solana_program_entrypoint/

lib.rs

//! The Rust-based BPF program entrypoint supported by the latest BPF loader.
//!
//! For more information see the [`bpf_loader`] module.
//!
//! [`bpf_loader`]: crate::bpf_loader

extern crate alloc;
use {
    alloc::vec::Vec,
    solana_account_info::AccountInfo,
    solana_pubkey::Pubkey,
    std::{
        alloc::Layout,
        cell::RefCell,
        mem::{size_of, MaybeUninit},
        ptr::null_mut,
        rc::Rc,
        slice::{from_raw_parts, from_raw_parts_mut},
    },
};
// need to re-export msg for custom_heap_default macro
pub use {
    solana_account_info::MAX_PERMITTED_DATA_INCREASE, solana_msg::msg as __msg,
    solana_program_error::ProgramResult,
};

/// User implemented function to process an instruction
///
/// program_id: Program ID of the currently executing program accounts: Accounts
/// passed as part of the instruction instruction_data: Instruction data
pub type ProcessInstruction =
    fn(program_id: &Pubkey, accounts: &[AccountInfo], instruction_data: &[u8]) -> ProgramResult;

/// Programs indicate success with a return value of 0
pub const SUCCESS: u64 = 0;

/// Start address of the memory region used for program heap.
pub const HEAP_START_ADDRESS: u64 = 0x300000000;
/// Length of the heap memory region used for program heap.
pub const HEAP_LENGTH: usize = 32 * 1024;

/// Value used to indicate that a serialized account is not a duplicate
pub const NON_DUP_MARKER: u8 = u8::MAX;

/// Declare the program entrypoint and set up global handlers.
///
/// This macro emits the common boilerplate necessary to begin program
/// execution, calling a provided function to process the program instruction
/// supplied by the runtime, and reporting its result to the runtime.
///
/// It also sets up a [global allocator] and [panic handler], using the
/// [`custom_heap_default`] and [`custom_panic_default`] macros.
///
/// [`custom_heap_default`]: crate::custom_heap_default
/// [`custom_panic_default`]: crate::custom_panic_default
///
/// [global allocator]: https://doc.rust-lang.org/stable/std/alloc/trait.GlobalAlloc.html
/// [panic handler]: https://doc.rust-lang.org/nomicon/panic-handler.html
///
/// The argument is the name of a function with this type signature:
///
/// ```ignore
/// fn process_instruction(
///     program_id: &Pubkey,      // Public key of the account the program was loaded into
///     accounts: &[AccountInfo], // All accounts required to process the instruction
///     instruction_data: &[u8],  // Serialized instruction-specific data
/// ) -> ProgramResult;
/// ```
///
/// # Cargo features
///
/// This macro emits symbols and definitions that may only be defined once
/// globally. As such, if linked to other Rust crates it will cause compiler
/// errors. To avoid this, it is common for Solana programs to define an
/// optional [Cargo feature] called `no-entrypoint`, and use it to conditionally
/// disable the `entrypoint` macro invocation, as well as the
/// `process_instruction` function. See a typical pattern for this in the
/// example below.
///
/// [Cargo feature]: https://doc.rust-lang.org/cargo/reference/features.html
///
/// The code emitted by this macro can be customized by adding cargo features
/// _to your own crate_ (the one that calls this macro) and enabling them:
///
/// - If the `custom-heap` feature is defined then the macro will not set up the
///   global allocator, allowing `entrypoint` to be used with your own
///   allocator. See documentation for the [`custom_heap_default`] macro for
///   details of customizing the global allocator.
///
/// - If the `custom-panic` feature is defined then the macro will not define a
///   panic handler, allowing `entrypoint` to be used with your own panic
///   handler. See documentation for the [`custom_panic_default`] macro for
///   details of customizing the panic handler.
///
/// # Examples
///
/// Defining an entrypoint and making it conditional on the `no-entrypoint`
/// feature. Although the `entrypoint` module is written inline in this example,
/// it is common to put it into its own file.
///
/// ```no_run
/// #[cfg(not(feature = "no-entrypoint"))]
/// pub mod entrypoint {
///
///     use solana_account_info::AccountInfo;
///     use solana_program_entrypoint::entrypoint;
///     use solana_program_entrypoint::ProgramResult;
///     use solana_msg::msg;
///     use solana_pubkey::Pubkey;
///
///     entrypoint!(process_instruction);
///
///     pub fn process_instruction(
///         program_id: &Pubkey,
///         accounts: &[AccountInfo],
///         instruction_data: &[u8],
///     ) -> ProgramResult {
///         msg!("Hello world");
///
///         Ok(())
///     }
///
/// }
/// ```
#[macro_export]
macro_rules! entrypoint {
    ($process_instruction:ident) => {
        /// # Safety
        #[no_mangle]
        pub unsafe extern "C" fn entrypoint(input: *mut u8) -> u64 {
            let (program_id, accounts, instruction_data) = unsafe { $crate::deserialize(input) };
            match $process_instruction(program_id, &accounts, instruction_data) {
                Ok(()) => $crate::SUCCESS,
                Err(error) => error.into(),
            }
        }
        $crate::custom_heap_default!();
        $crate::custom_panic_default!();
    };
}

