This pull request contains the following bug fixes for UML:

- Align signal stack correctly
 - Convert to raw spinlocks where needed (irq and virtio)
 - FPU related fixes
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Merge tag 'uml-for-linus-6.14-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/uml/linux

Pull UML fixes from Richard Weinberger:

 - Align signal stack correctly

 - Convert to raw spinlocks where needed (irq and virtio)

 - FPU related fixes

* tag 'uml-for-linus-6.14-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/uml/linux:
  um: convert irq_lock to raw spinlock
  um: virtio_uml: use raw spinlock
  um: virt-pci: don't use kmalloc()
  um: fix execve stub execution on old host OSs
  um: properly align signal stack on x86_64
  um: avoid copying FP state from init_task
  um: add back support for FXSAVE registers

arch/um/drivers/virt-pci.c

@@ -25,8 +25,10 @@
 #define MAX_IRQ_MSG_SIZE (sizeof(struct virtio_pcidev_msg) + sizeof(u32))
 #define NUM_IRQ_MSGS	10
 
-#define HANDLE_NO_FREE(ptr) ((void *)((unsigned long)(ptr) | 1))
+struct um_pci_message_buffer {
-#define HANDLE_IS_NO_FREE(ptr) ((unsigned long)(ptr) & 1)
+	struct virtio_pcidev_msg hdr;
+	u8 data[8];
+};
 
 struct um_pci_device {
 	struct virtio_device *vdev;
@@ -36,6 +38,11 @@ struct um_pci_device {
 
 	struct virtqueue *cmd_vq, *irq_vq;
 
+#define UM_PCI_WRITE_BUFS	20
+	struct um_pci_message_buffer bufs[UM_PCI_WRITE_BUFS + 1];
+	void *extra_ptrs[UM_PCI_WRITE_BUFS + 1];
+	DECLARE_BITMAP(used_bufs, UM_PCI_WRITE_BUFS);
+
 #define UM_PCI_STAT_WAITING	0
 	unsigned long status;
 
@@ -61,12 +68,40 @@ static unsigned long um_pci_msi_used[BITS_TO_LONGS(MAX_MSI_VECTORS)];
 static unsigned int um_pci_max_delay_us = 40000;
 module_param_named(max_delay_us, um_pci_max_delay_us, uint, 0644);
 
-struct um_pci_message_buffer {
+static int um_pci_get_buf(struct um_pci_device *dev, bool *posted)
-	struct virtio_pcidev_msg hdr;
+{
-	u8 data[8];
+	int i;
-};
 
-static struct um_pci_message_buffer __percpu *um_pci_msg_bufs;
+	for (i = 0; i < UM_PCI_WRITE_BUFS; i++) {
+		if (!test_and_set_bit(i, dev->used_bufs))
+			return i;
+	}
+
+	*posted = false;
+	return UM_PCI_WRITE_BUFS;
+}
+
+static void um_pci_free_buf(struct um_pci_device *dev, void *buf)
+{
+	int i;
+
+	if (buf == &dev->bufs[UM_PCI_WRITE_BUFS]) {
+		kfree(dev->extra_ptrs[UM_PCI_WRITE_BUFS]);
+		dev->extra_ptrs[UM_PCI_WRITE_BUFS] = NULL;
+		return;
+	}
+
+	for (i = 0; i < UM_PCI_WRITE_BUFS; i++) {
+		if (buf == &dev->bufs[i]) {
+			kfree(dev->extra_ptrs[i]);
+			dev->extra_ptrs[i] = NULL;
+			WARN_ON(!test_and_clear_bit(i, dev->used_bufs));
+			return;
+		}
+	}
+
+	WARN_ON(1);
+}
 
 static int um_pci_send_cmd(struct um_pci_device *dev,
 			   struct virtio_pcidev_msg *cmd,
@@ -82,7 +117,9 @@ static int um_pci_send_cmd(struct um_pci_device *dev,
 	};
 	struct um_pci_message_buffer *buf;
 	int delay_count = 0;
+	bool bounce_out;
 	int ret, len;
+	int buf_idx;
 	bool posted;
 
 	if (WARN_ON(cmd_size < sizeof(*cmd) || cmd_size > sizeof(*buf)))
@@ -101,26 +138,28 @@ static int um_pci_send_cmd(struct um_pci_device *dev,
 		break;
 	}
 
