Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add mohitmishra786/low-level-dev-skills --skill abi-and-calling-conventionsgit clone --depth 1 https://github.com/mohitmishra786/low-level-dev-skillsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/mohitmishra786/low-level-dev-skills/abi-and-calling-conventions)<a href="https://agentmods.dev/skills/mohitmishra786/low-level-dev-skills/abi-and-calling-conventions"><img src="https://agentmods.dev/badge/skills/mohitmishra786/low-level-dev-skills/abi-and-calling-conventions/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/mohitmishra786/low-level-dev-skills/abi-and-calling-conventions"><img src="https://agentmods.dev/badge/skills/mohitmishra786/low-level-dev-skills/abi-and-calling-conventions.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00080 | $0.01029 |
| Opus 5 | $0.00040 | $0.00515 |
| Sonnet 5 | $0.00016 | $0.00206 |
| Haiku 4.5 | $0.00008 | $0.00103 |
Grade A, and why
abi-and-calling-conventions scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 11d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 111 lines — stays where its author put it; the contents beside it link to each section on GitHub.
ABI and Calling Conventions
Purpose
Document application binary interface (ABI) rules: register roles, stack alignment, argument passing, return values, and variadic conventions across System V AMD64, ARM AAPCS, and RISC-V — essential for assembly, FFI, and debugging.
When to Use
- Writing assembly thunks or inline asm clobbers
- Debugging corrupted stack in mixed C/asm
- FFI between Rust/C/Zig (
skills/rust/rust-ffi,skills/zig/zig-cinterop) - Reading disassembly from
skills/debuggers/gdb
Workflow
1. System V AMD64 (Linux/macOS)
| Item | Rule |
|---|---|
| Integer args | rdi, rsi, rdx, rcx, r8, r9 |
| XMM args | xmm0–xmm7 (float) |
| Return int/ptr | rax (+ rdx for 128-bit) |
| Stack alignment | 16-byte before call |
| Red zone | 128 bytes below rsp (Linux) |
| Callee-saved | rbx, rbp, r12–r15 |
/* void foo(int a, int b, int c, int d, int e, int f, int g); */
/* a–f in regs, g on stack */
Windows x64 differs — see skills/compilers/msvc-cl.
2. ARM AAPCS (AArch32/AArch64)
AArch64:
| Item | Rule |
|---|---|
| Integer args | x0–x7 |
| Float args | v0–v7 |
| Return | x0/x1 or v0 |
| Stack align | 16-byte |
| Callee-saved | x19–x28, fp (x29), lr (x30) |
Thumb interworking: LSB of function pointer set for Thumb code.
See skills/low-level-programming/assembly-arm.
3. RISC-V psABI (RV64)
| Item | Rule |
|---|---|
| Integer args | a0–a7 |
| Callee-saved | s0–s11, sp |
| Return | a0, a1 |
| Stack align | 16-byte |
See skills/low-level-programming/assembly-riscv.
4. Stack frame layout (conceptual)
high addresses
├── return address
├── saved frame pointer
├── local variables
├── spill slots / alignment padding
└── outgoing args (if any)
low addresses (rsp)
5. Variadic functions
System V: al holds number of vector args used; register_save_area on stack for va_start. Prefer typed wrappers over raw va_arg in portable FFI.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 11d ago First seen · 111 lines · 80 tokens per session scan A f96270ff08af
abi-and-calling-conventions is a skill published in the GitHub repository mohitmishra786/low-level-dev-skills (202 stars, last pushed 2mo ago), licensed MIT. It adds 80 tokens to every session and 1,029 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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