/// Declare the program entrypoint and set up global handlers.
///
/// This is similar to the `entrypoint!` macro, except that it does not perform
/// any dynamic allocations, and instead writes the input accounts into a pre-
/// allocated array.
///
/// This version reduces compute unit usage by 20-30 compute units per unique
/// account in the instruction. It may become the default option in a future
/// release.
///
/// For more information about how the program entrypoint behaves and what it
/// does, please see the documentation for [`entrypoint!`].
///
/// NOTE: This entrypoint has a hard-coded limit of 64 input accounts.
#[macro_export]
macro_rules! entrypoint_no_alloc {
    ($process_instruction:ident) => {
        /// # Safety
        #[no_mangle]
        pub unsafe extern "C" fn entrypoint(input: *mut u8) -> u64 {
            use std::mem::MaybeUninit;
            // Clippy complains about this because a `const` with interior
            // mutability `RefCell` should use `static` instead to make it
            // clear that it can change.
            // In our case, however, we want to create an array of `AccountInfo`s,
            // and the only way to do it is through a `const` expression, and
            // we don't expect to mutate the internals of this `const` type.
            #[allow(clippy::declare_interior_mutable_const)]
            const UNINIT_ACCOUNT_INFO: MaybeUninit<AccountInfo> =
                MaybeUninit::<AccountInfo>::uninit();
            const MAX_ACCOUNT_INFOS: usize = 64;
            let mut accounts = [UNINIT_ACCOUNT_INFO; MAX_ACCOUNT_INFOS];
            let (program_id, num_accounts, instruction_data) =
                unsafe { $crate::deserialize_into(input, &mut accounts) };
            // Use `slice_assume_init_ref` once it's stabilized
            let accounts = &*(&accounts[..num_accounts] as *const [MaybeUninit<AccountInfo<'_>>]
                as *const [AccountInfo<'_>]);

            #[inline(never)]
            fn call_program(program_id: &Pubkey, accounts: &[AccountInfo], data: &[u8]) -> u64 {
                match $process_instruction(program_id, accounts, data) {
                    Ok(()) => $crate::SUCCESS,
                    Err(error) => error.into(),
                }
            }

            call_program(&program_id, accounts, &instruction_data)
        }
        $crate::custom_heap_default!();
        $crate::custom_panic_default!();
    };
}

/// Define the default global allocator.
///
/// The default global allocator is enabled only if the calling crate has not
/// disabled it using [Cargo features] as described below. It is only defined
/// for [BPF] targets.
///
/// [Cargo features]: https://doc.rust-lang.org/cargo/reference/features.html
/// [BPF]: https://solana.com/docs/programs/faq#berkeley-packet-filter-bpf
///
/// # Cargo features
///
/// A crate that calls this macro can provide its own custom heap
/// implementation, or allow others to provide their own custom heap
/// implementation, by adding a `custom-heap` feature to its `Cargo.toml`. After
/// enabling the feature, one may define their own [global allocator] in the
/// standard way.
///
/// [global allocator]: https://doc.rust-lang.org/stable/std/alloc/trait.GlobalAlloc.html
///
#[macro_export]
macro_rules! custom_heap_default {
    () => {
        #[cfg(all(not(feature = "custom-heap"), target_os = "solana"))]
        #[global_allocator]
        static A: $crate::BumpAllocator = $crate::BumpAllocator {
            start: $crate::HEAP_START_ADDRESS as usize,
            len: $crate::HEAP_LENGTH,
        };
    };
}

