From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 From: Daniel Axtens Date: Thu, 21 Apr 2022 15:24:14 +1000 Subject: [PATCH] mm: Assert that we preserve header vs region alignment 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 Reviewed-by: Daniel Kiper Tested-by: Patrick Steinhardt (cherry picked from commit 1df8fe66c57087eb33bd6dc69f786ed124615aa7) --- include/grub/mm_private.h | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/include/grub/mm_private.h b/include/grub/mm_private.h index 203533cc3d..a688b92a83 100644 --- a/include/grub/mm_private.h +++ b/include/grub/mm_private.h @@ -20,6 +20,7 @@ #define GRUB_MM_PRIVATE_H 1 #include +#include /* 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