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

Thomas Gleixner
2022-07-16T23:17:23Z

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@linutronix.de>
Cc: Juergen Gross <jgross@suse.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. */