compiler/examples/typephp-os/user

TypePHP-OS userspace direction

TypePHP-OS userspace must evolve toward programs that GCC and glibc can build and run directly. Every userspace ABI and API change must make that migration easier, or clearly isolate temporary OS-specific behavior.

The following rules are normative for this directory:

1. C programs use the standard int main(int argc, char **argv) entry point. The shared crt0.S owns _start and receives a Linux-style initial stack: argc, argv, envp, and auxv.
2. Prefer ISO C and POSIX APIs and data structures. Small temporary wrappers should match their eventual libc signatures wherever the kernel already has the required semantics.
3. A Linux x86-64 syscall number may be used only when the operation, argument layout, return value, and observable semantics are compatible. Temporary TypePHP-OS services use the private syscall range instead.
4. Keep OS-specific calls behind the userspace ABI layer. Application and command code should gradually stop including raw syscall helpers as libc coverage grows.
5. New kernel services should first consider the interfaces glibc needs: process startup, memory mapping, files and directories, clocks, TLS, signals, and process lifecycle. Socket support remains out of scope for the current system.
6. Freestanding test programs remain libc-free only as a bootstrap constraint; it is not the final userspace programming model.

The current bootstrap libc provides syscall, read, write, openat, open, close, lseek, getcwd, chdir, mkdir, rmdir, unlink, rename, time, brk, sbrk, mmap, mprotect, munmap, strlen, strerror, perror, and _exit with libc-compatible C signatures. It also translates kernel -errno results into -1 plus the single-task userspace errno. This list is a migration layer, not a reason to create project-specific variants of standard functions.

The resident shell and each launched command have independent x86-64 address spaces backed by recyclable 4 KiB physical pages. Current ELF files use page-separated RX text/rodata and RW data/bss segments; the 64 KiB user stack has an unmapped guard below it. The memory syscalls reserve their Linux x86-64 numbers and semantics, with one deliberate initial subset: mmap() accepts only MAP_PRIVATE | MAP_ANONYMOUS, fd == -1, and offset zero. File mappings, shared mappings, fixed mappings, remapping, and demand paging are not implemented yet. brk() and mmap() eagerly allocate zero-filled pages; munmap() and process teardown return them to the physical-page pool.

rename() currently accepts only source and destination paths with the same parent directory and does not replace an existing entry. Its transport uses a private TypePHP-OS syscall number until the kernel implements the complete Linux rename contract.

The shell and commands are independent ELF64 files installed under /BIN in the FAT16 image. Command names must fit the DOS 8.3 base-name limit. Lookup maps name to the path /BIN/name.ELF. The kernel streams and validates each ELF from the filesystem and confines the resident shell and transient command to separate page tables, even when they use overlapping virtual addresses. Adding a compatible command file does not require relinking the kernel.

The current int 0x80 entry is transitional. Before linking an ordinary x86-64 glibc build, the kernel must also accept the syscall instruction with the Linux register convention (rax, rdi, rsi, rdx, r10, r8, r9), negative errno returns, and the expected rcx/r11 clobbers.

Using unmodified upstream glibc will require substantially more than matching syscall numbers. The kernel must eventually provide the expected ELF process startup contract and enough Linux-compatible syscall behavior, or TypePHP-OS must carry a small glibc sysdeps port. Until then, private behavior must not masquerade as a Linux syscall.