112  * If size is 0, then to be compatible with regular stack we want it to be as big as
113  * regular stack. Else PAGE_ALIGN it and return back
124  * Writes on shadow stack can either be `sspush` or `ssamoswap`. `sspush` can happen
125  * implicitly on current shadow stack pointed to by CSR_SSP. `ssamoswap` takes pointer to
126  * shadow stack. To keep it simple, we plan to use `ssamoswap` to perform writes on shadow
127  * stack.
132 	 * Never expect -1 on shadow stack. Expect return addresses and zero  in amo_user_shstk()
155  * Create a restore token on the shadow stack.  A token is always XLEN wide
179  * Save user shadow stack pointer on the shadow stack itself and return a pointer to saved location.
203  * Restores the user shadow stack pointer from the token on the shadow stack for task 'tsk'.
274 	 * which perform writes to CSR_SSP properly, shadow stack pivoting is not possible. Since  in SYSCALL_DEFINE3()
275 	 * CSR_SSP is writable by user mode, it itself can setup a shadow stack token subsequent  in SYSCALL_DEFINE3()
296  * This gets called during clone/clone3/fork. And is needed to allocate a shadow stack for
297  * cases where CLONE_VM is specified and thus a different stack is specified by user. We
298  * thus need a separate shadow stack too. How a separate shadow stack is specified by
301  * stack allocation is not needed (like in case of !CLONE_VM)
308 	/* If shadow stack is not supported, return 0 */  in shstk_alloc_thread_stack()
313 	 * If shadow stack is not enabled on the new thread, skip any  in shstk_alloc_thread_stack()
314 	 * switch to a new shadow stack.  in shstk_alloc_thread_stack()
320 	 * For CLONE_VFORK the child will share the parents shadow stack.  in shstk_alloc_thread_stack()
331 	 * stack.  in shstk_alloc_thread_stack()
338 	 * stack is needed for new cloned thread. Note: below allocation is happening  in shstk_alloc_thread_stack()
354 	/* If shadow stack is not supported or not enabled, nothing to release */  in shstk_release()
360 	 * shadow stack allocated, and exit_thread() calls this function to  in shstk_release()
368 	 * We know shadow stack is enabled but if base is NULL, then  in shstk_release()
369 	 * this task is not managing its own shadow stack (CLONE_VFORK). So  in shstk_release()
387 	/* this means shadow stack is enabled on the task */  in arch_get_shadow_stack_status()
410 	/* Request is to enable shadow stack and shadow stack is not enabled already */  in arch_set_shadow_stack_status()
412 		/* shadow stack was allocated and enable request again  in arch_set_shadow_stack_status()
427 	 * If a request to disable shadow stack happens, let's go ahead and release it  in arch_set_shadow_stack_status()
429 	 * not releasing the shadow stack (because it might be needed in parent). Although  in arch_set_shadow_stack_status()
431 	 * then in that case, it'll get entirely new shadow stack because following condition  in arch_set_shadow_stack_status()
433 	 *  - shadow stack was not enabled for vforked child  in arch_set_shadow_stack_status()
434 	 *  - shadow stack base was anyways pointing to 0  in arch_set_shadow_stack_status()
436 	 * stack whenever VFORKed child releases resources via exit or exec but at the same  in arch_set_shadow_stack_status()
437 	 * time we want VFORKed child to break away and establish new shadow stack if it desires  in arch_set_shadow_stack_status()
533 …pr_info("RISC-V user CFI disabled via cmdline - shadow stack status : %s, landing pad status : %s\…  in setup_global_riscv_enable()