/// Define the default global panic handler.
///
/// This must be used if the [`entrypoint`] macro is not used, and no other
/// panic handler has been defined; otherwise compilation will fail with a
/// missing `custom_panic` symbol.
///
/// The default global allocator is enabled only if the calling crate has not
/// disabled it using [Cargo features] as described below. It is only defined
/// for [BPF] targets.
///
/// [Cargo features]: https://doc.rust-lang.org/cargo/reference/features.html
/// [BPF]: https://solana.com/docs/programs/faq#berkeley-packet-filter-bpf
///
/// # Cargo features
///
/// A crate that calls this macro can provide its own custom panic handler, or
/// allow others to provide their own custom panic handler, by adding a
/// `custom-panic` feature to its `Cargo.toml`. After enabling the feature, one
/// may define their own panic handler.
///
/// A good way to reduce the final size of the program is to provide a
/// `custom_panic` implementation that does nothing. Doing so will cut ~25kb
/// from a noop program. That number goes down the more the programs pulls in
/// Rust's standard library for other purposes.
///
/// # Defining a panic handler for Solana
///
/// _The mechanism for defining a Solana panic handler is different [from most
/// Rust programs][rpanic]._
///
/// [rpanic]: https://doc.rust-lang.org/nomicon/panic-handler.html
///
/// To define a panic handler one must define a `custom_panic` function
/// with the `#[no_mangle]` attribute, as below:
///
/// ```ignore
/// #[cfg(all(feature = "custom-panic", target_os = "solana"))]
/// #[no_mangle]
/// fn custom_panic(info: &core::panic::PanicInfo<'_>) {
///     $crate::msg!("{}", info);
/// }
/// ```
///
/// The above is how Solana defines the default panic handler.
#[macro_export]
macro_rules! custom_panic_default {
    () => {
        #[cfg(all(not(feature = "custom-panic"), target_os = "solana"))]
        #[no_mangle]
        fn custom_panic(info: &core::panic::PanicInfo<'_>) {
            // Full panic reporting
            $crate::__msg!("{}", info);
        }
    };
}

/// The bump allocator used as the default rust heap when running programs.
pub struct BumpAllocator {
    pub start: usize,
    pub len: usize,
}
/// Integer arithmetic in this global allocator implementation is safe when
/// operating on the prescribed `HEAP_START_ADDRESS` and `HEAP_LENGTH`. Any
/// other use may overflow and is thus unsupported and at one's own risk.
#[allow(clippy::arithmetic_side_effects)]
unsafe impl std::alloc::GlobalAlloc for BumpAllocator {
    #[inline]
    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
        let pos_ptr = self.start as *mut usize;

        let mut pos = *pos_ptr;
        if pos == 0 {
            // First time, set starting position
            pos = self.start + self.len;
        }
        pos = pos.saturating_sub(layout.size());
        pos &= !(layout.align().wrapping_sub(1));
        if pos < self.start + size_of::<*mut u8>() {
            return null_mut();
        }
        *pos_ptr = pos;
        pos as *mut u8
    }
    #[inline]
    unsafe fn dealloc(&self, _: *mut u8, _: Layout) {
        // I'm a bump allocator, I don't free
    }
}

/// `assert_eq(std::mem::align_of::<u128>(), 8)` is true for BPF but not for some host machines
pub const BPF_ALIGN_OF_U128: usize = 8;

#[allow(clippy::arithmetic_side_effects)]
#[inline(always)] // this reduces CU usage
unsafe fn deserialize_instruction_data<'a>(input: *mut u8, mut offset: usize) -> (&'a [u8], usize) {
    #[allow(clippy::cast_ptr_alignment)]
    let instruction_data_len = *(input.add(offset) as *const u64) as usize;
    offset += size_of::<u64>();

    let instruction_data = { from_raw_parts(input.add(offset), instruction_data_len) };
    offset += instruction_data_len;

