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       1                 :            : /*
       2                 :            :  * GCC stack protector support.
       3                 :            :  *
       4                 :            :  * Stack protector works by putting predefined pattern at the start of
       5                 :            :  * the stack frame and verifying that it hasn't been overwritten when
       6                 :            :  * returning from the function.  The pattern is called stack canary
       7                 :            :  * and gcc expects it to be defined by a global variable called
       8                 :            :  * "__stack_chk_guard" on ARM.  This unfortunately means that on SMP
       9                 :            :  * we cannot have a different canary value per task.
      10                 :            :  */
      11                 :            : 
      12                 :            : #ifndef _ASM_STACKPROTECTOR_H
      13                 :            : #define _ASM_STACKPROTECTOR_H 1
      14                 :            : 
      15                 :            : #include <linux/random.h>
      16                 :            : #include <linux/version.h>
      17                 :            : 
      18                 :            : extern unsigned long __stack_chk_guard;
      19                 :            : 
      20                 :            : /*
      21                 :            :  * Initialize the stackprotector canary value.
      22                 :            :  *
      23                 :            :  * NOTE: this must only be called from functions that never return,
      24                 :            :  * and it must always be inlined.
      25                 :            :  */
      26                 :            : static __always_inline void boot_init_stack_canary(void)
      27                 :            : {
      28                 :            :         unsigned long canary;
      29                 :            : 
      30                 :            :         /* Try to get a semi random initial value. */
      31                 :          0 :         get_random_bytes(&canary, sizeof(canary));
      32                 :          0 :         canary ^= LINUX_VERSION_CODE;
      33                 :            : 
      34                 :          0 :         current->stack_canary = canary;
      35                 :          0 :         __stack_chk_guard = current->stack_canary;
      36                 :            : }
      37                 :            : 
      38                 :            : #endif  /* _ASM_STACKPROTECTOR_H */