Fix BPF parameter alignment to work regardless of target ABI (#21271)

docs/src/developing/on-chain-programs/overview.md

@@ -199,9 +199,8 @@ encoding is little endian):
   - 1 byte indicating if this is a duplicate account, if not a duplicate then
     the value is 0xff, otherwise the value is the index of the account it is a
     duplicate of.
-  - 7 bytes of padding
+  - If duplicate: 7 bytes of padding
-    - if not duplicate
+  - If not duplicate:
-      - 1 byte padding
     - 1 byte boolean, true if account is a signer
     - 1 byte boolean, true if account is writable
     - 1 byte boolean, true if account is executable

programs/bpf_loader/src/serialization.rs

@@ -3,7 +3,7 @@ use solana_rbpf::{aligned_memory::AlignedMemory, ebpf::HOST_ALIGN};
 use solana_sdk::{
     account::{ReadableAccount, WritableAccount},
     bpf_loader_deprecated,
-    entrypoint::MAX_PERMITTED_DATA_INCREASE,
+    entrypoint::{MAX_PERMITTED_DATA_INCREASE, PARAMETER_ALIGNMENT},
     instruction::InstructionError,
     keyed_account::KeyedAccount,
     pubkey::Pubkey,
@@ -242,7 +242,7 @@ pub fn serialize_parameters_aligned(
                 .map_err(|_| InstructionError::InvalidArgument)?;
             v.resize(
                 MAX_PERMITTED_DATA_INCREASE
-                    + (v.write_index() as *const u8).align_offset(align_of::<u128>()),
+                    + (v.write_index() as *const u8).align_offset(PARAMETER_ALIGNMENT),
                 0,
             )
             .map_err(|_| InstructionError::InvalidArgument)?;

sdk/program/src/entrypoint.rs

@@ -7,7 +7,7 @@ use alloc::vec::Vec;
 use std::{
     alloc::Layout,
     cell::RefCell,
-    mem::{align_of, size_of},
+    mem::size_of,
     ptr::null_mut,
     rc::Rc,
     // Hide Result from bindgen gets confused about generics in non-generic type declarations
@@ -252,6 +252,9 @@ unsafe impl std::alloc::GlobalAlloc for BumpAllocator {
 /// Maximum number of bytes a program may add to an account during a single realloc
 pub const MAX_PERMITTED_DATA_INCREASE: usize = 1_024 * 10;
 
+// Parameters passed to the entrypoint input buffer are aligned on 8-byte boundaries
+pub const PARAMETER_ALIGNMENT: usize = 8;
+
 /// Deserialize the input arguments
 ///
 /// The integer arithmetic in this method is safe when called on a buffer that was
@@ -309,7 +312,7 @@ pub unsafe fn deserialize<'a>(input: *mut u8) -> (&'a Pubkey, Vec<AccountInfo<'a
                 from_raw_parts_mut(input.add(offset), data_len)
             }));
             offset += data_len + MAX_PERMITTED_DATA_INCREASE;
-            offset += (offset as *const u8).align_offset(align_of::<u128>()); // padding
+            offset += (offset as *const u8).align_offset(PARAMETER_ALIGNMENT); // padding
 
             #[allow(clippy::cast_ptr_alignment)]
             let rent_epoch = *(input.add(offset) as *const u64);