On Fri, Feb 09, 2024 at 09:32:04PM +0100, Lukas Wunner wrote: > On Tue, Oct 03, 2023 at 01:35:26PM +0300, Ilpo Järvinen wrote: > > On Thu, 28 Sep 2023, Lukas Wunner wrote: > > > + spdm_state->responder_caps = le32_to_cpu(rsp->flags); > > > > Earlier, unaligned accessors where used with the version_number_entries. > > Is it intentional they're not used here (I cannot see what would be > > reason for this difference)? > > Thanks, good catch. Indeed this is not necessarily naturally aligned > because the GET_CAPABILITIES request and response succeeds the > GET_VERSION response in the same allocation. And the GET_VERSION > response size is a multiple of 2, but not always a multiple of 4. Actually, scratch that. I've realized that since all the SPDM request/response structs are declared __packed, the alignment requirement for the struct members becomes 1 byte and hence they're automatically accessed byte-wise on arches which require that: https://stackoverflow.com/questions/73152859/accessing-unaligned-struct-member-using-pointers#73154825 E.g. this line... req->data_transfer_size = cpu_to_le32(spdm_state->transport_sz); ...becomes this on arm 32-bit (multi_v4t_defconfig)... ldr r3, [r5, #0x1c] ; load spdm_state->transport_sz into r3 lsr r2, r3, lsr #8 ; right-shift r3 into r2 by 8 bits strb r3, [r7, #0xc] ; copy lowest byte from r3 into request strb r2, [r7, #0xd] ; copy next byte from r2 into request lsr r2, r3, lsr #16 ; right-shift r3 into r2 by 16 bits lsr r3, r3, lsr #24 ; right-shift r3 into r3 by 24 bits strb r2, [r7, #0xe] ; copy next byte from r2 into request strb r3, [r7, #0xf] ; copy next byte from r3 into request ...and it becomes this on x64_64, which has no alignment requirements: mov eax, dword [r15+0x40] ; load spdm_state->transport_sz mov dword [r12+0xc], eax ; copy into request So for __packed structs, get_unaligned_*() / put_unaligned_*() accessors are not necessary and I will drop them when respinning. Thanks, Lukas
