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mm: Assert that we preserve header vs region alignment

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grub_mm_region_init() does:

  h = (grub_mm_header_t) (r + 1);

where h is a grub_mm_header_t and r is a grub_mm_region_t.

Cells are supposed to be GRUB_MM_ALIGN aligned, but while grub_mm_dump
ensures this vs the region header, grub_mm_region_init() does not.

It's better to be explicit than implicit here: rather than changing
grub_mm_region_init() to ALIGN_UP(), require that the struct is
explicitly a multiple of the header size.

Signed-off-by: Daniel Axtens <dja@axtens.net>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Tested-by: Patrick Steinhardt <ps@pks.im>
This commit is contained in:
Daniel Axtens 2022-04-21 15:24:14 +10:00 committed by Daniel Kiper
parent 188d2ff1c3
commit 1df8fe66c5
1 changed files with 14 additions and 0 deletions
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14
include/grub/mm_private.h
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@ -20,6 +20,7 @@
#define GRUB_MM_PRIVATE_H 1
#include <grub/mm.h>
#include <grub/misc.h>
/* For context, see kern/mm.c */
@ -89,4 +90,17 @@ typedef struct grub_mm_region
extern grub_mm_region_t EXPORT_VAR (grub_mm_base);
#endif
static inline void
grub_mm_size_sanity_check (void) {
/* Ensure we preserve alignment when doing h = (grub_mm_header_t) (r + 1). */
COMPILE_TIME_ASSERT ((sizeof (struct grub_mm_region) %
sizeof (struct grub_mm_header)) == 0);
/*
* GRUB_MM_ALIGN is supposed to represent cell size, and a mm_header is
* supposed to be 1 cell.
*/
COMPILE_TIME_ASSERT (sizeof (struct grub_mm_header) == GRUB_MM_ALIGN);
}
#endif