-	buf = get_cpu_var(um_pci_msg_bufs);
+	bounce_out = !posted && cmd_size <= sizeof(*cmd) &&
-	if (buf)
+		     out && out_size <= sizeof(buf->data);
+
+	buf_idx = um_pci_get_buf(dev, &posted);
+	buf = &dev->bufs[buf_idx];
 	memcpy(buf, cmd, cmd_size);
 
-	if (posted) {
+	if (posted && extra && extra_size > sizeof(buf) - cmd_size) {
-		u8 *ncmd = kmalloc(cmd_size + extra_size, GFP_ATOMIC);
+		dev->extra_ptrs[buf_idx] = kmemdup(extra, extra_size,
+						   GFP_ATOMIC);
 
-		if (ncmd) {
+		if (!dev->extra_ptrs[buf_idx]) {
-			memcpy(ncmd, cmd, cmd_size);
+			um_pci_free_buf(dev, buf);
-			if (extra)
+			return -ENOMEM;
-				memcpy(ncmd + cmd_size, extra, extra_size);
-			cmd = (void *)ncmd;
-			cmd_size += extra_size;
-			extra = NULL;
-			extra_size = 0;
-		} else {
-			/* try without allocating memory */
-			posted = false;
-			cmd = (void *)buf;
 		}
+		extra = dev->extra_ptrs[buf_idx];
+	} else if (extra && extra_size <= sizeof(buf) - cmd_size) {
+		memcpy((u8 *)buf + cmd_size, extra, extra_size);
+		cmd_size += extra_size;
+		extra_size = 0;
+		extra = NULL;
+		cmd = (void *)buf;
 	} else {
 		cmd = (void *)buf;
 	}
@@ -128,39 +167,40 @@ static int um_pci_send_cmd(struct um_pci_device *dev,
 	sg_init_one(&out_sg, cmd, cmd_size);
 	if (extra)
 		sg_init_one(&extra_sg, extra, extra_size);
-	if (out)
+	/* allow stack for small buffers */
+	if (bounce_out)
+		sg_init_one(&in_sg, buf->data, out_size);
+	else if (out)
 		sg_init_one(&in_sg, out, out_size);
 
 	/* add to internal virtio queue */
 	ret = virtqueue_add_sgs(dev->cmd_vq, sgs_list,
 				extra ? 2 : 1,
 				out ? 1 : 0,
-				posted ? cmd : HANDLE_NO_FREE(cmd),
+				cmd, GFP_ATOMIC);
-				GFP_ATOMIC);
 	if (ret) {
-		if (posted)
+		um_pci_free_buf(dev, buf);
-			kfree(cmd);
+		return ret;
-		goto out;
 	}
 
 	if (posted) {
 		virtqueue_kick(dev->cmd_vq);
-		ret = 0;
+		return 0;
-		goto out;
 	}
 
 	/* kick and poll for getting a response on the queue */
 	set_bit(UM_PCI_STAT_WAITING, &dev->status);
 	virtqueue_kick(dev->cmd_vq);
+	ret = 0;
 
 	while (1) {
 		void *completed = virtqueue_get_buf(dev->cmd_vq, &len);
 
-		if (completed == HANDLE_NO_FREE(cmd))
+		if (completed == buf)
 			break;
 
-		if (completed && !HANDLE_IS_NO_FREE(completed))
+		if (completed)
-			kfree(completed);
+			um_pci_free_buf(dev, completed);
 
 		if (WARN_ONCE(virtqueue_is_broken(dev->cmd_vq) ||
 			      ++delay_count > um_pci_max_delay_us,
@@ -172,8 +212,11 @@ static int um_pci_send_cmd(struct um_pci_device *dev,
 	}
 	clear_bit(UM_PCI_STAT_WAITING, &dev->status);
 
-out:
+	if (bounce_out)
-	put_cpu_var(um_pci_msg_bufs);
+		memcpy(out, buf->data, out_size);
+
+	um_pci_free_buf(dev, buf);
+
 	return ret;
 }
 
@@ -187,20 +230,13 @@ static unsigned long um_pci_cfgspace_read(void *priv, unsigned int offset,
 		.size = size,
 		.addr = offset,
 	};
-	/* buf->data is maximum size - we may only use parts of it */
+	/* max 8, we might not use it all */
-	struct um_pci_message_buffer *buf;
+	u8 data[8];
-	u8 *data;
-	unsigned long ret = ULONG_MAX;
-	size_t bytes = sizeof(buf->data);
 
 	if (!dev)
 		return ULONG_MAX;
 
