From b1a912a8a6ff472a49b2e0a09cfd433adfc2cb24 Mon Sep 17 00:00:00 2001
From: Benji Dial <benji@benjidial.net>
Date: Sat, 18 May 2024 21:53:38 -0400
Subject: reorganization, cross compiler

---
 kernel/source/application.asm | 171 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 171 insertions(+)
 create mode 100644 kernel/source/application.asm

(limited to 'kernel/source/application.asm')

diff --git a/kernel/source/application.asm b/kernel/source/application.asm
new file mode 100644
index 0000000..ed8b190
--- /dev/null
+++ b/kernel/source/application.asm
@@ -0,0 +1,171 @@
+bits 64
+
+extern do_syscall
+
+section .text
+
+syscall_entry:
+  mov r11, rsp
+  mov rsp, 0xfffffffffffff000
+  push r11
+  push rcx
+
+  push rdx
+  push rsi
+  push rdi
+  push rax
+
+  mov rdi, rsp
+  lea rsi, [rsp + 8]
+  lea rdx, [rsp + 16]
+  lea rcx, [rsp + 24]
+
+  call do_syscall
+
+  pop rax
+  pop rdi
+  pop rsi
+  pop rdx
+
+  xor r8, r8
+  xor r9, r9
+  xor r10, r10
+  xor r11, r11
+  or r11, 0x200
+  pop rcx
+  pop rsp
+
+  o64 sysret
+
+global init_applications_asm
+init_applications_asm:
+
+  ;efer <- efer | 0x1
+  mov rcx, 0xc0000080
+  rdmsr
+  or al, 1
+  wrmsr
+
+  ;lstar <- syscall_entry
+  mov rdx, syscall_entry
+  mov eax, edx
+  shr rdx, 32
+  mov ecx, 0xc0000082
+  wrmsr
+
+  ;star <- 0x0030.0028.0000.0000
+  mov edx, 0x00300028
+  xor eax, eax
+  mov ecx, 0xc0000081
+  wrmsr
+
+  ;sfmask <- 0x0000.0000.0000.0200 (if)
+  xor edx, edx
+  mov eax, 0x200
+  mov ecx, 0xc0000084
+  wrmsr
+
+  ret
+
+section .bss
+
+resume_stack:
+  resb 4096
+
+section .text
+
+extern restore_syscall_stack
+;rdi = pointer to copy
+;rsi = intended rsp
+
+global resume_thread
+resume_thread:
+;rdi = ptr to cpu_state
+;rdi is not inside stack
+;interrupts are disabled
+
+  mov al, byte [rdi + 160] ;in_syscall
+  test al, al
+  jnz .in_syscall
+
+  mov rax, 0x3b
+  mov rbx, 0x43
+
+.common:
+  push rax
+  mov rax, qword [rdi + 56] ;rsp
+  push rax
+  mov rax, qword [rdi + 128] ;rflags
+  push rax
+  push rbx
+  mov rax, qword [rdi + 136] ;rip
+  push rax
+
+  mov rax, qword [rdi + 144] ;cr3
+  mov cr3, rax
+
+  mov rax, qword [rdi]
+  mov rbx, qword [rdi + 8]
+  mov rcx, qword [rdi + 16]
+  mov rdx, qword [rdi + 24]
+  mov rsi, qword [rdi + 40]
+  mov rbp, qword [rdi + 48]
+  mov r8, qword [rdi + 64]
+  mov r9, qword [rdi + 72]
+  mov r10, qword [rdi + 80]
+  mov r11, qword [rdi + 88]
+  mov r12, qword [rdi + 96]
+  mov r13, qword [rdi + 104]
+  mov r14, qword [rdi + 112]
+  mov r15, qword [rdi + 120]
+  mov rdi, qword [rdi + 32]
+
+  iretq
+
+.in_syscall:
+  mov rsp, resume_stack + 4096
+
+  push rdi
+  mov rsi, qword [rdi + 56] ;rsp
+  mov rdi, qword [rdi + 152] ;kernel_stack_copy
+  call restore_syscall_stack
+  pop rdi
+
+  mov rax, 0x30
+  mov rbx, 0x28
+  jmp .common
+
+extern copy_syscall_stack
+;rdi = bottom
+
+global save_thread_state
+save_thread_state:
+;rdi = pointer to cpu state structure
+
+  ;only saving registers that need to be preserved by this function
+  mov qword [rdi + 8], rbx
+  mov qword [rdi + 48], rbp
+  mov qword [rdi + 56], rsp
+  mov qword [rdi + 96], r12
+  mov qword [rdi + 104], r13
+  mov qword [rdi + 112], r14
+  mov qword [rdi + 120], r15
+
+  mov qword [rdi + 136], .resume_to ;rip
+  mov rax, cr3
+  mov qword [rdi + 144], rax ;cr3
+
+  push rdi
+  lea rdi, [rsp + 8]
+  call copy_syscall_stack
+  pop rdi
+
+  mov qword [rdi + 152], rax ;kernel_stack_copy
+  mov byte [rdi + 160], 0x01 ;in_syscall
+
+  xor al, al
+  ret
+
+.resume_to:
+  mov al, 0x01
+  ret
-- 
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