https://github.com/mrkct/charm
A toy assembler for ARMv7
https://github.com/mrkct/charm
arm armv7a assembler assembly
Last synced: 2 months ago
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A toy assembler for ARMv7
- Host: GitHub
- URL: https://github.com/mrkct/charm
- Owner: mrkct
- Created: 2025-02-08T13:04:54.000Z (3 months ago)
- Default Branch: master
- Last Pushed: 2025-03-02T14:54:02.000Z (3 months ago)
- Last Synced: 2025-03-08T02:05:19.265Z (2 months ago)
- Topics: arm, armv7a, assembler, assembly
- Language: C
- Homepage:
- Size: 65.4 KB
- Stars: 0
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# Charm: a tiny assembler for 32-bit ARM
Charm is a toy assembler that aims to generate ARMv7-A assembly code.
It implements a very tiny subset of the ARMv7-A instruction set
and can either generate a flat binary or a static ELF executable.
Charm is implemented entirely in a single C file, without any
dependencies other than the standard C library.
## Usage
The following commands will assemble the `hello.S` into a static ELF
executable that can run on an ARM Linux machine:
./charm hello.S hello
./hello
Hello, world!
> [!TIP]
> If you're not on an ARM machine, you can use `qemu-arm` to run the generated executable.
Charm will use `_start` as the entry point of the program.
If the output file ends with `.bin` or `.obj`, the output will be
a flat binary.
## Compiling
Compiling charm only requires a C compiler.
To compile by yourself, run:
cc charm.c -o charm
If you want to develop charm, you should also get `make`, a POSIX shell
and the GNU tools in `arm-none-eabi-gcc` as the tools
`as` and `objdump` are used validation.
There is also a Makefile with a few targets that you might
be interested in; it's probably easiest to just see what's
there by yourself.
## Limitations
As the first line of this README says, Charm is a toy assembler and
therefore has many limitations compared to established assemblers
like GNU's `as`.
Here's a non-exhaustive list, you can either look at this to see if
charm is suitable for you use case or you can treat this as a potential
list of improvements you could contribute.
**Very few instructions are implemented**:
Charm implements less than 20 instructions, and some of them are not
even fully implemented.
**Not all invalid instructions are rejected**:
Charm doesn't implement all verification checks for all instructions,
and therefore it might allow you to assemble code that can generate
unpredictable results.
As an example, `mul pc, pc, pc` is marked as UNPREDICTABLE by the
ARMv7-A architecture, but charm will happily assemble that for you.
**No support for auto-generating literal pools**:
Charm doesn't implement any support for literal pools, so you'll
have to write them by hand.