libsel4utils/src/thread.c - 3p/sel4/sel4_libs - Git at Google

 /*
  * Copyright 2017, Data61
  * Commonwealth Scientific and Industrial Research Organisation (CSIRO)
  * ABN 41 687 119 230.
  *
  * This software may be distributed and modified according to the terms of
  * the BSD 2-Clause license. Note that NO WARRANTY is provided.
  * See "LICENSE_BSD2.txt" for details.
  *
  * @TAG(DATA61_BSD)
  */

 #include <autoconf.h>
 #include <sel4utils/gen_config.h>

 #include <inttypes.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>

 #include <sel4/sel4.h>
 #include <vka/vka.h>
 #include <vka/object.h>
 #include <vspace/vspace.h>
 #include <sel4runtime.h>
 #include <sel4utils/api.h>
 #include <sel4utils/mapping.h>
 #include <sel4utils/thread.h>
 #include <sel4utils/util.h>
 #include <sel4utils/arch/util.h>
 #include <sel4utils/helpers.h>
 #include <utils/stack.h>

 static int write_ipc_buffer_user_data(vka_t *vka, vspace_t *vspace, seL4_CPtr ipc_buf, uintptr_t buf_loc)
 {
     void *mapping = sel4utils_dup_and_map(vka, vspace, ipc_buf, seL4_PageBits);
     if (!mapping) {
         return -1;
     }
     seL4_IPCBuffer *buffer = mapping;
     buffer->userData = buf_loc;
     sel4utils_unmap_dup(vka, vspace, mapping, seL4_PageBits);
     return 0;
 }

 int sel4utils_configure_thread(vka_t *vka, vspace_t *parent, vspace_t *alloc, seL4_CPtr fault_endpoint,
                                seL4_CNode cspace, seL4_Word cspace_root_data, sel4utils_thread_t *res)
 {

     sel4utils_thread_config_t config = {0};
     config = thread_config_fault_endpoint(config, fault_endpoint);
     config = thread_config_cspace(config, cspace, cspace_root_data);
     config = thread_config_create_reply(config);
     return sel4utils_configure_thread_config(vka, parent, alloc, config, res);
 }

 int sel4utils_configure_thread_config(vka_t *vka, vspace_t *parent, vspace_t *alloc,
                                       sel4utils_thread_config_t config, sel4utils_thread_t *res)
 {
     memset(res, 0, sizeof(sel4utils_thread_t));

     int error = vka_alloc_tcb(vka, &res->tcb);
     if (error == -1) {
         ZF_LOGE("vka_alloc tcb failed");
         sel4utils_clean_up_thread(vka, alloc, res);
         return -1;
     }

     if (!config.no_ipc_buffer) {
         res->ipc_buffer_addr = (seL4_Word) vspace_new_ipc_buffer(alloc, &res->ipc_buffer);

         if (res->ipc_buffer_addr == 0) {
             ZF_LOGE("ipc buffer allocation failed");
             return -1;
         }

         if (write_ipc_buffer_user_data(vka, parent, res->ipc_buffer, res->ipc_buffer_addr)) {
             ZF_LOGE("failed to set user data word in IPC buffer");
             return -1;
         }
     }

     if (config_set(CONFIG_KERNEL_RT) && config.create_reply) {
         if (vka_alloc_reply(vka, &res->reply)) {
             ZF_LOGE("Failed to allocate reply");
             sel4utils_clean_up_thread(vka, alloc, res);
             return -1;
         }
         res->own_reply = true;
     } else {
         res->reply.cptr = config.reply;
     }

     if (config.sched_params.create_sc) {
         if (!config_set(CONFIG_KERNEL_RT)) {
             ZF_LOGE("Cannot create a scheduling context on a non-RT kernel");
             sel4utils_clean_up_thread(vka, alloc, res);
             return -1;
         }

         /* allocate a scheduling context */
         if (vka_alloc_sched_context(vka, &res->sched_context)) {
             ZF_LOGE("Failed to allocate sched context");
             sel4utils_clean_up_thread(vka, alloc, res);
             return -1;
         }

