Cleanup unsupported sysvars (#16390)

* Cleanup unsupported sysvars

* fix ser description

sdk/program/src/sysvar/instructions.rs

@@ -1,14 +1,14 @@
 #![allow(clippy::integer_arithmetic)]
 //! This account contains the serialized transaction instructions
 
-use crate::{instruction::Instruction, sanitize::SanitizeError, sysvar::Sysvar};
+use crate::{instruction::Instruction, sanitize::SanitizeError};
 
-pub type Instructions = Vec<Instruction>;
+// Instructions Sysvar, dummy type, use the associated helpers instead of the Sysvar trait
+pub struct Instructions();
 
 crate::declare_sysvar_id!("Sysvar1nstructions1111111111111111111111111", Instructions);
 
-impl Sysvar for Instructions {}
-
+/// Load the current instruction's index from the Instructions Sysvar data
 pub fn load_current_index(data: &[u8]) -> u16 {
     let mut instr_fixed_data = [0u8; 2];
     let len = data.len();
@@ -16,11 +16,13 @@ pub fn load_current_index(data: &[u8]) -> u16 {
     u16::from_le_bytes(instr_fixed_data)
 }
 
+/// Store the current instruction's index in the Instructions Sysvar data
 pub fn store_current_index(data: &mut [u8], instruction_index: u16) {
     let last_index = data.len() - 2;
     data[last_index..last_index + 2].copy_from_slice(&instruction_index.to_le_bytes());
 }
 
+/// Load an instruction at the specified index
 pub fn load_instruction_at(index: usize, data: &[u8]) -> Result<Instruction, SanitizeError> {
     crate::message::Message::deserialize_instruction(index, data)
 }

sdk/program/src/sysvar/slot_hashes.rs

@@ -4,7 +4,7 @@
 //!
 pub use crate::slot_hashes::SlotHashes;
 
-use crate::sysvar::Sysvar;
+use crate::{account_info::AccountInfo, program_error::ProgramError, sysvar::Sysvar};
 
 crate::declare_sysvar_id!("SysvarS1otHashes111111111111111111111111111", SlotHashes);
 
@@ -14,6 +14,10 @@ impl Sysvar for SlotHashes {
         // hard-coded so that we don't have to construct an empty
         20_488 // golden, update if MAX_ENTRIES changes
     }
+    fn from_account_info(_account_info: &AccountInfo) -> Result<Self, ProgramError> {
+        // This sysvar is too large to bincode::deserialize in-program
+        Err(ProgramError::UnsupportedSysvar)
+    }
 }
 
 #[cfg(test)]

sdk/program/src/sysvar/slot_history.rs

@@ -1,9 +1,11 @@
 //! named accounts for synthesized data accounts for bank state, etc.
 //!
 //! this account carries a bitvector of slots present over the past
-//!   epoch
+//! epoch
 //!
-pub use crate::slot_history::SlotHistory;
+pub use crate::{
+    account_info::AccountInfo, program_error::ProgramError, slot_history::SlotHistory,
+};
 
 use crate::sysvar::Sysvar;
 
@@ -15,6 +17,10 @@ impl Sysvar for SlotHistory {
         // hard-coded so that we don't have to construct an empty
         131_097 // golden, update if MAX_ENTRIES changes
     }
+    fn from_account_info(_account_info: &AccountInfo) -> Result<Self, ProgramError> {
+        // This sysvar is too large to bincode::deserialize in-program
+        Err(ProgramError::UnsupportedSysvar)
+    }
 }
 
 #[cfg(test)]