RFC33: ckb vm version1 changes

README.md

@@ -80,6 +80,8 @@ The maintainers of RFCs will review the proposal, ask if there's any objections,
 | [25](rfcs/0025-simple-udt) | [Simple UDT](rfcs/0025-simple-udt/0025-simple-udt.md) | Xuejie Xiao | Standards Track | Proposal
 | [26](rfcs/0026-anyone-can-pay) | [Anyone-Can-Pay Lock](rfcs/0026-anyone-can-pay/0026-anyone-can-pay.md) | Xuejie Xiao | Standards Track | Proposal
 | [27](rfcs/0027-block-structure) | [CKB Block Structure](rfcs/0027-block-structure/0027-block-structure.md) | Ian Yang | Informational | Draft
+| [28](rfcs/0028-ckb-vm-version-1) | [VM version 1](rfcs/0028-ckb-vm-version-1/0028-ckb-vm-version-1.md) | Wanbiao Ye | Standards Track | Proposal
+| [29](rfcs/0029-ckb-hardfork) | [CKB Hardfork](rfcs/0029-ckb-hardfork/0029-ckb-hardfork.md) | Wanbiao Ye | Standards Track | Proposal
 
 ## License
 

rfcs/0028-ckb-vm-version-1/0028-ckb-vm-version-1.md

@@ -0,0 +1,147 @@
+---
+Number: "0028"
+Category: Standards Track
+Status: Proposal
+Author: Wanbiao Ye
+Organization: Nervos Foundation
+Created: 2021-05-25
+---
+
+# VM version1
+
+This RFC describes version 1 of the CKB-VM, in comparison to version 0, which
+
+- Fixed several bugs
+- Behavioural changes not affecting execution results
+- New features
+- Performance optimisations
+
+## 1 Fixed Several Bugs
+
+CKB-VM Version 1 has fixed identified bugs discovered in Version 0.
+
+### 1.1 Enabling Stack Pointer SP To Be Always 16-byte Aligned
+
+In the previous version, SP incorrectly aligned during stack initialisation. See [issue](https://github.com/nervosnetwork/ckb-vm/issues/97).
+
+### 1.2 Added a NULL To Argv
+
+C Standard 5.1.2.2.1/2 states: `argv[argc]` should be a null pointer. `NULL` was unfortunately omitted during the initialization of the stack, and now it has returned. See [issue](https://github.com/nervosnetwork/ckb-vm/issues/98).
+
+### 1.3 JALR Caused Erroneous Behaviour on AsmMachine When rs1 and rd utilised the same register
+
+The problem arose with the JALR instruction, where the CKB-VM had made an error in the sequence of its different steps. The correct step to follow would be to calculate the pc first and then update the rd. See [problem](https://github.com/nervosnetwork/ckb-vm/issues/92).
+
+### 1.4 Error OutOfBound was triggered by reading the last byte of memory
+
+We have fixed it, as described in the title.
+
+### 1.5 Unaligned executable pages from loading binary would raise an error
+
+We have fixed it, as described in the title.
+
+### 1.6 Frozen writable pages by error
+
+This error occurred during the loading of elf. The CKB-VM has incorrectly set a freeze flag on a writeable page, which made the page unmodifiable.
+
+It happened mainly with external variables that have dynamic links.
+
+### 1.7 Update crate goblib
+
+goblin is a cross-platform trifecta of binary parsing and loading fun. ckb-vm uses it to load RISC-V programs. But in the past period of time goblin fixed many bugs and produced destructive upgrades, we decided to upgrade goblin: this will cause the binary that could not be loaded before can now be normal Load, or vice versa.
+
+## 2 Behavioural Changes that will not affect the execution outcomes
+
+### 2.1 Skip writing 0 to memory when argc equals 0 during stack initialisation
+
+For ckb scripts, argc is always 0 and the memory is initialised to 0, so memory writing can be safely skipped. Note that when "chaos_mode" is enabled and "argv" is empty, the reading of "argc" will return an unexpected data. This happens uncommonly, and never happens on the mainnet.
+
+### 2.2 Redesign of the internal instruction format
+
+For the sake of fast decoding and cache convenience, RISC-V instruction is decoded into the 64-bit unsigned integer. Such a format used only internally in ckb-vm rather than the original RISC-V instruction format.
+
+## 3 New features
+
+### 3.1 B extension
+