         /* configure the scheduling context */
         if (config_set(CONFIG_KERNEL_RT)) {
             error = api_sched_ctrl_configure(config.sched_params.sched_ctrl, res->sched_context.cptr,
                                              config.sched_params.budget, config.sched_params.period,
                                              config.sched_params.extra_refills, config.sched_params.badge);
         }
         if (error != seL4_NoError) {
             ZF_LOGE("Failed to configure sched context");
             sel4utils_clean_up_thread(vka, alloc, res);
             return -1;
         }
         res->own_sc = true;
     } else {
         res->sched_context.cptr = config.sched_params.sched_context;
     }
     seL4_Word null_cap_data = seL4_NilData;
     error = api_tcb_configure(res->tcb.cptr, config.fault_endpoint,
                               seL4_CapNull,
                               res->sched_context.cptr,
                               config.cspace,
                               config.cspace_root_data, vspace_get_root(alloc),
                               null_cap_data, res->ipc_buffer_addr, res->ipc_buffer);

     if (error != seL4_NoError) {
         ZF_LOGE("TCB configure failed with seL4 error code %d", error);
         sel4utils_clean_up_thread(vka, alloc, res);
         return -1;
     }

     /* only set the prio fields if the value is > 0. As we just allocated the
      * TCB above, the prio and mcp are already 0. */
     if (config.sched_params.mcp) {
         error = seL4_TCB_SetMCPriority(res->tcb.cptr, config.sched_params.auth,
                                        config.sched_params.mcp);
         if (error) {
             ZF_LOGE("Failed to set mcpriority, %d", error);
             return -1;
         }
     }

     if (config.sched_params.priority) {
         error = seL4_TCB_SetPriority(res->tcb.cptr, config.sched_params.auth,
                                      config.sched_params.priority);
         if (error) {
             ZF_LOGE("Failed to set priority, %d", error);
             sel4utils_clean_up_thread(vka, alloc, res);
             return -1;
         }
     }

     if (config.custom_stack_size) {
         res->stack_size = config.stack_size;
     } else {
         res->stack_size = BYTES_TO_4K_PAGES(CONFIG_SEL4UTILS_STACK_SIZE);
     }

     if (res->stack_size > 0) {
         res->stack_top = vspace_new_sized_stack(alloc, res->stack_size);

         if (res->stack_top == NULL) {
             ZF_LOGE("Stack allocation failed!");
             sel4utils_clean_up_thread(vka, alloc, res);
             return -1;
         }

         res->initial_stack_pointer = res->stack_top;
     }

     return 0;
 }

 int sel4utils_start_thread(sel4utils_thread_t *thread, sel4utils_thread_entry_fn entry_point,
                            void *arg0, void *arg1, int resume)
 {
     seL4_UserContext context = {0};
     size_t context_size = sizeof(seL4_UserContext) / sizeof(seL4_Word);

     size_t tls_size = sel4runtime_get_tls_size();
     /* make sure we're not going to use too much of the stack */
     if (tls_size > thread->stack_size * PAGE_SIZE_4K / 8) {
         ZF_LOGE("TLS would use more than 1/8th of the application stack %zu/%zu", tls_size, thread->stack_size);
         return -1;
     }
     uintptr_t tls_base = (uintptr_t)thread->initial_stack_pointer - tls_size;
     uintptr_t tp = (uintptr_t)sel4runtime_write_tls_image((void *)tls_base);
     seL4_IPCBuffer *ipc_buffer_addr = (void *)thread->ipc_buffer_addr;
     sel4runtime_set_tls_variable(tp, __sel4_ipc_buffer, ipc_buffer_addr);

     uintptr_t aligned_stack_pointer = ALIGN_DOWN(tls_base, STACK_CALL_ALIGNMENT);

     int error = sel4utils_arch_init_local_context(entry_point, arg0, arg1,
                                                   (void *) thread->ipc_buffer_addr,
                                                   (void *) aligned_stack_pointer,
                                                   &context);
     if (error) {
         return error;
     }

