13  *   a thread as a stack and expect the mapping to grow when we touch the
15  *   growable mapping as a stack.
17  *   The kernel only grows the memory region when the stack pointer is within
22  *   'stack_guard_gap' pages to an existing mapping. So when we map the stack we
23  *   make sure there is enough of free address space before the lowest stack
28  *   The stack memory map would look like:
36  *   ^           |  -  -  stack size  -  -  |
39  *               stack bottom       stack top
43  *   We allocate stack as we do in the first test but we mmap a page in the
44  *   space the stack is supposed to grow into and we expect the thread to
77 		tst_brk(TCONF, "Test can't be performed with stack grows up architecture");  in setup()
83  * Returns stack lowest address. Note that the address is not mapped and will
84  * be mapped on page fault when we grow the stack to the lowest address possible.
103 	tst_res(TINFO, "start = %p, stack_top = %p, stack bottom = %p",  in allocate_stack()
105 	tst_res(TINFO, "mapped pages %zu, stack pages %zu",  in allocate_stack()
122  * We set the limit one page above the stack bottom to make sure that the stack
126  * Generally the stack frame would be much smaller than page_size so moving the
130 static void grow_stack(void *stack, size_t size)  in grow_stack()  argument
135 	void *limit = stack + page_size;  in grow_stack()
141 	ret = pthread_attr_setstack(&attr, stack, size);  in grow_stack()
155 	void *stack;  in grow_stack_success()  local
159 		stack = allocate_stack(stack_size, mapped_size);  in grow_stack_success()
160 		grow_stack(stack, stack_size);  in grow_stack_success()
165 		tst_res(TPASS, "Stack grows in unmapped region");  in grow_stack_success()
172  * We map a page at the bottom of the stack which will cause the thread to be
179 	void *stack;  in grow_stack_fail()  local
184 		stack = allocate_stack(stack_size, mapped_size);  in grow_stack_fail()
186 		SAFE_MMAP(stack, page_size, PROT_READ | PROT_WRITE,  in grow_stack_fail()
189 		tst_res(TINFO, "mapped page at %p", stack);  in grow_stack_fail()
191 		grow_stack(stack, stack_size);  in grow_stack_fail()