[USER] System calls

kernel/syscall/syscall.c

@@ -0,0 +1,65 @@
+#include <syscall.h>
+#include <debug.h>
+#include <int.h>
+#include <msr.h>
+#include <gdt.h>
+#include <registers.h>
+
+extern void syscall_entry();
+
+syscall_handler_t syscall_handlers[1024];
+
+SYSCALL_DECL(debug);
+
+registers_t *syscall_handler(registers_t *r)
+{
+  // Syscall number: RAX
+  // Order of arguments:
+  // RDI
+  // RSI
+  // RDX
+  // R10
+  // R8
+  // R9
+  // stack
+  //
+  // Return value:
+  // RAX
+
+  if(syscall_handlers[r->rax])
+  {
+    r->rax = syscall_handlers[r->rax](r->rax, r->rdi, r->rsi, r->rdx, r->r10, r->r8, r->r9);
+    return r;
+  }
+
+  debug_error("Unknown syscall, No:%d\n", r->rax);
+  debug("syscall_%d(%x, %x, %x, %x, %x, %x)\n", r->rax, r->rdi, r->rsi, r->rdx, r->r10, r->r8, r->r9);
+  for(;;);
+}
+
+int syscall_installed = 0;
+
+void syscall_init()
+{
+  msr_write(MSR_REG_STAR, (((uint64_t)SEG_KDATA | 0x3)<<48 | ((uint64_t)SEG_KCODE)<<32));
+  msr_write(MSR_REG_LSTAR, (uint64_t)syscall_entry);
+  msr_write(MSR_REG_EFER, msr_read(MSR_REG_EFER)| 1);
+  msr_write(MSR_REG_FMASK, RFLAGS_IF);
+
+  if(!syscall_installed)
+  {
+    register_int_handler(INT_SYSCALL, syscall_handler);
+    syscall_installed = 1;
+    memset(syscall_handlers, 0, 1024*sizeof(syscall_handler_t));
+
+    SYSCALL_REGISTER(debug, 0x3FF);
+  }
+
+}
+
+SYSCALL_DEF(debug)
+{
+  SYSCALL_INIT(char*, message);
+  debug_puts(message);
+  return 0;
+}

kernel/syscall/syscall_entry.S

@@ -0,0 +1,38 @@
+#include <mem.h>
+#include <gdt.h>
+#include <int.h>
+#include <cpu.h>
+.intel_syntax noprefix
+
+
+.global syscall_entry
+.global syscall_return
+.extern syscall_handler
+
+syscall_entry:
+
+  swapgs
+  mov [gs:GS_OFFSET_SCTEMP], rsp
+  mov rsp, [gs:GS_OFFSET_STACK]
+
+  // Prepare a fake interrupt stack
+  pushq SEG_UDATA // SS
+  push [gs:GS_OFFSET_SCTEMP] // RSP
+  push r11 // RFLAGS
+  pushq SEG_UCODE // CS
+  push rcx // RIP
+  pushq 0 // Error code
+  pushq INT_SYSCALL // Interrupt id
+  swapgs
+
+  jmp isr_common
+syscall_return:
+
+  pop rax
+  add rsp, 16
+  pop rcx
+  add rsp, 8
+  pop r11
+  pop rsp
+
+  sysretq