The current alignment of 4 bytes is too low. Access to 64-bit data via ldrd/strd requires at least an eight byte alignment: | Prior to ARMv6, if the memory address is not 64-bit aligned, the | data read from memory is UNPREDICTABLE. Alignment checking (taking | a data abort), and support for a big-endian (BE-32) data format are | implementation options. We already have at least an 8 byte alignment for dlmalloc, so have TLSF follow suit by aligning the accounting structures appropriately. Instead of adding manual padding, we could also enlarge block_header_t::size to an uint64_t unconditionally, but mark block_header_t __packed. This comes with a runtime cost though or ugly __builtin_assume_aligned annotations, so we stick to the simpler version. Reported-by: Enrico Scholz <enrico.scholz@xxxxxxxxxxxxxxxxx> Link: https://lore.barebox.org/barebox/ly7d1z1qvs.fsf@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ Signed-off-by: Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx> --- common/tlsf.c | 12 ++++++------ include/linux/bitops.h | 1 + 2 files changed, 7 insertions(+), 6 deletions(-) diff --git a/common/tlsf.c b/common/tlsf.c index 0986c7c457e3..692dabbdedd9 100644 --- a/common/tlsf.c +++ b/common/tlsf.c @@ -30,13 +30,8 @@ enum tlsf_public /* Private constants: do not modify. */ enum tlsf_private { -#if defined (TLSF_64BIT) /* All allocation sizes and addresses are aligned to 8 bytes. */ ALIGN_SIZE_LOG2 = 3, -#else - /* All allocation sizes and addresses are aligned to 4 bytes. */ - ALIGN_SIZE_LOG2 = 2, -#endif ALIGN_SIZE = (1 << ALIGN_SIZE_LOG2), /* @@ -122,6 +117,7 @@ typedef struct block_header_t /* The size of this block, excluding the block header. */ size_t size; + u32 : BYTES_TO_BITS(ALIGN_SIZE - sizeof(size_t)); /* Next and previous free blocks. */ struct block_header_t* next_free; @@ -142,7 +138,7 @@ typedef struct block_header_t ** The prev_phys_block field is stored *inside* the previous free block. */ #define block_header_shift offsetof(block_header_t, size) -#define block_header_overhead sizeof(size_t) +#define block_header_overhead ALIGN_SIZE /* User data starts directly after the size field in a used block. */ #define block_start_offset (block_header_shift + block_header_overhead) @@ -155,6 +151,8 @@ typedef struct block_header_t #define block_size_min (sizeof(block_header_t) - sizeof(block_header_t*)) #define block_size_max (tlsf_cast(size_t, 1) << FL_INDEX_MAX) +tlsf_static_assert(block_size_min % ALIGN_SIZE == 0); +tlsf_static_assert(block_size_max % ALIGN_SIZE == 0); /* The TLSF control structure. */ typedef struct control_t @@ -165,10 +163,12 @@ typedef struct control_t /* Bitmaps for free lists. */ unsigned int fl_bitmap; unsigned int sl_bitmap[FL_INDEX_COUNT]; + u32 : BYTES_TO_BITS(ALIGN_SIZE - sizeof(size_t)); /* Head of free lists. */ block_header_t* blocks[FL_INDEX_COUNT][SL_INDEX_COUNT]; } control_t; +tlsf_static_assert(sizeof(control_t) % ALIGN_SIZE == 0); /* A type used for casting when doing pointer arithmetic. */ typedef ptrdiff_t tlsfptr_t; diff --git a/include/linux/bitops.h b/include/linux/bitops.h index a5f6ac6545ee..b0d6ca6ac87f 100644 --- a/include/linux/bitops.h +++ b/include/linux/bitops.h @@ -19,6 +19,7 @@ #define BITS_TO_U64(nr) DIV_ROUND_UP(nr, BITS_PER_TYPE(u64)) #define BITS_TO_U32(nr) DIV_ROUND_UP(nr, BITS_PER_TYPE(u32)) #define BITS_TO_BYTES(nr) DIV_ROUND_UP(nr, BITS_PER_TYPE(char)) +#define BYTES_TO_BITS(nb) (((BITS_PER_LONG * (nb)) / sizeof(long))) #endif /* -- 2.39.2