     error = seL4_TCB_WriteRegisters(thread->tcb.cptr, false, 0, context_size, &context);
     if (error) {
         return error;
     }

     error = seL4_TCB_SetTLSBase(thread->tcb.cptr, tp);
     if (error) {
         return error;
     }

     if (resume) {
         return seL4_TCB_Resume(thread->tcb.cptr);
     }
     return 0;
 }

 void sel4utils_clean_up_thread(vka_t *vka, vspace_t *alloc, sel4utils_thread_t *thread)
 {
     if (thread->tcb.cptr != 0) {
         vka_free_object(vka, &thread->tcb);
     }

     if (thread->ipc_buffer_addr != 0) {
         vspace_free_ipc_buffer(alloc, (seL4_Word *) thread->ipc_buffer_addr);
     }

     if (thread->stack_top != 0) {
         vspace_free_sized_stack(alloc, thread->stack_top, thread->stack_size);
     }

     if (thread->own_sc && thread->sched_context.cptr != 0) {
         vka_free_object(vka, &thread->sched_context);
     }

     if (thread->own_reply && thread->reply.cptr != 0) {
         vka_free_object(vka, &thread->reply);
     }

     memset(thread, 0, sizeof(sel4utils_thread_t));
 }

 void sel4utils_print_fault_message(seL4_MessageInfo_t tag, const char *thread_name)
 {
     seL4_Fault_t fault = seL4_getFault(tag);

     switch (seL4_Fault_get_seL4_FaultType(fault)) {
     case seL4_Fault_VMFault:
         assert(seL4_MessageInfo_get_length(tag) == seL4_VMFault_Length);
         printf("%sPagefault from [%s]: %s %s at PC: %p vaddr: %p, FSR %p%s\n",
                COLOR_ERROR,
                thread_name,
                sel4utils_is_read_fault() ? "read" : "write",
                seL4_Fault_VMFault_get_PrefetchFault(fault) ? "prefetch fault" : "fault",
                (void *)seL4_Fault_VMFault_get_IP(fault),
                (void *)seL4_Fault_VMFault_get_Addr(fault),
                (void *)seL4_Fault_VMFault_get_FSR(fault),
                COLOR_NORMAL);
         break;

     case seL4_Fault_UnknownSyscall:
         assert(seL4_MessageInfo_get_length(tag) == seL4_UnknownSyscall_Length);
         printf("%sBad syscall from [%s]: scno %"PRIuPTR" at PC: %p%s\n",
                COLOR_ERROR,
                thread_name,
                seL4_Fault_UnknownSyscall_get_Syscall(fault),
                (void *) seL4_Fault_UnknownSyscall_get_FaultIP(fault),
                COLOR_NORMAL
               );

         break;

     case seL4_Fault_UserException:
         assert(seL4_MessageInfo_get_length(tag) == seL4_UserException_Length);
         printf("%sInvalid instruction from [%s] at PC: %p%s\n",
                COLOR_ERROR,
                thread_name,
                (void *)seL4_Fault_UserException_get_FaultIP(fault),
                COLOR_NORMAL);
         break;

     case seL4_Fault_CapFault:
         printf("%sCap fault from [%s] in phase %s\nPC = %p\nCPtr = %p%s\n",
                COLOR_ERROR, thread_name,
                seL4_Fault_CapFault_get_InRecvPhase(fault) ? "receive" : "send",
                (void *) seL4_Fault_CapFault_get_IP(fault),
                (void *) seL4_Fault_CapFault_get_Addr(fault),
                COLOR_NORMAL);
         break;
 #ifdef CONFIG_KERNEL_RT
     case seL4_Fault_Timeout:
         printf("Timeout fault from %s\n", thread_name);
         break;
 #endif

     default:
         /* What? Why are we here? What just happened? */
         printf("Unknown fault from [%s]: %"PRIuPTR" (length = %"PRIuPTR")\n", thread_name, seL4_MessageInfo_get_label(tag), seL4_MessageInfo_get_length(tag));
         break;
     }
 }

