Userspace

Userspace

Ring-3 ELF64 loading with full address-space isolation.

See also: Syscalls, Process Management, Security, Architecture

ELF loader (elf.c)

Validates ELF64 magic, parses PT_LOAD segments, maps code/data at p_vaddr, allocates stack at 0xD0000000.

Process isolation

• Private PML4 per process (no identity mapping in user tables)
• NX bit on user stack and data pages
• SMEP (optional): kernel can't execute user pages
• Kernel entry at PML4[511] cloned from master kernel PML4

libc (user/libc.c)

Minimal C library: printf, snprintf, malloc, free, file I/O wrappers via Syscalls.

crt0 (user/crt0.asm)

Assembly entry that extracts argc/argv from stack, calls main(), then exit().

Available programs

Binary	Description
hello.elf	Minimal "Hello World" in assembly
init.elf	Syscall regression test (getpid, malloc, file I/O)
spin.elf	Spin loop for multitasking testing
fdleak.elf	Tests fd cleanup on process exit