+We have added the RISC-V B extension (v0.92) [1]. This extension aims at covering the four major categories of bit manipulation: counting, extracting, inserting and swapping. The execution of B instructions has been divided into two directions, a slow path and a fast path.  The slow path always generates a context switching overhead. For all B instructions, 1 cycle will be consumed, excluding the followings:
+
+| Instruction |        Cycles        |
+| ----------- | -------------------- |
+| GREV        | CONTEXT_SWITCH + 20  |
+| GREVI       | CONTEXT_SWITCH + 20  |
+| GREVW       | CONTEXT_SWITCH + 18  |
+| GREVIW      | CONTEXT_SWITCH + 18  |
+| SHFL        | CONTEXT_SWITCH + 20  |
+| UNSHFL      | CONTEXT_SWITCH + 20  |
+| SHFLI       | CONTEXT_SWITCH + 20  |
+| UNSHFLI     | CONTEXT_SWITCH + 20  |
+| SHFLW       | CONTEXT_SWITCH + 18  |
+| UNSHFLW     | CONTEXT_SWITCH + 18  |
+| GORC        | CONTEXT_SWITCH + 20  |
+| GORCI       | CONTEXT_SWITCH + 20  |
+| GORCW       | CONTEXT_SWITCH + 18  |
+| GORCIW      | CONTEXT_SWITCH + 18  |
+| BFP         | CONTEXT_SWITCH + 15  |
+| BFPW        | CONTEXT_SWITCH + 15  |
+| BDEP        | CONTEXT_SWITCH + 350 |
+| BEXT        | CONTEXT_SWITCH + 270 |
+| BDEPW       | CONTEXT_SWITCH + 180 |
+| BEXTW       | CONTEXT_SWITCH + 140 |
+| CLMUL       | CONTEXT_SWITCH + 320 |
+| CLMULR      | CONTEXT_SWITCH + 380 |
+| CLMULH      | CONTEXT_SWITCH + 400 |
+| CLMULW      | CONTEXT_SWITCH + 60  |
+| CLMULRW     | CONTEXT_SWITCH + 60  |
+| CLMULHW     | CONTEXT_SWITCH + 60  |
+| CRC32B      | CONTEXT_SWITCH + 15  |
+| CRC32H      | CONTEXT_SWITCH + 30  |
+| CRC32W      | CONTEXT_SWITCH + 45  |
+| CRC32D      | CONTEXT_SWITCH + 60  |
+| CRC32CB     | CONTEXT_SWITCH + 15  |
+| CRC32CH     | CONTEXT_SWITCH + 30  |
+| CRC32CW     | CONTEXT_SWITCH + 45  |
+| CRC32CD     | CONTEXT_SWITCH + 60  |
+| BMATFLIP    | CONTEXT_SWITCH + 40  |
+| BMATOR      | CONTEXT_SWITCH + 500 |
+| BMATXOR     | CONTEXT_SWITCH + 800 |
+
+Where CONTEXT_SWITCH = 500.
+
+### 3.2 Chaos memory mode
+
+Chaos memory mode was added for the debugging tools. Under this mode, the program memory forcibly initializes randomly, helping us to discover uninitialized objects/values in the script.
+
+### 3.3 Suspend/resume a running VM
+
+It is possible to suspend a running CKB VM, save the state to a certain place and to resume the previously running VM later on, possibly even on a different machine.
+
+## 4 Performance optimization
+
+### 4.1 Lazy initialization memory
+
+In version 0, when the VM was initialised, the program memory would be initialised to zero value. Now, we have deferred the initialisation of program memory. The program memory is divided into several different frames, so that only when a frame is used (read, write), the corresponding program memory area of that frame will be initialised with zero value. As a result , small programs that do not need to use large volumes of memory will be able to run faster.
+
+### 4.2 MOP
+
+Macro-Operation Fusion (also Macro-Op Fusion, MOP Fusion, or Macrofusion) is a hardware optimization technique found in many modern microarchitectures whereby a series of adjacent macro-operations are merged into a single macro-operation prior or during decoding. Those instructions are later decoded into fused-µOPs.
+
+The cycle consumption of the merged instructions is the maximum cycle value of the two instructions before the merge. We have verified that the use of MOPs can lead to significant improvements in some encryption algorithms.
+
+
+|            Opcode            |    Origin    | Cycles |
+| ---------------------------- | ------------ | ------ |
+| WIDE_MUL                     | mulh + mul   | 5 + 0  |
+| WIDE_MULU                    | mulhu + mul  | 5 + 0  |
+| WIDE_MULSU                   | mulhsu + mul | 5 + 0  |
+| WIDE_DIV                     | div + rem    | 32 + 0 |
+| WIDE_DIVU                    | divu + remu  | 32 + 0 |
+| FAR_JUMP_REL                 | auipc + jalr | 0 + 3  |
+| FAR_JUMP_ABS                 | lui + jalr   | 0 + 3  |
+| LD_SIGN_EXTENDED_32_CONSTANT | lui + addiw  | 1 + 0  |
+
+# Reference
+
+* [1]: [B extension][1]
+
+[1]: https://github.com/riscv/riscv-bitmanip