-	buf = get_cpu_var(um_pci_msg_bufs);
+	memset(data, 0xff, sizeof(data));
-	data = buf->data;
-
-	if (buf)
-		memset(data, 0xff, bytes);
 
 	switch (size) {
 	case 1:
@@ -212,34 +248,26 @@ static unsigned long um_pci_cfgspace_read(void *priv, unsigned int offset,
 		break;
 	default:
 		WARN(1, "invalid config space read size %d\n", size);
-		goto out;
+		return ULONG_MAX;
 	}
 
-	if (um_pci_send_cmd(dev, &hdr, sizeof(hdr), NULL, 0, data, bytes))
+	if (um_pci_send_cmd(dev, &hdr, sizeof(hdr), NULL, 0, data, size))
-		goto out;
+		return ULONG_MAX;
 
 	switch (size) {
 	case 1:
-		ret = data[0];
+		return data[0];
-		break;
 	case 2:
-		ret = le16_to_cpup((void *)data);
+		return le16_to_cpup((void *)data);
-		break;
 	case 4:
-		ret = le32_to_cpup((void *)data);
+		return le32_to_cpup((void *)data);
-		break;
 #ifdef CONFIG_64BIT
 	case 8:
-		ret = le64_to_cpup((void *)data);
+		return le64_to_cpup((void *)data);
-		break;
 #endif
 	default:
-		break;
+		return ULONG_MAX;
 	}
-
-out:
-	put_cpu_var(um_pci_msg_bufs);
-	return ret;
 }
 
 static void um_pci_cfgspace_write(void *priv, unsigned int offset, int size,
@@ -312,13 +340,8 @@ static void um_pci_bar_copy_from(void *priv, void *buffer,
 static unsigned long um_pci_bar_read(void *priv, unsigned int offset,
 				     int size)
 {
-	/* buf->data is maximum size - we may only use parts of it */
+	/* 8 is maximum size - we may only use parts of it */
-	struct um_pci_message_buffer *buf;
+	u8 data[8];
-	u8 *data;
-	unsigned long ret = ULONG_MAX;
-
-	buf = get_cpu_var(um_pci_msg_bufs);
-	data = buf->data;
 
 	switch (size) {
 	case 1:
@@ -330,33 +353,25 @@ static unsigned long um_pci_bar_read(void *priv, unsigned int offset,
 		break;
 	default:
 		WARN(1, "invalid config space read size %d\n", size);
-		goto out;
+		return ULONG_MAX;
 	}
 
 	um_pci_bar_copy_from(priv, data, offset, size);
 
 	switch (size) {
 	case 1:
-		ret = data[0];
+		return data[0];
-		break;
 	case 2:
-		ret = le16_to_cpup((void *)data);
+		return le16_to_cpup((void *)data);
-		break;
 	case 4:
-		ret = le32_to_cpup((void *)data);
+		return le32_to_cpup((void *)data);
-		break;
 #ifdef CONFIG_64BIT
 	case 8:
-		ret = le64_to_cpup((void *)data);
+		return le64_to_cpup((void *)data);
-		break;
 #endif
 	default:
-		break;
+		return ULONG_MAX;
 	}
-
-out:
-	put_cpu_var(um_pci_msg_bufs);
-	return ret;
 }
 
 static void um_pci_bar_copy_to(void *priv, unsigned int offset,
@@ -523,11 +538,8 @@ static void um_pci_cmd_vq_cb(struct virtqueue *vq)
 	if (test_bit(UM_PCI_STAT_WAITING, &dev->status))
 		return;
 
-	while ((cmd = virtqueue_get_buf(vq, &len))) {
+	while ((cmd = virtqueue_get_buf(vq, &len)))
-		if (WARN_ON(HANDLE_IS_NO_FREE(cmd)))
+		um_pci_free_buf(dev, cmd);
-			continue;
-		kfree(cmd);
-	}
 }
 
 static void um_pci_irq_vq_cb(struct virtqueue *vq)
@@ -1006,10 +1018,6 @@ static int __init um_pci_init(void)
 		 "No virtio device ID configured for PCI - no PCI support\n"))
 		return 0;
 
