[tip: x86/paravirt] x86/paravirt: Ensure proper alignment

tip-bot2 for Thomas Gleixner
2022-09-21T11:08:51Z

The following commit has been merged into the x86/paravirt branch of tip:

Commit-ID: f92ff8f5dca2acfa475842c71212657b0703c3be
Gitweb: https://git.kernel.org/tip/f92ff8f5dca2acfa475842c71212657b0703c3be
Author: Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Thu, 15 Sep 2022 13:10:40 +02:00
Committer: Borislav Petkov <bp@suse.de>
CommitterDate: Wed, 21 Sep 2022 12:30:16 +02:00

x86/paravirt: Ensure proper alignment

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

Though the pushed entries are only using 12 bytes, __parainstructions_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.

[ bp: Add the proper struct and section names. ]

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20220915111142.992398801@infradead.org
---
arch/x86/include/asm/paravirt.h | 1 +
arch/x86/include/asm/paravirt_types.h | 1 +
2 files changed, 2 insertions(+)

diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index 964442b..2a0b8dd 100644
--- 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

diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index 89df6c6..27b036a 100644
--- 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_ops;
" .byte " type "\n" \
" .byte 772b-771b\n" \
" .short " clobber "\n" \
+ _ASM_ALIGN "\n" \
".popsection\n"

/* Generate patchable code, with the default asm parameters. */