abi-and-calling-conventions

Name: abi-and-calling-conventions
Author: mohitmishra786

66installs19forks

How to install abi-and-calling-conventions?

mohitmishra786/low-level-dev-skills/abi-and-calling-conventions

$npx -y skills add mohitmishra786/low-level-dev-skills --skill abi-and-calling-conventions

Installs into the current project.

Summary

ABI and calling conventions skill for cross-language boundaries. Use when explaining System V AMD64, ARM AAPCS, RISC-V psABI, stack frames, variadic calls, or FFI register rules. Activates on queries about calling convention, ABI, System V AMD64, AAPCS, stack frame, variadic func

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SKILL.md

1	# ABI and Calling Conventions
2
3	## Purpose
4
5	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.
6
7	## When to Use
8
9	- Writing assembly thunks or inline asm clobbers
10	- Debugging corrupted stack in mixed C/asm
11	- FFI between Rust/C/Zig (`skills/rust/rust-ffi`, `skills/zig/zig-cinterop`)
12	- Reading disassembly from `skills/debuggers/gdb`
13
14	## Workflow
15
16	### 1. System V AMD64 (Linux/macOS)
17
18	\| Item \| Rule \|
19	\|------\|------\|
20	\| Integer args \| `rdi, rsi, rdx, rcx, r8, r9` \|
21	\| XMM args \| `xmm0`–`xmm7` (float) \|
22	\| Return int/ptr \| `rax` (+ `rdx` for 128-bit) \|
23	\| Stack alignment \| 16-byte before `call` \|
24	\| Red zone \| 128 bytes below `rsp` (Linux) \|
25	\| Callee-saved \| `rbx, rbp, r12–r15` \|
26
27	```c
28	/* void foo(int a, int b, int c, int d, int e, int f, int g); */
29	/* a–f in regs, g on stack */
30	```
31
32	Windows x64 differs — see `skills/compilers/msvc-cl`.
33
34	### 2. ARM AAPCS (AArch32/AArch64)
35
36	AArch64:
37
38	\| Item \| Rule \|
39	\|------\|------\|
40	\| Integer args \| `x0`–`x7` \|
41	\| Float args \| `v0`–`v7` \|
42	\| Return \| `x0`/`x1` or `v0` \|
43	\| Stack align \| 16-byte \|
44	\| Callee-saved \| `x19`–`x28`, `fp` (`x29`), `lr` (`x30`) \|
45
46	Thumb interworking: LSB of function pointer set for Thumb code.
47
48	See `skills/low-level-programming/assembly-arm`.
49
50	### 3. RISC-V psABI (RV64)
51
52	\| Item \| Rule \|
53	\|------\|------\|
54	\| Integer args \| `a0`–`a7` \|
55	\| Callee-saved \| `s0`–`s11`, `sp` \|
56	\| Return \| `a0`, `a1` \|
57	\| Stack align \| 16-byte \|
58
59	See `skills/low-level-programming/assembly-riscv`.
60
61	### 4. Stack frame layout (conceptual)
62
63	```
64	high addresses
65	├── return address
66	├── saved frame pointer
67	├── local variables
68	├── spill slots / alignment padding
69	└── outgoing args (if any)
70	low addresses (rsp)
71	```
72
73	### 5. Variadic functions
74
75	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.
76
77	### 6. Verify in compiler output
78
79	```bash
80	gcc -O2 -S -o - foo.c # study .cfi_* and mov args
81	objdump -d -M intel ./a.out
82	```
83
84	### 7. Agent usage
85
86	```
87	/abi-and-calling-conventions Which registers hold args 5–8 in AArch64 for my C function?
88	```
89
90	## Common Problems
91
92	\| Symptom \| Cause \| Fix \|
93	\|---------\|-------\|-----\|
94	\| Crash on `call` \| Stack misaligned \| Align `rsp` mod 16 \|
95	\| Wrong float arg \| XMM vs GPR mismatch \| Match prototype \|
96	\| Corrupt callee-saved \| Asm clobber missing \| List in clobber or save \|
97	\| FFI garbage \| Windows vs SysV mix \| Match toolchain ABI \|
98	\| Variadic UB \| Wrong type to `va_arg` \| Cast to promoted type \|
99
100	## Related Skills
101
102	- `skills/low-level-programming/assembly-x86` — x86-64 asm
103	- `skills/low-level-programming/assembly-arm` — AAPCS examples
104	- `skills/low-level-programming/assembly-riscv` — RISC-V asm
105	- `skills/rust/rust-ffi` — `extern "C"` guarantees
106	- `skills/binaries/elf-inspection` — symbol and relocation views

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abi-and-calling-conventions

66installs19forks

View on GitHub

How to install abi-and-calling-conventions?

mohitmishra786/low-level-dev-skills/abi-and-calling-conventions

$npx -y skills add mohitmishra786/low-level-dev-skills --skill abi-and-calling-conventions

Installs into the current project.