    (instruction_data, offset)
}

#[allow(clippy::arithmetic_side_effects)]
#[inline(always)] // this reduces CU usage by half!
unsafe fn deserialize_account_info<'a>(
    input: *mut u8,
    mut offset: usize,
) -> (AccountInfo<'a>, usize) {
    #[allow(clippy::cast_ptr_alignment)]
    let is_signer = *(input.add(offset) as *const u8) != 0;
    offset += size_of::<u8>();

    #[allow(clippy::cast_ptr_alignment)]
    let is_writable = *(input.add(offset) as *const u8) != 0;
    offset += size_of::<u8>();

    #[allow(clippy::cast_ptr_alignment)]
    let executable = *(input.add(offset) as *const u8) != 0;
    offset += size_of::<u8>();

    // The original data length is stored here because these 4 bytes were
    // originally only used for padding and served as a good location to
    // track the original size of the account data in a compatible way.
    let original_data_len_offset = offset;
    offset += size_of::<u32>();

    let key: &Pubkey = &*(input.add(offset) as *const Pubkey);
    offset += size_of::<Pubkey>();

    let owner: &Pubkey = &*(input.add(offset) as *const Pubkey);
    offset += size_of::<Pubkey>();

    #[allow(clippy::cast_ptr_alignment)]
    let lamports = Rc::new(RefCell::new(&mut *(input.add(offset) as *mut u64)));
    offset += size_of::<u64>();

    #[allow(clippy::cast_ptr_alignment)]
    let data_len = *(input.add(offset) as *const u64) as usize;
    offset += size_of::<u64>();

    // Store the original data length for detecting invalid reallocations and
    // requires that MAX_PERMITTED_DATA_LENGTH fits in a u32
    *(input.add(original_data_len_offset) as *mut u32) = data_len as u32;

    let data = Rc::new(RefCell::new({
        from_raw_parts_mut(input.add(offset), data_len)
    }));
    offset += data_len + MAX_PERMITTED_DATA_INCREASE;
    offset += (offset as *const u8).align_offset(BPF_ALIGN_OF_U128); // padding

    #[allow(clippy::cast_ptr_alignment)]
    let rent_epoch = *(input.add(offset) as *const u64);
    offset += size_of::<u64>();

    (
        AccountInfo {
            key,
            is_signer,
            is_writable,
            lamports,
            data,
            owner,
            executable,
            rent_epoch,
        },
        offset,
    )
}

/// Deserialize the input arguments
///
/// The integer arithmetic in this method is safe when called on a buffer that was
/// serialized by runtime. Use with buffers serialized otherwise is unsupported and
/// done at one's own risk.
///
/// # Safety
#[allow(clippy::arithmetic_side_effects)]
pub unsafe fn deserialize<'a>(input: *mut u8) -> (&'a Pubkey, Vec<AccountInfo<'a>>, &'a [u8]) {
    let mut offset: usize = 0;

    // Number of accounts present

    #[allow(clippy::cast_ptr_alignment)]
    let num_accounts = *(input.add(offset) as *const u64) as usize;
    offset += size_of::<u64>();

    // Account Infos

    let mut accounts = Vec::with_capacity(num_accounts);
    for _ in 0..num_accounts {
        let dup_info = *(input.add(offset) as *const u8);
        offset += size_of::<u8>();
        if dup_info == NON_DUP_MARKER {
            let (account_info, new_offset) = deserialize_account_info(input, offset);
            offset = new_offset;
            accounts.push(account_info);
        } else {
            offset += 7; // padding

            // Duplicate account, clone the original
            accounts.push(accounts[dup_info as usize].clone());
        }
    }

    // Instruction data

    let (instruction_data, new_offset) = deserialize_instruction_data(input, offset);
    offset = new_offset;

    // Program Id

    let program_id: &Pubkey = &*(input.add(offset) as *const Pubkey);

    (program_id, accounts, instruction_data)
}

/// Deserialize the input arguments
///
/// Differs from `deserialize` by writing the account infos into an uninitialized
/// slice, which provides better performance, roughly 30 CUs per unique account
/// provided to the instruction.
///
/// Panics if the input slice is not large enough.
///
/// The integer arithmetic in this method is safe when called on a buffer that was
/// serialized by runtime. Use with buffers serialized otherwise is unsupported and
/// done at one's own risk.
///
/// # Safety
#[allow(clippy::arithmetic_side_effects)]
pub unsafe fn deserialize_into<'a>(
    input: *mut u8,
    accounts: &mut [MaybeUninit<AccountInfo<'a>>],
) -> (&'a Pubkey, usize, &'a [u8]) {
    let mut offset: usize = 0;

