[PATCH] ANDROID: staging: add userpanic-dev driver

[Woody Lin]

Add char device driver 'userpanic-dev' that exposes an interface to
userspace processes to request a system panic with customized panic
message.

Signed-off-by: Woody Lin <woodylin@xxxxxxxxxx>
---
 drivers/staging/android/Kconfig         |  12 +++
 drivers/staging/android/Makefile        |   1 +
 drivers/staging/android/userpanic-dev.c | 110 ++++++++++++++++++++++++
 3 files changed, 123 insertions(+)
 create mode 100644 drivers/staging/android/userpanic-dev.c

diff --git a/drivers/staging/android/Kconfig b/drivers/staging/android/Kconfig
index 70498adb1575..b1968a1ee821 100644
--- a/drivers/staging/android/Kconfig
+++ b/drivers/staging/android/Kconfig
@@ -14,6 +14,18 @@ config ASHMEM
 	  It is, in theory, a good memory allocator for low-memory devices,
 	  because it can discard shared memory units when under memory pressure.
 
+config USERPANIC_CHARDEV
+	bool "User-panic device interface"
+	help
+	  Say Y here to use user-panic device for user space processes to
+	  request a system panic with customized panic message.
+
+	  A char device '/dev/userspace_panic' is created by this driver
+	  when selecting 'Y'. User processes can request panic and attach
+	  customized panic message and title by ioctl(CRASH_INFO). Later any
+	  panic handler can collect the panic message to build debugging
+	  reports.
+
 endif # if ANDROID
 
 endmenu
diff --git a/drivers/staging/android/Makefile b/drivers/staging/android/Makefile
index e9a55a5e6529..851efb3435ac 100644
--- a/drivers/staging/android/Makefile
+++ b/drivers/staging/android/Makefile
@@ -2,3 +2,4 @@
 ccflags-y += -I$(src)			# needed for trace events
 
 obj-$(CONFIG_ASHMEM)			+= ashmem.o
+obj-$(CONFIG_USERPANIC_CHARDEV)	+= userpanic-dev.o
diff --git a/drivers/staging/android/userpanic-dev.c b/drivers/staging/android/userpanic-dev.c
new file mode 100644
index 000000000000..b9a0f0c01826
--- /dev/null
+++ b/drivers/staging/android/userpanic-dev.c
@@ -0,0 +1,110 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* userpanic-dev.c
+ *
+ * User-panic Device Interface
+ *
+ * Copyright 2021 Google LLC
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ":%s: " fmt, __func__
+
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/string.h>
+#include <linux/miscdevice.h>
+
+struct userpanic_crash_info {
+	void __user *title_uaddr;
+	void __user *msg_uaddr;
+};
+
+#define CRASH_INFO		(_IOW('U', 179, struct userpanic_crash_info))
+
+static int do_userpanic(const char *title, const char *msg)
+{
+	const size_t msgbuf_sz = PAGE_SIZE;
+	char *msgbuf;
+
+	msgbuf = kmalloc(msgbuf_sz, GFP_KERNEL);
+	if (!msgbuf)
+		return -ENOMEM;
+
+	pr_emerg("User process '%.*s' %d requesting kernel panic\n",
+		 sizeof(current->comm), current->comm, current->pid);
+	if (msg)
+		pr_emerg("   with message: %s\n", msg);
+
+	/* Request panic with customized panic title. */
+	snprintf(msgbuf, msgbuf_sz, "U: %s: %s", current->comm, title);
+	panic(msgbuf);
+	kfree(msgbuf);
+	return -EFAULT;
+}
+
+static long userpanic_device_ioctl(struct file *file, u_int cmd, u_long arg)
+{
+	struct userpanic_crash_info crash_info;
+	char *title;
+	char *msg = NULL;
+	int ret;
+
+	switch (cmd) {
+	case CRASH_INFO:
+		if (copy_from_user(&crash_info, (void __user *)arg, sizeof(crash_info)))
+			return -EFAULT;
+
+		if (!crash_info.title_uaddr)
+			return -EINVAL;
+
+		title = strndup_user(crash_info.title_uaddr, PAGE_SIZE);
+		if (IS_ERR(title)) {
+			pr_err("failed to strndup .title_uaddr: %d\n", PTR_ERR(title));
+			return -EINVAL;
+		}
+
+		if (crash_info.msg_uaddr) {
+			msg = strndup_user(crash_info.msg_uaddr, PAGE_SIZE);
+			if (IS_ERR(msg)) {
+				kfree(title);
+				pr_err("failed to strndup .msg_uaddr: %d\n", PTR_ERR(msg));
+				return -EINVAL;
+			}
+		}
+
+		ret = do_userpanic(title, msg);
+		kfree(msg);
+		kfree(title);
+		return ret;
+	}
+
+	return -EINVAL;
+}
+
+static const struct file_operations userpanic_device_fops = {
+	.owner          = THIS_MODULE,
+	.unlocked_ioctl = userpanic_device_ioctl,
+	.compat_ioctl   = compat_ptr_ioctl,
+};
+
+static struct miscdevice userpanic_device = {
+	.minor = MISC_DYNAMIC_MINOR,
+	.name  = "userspace_panic",
+	.fops  = &userpanic_device_fops,
+};
+
+static int __init userspace_panic_dev_init(void)
+{
+	int ret;
+
+	ret = misc_register(&userpanic_device);
+	if (ret)
+		pr_err("misc_register failed for userspace_panic device\n");
+
+	return ret;
+}
+
+device_initcall(userspace_panic_dev_init);
+
+MODULE_DESCRIPTION("User-panic interface device driver");
+MODULE_AUTHOR("Woody Lin <woodylin@xxxxxxxxxx>");
+MODULE_LICENSE("GPL v2");
-- 
2.33.0.rc2.250.ged5fa647cd-goog