MerlionOS v100.4 — Full Userspace: exec, sockets, syscall returns

MerlionOS v100.4 — Full Userspace U1-U4

Stats

• 140,204 lines of Rust
• ~380 modules, 7 built-in user programs
• 45 syscalls with proper return values
• 0 errors, 0 warnings

Userspace Complete (U1-U4)

U1: Ring 3 Execution ✅

• ELF loader maps user code at 0x400000
• iretq switches Ring 0 → Ring 3
• int 0x80 syscall returns Ring 3 → Ring 0
• [user] Hello from MerlionOS userspace!

U2: Syscall Return Values ✅

• All 45 syscalls set rax via trampoline
• open returns fd, read returns bytes, getpid returns pid
• -1 on failure, proper error semantics

U3: exec ✅

• SYS_EXEC loads and runs a new program
• exec-test → exec("hello") → Hello World chain
• Old process cleaned up on exec

U4: Socket Syscalls ✅

• SYS_SOCKET, SYS_CONNECT, SYS_SENDTO, SYS_RECVFROM
• connect() uses real TCP stack (tcp_real::connect)
• Foundation for userspace networking

7 Built-in User Programs

• hello, cat-test, qfc-test, counter, getpid, syscall-test, open-test, exec-test

Build

make build && make run
merlion> run-user hello
[user] Hello from MerlionOS userspace!
merlion> run-user exec-test
merlion> run-user syscall-test

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