parainstr sections are 8 byte aligned and the
corresponding C struct makes the array offset 16 bytes.

Though the pushed entries are only using 12 bytes. .parainstr_end is
therefore 4 bytes short.

That works by chance because it's only used in a loop:

     for (p = start; p < end; p++)

But this falls flat when calculating the number of elements:

    n = end - start

That's obviously off by one.

Ensure that the gap is filled and the last entry is occupying 16 bytes.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Juergen Gross <jgross@...e.com>
---
 arch/x86/include/asm/paravirt.h       |    1 +
 arch/x86/include/asm/paravirt_types.h |    1 +
 2 files changed, 2 insertions(+)

--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -743,6 +743,7 @@ extern void default_banner(void);
 	 word 771b;				\
 	 .byte ptype;				\
 	 .byte 772b-771b;			\
+	 _ASM_ALIGN;				\
 	.popsection
 
 
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -294,6 +294,7 @@ extern struct paravirt_patch_template pv
 	"  .byte " type "\n"				\
 	"  .byte 772b-771b\n"				\
 	"  .short " clobber "\n"			\
+	_ASM_ALIGN "\n"					\
 	".popsection\n"
 
 /* Generate patchable code, with the default asm parameters. */