CPI Account Reuse

[Lichtso]

Problem

CPI needs an overhaul for inter-operation between the two ABI versions (see #19191).

• The code around CPI is hard to read & understand, needs cleanup
• native_invoke performs two unnecessary account copy steps:
  • Rc::new(keyed_account.account.clone())
  • dst_keyed_account.try_account_ref_mut()?.set_data(src_keyed_account.data().to_vec());
• Syscall translate_accounts creates new Account structs as well:
  • Rc::new(RefCell::new(AccountSharedData::from(Account { .. })))
• Both syscall and native_invoke should be recycling the existing account structs instead of secretly having their own internally, in order to interoperate with ABI v2.

Summary of Changes

• General code cleanup, deleted about 200 LOC net
• Consolidated the code around callee_keyed_accounts, caller_write_privileges and program_indices of the CPI syscall and native_invoke both into one in InstructionProcessor::create_message().
• Removed the two account copy steps from native_invoke.
• Recycles the existing account structs in both syscall and native_invoke.

Fixes #

[codecov]

Codecov Report

Merging #19762 (81b3ba9) into master (4675fa6) will increase coverage by 0.1%.
The diff coverage is 83.3%.

@@            Coverage Diff            @@
##           master   #19762     +/-   ##
=========================================
+ Coverage    82.6%    82.8%   +0.1%     
=========================================
  Files         478      487      +9     
  Lines      133547   134483    +936     
=========================================
+ Hits       110369   111386   +1017     
+ Misses      23178    23097     -81     

[jackcmay]

This is neccessary because a CPI call will change the length of the account within this call?

[Lichtso]

Yes, that was the missing puzzle piece I searched for the entire day.
The hidden purpose of the additional temporary account structs.

Because once the CPI calls recycle the existing account structs, it overwrites the length and so the deserialize of the caller program afterwards parses and writes back garbage.

[jackcmay]

This was mainly a copy-paste from the BPF version, thanks for cleaning it up