JitDasm
Disassembles one or more .NET methods / types to stdout or file(s). It can also create diffable disassembly.
.NET global tool
It's available as a .NET global tool
dotnet tool install -g JitDasm.0xd4dTips
- .NET Core: Disable tiered compilation in target process:
COMPlus_TieredCompilation=0 - Use release builds
- Generate a pdb file if you want to see the source code
- Target process must be a .NET Framework 4.5+ / .NET Core process
Example
jitdasm -p 1234 --diffable -m ConsoleApp1 --method TestMethod; ================================================================================
; ConsoleApp1.Program.TestMethod(System.String[])
; 87 (0x57) bytes
; 27 (0x1B) instructions
push rdi
push rsi
push rbx
sub rsp,20h
mov rsi,rcx
mov rcx,offset <diffable-addr>
mov edx,58h
call CORINFO_HELP_CLASSINIT_SHARED_DYNAMICCLASS
mov rcx,offset <diffable-addr>
mov rcx,[rcx]
mov ecx,[rcx+8]
call System.Console.WriteLine(Int32)
; for (int i = 0; i < args.Length; i++)
; ^^^^^^^^^
xor edi,edi
; for (int i = 0; i < args.Length; i++)
; ^^^^^^^^^^^^^^^
mov ebx,[rsi+8]
test ebx,ebx
jle LBL_1
LBL_0:
; Console.WriteLine(args[i]);
movsxd rcx,edi
mov rcx,[rsi+rcx*8+10h]
call System.Console.WriteLine(System.String)
; for (int i = 0; i < args.Length; i++)
; ^^^
inc edi
; for (int i = 0; i < args.Length; i++)
; ^^^^^^^^^^^^^^^
cmp ebx,edi
jg LBL_0
LBL_1:
; }
add rsp,20h
pop rbx
pop rsi
pop rdi
retKnown issues
- Generic methods and methods in generic types can't be disassembled. It's possibly a DAC API limitation. Try
--heap-searchto find instantiated generic types on the heap. - IL <-> native IP mapping that JitDasm gets from the CLR isn't always accurate so some source code statements aren't shown, especially in optimized methods. This gets worse if there are a lot of inlined methods.
- .NET Framework:
-lcallsPrepareMethod()to jit methods in the loaded module. The jitted code isn't always identical to the code the jitter generates if the method is actually called at runtime. See coreclr's pmi.cs for more info. You can create a test app that calls the methods at runtime and then use the-por-pnJitDasm command line options to disassemble the code.
Help message (jitdasm -h)
Disassembles jitted methods in .NET processes
-p, --pid <pid> Process id
-pn, --process <name> Process name
-m, --module <name> Name of module to disassemble
-l, --load <module> Load module (for execution) into this process and jit every method
--no-run-cctor Don't run all .cctors before jitting methods (used with -l)
--filename-format <fmt> Filename format. <fmt>:
name => (default) member name
tokname => token + member name
token => token
-f, --file <kind> Output file. <kind>:
stdout => (default) stdout
file => One file, use -o to set filename
type => One file per type, use -o to set directory
method => One file per method, use -o to set directory
-d, --disasm <kind> Disassembler. <kind>:
masm => (default) MASM syntax
nasm => NASM syntax
gas => GNU assembler (AT&T) syntax
att => same as gas
intel => Intel (XED) syntax
-o, --output <path> Output filename or directory
--type <tok-or-name> Disassemble this type (wildcards supported) or type token
--type-exclude <tok-or-name> Don't disassemble this type (wildcards supported) or type token
--method <tok-or-name> Disassemble this method (wildcards supported) or method token
--method-exclude <tok-or-name> Don't disassemble this method (wildcards supported) or method token
--diffable Create diffable disassembly
--no-addr Don't show instruction addresses
--no-bytes Don't show instruction bytes
--no-source Don't show source code
--heap-search Check the GC heap for instantiated generic types
-s, --search <path> Add assembly search paths (used with -l), ;-delimited
-h, --help Show this help message
<tok-or-name> can be semicolon separated or multiple options can be used. Names support wildcards.
Token ranges are also supported eg. 0x06000001-0x06001234.
Generic methods and methods in generic types aren't 100% supported. Try --heap-search.
Examples:
JitDasm -m MyModule -pn myexe -f type -o c:\out\dir --method Decode
JitDasm -p 1234 -m System.Private.CoreLib -o C:\out\dir --diffable -f type
JitDasm -l c:\path\to\mymodule.dll
Similar tools
- coreclr debug builds can create disasm
- JitBuddy disassembles a .NET method in the current process
- Disasmo VS extension uses coreclr to disassemble .NET methods
Build
git clone --recursive https://github.com/0xd4d/JitDasm.git
cd JitDasm
dotnet restore
dotnet build -c Release
License
MIT