assembly
RISC-V
The best way to try out RISC-V is by riscv-tools. Checkout out git organization riscv-software-src. It contains RISC-V installer, compiler and emulator.
Using Macbook M1 as an example,
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brew tap riscv-software-src/riscv
brew install riscv-tools
Write a simple C program
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#include <stdio.h>
int main() {
printf("hello world\n");
return 0;
}
Then compile it
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riscv64-unknown-elf-gcc -S hello.c
riscv64-unknown-elf-gcc -c hello.s -o hello.o
riscv64-unknown-elf-gcc hello.o -o hello
and run it
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$ spike pk hello
bbl loader
hello world
Registers and instruction set
See manual
amd64
Registers
I have a hard time of remembering the meaning of registers in amd64 architecture until I found this post. Just cite the summary below:
EAX, EBX, ECX, EDX = A, B, C, D; Note that the ‘A’ register holds function return values
ESI, EDI = Source, Destination (for string operations) - ECX may be the counter and EAX may used, too.
ESP, EBP = Stack Pointer, Base Pointer
EIP = Instruction Pointer
CS, DS, SS, ES, FS, GS = Code, Data, Stack, and Extra segments, followed by F and G Segments
Syntax
x86 assembly language has two main syntax branches: Intel syntax and AT&T syntax. Check wiki for details of their differences. Gnu assembler (gas or as) is probably the most popular one that uses AT&T syntax. And nasm is most popular one uses Intel syntax.
RIP-relative addressing
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lea rsi, [rel msg]
References
- https://cs.lmu.edu/~ray/notes/nasmtutorial/
aarch64
Aarch64 is just arm64. The instruction set used in aarch64 is called A64.
as
CFI (Call Frame Information) directives
Assembly Sections
.data.text.bss
FAQ
Difference between stack pointer and frame pointer
TODO: write it up.
How to compile with frame pointer enabled/disabled?