rfcs/0029-ckb-hardfork/0029-ckb-hardfork.md

@@ -0,0 +1,91 @@
+---
+Number: "0029"
+Category: Standards Track
+Status: Proposal
+Author: Wanbiao Ye
+Organization: Nervos Foundation
+Created: 2021-05-25
+---
+
+# CKB Hardfork
+
+## Abstract
+
+This document describes the first hard fork of ckb.
+
+- [VM Syscalls]
+  - [VM Version]
+  - [Current Cycles]
+  - [Exec]
+
+## VM Syscalls
+[vm syscalls]: #vm-syscalls
+
+### VM Version
+[vm version]: #vm-version
+
+As shown above, *VM Version* syscall has a signature like following:
+
+```c
+int ckb_vm_version()
+{
+  return syscall(2041, 0, 0, 0, 0, 0, 0);
+}
+```
+
+*VM version* syscall returns current running VM version, so far 2 values will be returned: 0 for Lina CKB-VM version, 1 for the new hardfork version. This syscall consumes 500 cycles.
+
+### Current Cycles
+[current cycles]: #current-cycles
+
+*Current Cycles* syscall has a signature like following:
+
+```c
+uint64_t ckb_current_cycles()
+{
+  return syscall(2042, 0, 0, 0, 0, 0, 0);
+}
+```
+
+*Current Cycles* returns current cycle consumption just before executing this syscall. This syscall consumes 500 cycles.
+
+
+### Exec
+[exec]: #exec
+
+Exec runs an executable file from specified cell data in the context of an already existing machine, replacing the previous executable. The used cycles does not change, but the code, registers and memory of the vm are replaced by those of the new program. It's cycles consumption consists of two parts:
+
+- Fixed 500 cycles
+- Initial Loading Cycles [1]
+
+*Exec* syscall has a signature like following:
+
+```c
+int ckb_exec(size_t index, size_t source, size_t place, size_t bounds, int argc, char* argv[])
+{
+  return syscall(2043, index, source, place, bounds, argc, argv);
+}
+```
+
+The arguments used here are:
+
+* `index`: an index value denoting the index of entries to read.
+* `source`: a flag denoting the source of cells or witnesses to locate, possible values include:
+    + 1: input cells.
+    + `0x0100000000000001`: input cells with the same running script as current script
+    + 2: output cells.
+    + `0x0100000000000002`: output cells with the same running script as current script
+    + 3: dep cells.
+* `place`: A value of 0 or 1:
+    + 0: read from cell data
+    + 1: read from witness
+* `bounds`: high 32 bits means `offset`, low 32 bits means `length`. if `length` equals to zero, it read to end instead of reading 0 bytes.
+* `argc`: argc contains the number of arguments passed to the program
+* `argv`: argv is a one-dimensional array of strings
+
+
+# Reference
+
+* [1]: [Vm Cycle Limits][1]
+
+[1]: ../0014-vm-cycle-limits/0014-vm-cycle-limits.md