 static int
 fault_handler(char *name, seL4_CPtr endpoint)
 {
     seL4_MessageInfo_t info;
     while (1) {
         /* sleep so other things can run */
         info = api_wait(endpoint, NULL);
         sel4utils_print_fault_message(info, name);
     }
     return 0;
 }

 int
 sel4utils_start_fault_handler(seL4_CPtr fault_endpoint, vka_t *vka, vspace_t *vspace,
                               seL4_CPtr cspace, seL4_Word cap_data, char *name,
                               sel4utils_thread_t *res)
 {
     int error = sel4utils_configure_thread(vka, vspace, vspace, 0, cspace,
                                            cap_data, res);

     if (error) {
         ZF_LOGE("Failed to configure fault handling thread\n");
         return -1;
     }

     return sel4utils_start_thread(res, (sel4utils_thread_entry_fn)fault_handler, name,
                                   (void *) fault_endpoint, 1);
 }

 int
 sel4utils_checkpoint_thread(sel4utils_thread_t *thread, sel4utils_checkpoint_t *checkpoint, bool suspend)
 {
     assert(checkpoint != NULL);

     int error = seL4_TCB_ReadRegisters(thread->tcb.cptr, suspend, 0, sizeof(seL4_UserContext) / sizeof(seL4_Word),
             &checkpoint->regs);
     if (error) {
         ZF_LOGE("Failed to read registers of tcb while checkpointing\n");
         return error;
     }

     checkpoint->sp = sel4utils_get_sp(checkpoint->regs);
 #ifdef CONFIG_ARCH_X86_64
     if (config_set(CONFIG_SYSENTER)) {
         /* on x64, using sysenter, the kernel ABI expects rcx to be set to rsp,
          * and rdx to be set to the fault instruction. Simulate this behaviour here
          * before resuming. Note that this will only work for threads checkpointed
          * at sysenter, e.g. while in a system call (eg seL4_Recv). */
         checkpoint->regs.rcx = checkpoint->regs.rsp;
         checkpoint->regs.rdx = checkpoint->regs.rip;
     } else if (config_set(CONFIG_SYSCALL)) {
         /* on x64, using syscall, when a thread is in the kernel,
          * sp is stored in rbx. So use rbx for stack calculations */
          checkpoint->sp = checkpoint->regs.rbx;
     }
 #endif /* CONFIG_ARCH_X86_64 */

     size_t stack_size = (uintptr_t) thread->stack_top - checkpoint->sp;
     checkpoint->stack = malloc(stack_size);
     if (checkpoint->stack == NULL) {
         ZF_LOGE("Failed to malloc stack of size %zu\n", stack_size);
         return -1;
     }

     memcpy(checkpoint->stack, (void *) checkpoint->sp, stack_size);
     checkpoint->thread = thread;

     return error;
 }

 int
 sel4utils_checkpoint_restore(sel4utils_checkpoint_t *checkpoint, bool free_memory, bool resume)
 {
     assert(checkpoint != NULL);

     size_t stack_size = (uintptr_t) checkpoint->thread->stack_top - checkpoint->sp;
     memcpy((void *) checkpoint->sp, checkpoint->stack, stack_size);

     int error = seL4_TCB_WriteRegisters(checkpoint->thread->tcb.cptr, resume, 0,
             sizeof(seL4_UserContext) / sizeof (seL4_Word),
             &checkpoint->regs);
     if (error) {
         ZF_LOGE("Failed to restore registers of tcb while restoring checkpoint\n");
         return error;
     }

     if (free_memory) {
        sel4utils_free_checkpoint(checkpoint);
     }

     return error;
 }

 void
 sel4utils_free_checkpoint(sel4utils_checkpoint_t *checkpoint)
 {
     free(checkpoint->stack);
 }

 int sel4utils_set_sched_affinity(sel4utils_thread_t *thread, sched_params_t params) {
 #if CONFIG_MAX_NUM_NODES > 1
 #ifdef CONFIG_KERNEL_RT
     return api_sched_ctrl_configure(params.sched_ctrl, thread->sched_context.cptr, params.budget, params.period,
                                     params.extra_refills, params.badge);