-	um_pci_msg_bufs = alloc_percpu(struct um_pci_message_buffer);
-	if (!um_pci_msg_bufs)
-		return -ENOMEM;
-
 	bridge = pci_alloc_host_bridge(0);
 	if (!bridge) {
 		err = -ENOMEM;
@@ -1070,7 +1078,6 @@ free:
 		pci_free_resource_list(&bridge->windows);
 		pci_free_host_bridge(bridge);
 	}
-	free_percpu(um_pci_msg_bufs);
 	return err;
 }
 module_init(um_pci_init);
@@ -1082,6 +1089,5 @@ static void __exit um_pci_exit(void)
 	irq_domain_remove(um_pci_inner_domain);
 	pci_free_resource_list(&bridge->windows);
 	pci_free_host_bridge(bridge);
-	free_percpu(um_pci_msg_bufs);
 }
 module_exit(um_pci_exit);

arch/um/drivers/virtio_uml.c

@@ -52,7 +52,7 @@ struct virtio_uml_device {
 	struct platform_device *pdev;
 	struct virtio_uml_platform_data *pdata;
 
-	spinlock_t sock_lock;
+	raw_spinlock_t sock_lock;
 	int sock, req_fd, irq;
 	u64 features;
 	u64 protocol_features;
@@ -246,7 +246,7 @@ static int vhost_user_send(struct virtio_uml_device *vu_dev,
 	if (request_ack)
 		msg->header.flags |= VHOST_USER_FLAG_NEED_REPLY;
 
-	spin_lock_irqsave(&vu_dev->sock_lock, flags);
+	raw_spin_lock_irqsave(&vu_dev->sock_lock, flags);
 	rc = full_sendmsg_fds(vu_dev->sock, msg, size, fds, num_fds);
 	if (rc < 0)
 		goto out;
@@ -266,7 +266,7 @@ static int vhost_user_send(struct virtio_uml_device *vu_dev,
 	}
 
 out:
-	spin_unlock_irqrestore(&vu_dev->sock_lock, flags);
+	raw_spin_unlock_irqrestore(&vu_dev->sock_lock, flags);
 	return rc;
 }
 
@@ -1239,7 +1239,7 @@ static int virtio_uml_probe(struct platform_device *pdev)
 		goto error_free;
 	vu_dev->sock = rc;
 
-	spin_lock_init(&vu_dev->sock_lock);
+	raw_spin_lock_init(&vu_dev->sock_lock);
 
 	rc = vhost_user_init(vu_dev);
 	if (rc)

arch/um/kernel/irq.c

@@ -52,7 +52,7 @@ struct irq_entry {
 	bool sigio_workaround;
 };
 
-static DEFINE_SPINLOCK(irq_lock);
+static DEFINE_RAW_SPINLOCK(irq_lock);
 static LIST_HEAD(active_fds);
 static DECLARE_BITMAP(irqs_allocated, UM_LAST_SIGNAL_IRQ);
 static bool irqs_suspended;
@@ -257,7 +257,7 @@ static struct irq_entry *get_irq_entry_by_fd(int fd)
 	return NULL;
 }
 
-static void free_irq_entry(struct irq_entry *to_free, bool remove)
+static void remove_irq_entry(struct irq_entry *to_free, bool remove)
 {
 	if (!to_free)
 		return;
@@ -265,7 +265,6 @@ static void free_irq_entry(struct irq_entry *to_free, bool remove)
 	if (remove)
 		os_del_epoll_fd(to_free->fd);
 	list_del(&to_free->list);
-	kfree(to_free);
 }
 
 static bool update_irq_entry(struct irq_entry *entry)
@@ -286,17 +285,19 @@ static bool update_irq_entry(struct irq_entry *entry)
 	return false;
 }
 
-static void update_or_free_irq_entry(struct irq_entry *entry)
+static struct irq_entry *update_or_remove_irq_entry(struct irq_entry *entry)
 {
-	if (!update_irq_entry(entry))
+	if (update_irq_entry(entry))
-		free_irq_entry(entry, false);
+		return NULL;
+	remove_irq_entry(entry, false);
+	return entry;
 }
 
 static int activate_fd(int irq, int fd, enum um_irq_type type, void *dev_id,
 		       void (*timetravel_handler)(int, int, void *,
 						  struct time_travel_event *))
 {
-	struct irq_entry *irq_entry;
+	struct irq_entry *irq_entry, *to_free = NULL;
 	int err, events = os_event_mask(type);
 	unsigned long flags;
 
