Initial Commit

src/syscall/syscall_entry.S

@@ -0,0 +1,30 @@
+.global syscall_entry
+
+syscall_entry:
+    swapgs
+
+    push %rcx
+    push %r11
+
+    # Save original args before we clobber them
+    push %rdi        # orig rdi (arg1)
+    push %rsi        # orig rsi (arg2)
+    push %rdx        # orig rdx (arg3)
+
+    # Handle r8/r9 before r8 gets clobbered
+    mov %r8,  %r9    # r9  = orig r8  (6th param)
+    mov %r10, %r8    # r8  = orig r10 (5th param)
+
+    # Pop in reverse order to place into correct SysV registers
+    pop  %rcx        # rcx = orig rdx (4th param)
+    pop  %rdx        # rdx = orig rsi (3rd param)
+    pop  %rsi        # rsi = orig rdi (2nd param)
+    mov  %rax, %rdi  # rdi = rax      (1st param = syscall number)
+
+    call syscall_handler
+
+    pop %r11
+    pop %rcx
+
+    swapgs
+    sysretq