fix wrong bpfUpgradeableLoader layout (#704)

Author: nonergodic

platforms/solana/src/utils/utils/bpfLoaderUpgradeable.ts

@@ -15,33 +15,45 @@ export function deriveProgramDataAddress(programId: PublicKeyInitData): PublicKe
   );
 }
 
+//the program data pda coincides with the address that's stored in the program id account (i.e. the
+//  account that's found at the program id address), which is of type UpgradeLoaderState::Program:
+//  https://docs.rs/solana-program/latest/src/solana_program/bpf_loader_upgradeable.rs.html#40-43
+export function programDataAddress(programId: PublicKeyInitData) {
+  return PublicKey.findProgramAddressSync([new PublicKey(programId).toBytes()], BPF_LOADER_UPGRADEABLE_PROGRAM_ID)[0];
+}
+
+const onChainUint = { binary: "uint", endianness: "little" } as const;
+
 const pubKeyConversion = { //TODO find a better place for this
   to: (encoded: Uint8Array) => new PublicKey(encoded),
   from: (decoded: PublicKey) => decoded.toBytes(),
 } as const satisfies CustomConversion<Uint8Array, PublicKey>;
 
-//neither anchor nor solana web3 have a built-in way to parse this
-//see here: https://docs.rs/solana-program/latest/solana_program/bpf_loader_upgradeable/enum.UpgradeableLoaderState.html
+//Describes the layout of an account that holds a UpgradeableLoaderState::ProgramData enum:
+//  https://docs.rs/solana-program/latest/src/solana_program/bpf_loader_upgradeable.rs.html#45-52
+//  because neither Anchor nor Solana web3 seem to have a built-in way to parse this.
+//The bpf_loader_upgradeable program uses Rust's serde crate and bincode to serialize its structs,
+//  which encodes enum variants as 4 byte little endian uints:
+//    https://github.com/serde-rs/serde/blob/9f8c579bf5f7478f91108c1186cd0d3f85aff29d/serde_derive/src/ser.rs#L399-L408
+//  and Options with a single byte 0 or 1 tag:
+//    https://docs.rs/bincode/latest/src/bincode/ser/mod.rs.html#137-147
+//However, even if the program is made immutable the bpf_loader_upgradeable program will keep the
+//  last value of the enum variant and only set the option byte tag to 0, presumably so they don't
+//  have to memcopy the entire subsequent bytecode (they didn't really think that one through).
+//See https://explorer.solana.com/address/GDDMwNyyx8uB6zrqwBFHjLLG3TBYk2F8Az4yrQC5RzMp
+//  as an example of an immutable program data account.
 export const programDataLayout = [
-  { name: "slot", binary: "uint", endianness: "little", size: 8 },
+  { name: "programDataEnumVariant", ...onChainUint, size: 4, custom: 3, omit: true },
+  { name: "slot", ...onChainUint, size: 8 },
   {
     name: "upgradeAuthority",
     binary: "switch",
     idSize: 1,
     idTag: "isSome",
     layouts: [
-      [[0, false], []],
-      [
-        [1, true],
-        [
-          {
-            name: "value",
-            binary: "bytes",
-            size: 32,
-            custom: pubKeyConversion,
-          },
-        ],
-      ],
+      [[0, false], [{ name: "_lastValueBeforeImmutability", binary: "bytes", size: 32 }]],
+      [[1, true], [{ name: "value", binary: "bytes", size: 32, custom: pubKeyConversion }]],
     ],
   },
+  { name: "bytecode", binary: "bytes" },
 ] as const satisfies Layout;