feat: scheduling, usermode, shell

2026-02-17 19:17:01 +01:00
parent 20fa8a9be2
commit 605fbcbe42
46 changed files with 2622 additions and 98 deletions
@@ -0,0 +1,89 @@
+;
+;   SyscallEntry.asm
+;   SYSCALL/SYSRET entry point and user-mode transition
+;   Copyright (c) 2025 Daniel Hammer
+;
+
+[bits 64]
+section .text
+
+extern SyscallDispatch
+extern g_kernelRsp
+
+; ============================================================
+; SyscallEntry — called by the SYSCALL instruction
+;   RCX = user RIP, R11 = user RFLAGS, RAX = syscall number
+;   Args: RDI, RSI, RDX, R10, R8, R9
+;   Interrupts are masked (FMASK clears IF)
+; ============================================================
+global SyscallEntry
+SyscallEntry:
+    mov [rel g_userRsp], rsp            ; stash user RSP
+    mov rsp, [rel g_kernelRsp]          ; switch to kernel stack
+
+    ; Build SyscallFrame on kernel stack (push order matches struct)
+    push qword [rel g_userRsp]          ; user_rsp
+    push rcx                            ; user_rip
+    push r11                            ; user_rflags
+    push rax                            ; syscall_nr
+    push rdi                            ; arg1
+    push rsi                            ; arg2
+    push rdx                            ; arg3
+    push r10                            ; arg4
+    push r8                             ; arg5
+    push r9                             ; arg6
+
+    ; Callee-saved registers (preserve for user)
+    push rbx
+    push rbp
+    push r12
+    push r13
+    push r14
+    push r15
+
+    sti                                 ; safe to take interrupts now
+
+    mov rdi, rsp                        ; arg1 = pointer to SyscallFrame
+    call SyscallDispatch                ; returns int64_t in rax
+
+    cli                                 ; disable interrupts for sysret
+
+    pop r15
+    pop r14
+    pop r13
+    pop r12
+    pop rbp
+    pop rbx
+
+    add rsp, 56                         ; skip arg6..arg1 (6*8) + syscall_nr (1*8) = 56
+
+    pop r11                             ; user RFLAGS
+    pop rcx                             ; user RIP
+    pop rsp                             ; user RSP
+
+    o64 sysret
+
+; ============================================================
+; JumpToUserMode — initial transition to ring 3 via IRETQ
+;   RDI = user RIP (entry point)
+;   RSI = user RSP (top of user stack)
+; ============================================================
+global JumpToUserMode
+JumpToUserMode:
+    mov ax, 0x1B                        ; UserData | RPL3
+    mov ds, ax
+    mov es, ax
+
+    push 0x1B                           ; SS  = UserData | RPL3
+    push rsi                            ; RSP = user stack top
+    push 0x202                          ; RFLAGS (IF=1)
+    push 0x23                           ; CS  = UserCode | RPL3
+    push rdi                            ; RIP = entry point
+    iretq
+
+; ============================================================
+; BSS: scratch space for user RSP save
+; ============================================================
+section .bss
+global g_userRsp
+g_userRsp: resq 1