Summary

Files · 1

View on GitHub

SKILL.md

1	# ABI and Calling Conventions
2
3	## Purpose
4
5	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.
6
7	## When to Use
8
9	- Writing assembly thunks or inline asm clobbers
10	- Debugging corrupted stack in mixed C/asm
11	- FFI between Rust/C/Zig (`skills/rust/rust-ffi`, `skills/zig/zig-cinterop`)
12	- Reading disassembly from `skills/debuggers/gdb`
13
14	## Workflow
15
16	### 1. System V AMD64 (Linux/macOS)
17
18	\| Item \| Rule \|
19	\|------\|------\|
20	\| Integer args \| `rdi, rsi, rdx, rcx, r8, r9` \|
21	\| XMM args \| `xmm0`–`xmm7` (float) \|
22	\| Return int/ptr \| `rax` (+ `rdx` for 128-bit) \|
23	\| Stack alignment \| 16-byte before `call` \|
24	\| Red zone \| 128 bytes below `rsp` (Linux) \|
25	\| Callee-saved \| `rbx, rbp, r12–r15` \|
26
27	```c
28	/* void foo(int a, int b, int c, int d, int e, int f, int g); */
29	/* a–f in regs, g on stack */
30	```
31
32	Windows x64 differs — see `skills/compilers/msvc-cl`.
33
34	### 2. ARM AAPCS (AArch32/AArch64)
35
36	AArch64:
37
38	\| Item \| Rule \|
39	\|------\|------\|
40	\| Integer args \| `x0`–`x7` \|
41	\| Float args \| `v0`–`v7` \|
42	\| Return \| `x0`/`x1` or `v0` \|
43	\| Stack align \| 16-byte \|
44	\| Callee-saved \| `x19`–`x28`, `fp` (`x29`), `lr` (`x30`) \|
45
46	Thumb interworking: LSB of function pointer set for Thumb code.
47
48	See `skills/low-level-programming/assembly-arm`.
49
50	### 3. RISC-V psABI (RV64)
51
52	\| Item \| Rule \|
53	\|------\|------\|
54	\| Integer args \| `a0`–`a7` \|
55	\| Callee-saved \| `s0`–`s11`, `sp` \|
56	\| Return \| `a0`, `a1` \|
57	\| Stack align \| 16-byte \|
58
59	See `skills/low-level-programming/assembly-riscv`.
60
61	### 4. Stack frame layout (conceptual)
62
63	```
64	high addresses
65	├── return address
66	├── saved frame pointer
67	├── local variables
68	├── spill slots / alignment padding
69	└── outgoing args (if any)
70	low addresses (rsp)
71	```
72
73	### 5. Variadic functions
74
75	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.
76
77	### 6. Verify in compiler output
78
79	```bash
80	gcc -O2 -S -o - foo.c # study .cfi_* and mov args
81	objdump -d -M intel ./a.out
82	```
83
84	### 7. Agent usage
85
86	```
87	/abi-and-calling-conventions Which registers hold args 5–8 in AArch64 for my C function?
88	```
89
90	## Common Problems
91
92	\| Symptom \| Cause \| Fix \|
93	\|---------\|-------\|-----\|
94	\| Crash on `call` \| Stack misaligned \| Align `rsp` mod 16 \|
95	\| Wrong float arg \| XMM vs GPR mismatch \| Match prototype \|
96	\| Corrupt callee-saved \| Asm clobber missing \| List in clobber or save \|
97	\| FFI garbage \| Windows vs SysV mix \| Match toolchain ABI \|
98	\| Variadic UB \| Wrong type to `va_arg` \| Cast to promoted type \|
99
100	## Related Skills
101
102	- `skills/low-level-programming/assembly-x86` — x86-64 asm
103	- `skills/low-level-programming/assembly-arm` — AAPCS examples
104	- `skills/low-level-programming/assembly-riscv` — RISC-V asm
105	- `skills/rust/rust-ffi` — `extern "C"` guarantees
106	- `skills/binaries/elf-inspection` — symbol and relocation views

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