 #else
     return seL4_TCB_SetAffinity(thread->tcb.cptr, params.core);
 #endif
 #else
     return -ENOSYS;
 #endif
 }
	/*
	* Copyright 2017, Data61
	* Commonwealth Scientific and Industrial Research Organisation (CSIRO)
	* ABN 41 687 119 230.
	*
	* This software may be distributed and modified according to the terms of
	* the BSD 2-Clause license. Note that NO WARRANTY is provided.
	* See "LICENSE_BSD2.txt" for details.
	*
	* @TAG(DATA61_BSD)
	*/

	#include <autoconf.h>
	#include <sel4utils/gen_config.h>

	#include <inttypes.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include <string.h>

	#include <sel4/sel4.h>
	#include <vka/vka.h>
	#include <vka/object.h>
	#include <vspace/vspace.h>
	#include <sel4runtime.h>
	#include <sel4utils/api.h>
	#include <sel4utils/mapping.h>
	#include <sel4utils/thread.h>
	#include <sel4utils/util.h>
	#include <sel4utils/arch/util.h>
	#include <sel4utils/helpers.h>
	#include <utils/stack.h>

	static int write_ipc_buffer_user_data(vka_t vka, vspace_t vspace, seL4_CPtr ipc_buf, uintptr_t buf_loc)
	{
	void *mapping = sel4utils_dup_and_map(vka, vspace, ipc_buf, seL4_PageBits);
	if (!mapping) {
	return -1;
	}
	seL4_IPCBuffer *buffer = mapping;
	buffer->userData = buf_loc;
	sel4utils_unmap_dup(vka, vspace, mapping, seL4_PageBits);
	return 0;
	}

	int sel4utils_configure_thread(vka_t vka, vspace_t parent, vspace_t *alloc, seL4_CPtr fault_endpoint,
	seL4_CNode cspace, seL4_Word cspace_root_data, sel4utils_thread_t *res)
	{

	sel4utils_thread_config_t config = {0};
	config = thread_config_fault_endpoint(config, fault_endpoint);
	config = thread_config_cspace(config, cspace, cspace_root_data);
	config = thread_config_create_reply(config);
	return sel4utils_configure_thread_config(vka, parent, alloc, config, res);
	}

	int sel4utils_configure_thread_config(vka_t vka, vspace_t parent, vspace_t *alloc,
	sel4utils_thread_config_t config, sel4utils_thread_t *res)
	{
	memset(res, 0, sizeof(sel4utils_thread_t));

	int error = vka_alloc_tcb(vka, &res->tcb);
	if (error == -1) {
	ZF_LOGE("vka_alloc tcb failed");
	sel4utils_clean_up_thread(vka, alloc, res);
	return -1;
	}

	if (!config.no_ipc_buffer) {
	res->ipc_buffer_addr = (seL4_Word) vspace_new_ipc_buffer(alloc, &res->ipc_buffer);

	if (res->ipc_buffer_addr == 0) {
	ZF_LOGE("ipc buffer allocation failed");
	return -1;
	}

	if (write_ipc_buffer_user_data(vka, parent, res->ipc_buffer, res->ipc_buffer_addr)) {
	ZF_LOGE("failed to set user data word in IPC buffer");
	return -1;
	}
	}

	if (config_set(CONFIG_KERNEL_RT) && config.create_reply) {
	if (vka_alloc_reply(vka, &res->reply)) {
	ZF_LOGE("Failed to allocate reply");
	sel4utils_clean_up_thread(vka, alloc, res);
	return -1;
	}
	res->own_reply = true;
	} else {
	res->reply.cptr = config.reply;
	}

	if (config.sched_params.create_sc) {
	if (!config_set(CONFIG_KERNEL_RT)) {
	ZF_LOGE("Cannot create a scheduling context on a non-RT kernel");
	sel4utils_clean_up_thread(vka, alloc, res);
	return -1;
	}

	/* allocate a scheduling context */
	if (vka_alloc_sched_context(vka, &res->sched_context)) {
	ZF_LOGE("Failed to allocate sched context");
	sel4utils_clean_up_thread(vka, alloc, res);
	return -1;
	}