    // Number of accounts present

    #[allow(clippy::cast_ptr_alignment)]
    let num_accounts = *(input.add(offset) as *const u64) as usize;
    offset += size_of::<u64>();

    if num_accounts > accounts.len() {
        panic!(
            "{} accounts provided, but only {} are supported",
            num_accounts,
            accounts.len()
        );
    }

    // Account Infos

    for i in 0..num_accounts {
        let dup_info = *(input.add(offset) as *const u8);
        offset += size_of::<u8>();
        if dup_info == NON_DUP_MARKER {
            let (account_info, new_offset) = deserialize_account_info(input, offset);
            offset = new_offset;
            accounts[i].write(account_info);
        } else {
            offset += 7; // padding

            // Duplicate account, clone the original
            accounts[i].write(accounts[dup_info as usize].assume_init_ref().clone());
        }
    }

    // Instruction data

    let (instruction_data, new_offset) = deserialize_instruction_data(input, offset);
    offset = new_offset;

    // Program Id

    let program_id: &Pubkey = &*(input.add(offset) as *const Pubkey);

    (program_id, num_accounts, instruction_data)
}

#[cfg(test)]
mod test {
    use {super::*, std::alloc::GlobalAlloc};

    #[test]
    fn test_bump_allocator() {
        // alloc the entire
        {
            let heap = [0u8; 128];
            let allocator = BumpAllocator {
                start: heap.as_ptr() as *const _ as usize,
                len: heap.len(),
            };
            for i in 0..128 - size_of::<*mut u8>() {
                let ptr = unsafe {
                    allocator.alloc(Layout::from_size_align(1, size_of::<u8>()).unwrap())
                };
                assert_eq!(
                    ptr as *const _ as usize,
                    heap.as_ptr() as *const _ as usize + heap.len() - 1 - i
                );
            }
            assert_eq!(null_mut(), unsafe {
                allocator.alloc(Layout::from_size_align(1, 1).unwrap())
            });
        }
        // check alignment
        {
            let heap = [0u8; 128];
            let allocator = BumpAllocator {
                start: heap.as_ptr() as *const _ as usize,
                len: heap.len(),
            };
            let ptr =
                unsafe { allocator.alloc(Layout::from_size_align(1, size_of::<u8>()).unwrap()) };
            assert_eq!(0, ptr.align_offset(size_of::<u8>()));
            let ptr =
                unsafe { allocator.alloc(Layout::from_size_align(1, size_of::<u16>()).unwrap()) };
            assert_eq!(0, ptr.align_offset(size_of::<u16>()));
            let ptr =
                unsafe { allocator.alloc(Layout::from_size_align(1, size_of::<u32>()).unwrap()) };
            assert_eq!(0, ptr.align_offset(size_of::<u32>()));
            let ptr =
                unsafe { allocator.alloc(Layout::from_size_align(1, size_of::<u64>()).unwrap()) };
            assert_eq!(0, ptr.align_offset(size_of::<u64>()));
            let ptr =
                unsafe { allocator.alloc(Layout::from_size_align(1, size_of::<u128>()).unwrap()) };
            assert_eq!(0, ptr.align_offset(size_of::<u128>()));
            let ptr = unsafe { allocator.alloc(Layout::from_size_align(1, 64).unwrap()) };
            assert_eq!(0, ptr.align_offset(64));
        }
        // alloc entire block (minus the pos ptr)
        {
            let heap = [0u8; 128];
            let allocator = BumpAllocator {
                start: heap.as_ptr() as *const _ as usize,
                len: heap.len(),
            };
            let ptr =
                unsafe { allocator.alloc(Layout::from_size_align(120, size_of::<u8>()).unwrap()) };
            assert_ne!(ptr, null_mut());
            assert_eq!(0, ptr.align_offset(size_of::<u64>()));
        }
    }
}