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Assembler

The assembler Command-Line utility allows you to assemble the Ethers ASM Dialect into deployable EVM bytecode and disassemble EVM bytecode into human-readable mnemonics.

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Help

Usage: ethers-asm [ FILENAME ] [ OPTIONS ] OPTIONS --define KEY=VALUE provide assembler defines --disassemble Disassemble input bytecode --ignore-warnings Ignore warnings --pic generate position independent code --target LABEL output LABEL bytecode (default: _) OTHER OPTIONS --debug Show stack traces for errors --help Show this usage and exit --version Show this version and exit

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Example Input Files

SimpleStore.asm
; SimpleStore (uint) ; Set the initial value of 42 sstore(0, 42) ; Init code to deploy myContract codecopy(0, $myContract, #myContract) return(0, #myContract) @myContract { ; Non-payable jumpi($error, callvalue) ; Get the Sighash shr({{= 256 - 32 }}, calldataload(0)) ; getValue() dup1 {{= sighash("getValue()") }} jumpi($getValue, eq) ; setValue(uint) dup1 {{= sighash("setValue(uint)") }} jumpi($setValue, eq) ; No matching signature @error: revert(0, 0) @getValue: mstore(0, sload(0)) return (0, 32) @setValue: ; Make sure we have exactly a uint jumpi($error, iszero(eq(calldatasize, 36))) ; Store the value sstore(0, calldataload(4)) return (0, 0) ; There is no *need* for the PUSH32, it just makes ; decompiled code look nicer @checksum[ {{= (defines.checksum ? concat([ Opcode.from("PUSH32"), id(myContract.source) ]): "0x") }} ] }
SimpleStore.bin
0x602a6000556044601160003960446000f334601e5760003560e01c8063209652 0x5514602457806355241077146030575b60006000fd5b60005460005260206000 0xf35b6024361415601e5760043560005560006000f3
Note: Bytecode File Syntax

A bin file may be made up of multiple blocks of bytecode, each may optionally begin with a `0x` prefix, all of which must be of even length (since bytes are required, with 2 nibbles per byte)

All whitespace is ignored.

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Assembler Examples

The assembler converts an Ethers ASM Dialect into bytecode by running multiple passes of an assemble stage, each pass more closely approximating the final result.

This allows small portions of the bytecode to be massaged and tweaked until the bytecode stabilizes. This allows for more compact jump destinations and for code to include more advanced meta-programming techniques.

/home/ethers> ethers-asm SimpleStore.asm 0x602a6000556044601160003960446000f334601e5760003560e01c80632096525514602457806355241077146030575b60006000fd5b60005460005260206000f35b6024361415601e5760043560005560006000f3 # Piping in ASM source code /home/ethers> cat SimpleStore.asm | ethers-asm # Same as above # Setting a define which the ASM file checks and adds a checksum /home/ethers> ethers-asm --define checksum SimpleStore.asm 0x602a6000556065601160003960656000f334601e5760003560e01c80632096525514602457806355241077146030575b60006000fd5b60005460005260206000f35b6024361415601e5760043560005560006000f37f10358310d664c9aeb4bf4ce7a10a6a03176bd23194c8ccbd3160a6dac90774d6

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Options

--define KEY=VALUE or --define FLAG

This allows key/value pairs (where the value is a string) and flags (which the value is `true`) to be passed along to the assembler, which can be accessed in Scripting Blocks, such as `{{= defined.someKey }}`.

--ignore-warnings

By default any warning will be treated like an error. This enabled by-passing warnings.

--pic

When a program is assembled, the labels are usually given as an absolute byte position, which can be jumped to for loops and control flow. This means that a program must be installed at a specific location.

Byt specifying the Position Independent Code flag, code will be generated in a way such that all offsets are relative, allowing the program to be moved without any impact to its logic.

This does incur an additional gas cost of 8 gas per offset access though.

--target LABEL

All programs have a root scope named `_` which is by default assembled. This option allows another labelled target (either a Scopes or a Data Segment to be assembled instead. The entire program is still assembled per usual, so this only impacts which part of the program is output.

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Disassembler Examples

A disassembled program shows offsets and mnemonics for the given bytecode. This format may change in the future to be more human-readable.

/home/ethers> ethers-asm --disassemble SimpleStore.bin 0000 : 0x2a ; #1 0002 : 0x00 ; #1 0004 : SSTORE 0005 : 0x44 ; #1 0007 : 0x11 ; #1 0009 : 0x00 ; #1 000b : CODECOPY 000c : 0x44 ; #1 000e : 0x00 ; #1 0010 : RETURN 0011 : CALLVALUE 0012 : 0x1e ; #1 0014 : JUMPI 0015 : 0x00 ; #1 0017 : CALLDATALOAD 0018 : 0xe0 ; #1 001a : SHR 001b : DUP1 001c : 0x20965255 ; #4 0021 : EQ 0022 : 0x24 ; #1 0024 : JUMPI 0025 : DUP1 0026 : 0x55241077 ; #4 002b : EQ 002c : 0x30 ; #1 002e : JUMPI 002f*: JUMPDEST 0030 : 0x00 ; #1 0032 : 0x00 ; #1 0034 : REVERT 0035*: JUMPDEST 0036 : 0x00 ; #1 0038 : SLOAD 0039 : 0x00 ; #1 003b : MSTORE 003c : 0x20 ; #1 003e : 0x00 ; #1 0040 : RETURN 0041*: JUMPDEST 0042 : 0x24 ; #1 0044 : CALLDATASIZE 0045 : EQ 0046 : ISZERO 0047 : 0x1e ; #1 0049 : JUMPI 004a : 0x04 ; #1 004c : CALLDATALOAD 004d : 0x00 ; #1 004f : SSTORE 0050 : 0x00 ; #1 0052 : 0x00 ; #1 0054 : RETURN /home/ethers> cat SimpleStore.bin | ethers-asm --disassemble # Same as above
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