base: provide Thread_base::stack_size(size_t)

The new method enhances the stack of the targeted thread if it is smaller
than a given size.

ref #1075

base-foc/src/base/thread/thread.cc

@@ -31,6 +31,40 @@ namespace Genode {
 }
 
 
+void Thread_base::Context::stack_size(size_t const size)
+{
+	/* check if the stack needs to be enhanced */
+	size_t const stack_size = (addr_t)_stack - stack_base;
+	if (stack_size >= size) { return; }
+
+	/* check if the stack enhancement fits the context region */
+	enum {
+		CONTEXT_SIZE      = Native_config::context_virtual_size(),
+		CONTEXT_AREA_BASE = Native_config::context_area_virtual_base(),
+		UTCB_SIZE         = sizeof(Native_utcb),
+		PAGE_SIZE_LOG2    = 12,
+		PAGE_SIZE         = (1UL << PAGE_SIZE_LOG2),
+	};
+	addr_t const context_base = Context_allocator::addr_to_base(this);
+	size_t const ds_size = align_addr(size - stack_size, PAGE_SIZE_LOG2);
+	if (stack_base - ds_size < context_base) { throw Stack_too_large(); }
+
+	/* allocate and attach backing store for the stack enhancement */
+	addr_t const ds_addr = stack_base - ds_size - CONTEXT_AREA_BASE;
+	try {
+		Ram_session * const ram = env_context_area_ram_session();
+		Ram_dataspace_capability const ds_cap = ram->alloc(ds_size);
+		Rm_session * const rm = env_context_area_rm_session();
+		void * const attach_addr = rm->attach_at(ds_cap, ds_addr, ds_size);
+		if (ds_addr != (addr_t)attach_addr) { throw Stack_alloc_failed(); }
+	}
+	catch (Ram_session::Alloc_failed) { throw Stack_alloc_failed(); }
+
+	/* update context information */
+	stack_base -= ds_size;
+}
+
+
 Thread_base::Context *
 Thread_base::_alloc_context(size_t stack_size, bool main_thread)
 {

base/include/base/thread.h

@@ -112,6 +112,16 @@ namespace Genode {
 					return ((addr_t)_stack & ~0xf) - Abi::stack_adjustment();
 				}
 
+				/**
+				 * Ensure that the stack has a given size at the minimum
+				 *
+				 * \param size  minimum stack size
+				 *
+				 * \throw Stack_too_large
+				 * \throw Stack_alloc_failed
+				 */
+				void stack_size(size_t const size);
+
 				/**
 				 * Virtual address of the start of the stack
 				 *
@@ -421,6 +431,16 @@ namespace Genode {
 			 */
 			static Thread_base *myself();
 
+			/**
+			 * Ensure that the stack has a given size at the minimum
+			 *
+			 * \param size  minimum stack size
+			 *
+			 * \throw Context::Stack_too_large
+			 * \throw Context::Stack_alloc_failed
+			 */
+			void stack_size(size_t const size) { _context->stack_size(size); }
+
 			/**
 			 * Return user-level thread control block
 			 *

base/src/base/thread/thread.cc

@@ -31,6 +31,40 @@ namespace Genode {
 }
 
 
+void Thread_base::Context::stack_size(size_t const size)
+{
+	/* check if the stack needs to be enhanced */
+	size_t const stack_size = (addr_t)_stack - stack_base;
+	if (stack_size >= size) { return; }
+
+	/* check if the stack enhancement fits the context region */
+	enum {
+		CONTEXT_SIZE      = Native_config::context_virtual_size(),
+		CONTEXT_AREA_BASE = Native_config::context_area_virtual_base(),
+		UTCB_SIZE         = sizeof(Native_utcb),
+		PAGE_SIZE_LOG2    = 12,
+		PAGE_SIZE         = (1UL << PAGE_SIZE_LOG2),
+	};
+	addr_t const context_base = Context_allocator::addr_to_base(this);
+	size_t const ds_size = align_addr(size - stack_size, PAGE_SIZE_LOG2);
+	if (stack_base - ds_size < context_base) { throw Stack_too_large(); }
+
+	/* allocate and attach backing store for the stack enhancement */
+	addr_t const ds_addr = stack_base - ds_size - CONTEXT_AREA_BASE;
+	try {
+		Ram_session * const ram = env_context_area_ram_session();
+		Ram_dataspace_capability const ds_cap = ram->alloc(ds_size);
+		Rm_session * const rm = env_context_area_rm_session();
+		void * const attach_addr = rm->attach_at(ds_cap, ds_addr, ds_size);
+		if (ds_addr != (addr_t)attach_addr) { throw Stack_alloc_failed(); }
+	}
+	catch (Ram_session::Alloc_failed) { throw Stack_alloc_failed(); }
+
+	/* update context information */
+	stack_base -= ds_size;
+}
+
+
 Thread_base::Context *
 Thread_base::_alloc_context(size_t stack_size, bool main_thread)
 {