	/* configure the scheduling context */
	if (config_set(CONFIG_KERNEL_RT)) {
	error = api_sched_ctrl_configure(config.sched_params.sched_ctrl, res->sched_context.cptr,
	config.sched_params.budget, config.sched_params.period,
	config.sched_params.extra_refills, config.sched_params.badge);
	}
	if (error != seL4_NoError) {
	ZF_LOGE("Failed to configure sched context");
	sel4utils_clean_up_thread(vka, alloc, res);
	return -1;
	}
	res->own_sc = true;
	} else {
	res->sched_context.cptr = config.sched_params.sched_context;
	}
	seL4_Word null_cap_data = seL4_NilData;
	error = api_tcb_configure(res->tcb.cptr, config.fault_endpoint,
	seL4_CapNull,
	res->sched_context.cptr,
	config.cspace,
	config.cspace_root_data, vspace_get_root(alloc),
	null_cap_data, res->ipc_buffer_addr, res->ipc_buffer);

	if (error != seL4_NoError) {
	ZF_LOGE("TCB configure failed with seL4 error code %d", error);
	sel4utils_clean_up_thread(vka, alloc, res);
	return -1;
	}

	/* only set the prio fields if the value is > 0. As we just allocated the
	* TCB above, the prio and mcp are already 0. */
	if (config.sched_params.mcp) {
	error = seL4_TCB_SetMCPriority(res->tcb.cptr, config.sched_params.auth,
	config.sched_params.mcp);
	if (error) {
	ZF_LOGE("Failed to set mcpriority, %d", error);
	return -1;
	}
	}

	if (config.sched_params.priority) {
	error = seL4_TCB_SetPriority(res->tcb.cptr, config.sched_params.auth,
	config.sched_params.priority);
	if (error) {
	ZF_LOGE("Failed to set priority, %d", error);
	sel4utils_clean_up_thread(vka, alloc, res);
	return -1;
	}
	}

	if (config.custom_stack_size) {
	res->stack_size = config.stack_size;
	} else {
	res->stack_size = BYTES_TO_4K_PAGES(CONFIG_SEL4UTILS_STACK_SIZE);
	}

	if (res->stack_size > 0) {
	res->stack_top = vspace_new_sized_stack(alloc, res->stack_size);

	if (res->stack_top == NULL) {
	ZF_LOGE("Stack allocation failed!");
	sel4utils_clean_up_thread(vka, alloc, res);
	return -1;
	}

	res->initial_stack_pointer = res->stack_top;
	}

	return 0;
	}

	int sel4utils_start_thread(sel4utils_thread_t *thread, sel4utils_thread_entry_fn entry_point,
	void arg0, void arg1, int resume)
	{
	seL4_UserContext context = {0};
	size_t context_size = sizeof(seL4_UserContext) / sizeof(seL4_Word);

	size_t tls_size = sel4runtime_get_tls_size();
	/* make sure we're not going to use too much of the stack */
	if (tls_size > thread->stack_size * PAGE_SIZE_4K / 8) {
	ZF_LOGE("TLS would use more than 1/8th of the application stack %zu/%zu", tls_size, thread->stack_size);
	return -1;
	}
	uintptr_t tls_base = (uintptr_t)thread->initial_stack_pointer - tls_size;
	uintptr_t tp = (uintptr_t)sel4runtime_write_tls_image((void *)tls_base);
	seL4_IPCBuffer ipc_buffer_addr = (void )thread->ipc_buffer_addr;
	sel4runtime_set_tls_variable(tp, __sel4_ipc_buffer, ipc_buffer_addr);

	uintptr_t aligned_stack_pointer = ALIGN_DOWN(tls_base, STACK_CALL_ALIGNMENT);

	int error = sel4utils_arch_init_local_context(entry_point, arg0, arg1,
	(void *) thread->ipc_buffer_addr,
	(void *) aligned_stack_pointer,
	&context);
	if (error) {
	return error;
	}

	error = seL4_TCB_WriteRegisters(thread->tcb.cptr, false, 0, context_size, &context);
	if (error) {
	return error;
	}

