user mode : entry

[Martins3]

Context Switch && Interrupt, here I came.

• dune_config
• dune_trap_regs : general purpose regs + rip + rflags, we can ignore it savely.

[Martins3]

arch	MIPS	x86
interrupt	??	ss ip cs ??
context switch	??

• analyze the ptregs, callee saved register / caller saved register

• analyze context switch : cpu state other than regular regs

  • cp0
  • cr3

• mips syscall convention

• calling convention

[Martins3]

R0  R1  R2  R3  R4  R5  R6  R7  R8  R9  R10  R11  R12  R13  R14  R15
RAX RCX RDX RBX RSP RBP RSI RDI

ref : https://cs.lmu.edu/~ray/notes/nasmtutorial/

[Martins3]

代码 sysdeps/unix/sysv/linux/x86_64/syscall.S：

/* Usage: long syscall (syscall_number, arg1, arg2, arg3, arg4, arg5, arg6)
   We need to do some arg shifting, the syscall_number will be in
   rax.  */


        .text
ENTRY (syscall)
        movq %rdi, %rax         /* Syscall number -> rax.  */
        movq %rsi, %rdi         /* shift arg1 - arg5.  */
        movq %rdx, %rsi
        movq %rcx, %rdx
        movq %r8, %r10
        movq %r9, %r8
        movq 8(%rsp),%r9        /* arg6 is on the stack.  */
        syscall                 /* Do the system call.  */
        cmpq $-4095, %rax       /* Check %rax for error.  */
        jae SYSCALL_ERROR_LABEL /* Jump to error handler if error.  */
L(pseudo_end):
        ret                     /* Return to caller.  */

[Martins3]

GPR	parameter
%rdi	1st
%rsi	2st
%rdx	3st
%rcx	4st
%r8	5st
%r9	5st

[Martins3]

	ret = __dune_enter(dune_fd, conf); // %rdi -> dune_fd     %rsi->dune_conf

.globl __dune_enter
__dune_enter:
	pushfq
	subq	$REG_END, %rsp
	SAVE_REGS 1, 0
	SAVE_REST
	movq	%rsp, DUNE_CFG_RSP(%rsi) /* move %rsp to dune_conf::rsp */
	movq	%rsi, %rdx                                / *  dune_conf : rdx, parameter 4 */
	movq	$IOCTL_DUNE_ENTER, %rsi /* paramter 3 */
	movq	$16, %rax /* __NR_ioctl */       /* paramter 1, and dune_fd in %rdi, the paramter 2 */
	syscall