@@ -304,9 +305,10 @@ static int activate_fd(int irq, int fd, enum um_irq_type type, void *dev_id,
 	if (err < 0)
 		goto out;
 
-	spin_lock_irqsave(&irq_lock, flags);
+	raw_spin_lock_irqsave(&irq_lock, flags);
 	irq_entry = get_irq_entry_by_fd(fd);
 	if (irq_entry) {
+already:
 		/* cannot register the same FD twice with the same type */
 		if (WARN_ON(irq_entry->reg[type].events)) {
 			err = -EALREADY;
@@ -316,11 +318,22 @@ static int activate_fd(int irq, int fd, enum um_irq_type type, void *dev_id,
 		/* temporarily disable to avoid IRQ-side locking */
 		os_del_epoll_fd(fd);
 	} else {
-		irq_entry = kzalloc(sizeof(*irq_entry), GFP_ATOMIC);
+		struct irq_entry *new;
-		if (!irq_entry) {
+
-			err = -ENOMEM;
+		/* don't restore interrupts */
-			goto out_unlock;
+		raw_spin_unlock(&irq_lock);
+		new = kzalloc(sizeof(*irq_entry), GFP_ATOMIC);
+		if (!new) {
+			local_irq_restore(flags);
+			return -ENOMEM;
 		}
+		raw_spin_lock(&irq_lock);
+		irq_entry = get_irq_entry_by_fd(fd);
+		if (irq_entry) {
+			to_free = new;
+			goto already;
+		}
+		irq_entry = new;
 		irq_entry->fd = fd;
 		list_add_tail(&irq_entry->list, &active_fds);
 		maybe_sigio_broken(fd);
@@ -339,12 +352,11 @@ static int activate_fd(int irq, int fd, enum um_irq_type type, void *dev_id,
 #endif
 
 	WARN_ON(!update_irq_entry(irq_entry));
-	spin_unlock_irqrestore(&irq_lock, flags);
+	err = 0;
-
-	return 0;
 out_unlock:
-	spin_unlock_irqrestore(&irq_lock, flags);
+	raw_spin_unlock_irqrestore(&irq_lock, flags);
 out:
+	kfree(to_free);
 	return err;
 }
 
@@ -358,19 +370,20 @@ void free_irq_by_fd(int fd)
 	struct irq_entry *to_free;
 	unsigned long flags;
 
-	spin_lock_irqsave(&irq_lock, flags);
+	raw_spin_lock_irqsave(&irq_lock, flags);
 	to_free = get_irq_entry_by_fd(fd);
-	free_irq_entry(to_free, true);
+	remove_irq_entry(to_free, true);
-	spin_unlock_irqrestore(&irq_lock, flags);
+	raw_spin_unlock_irqrestore(&irq_lock, flags);
+	kfree(to_free);
 }
 EXPORT_SYMBOL(free_irq_by_fd);
 
 static void free_irq_by_irq_and_dev(unsigned int irq, void *dev)
 {
-	struct irq_entry *entry;
+	struct irq_entry *entry, *to_free = NULL;
 	unsigned long flags;
 
-	spin_lock_irqsave(&irq_lock, flags);
+	raw_spin_lock_irqsave(&irq_lock, flags);
 	list_for_each_entry(entry, &active_fds, list) {
 		enum um_irq_type i;
 
@@ -386,12 +399,13 @@ static void free_irq_by_irq_and_dev(unsigned int irq, void *dev)
 
 			os_del_epoll_fd(entry->fd);
 			reg->events = 0;
-			update_or_free_irq_entry(entry);
+			to_free = update_or_remove_irq_entry(entry);
 			goto out;
 		}
 	}
 out:
-	spin_unlock_irqrestore(&irq_lock, flags);
+	raw_spin_unlock_irqrestore(&irq_lock, flags);
+	kfree(to_free);
 }
 
 void deactivate_fd(int fd, int irqnum)
@@ -402,7 +416,7 @@ void deactivate_fd(int fd, int irqnum)
 
 	os_del_epoll_fd(fd);
 
-	spin_lock_irqsave(&irq_lock, flags);
+	raw_spin_lock_irqsave(&irq_lock, flags);
 	entry = get_irq_entry_by_fd(fd);
 	if (!entry)
 		goto out;
@@ -414,9 +428,10 @@ void deactivate_fd(int fd, int irqnum)
 			entry->reg[i].events = 0;
 	}
 