	error = seL4_TCB_SetTLSBase(thread->tcb.cptr, tp);
	if (error) {
	return error;
	}

	if (resume) {
	return seL4_TCB_Resume(thread->tcb.cptr);
	}
	return 0;
	}

	void sel4utils_clean_up_thread(vka_t vka, vspace_t alloc, sel4utils_thread_t *thread)
	{
	if (thread->tcb.cptr != 0) {
	vka_free_object(vka, &thread->tcb);
	}

	if (thread->ipc_buffer_addr != 0) {
	vspace_free_ipc_buffer(alloc, (seL4_Word *) thread->ipc_buffer_addr);
	}

	if (thread->stack_top != 0) {
	vspace_free_sized_stack(alloc, thread->stack_top, thread->stack_size);
	}

	if (thread->own_sc && thread->sched_context.cptr != 0) {
	vka_free_object(vka, &thread->sched_context);
	}

	if (thread->own_reply && thread->reply.cptr != 0) {
	vka_free_object(vka, &thread->reply);
	}

	memset(thread, 0, sizeof(sel4utils_thread_t));
	}

	void sel4utils_print_fault_message(seL4_MessageInfo_t tag, const char *thread_name)
	{
	seL4_Fault_t fault = seL4_getFault(tag);

	switch (seL4_Fault_get_seL4_FaultType(fault)) {
	case seL4_Fault_VMFault:
	assert(seL4_MessageInfo_get_length(tag) == seL4_VMFault_Length);
	printf("%sPagefault from [%s]: %s %s at PC: %p vaddr: %p, FSR %p%s\n",
	COLOR_ERROR,
	thread_name,
	sel4utils_is_read_fault() ? "read" : "write",
	seL4_Fault_VMFault_get_PrefetchFault(fault) ? "prefetch fault" : "fault",
	(void *)seL4_Fault_VMFault_get_IP(fault),
	(void *)seL4_Fault_VMFault_get_Addr(fault),
	(void *)seL4_Fault_VMFault_get_FSR(fault),
	COLOR_NORMAL);
	break;

	case seL4_Fault_UnknownSyscall:
	assert(seL4_MessageInfo_get_length(tag) == seL4_UnknownSyscall_Length);
	printf("%sBad syscall from [%s]: scno %"PRIuPTR" at PC: %p%s\n",
	COLOR_ERROR,
	thread_name,
	seL4_Fault_UnknownSyscall_get_Syscall(fault),
	(void *) seL4_Fault_UnknownSyscall_get_FaultIP(fault),
	COLOR_NORMAL
	);

	break;

	case seL4_Fault_UserException:
	assert(seL4_MessageInfo_get_length(tag) == seL4_UserException_Length);
	printf("%sInvalid instruction from [%s] at PC: %p%s\n",
	COLOR_ERROR,
	thread_name,
	(void *)seL4_Fault_UserException_get_FaultIP(fault),
	COLOR_NORMAL);
	break;

	case seL4_Fault_CapFault:
	printf("%sCap fault from [%s] in phase %s\nPC = %p\nCPtr = %p%s\n",
	COLOR_ERROR, thread_name,
	seL4_Fault_CapFault_get_InRecvPhase(fault) ? "receive" : "send",
	(void *) seL4_Fault_CapFault_get_IP(fault),
	(void *) seL4_Fault_CapFault_get_Addr(fault),
	COLOR_NORMAL);
	break;
	#ifdef CONFIG_KERNEL_RT
	case seL4_Fault_Timeout:
	printf("Timeout fault from %s\n", thread_name);
	break;
	#endif

	default:
	/* What? Why are we here? What just happened? */
	printf("Unknown fault from [%s]: %"PRIuPTR" (length = %"PRIuPTR")\n", thread_name, seL4_MessageInfo_get_label(tag), seL4_MessageInfo_get_length(tag));
	break;
	}
	}

	static int
	fault_handler(char *name, seL4_CPtr endpoint)
	{
	seL4_MessageInfo_t info;
	while (1) {
	/* sleep so other things can run */
	info = api_wait(endpoint, NULL);
	sel4utils_print_fault_message(info, name);
	}
	return 0;
	}

