Posted on 2012-10-15 10:37
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linux內核
Linux通過slab分配器動態分配task_struct結構，該結構定義在了<include/linux/sched.h>文件中，進程描述符中包含一個具體進程的所有信息，各個進程的task_struct存放在它們內核棧的尾端。在棧底（對于向下增長的棧）或棧頂（對于向上增長的棧）創建一個新的結構struct thread_info。利用這個新的機構來迅速的找到task_struct的位置。 下面是kernel2.6.32.10里task_struct的定義（對于x86類型的CPU來說文件位于：arch/x86/include/asm /include/asm/thread_info.h）：- struct thread_info {
- struct task_struct *task; /* main task structure */
- struct exec_domain *exec_domain; /* execution domain */
- __u32 flags; /* low level flags */
- __u32 status; /* thread synchronous flags */
- __u32 cpu; /* current CPU */
- int preempt_count; /* 0 => preemptable, <0 => BUG */
- mm_segment_t addr_limit;
- struct restart_block restart_block;
- void __user *sysenter_return;
- #ifdef CONFIG_X86_32
- unsigned long previous_esp; /* ESP of the previous stack in case of nested (IRQ) stacks*/
- __u8 supervisor_stack[0];
- #endif
- int uaccess_err;
- };
- /* how to get the current stack pointer from C */
- register unsigned long current_stack_pointer asm("esp") __used;
- /* how to get the thread information struct from C */
- static inline struct thread_info *current_thread_info(void)
- {
- return (struct thread_info *)
- (current_stack_pointer & ~(THREAD_SIZE - 1));
- };