-	update_or_free_irq_entry(entry);
+	entry = update_or_remove_irq_entry(entry);
 out:
-	spin_unlock_irqrestore(&irq_lock, flags);
+	raw_spin_unlock_irqrestore(&irq_lock, flags);
+	kfree(entry);
 
 	ignore_sigio_fd(fd);
 }
@@ -546,7 +561,7 @@ void um_irqs_suspend(void)
 
 	irqs_suspended = true;
 
-	spin_lock_irqsave(&irq_lock, flags);
+	raw_spin_lock_irqsave(&irq_lock, flags);
 	list_for_each_entry(entry, &active_fds, list) {
 		enum um_irq_type t;
 		bool clear = true;
@@ -579,7 +594,7 @@ void um_irqs_suspend(void)
 				!__ignore_sigio_fd(entry->fd);
 		}
 	}
-	spin_unlock_irqrestore(&irq_lock, flags);
+	raw_spin_unlock_irqrestore(&irq_lock, flags);
 }
 
 void um_irqs_resume(void)
@@ -588,7 +603,7 @@ void um_irqs_resume(void)
 	unsigned long flags;
 
 
-	spin_lock_irqsave(&irq_lock, flags);
+	raw_spin_lock_irqsave(&irq_lock, flags);
 	list_for_each_entry(entry, &active_fds, list) {
 		if (entry->suspended) {
 			int err = os_set_fd_async(entry->fd);
@@ -602,7 +617,7 @@ void um_irqs_resume(void)
 			}
 		}
 	}
-	spin_unlock_irqrestore(&irq_lock, flags);
+	raw_spin_unlock_irqrestore(&irq_lock, flags);
 
 	irqs_suspended = false;
 	send_sigio_to_self();
@@ -613,7 +628,7 @@ static int normal_irq_set_wake(struct irq_data *d, unsigned int on)
 	struct irq_entry *entry;
 	unsigned long flags;
 
-	spin_lock_irqsave(&irq_lock, flags);
+	raw_spin_lock_irqsave(&irq_lock, flags);
 	list_for_each_entry(entry, &active_fds, list) {
 		enum um_irq_type t;
 
@@ -628,7 +643,7 @@ static int normal_irq_set_wake(struct irq_data *d, unsigned int on)
 		}
 	}
 unlock:
-	spin_unlock_irqrestore(&irq_lock, flags);
+	raw_spin_unlock_irqrestore(&irq_lock, flags);
 	return 0;
 }
 #else

arch/um/kernel/process.c

@@ -191,7 +191,15 @@ void initial_thread_cb(void (*proc)(void *), void *arg)
 int arch_dup_task_struct(struct task_struct *dst,
 			 struct task_struct *src)
 {
+	/* init_task is not dynamically sized (missing FPU state) */
+	if (unlikely(src == &init_task)) {
+		memcpy(dst, src, sizeof(init_task));
+		memset((void *)dst + sizeof(init_task), 0,
+		       arch_task_struct_size - sizeof(init_task));
+	} else {
 		memcpy(dst, src, arch_task_struct_size);
+	}
+
 	return 0;
 }
 

arch/um/os-Linux/skas/process.c

@@ -181,6 +181,10 @@ extern char __syscall_stub_start[];
 
 static int stub_exe_fd;
 
+#ifndef CLOSE_RANGE_CLOEXEC
+#define CLOSE_RANGE_CLOEXEC	(1U << 2)
+#endif
+
 static int userspace_tramp(void *stack)
 {
 	char *const argv[] = { "uml-userspace", NULL };
@@ -202,8 +206,12 @@ static int userspace_tramp(void *stack)
 	init_data.stub_data_fd = phys_mapping(uml_to_phys(stack), &offset);
 	init_data.stub_data_offset = MMAP_OFFSET(offset);
 
-	/* Set CLOEXEC on all FDs and then unset on all memory related FDs */
+	/*
-	close_range(0, ~0U, CLOSE_RANGE_CLOEXEC);
+	 * Avoid leaking unneeded FDs to the stub by setting CLOEXEC on all FDs
+	 * and then unsetting it on all memory related FDs.
+	 * This is not strictly necessary from a safety perspective.
+	 */
+	syscall(__NR_close_range, 0, ~0U, CLOSE_RANGE_CLOEXEC);
 
 	fcntl(init_data.stub_data_fd, F_SETFD, 0);
 	for (iomem = iomem_regions; iomem; iomem = iomem->next)
@@ -224,7 +232,9 @@ static int userspace_tramp(void *stack)
 	if (ret != sizeof(init_data))
 		exit(4);
 
