Solana Memo Program - sBPF Assembly

A Solana memo program written in pure sBPF assembly with type safety and test coverage.

Overview

This project demonstrates how to build Solana programs directly in assembly language. The memo program accepts text messages and logs them to the blockchain, implemented in sBPF assembly.

Features

• Pure sBPF Assembly - Written directly in assembly
• No Signer Requirement - Accepts 0+ accounts (matches official Solana Memo Program)
• Empty Memo Protection - Rejects transactions with no memo text
• Type-Safe TypeScript - type definitions with runtime validation
• Comprehensive Testing - 7 test cases covering all scenarios
• Error Code Validation - Typed error codes with human-readable messages
• Code Quality - Proper error handling and edge case coverage

Installation

1. Clone the repository

   git clone https://github.com/Code-Parth/memo-program-sbpf.git

   cd memo-program-sbpf

2. Install dependencies

   yarn install

3. Start local Solana validator (in a separate terminal)

   solana-test-validator

4. Generate program keypair

   solana-keygen new --outfile deploy/memo-program-sbpf-keypair.json --force --no-passphrase

Project Structure

memo-program-ts/
├── src/
│   └── memo-program-ts/
│       └── memo-program-ts.s             # sBPF assembly source code
├── tests/
│   ├── types.ts                          # TypeScript type definitions
│   └── memo-program-sbpf.test.ts         # Comprehensive test suite
├── deploy/
│   └── memo-program-sbpf-keypair.json    # Program keypair (generated)
├── package.json                          # Node.js dependencies
├── tsconfig.json                         # TypeScript configuration
└── README.md                             # This file

Usage

Available Commands

# Compile the assembly program
sbpf build

# Deploy to local validator
sbpf deploy

# Run tests
sbpf test
# or
yarn test

# Build, deploy, and test in one command
sbpf e2e

Quick Start Workflow

# 1. Start validator (separate terminal)
solana-test-validator

# 2. Build, deploy, and test
sbpf e2e

How It Works

Assembly Program Logic

The memo program (src/memo-program-sbpf/memo-program-sbpf.s) follows this flow:

1. Read Account Count - Load number of accounts from input buffer
2. Fast Path Check - If zero accounts, jump directly to instruction data
3. Skip Accounts - Efficiently iterate through accounts (real and duplicate) to reach instruction data
4. Read Memo Data - Extract instruction data length and pointer
5. Validate Length - Ensure memo is not empty (error 0x1 if empty)
6. Log Memo - Call sol_log_ syscall to log the memo text
7. Return Success - Exit with code 0

Memory Layout (Aligned BPF Format)

The program parses Solana's aligned BPF input buffer:

Offset 0x00: num_accounts (8 bytes)

For each account:
  +0x00: marker (1 byte) - 0xFF for real, index for duplicate
  +0x01: is_signer (1 byte)
  +0x02: is_writable (1 byte)
  +0x03: is_executable (1 byte)
  +0x04: padding (4 bytes)
  +0x08: pubkey (32 bytes)
  +0x28: owner (32 bytes)
  +0x48: lamports (8 bytes)
  +0x50: data_len (8 bytes)
  +0x58: data (data_len bytes)
  +0x58+data_len: reserved (10,240 bytes) - MAX_PERMITTED_DATA_INCREASE
  +0x58+data_len+10240: rent_epoch (8 bytes)

Total account size = 10,336 + data_len

After all accounts:
  instruction_data_len (8 bytes)
  instruction_data (variable bytes) - the memo text

Key Insight: Account Size Calculation

The critical fix was calculating the correct account size:

.equ MAX_PERMITTED_DATA_INCREASE, 10240
.equ ACCOUNT_FIXED_SIZE, 10336          # 88 + 10240 + 8

add64 r7, ACCOUNT_FIXED_SIZE            # Add 10336
add64 r7, r3                            # Add data_len

Testing

Test Suite

The project includes 7 comprehensive tests:

#	Test Name	Description	Expected Result
1	Valid memo with signer	Standard memo operation	✅ Success
2	Memo without signer	No signer required (optimized)	✅ Success
3	Empty memo	Zero-length instruction data	❌ Error 0x1
4	Long memo (256+ chars)	Large instruction data	✅ Success
5	Multiple memos	3 memos in one transaction	✅ All logged
6	Multiple signers	3 signers on one memo	✅ Success
7	Type validation	TypeScript type safety checks	✅ All types valid

Running Tests

# Run all tests
yarn test

# Run tests with sbpf (includes build & deploy)
sbpf e2e

Error Codes

Code	Hex	Name	Description
0	0x0	Success	Transaction completed successfully
1	0x1	EmptyMemo	Instruction data is empty (no memo text)

Development

Modifying the Assembly Program

1. Edit src/memo-program-ts/memo-program-ts.s
2. Rebuild: sbpf build
3. Deploy: sbpf deploy
4. Test: yarn test

Adding New Tests

1. Open tests/memo-program-sbpf.test.ts
2. Add new test case:

   it("should handle your test case", async function () {
     // Your test logic here
   });

3. Run: yarn test

Resources

sBPF & Assembly

• Blueshift sBPF Course
• Assembly Memo Challenge
• sBPF GitHub

Solana Development

• Solana Docs
• Solana Cookbook
• BPF Loader Source

TypeScript & Testing

• Mocha Documentation
• Chai Assertions
• TypeScript Handbook

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

1. Fork the repository
2. Create your feature branch (git checkout -b feature/AmazingFeature)
3. Commit your changes (git commit -m 'Add some AmazingFeature')
4. Push to the branch (git push origin feature/AmazingFeature)
5. Open a Pull Request

License

This project is licensed under the MIT License.

Acknowledgments

• Built with sBPF by Blueshift
• Inspired by the Blueshift Assembly Course
• Solana BPF loader serialisation format