On 2/21/24 6:03 PM, 'Andrew Cooper' via trenchboot-devel wrote:
On 15/02/2024 8:08 am, Ard Biesheuvel wrote:
On Wed, 14 Feb 2024 at 23:31, Ross Philipson <ross.philipson@xxxxxxxxxx> wrote:
+/*
+ * Primary SLR Table Header
I know it's just a comment, but SLR ought to be written in longhand here.
Will do, thanks. Ross.
+ */
+struct slr_table {
+ u32 magic;
+ u16 revision;
+ u16 architecture;
+ u32 size;
+ u32 max_size;
+ /* entries[] */
+} __packed;
Packing this struct has no effect on the layout so better drop the
__packed here. If this table is part of a structure that can appear
misaligned in memory, better to pack the outer struct or deal with it
there in another way.
As you note, __packed does two things not one.
The consumer of the random integer that is expected to be a pointer to a
struct lsr_table doesn't know whether it was invoked by a 16bit
bootloader or a 32bit bootloader, and this really does make a difference
for an ABI described only in C.
Then again, we're holding off on setting the spec in stone until there's
an agreement in principle, so we could retrofit a statement about the
expected alignment of this structure in memory.
The sane choices are either 8b alignment (there are uint64_t's in
entires[], but I also see there are some misaligned uint64_t's too,
which is dull), or using the good old x86 fallback or paragraph
alignment just in case we really want to extend it with a uint128_t in
future.
Thoughts?
~Andrew