-	execveat(stub_exe_fd, "", argv, NULL, AT_EMPTY_PATH);
+	/* Raw execveat for compatibility with older libc versions */
+	syscall(__NR_execveat, stub_exe_fd, (unsigned long)"",
+		(unsigned long)argv, NULL, AT_EMPTY_PATH);
 
 	exit(5);
 }

arch/x86/um/os-Linux/registers.c

@@ -18,6 +18,7 @@
 #include <registers.h>
 #include <sys/mman.h>
 
+static unsigned long ptrace_regset;
 unsigned long host_fp_size;
 
 int get_fp_registers(int pid, unsigned long *regs)
@@ -27,7 +28,7 @@ int get_fp_registers(int pid, unsigned long *regs)
 		.iov_len = host_fp_size,
 	};
 
-	if (ptrace(PTRACE_GETREGSET, pid, NT_X86_XSTATE, &iov) < 0)
+	if (ptrace(PTRACE_GETREGSET, pid, ptrace_regset, &iov) < 0)
 		return -errno;
 	return 0;
 }
@@ -39,7 +40,7 @@ int put_fp_registers(int pid, unsigned long *regs)
 		.iov_len = host_fp_size,
 	};
 
-	if (ptrace(PTRACE_SETREGSET, pid, NT_X86_XSTATE, &iov) < 0)
+	if (ptrace(PTRACE_SETREGSET, pid, ptrace_regset, &iov) < 0)
 		return -errno;
 	return 0;
 }
@@ -58,9 +59,23 @@ int arch_init_registers(int pid)
 		return -ENOMEM;
 
 	/* GDB has x86_xsave_length, which uses x86_cpuid_count */
-	ret = ptrace(PTRACE_GETREGSET, pid, NT_X86_XSTATE, &iov);
+	ptrace_regset = NT_X86_XSTATE;
+	ret = ptrace(PTRACE_GETREGSET, pid, ptrace_regset, &iov);
 	if (ret)
 		ret = -errno;
+
+	if (ret == -ENODEV) {
+#ifdef CONFIG_X86_32
+		ptrace_regset = NT_PRXFPREG;
+#else
+		ptrace_regset = NT_PRFPREG;
+#endif
+		iov.iov_len = 2 * 1024 * 1024;
+		ret = ptrace(PTRACE_GETREGSET, pid, ptrace_regset, &iov);
+		if (ret)
+			ret = -errno;
+	}
+
 	munmap(iov.iov_base, 2 * 1024 * 1024);
 
 	host_fp_size = iov.iov_len;

arch/x86/um/signal.c

@@ -187,7 +187,12 @@ static int copy_sc_to_user(struct sigcontext __user *to,
 	 * Put magic/size values for userspace. We do not bother to verify them
 	 * later on, however, userspace needs them should it try to read the
 	 * XSTATE data. And ptrace does not fill in these parts.
+	 *
+	 * Skip this if we do not have an XSTATE frame.
 	 */
+	if (host_fp_size <= sizeof(to_fp64->fpstate))
+		return 0;
+
 	BUILD_BUG_ON(sizeof(int) != FP_XSTATE_MAGIC2_SIZE);
 #ifdef CONFIG_X86_32
 	__put_user(offsetof(struct _fpstate_32, _fxsr_env) +
@@ -367,11 +372,13 @@ int setup_signal_stack_si(unsigned long stack_top, struct ksignal *ksig,
 	int err = 0, sig = ksig->sig;
 	unsigned long fp_to;
 
-	frame = (struct rt_sigframe __user *)
+	frame = (void __user *)stack_top - sizeof(struct rt_sigframe);
-		round_down(stack_top - sizeof(struct rt_sigframe), 16);
 
 	/* Add required space for math frame */
-	frame = (struct rt_sigframe __user *)((unsigned long)frame - math_size);
+	frame = (void __user *)((unsigned long)frame - math_size);
+
+	/* ABI requires 16 byte boundary alignment */
+	frame = (void __user *)round_down((unsigned long)frame, 16);
 
 	/* Subtract 128 for a red zone and 8 for proper alignment */
 	frame = (struct rt_sigframe __user *) ((unsigned long) frame - 128 - 8);