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  1. Nov 29, 2024
    • Alexander Theißen's avatar
      pallet_revive: Switch to 64bit RISC-V (#6565) · 447902ef
      Alexander Theißen authored
      
      This PR updates pallet_revive to the newest PolkaVM version and adapts
      the test fixtures and syscall interface to work under 64bit.
      
      Please note that after this PR no 32bit contracts can be deployed (they
      will be rejected at deploy time). Pre-deployed 32bit contracts are now
      considered defunct since we changes how parameters are passed for
      functions with more than 6 arguments.
      
      ## Fixtures
      
      The fixtures are now built for the 64bit target. I also removed the
      temporary directory mechanism that triggered a full rebuild every time.
      It also makes it easier to find the compiled fixtures since they are now
      always in `target/pallet-revive-fixtures`.
      
      ## Syscall interface
      
      ### Passing pointer
      
      Registers and pointers are now 64bit wide. This allows us to pass u64
      arguments in a single register. Before we needed two registers to pass
      them. This means that just as before we need one register per pointer we
      pass. We keep pointers as `u32` argument by truncating the register.
      This is done since the memory space of PolkaVM is 32bit.
      
      ### Functions with more than 6 arguments
      
      We only have 6 registers to pass arguments. This is why we pass a
      pointer to a struct when we need more than 6. Before this PR we expected
      a packed struct and interpreted it as SCALE encoded tuple. However, this
      was buggy because the `MaxEncodedLen` returned something that was larger
      than the packed size of the structure. This wasn't a problem before. But
      now the memory space changed in a way that things were placed at the
      edges of the memory space and those extra bytes lead to an out of bound
      access.
      
      This is why this PR drops SCALE and expects the arguments to be passed
      as a pointer to a `C` aligned struct. This avoids unaligned accesses.
      However, revive needs to adapt its codegen to properly align the
      structure fields.
      
      ## TODO
      - [ ] Add multi block migration that wipes all existing contracts as we
      made breaking changes to the syscall interface
      
      ---------
      
      Co-authored-by: default avatarGitHub Action <action@github.com>