3  * shstk.c - Intel shadow stack support
47  * Create a restore token on the shadow stack.  A token is always 8-byte
79  * The shadow stack pointer(SSP) is moved by CALL, RET, and INCSSPQ. The
80  * INCSSP instruction can increment the shadow stack pointer. It is the
81  * shadow stack analog of an instruction like:
91  * ssp += nr_to_pop * 8; // move the shadow stack
145 	 * case it is ok to leak a shadow stack, so just exit out.  in unmap_shadow_stack()
201 	 * If shadow stack is not enabled on the new thread, skip any  in shstk_alloc_thread_stack()
202 	 * switch to a new shadow stack.  in shstk_alloc_thread_stack()
208 	 * For CLONE_VFORK the child will share the parents shadow stack.  in shstk_alloc_thread_stack()
209 	 * Make sure to clear the internal tracking of the thread shadow  in shstk_alloc_thread_stack()
219 	 * For !CLONE_VM the child will use a copy of the parents shadow  in shstk_alloc_thread_stack()
303 	 * It is possible for the SSP to be off the end of a shadow stack by 4  in shstk_pop_sigframe()
304 	 * or 8 bytes. If the shadow stack is at the start of a page or 4 bytes  in shstk_pop_sigframe()
306 	 * read is actually shadow stack.  in shstk_pop_sigframe()
415 	 * shadow stack allocated, and exit_thread() calls this function to  in shstk_free()
424 	 * own shadow stack (CLONE_VFORK). So skip freeing it.  in shstk_free()
432 	 * indicated an attempt to free the thread shadow stack twice.  in shstk_free()
451 	 * Only enable WRSS if shadow stack is enabled. If shadow stack is not  in wrss_control()
494 	/* Disable WRSS too when disabling shadow stack */  in shstk_disable()