On Tue, Mar 10, 2020 at 07:58:28PM +0100, Patrick Steinhardt wrote: > By default, GRUB will allocate a quarter of the pages it got available > in the EFI subsystem. On many current systems, this will amount to > roughly 800MB of RAM assuming an address space of 32 bits. This is > plenty for most use cases, but it doesn't suffice when using full disk > encryption with a key derival function based on Argon2. > > Besides the usual iteration count known from PBKDF2, Argon2 introduces > two additional parameters "memory" and "parallelism". While the latter > doesn't really matter to us, the memory parameter is quite interesting. > If encrypting a partition with LUKS2 using Argon2 as KDF, then > cryptsetup will default to a memory parameter of 1GB. Meaning we need to > allocate a buffer of 1GB in size in order to be able to derive the key, > which definitely won't squeeze into the limit of 800MB. > > To prepare for Argon2, this commit reworks the memory allocation > algorithm for EFI platforms. Instead of trying to allocate a quarter of > memory available, let's instead introduce a constant target amount of > bytes that we try to allocate. The target is set to the previous value > of MAX_HEAP_SIZE, which amounts to 1.6GB and thus sufficiently high to > accomodate for both Argon2 as well as other functionality. The value is > then clamped to at most half of available memory but at least 100MB.
It seems to me that 0x100000 (MIN_HEAP_PAGES) equals to 1 MiB... > Signed-off-by: Patrick Steinhardt <p...@pks.im> > --- > grub-core/kern/efi/mm.c | 21 +++++++++++---------- > 1 file changed, 11 insertions(+), 10 deletions(-) > > diff --git a/grub-core/kern/efi/mm.c b/grub-core/kern/efi/mm.c > index b02fab1b1..367a726c6 100644 > --- a/grub-core/kern/efi/mm.c > +++ b/grub-core/kern/efi/mm.c > @@ -39,8 +39,8 @@ > #define MEMORY_MAP_SIZE 0x3000 > > /* The minimum and maximum heap size for GRUB itself. */ > -#define MIN_HEAP_SIZE 0x100000 > -#define MAX_HEAP_SIZE (1600 * 0x100000) > +#define MIN_HEAP_PAGES BYTES_TO_PAGES( 0x100000) > +#define TARGET_HEAP_PAGES BYTES_TO_PAGES(1600 * 0x100000) > > static void *finish_mmap_buf = 0; > static grub_efi_uintn_t finish_mmap_size = 0; > @@ -559,7 +559,7 @@ grub_efi_mm_init (void) > grub_efi_uintn_t map_size; > grub_efi_uintn_t desc_size; > grub_efi_uint64_t total_pages; > - grub_efi_uint64_t required_pages; > + grub_efi_uint64_t target_heap_pages; > int mm_status; > > /* Prepare a memory region to store two memory maps. */ > @@ -599,14 +599,15 @@ grub_efi_mm_init (void) > filtered_memory_map_end = filter_memory_map (memory_map, > filtered_memory_map, > desc_size, memory_map_end); > > - /* By default, request a quarter of the available memory. */ > + /* By default, request TARGET_HEAP_PAGES pages. If that exceeds half of > meory > + * available, clamp it, but request at least MIN_HEAP_PAGES. */ > total_pages = get_total_pages (filtered_memory_map, desc_size, > filtered_memory_map_end); > - required_pages = (total_pages >> 2); > - if (required_pages < BYTES_TO_PAGES (MIN_HEAP_SIZE)) > - required_pages = BYTES_TO_PAGES (MIN_HEAP_SIZE); > - else if (required_pages > BYTES_TO_PAGES (MAX_HEAP_SIZE)) > - required_pages = BYTES_TO_PAGES (MAX_HEAP_SIZE); > + target_heap_pages = TARGET_HEAP_PAGES; > + if (target_heap_pages > (total_pages / 2)) > + target_heap_pages = total_pages / 2; > + if (target_heap_pages < MIN_HEAP_PAGES) > + target_heap_pages = MIN_HEAP_PAGES; target_heap_pages = grub_min (total_pages / 2, TARGET_HEAP_PAGES); target_heap_pages = grub_max (target_heap_pages, MIN_HEAP_PAGES); Except that algorithm LGTM. Leif? Daniel _______________________________________________ Grub-devel mailing list Grub-devel@gnu.org https://lists.gnu.org/mailman/listinfo/grub-devel
