Linux内核分析之系统调用
Linux内核分析之系统调用
在内核入口函数start_kernel中调用trap_init实现系统调用的初始化工作
- void __init trap_init(void)
- {
- ...
- set_system_trap_gate(SYSCALL_VECTOR, &system_call);
- ....
- }
- ENTRY(system_call)
- RING0_INT_FRAME # can't unwind into user space anyway
- pushl %eax # save orig_eax
- CFI_ADJUST_CFA_OFFSET 4
- SAVE_ALL
- GET_THREAD_INFO(%ebp)
- # system call tracing in operation / emulation
- testl $_TIF_WORK_SYSCALL_ENTRY,TI_flags(%ebp)
- jnz syscall_trace_entry
- cmpl $(nr_syscalls), %eax
- jae syscall_badsys
- syscall_call:
- call *sys_call_table(,%eax,4)/*跳转到具体的系统调用函数*/
- movl %eax,PT_EAX(%esp) # store the return value
- syscall_exit:
- LOCKDEP_SYS_EXIT
- DISABLE_INTERRUPTS(CLBR_ANY) # make sure we don't miss an interrupt
- # setting need_resched or sigpending
- # between sampling and the iret
- TRACE_IRQS_OFF
- movl TI_flags(%ebp), %ecx
- testl $_TIF_ALLWORK_MASK, %ecx # current->work
- jne syscall_exit_work
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