	int
	sel4utils_start_fault_handler(seL4_CPtr fault_endpoint, vka_t vka, vspace_t vspace,
	seL4_CPtr cspace, seL4_Word cap_data, char *name,
	sel4utils_thread_t *res)
	{
	int error = sel4utils_configure_thread(vka, vspace, vspace, 0, cspace,
	cap_data, res);

	if (error) {
	ZF_LOGE("Failed to configure fault handling thread\n");
	return -1;
	}

	return sel4utils_start_thread(res, (sel4utils_thread_entry_fn)fault_handler, name,
	(void *) fault_endpoint, 1);
	}

	int
	sel4utils_checkpoint_thread(sel4utils_thread_t thread, sel4utils_checkpoint_t checkpoint, bool suspend)
	{
	assert(checkpoint != NULL);

	int error = seL4_TCB_ReadRegisters(thread->tcb.cptr, suspend, 0, sizeof(seL4_UserContext) / sizeof(seL4_Word),
	&checkpoint->regs);
	if (error) {
	ZF_LOGE("Failed to read registers of tcb while checkpointing\n");
	return error;
	}

	checkpoint->sp = sel4utils_get_sp(checkpoint->regs);
	#ifdef CONFIG_ARCH_X86_64
	if (config_set(CONFIG_SYSENTER)) {
	/* on x64, using sysenter, the kernel ABI expects rcx to be set to rsp,
	* and rdx to be set to the fault instruction. Simulate this behaviour here
	* before resuming. Note that this will only work for threads checkpointed
	* at sysenter, e.g. while in a system call (eg seL4_Recv). */
	checkpoint->regs.rcx = checkpoint->regs.rsp;
	checkpoint->regs.rdx = checkpoint->regs.rip;
	} else if (config_set(CONFIG_SYSCALL)) {
	/* on x64, using syscall, when a thread is in the kernel,
	* sp is stored in rbx. So use rbx for stack calculations */
	checkpoint->sp = checkpoint->regs.rbx;
	}
	#endif /* CONFIG_ARCH_X86_64 */

	size_t stack_size = (uintptr_t) thread->stack_top - checkpoint->sp;
	checkpoint->stack = malloc(stack_size);
	if (checkpoint->stack == NULL) {
	ZF_LOGE("Failed to malloc stack of size %zu\n", stack_size);
	return -1;
	}

	memcpy(checkpoint->stack, (void *) checkpoint->sp, stack_size);
	checkpoint->thread = thread;

	return error;
	}

	int
	sel4utils_checkpoint_restore(sel4utils_checkpoint_t *checkpoint, bool free_memory, bool resume)
	{
	assert(checkpoint != NULL);

	size_t stack_size = (uintptr_t) checkpoint->thread->stack_top - checkpoint->sp;
	memcpy((void *) checkpoint->sp, checkpoint->stack, stack_size);

	int error = seL4_TCB_WriteRegisters(checkpoint->thread->tcb.cptr, resume, 0,
	sizeof(seL4_UserContext) / sizeof (seL4_Word),
	&checkpoint->regs);
	if (error) {
	ZF_LOGE("Failed to restore registers of tcb while restoring checkpoint\n");
	return error;
	}

	if (free_memory) {
	sel4utils_free_checkpoint(checkpoint);
	}

	return error;
	}

	void
	sel4utils_free_checkpoint(sel4utils_checkpoint_t *checkpoint)
	{
	free(checkpoint->stack);
	}

	int sel4utils_set_sched_affinity(sel4utils_thread_t *thread, sched_params_t params) {
	#if CONFIG_MAX_NUM_NODES > 1
	#ifdef CONFIG_KERNEL_RT
	return api_sched_ctrl_configure(params.sched_ctrl, thread->sched_context.cptr, params.budget, params.period,
	params.extra_refills, params.badge);

	#else
	return seL4_TCB_SetAffinity(thread->tcb.cptr, params.core);
	#endif
	#else
	return -ENOSYS;
	#endif
	}