Merge tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-nextgrafted

Pull networking updates from Jakub Kicinski:
 "Core:

   - Add dedicated kmem_cache for typical/small skb->head, avoid having
     to access struct page at kfree time, and improve memory use.

   - Introduce sysctl to set default RPS configuration for new netdevs.

   - Define Netlink protocol specification format which can be used to
     describe messages used by each family and auto-generate parsers.
     Add tools for generating kernel data structures and uAPI headers.

   - Expose all net/core sysctls inside netns.

   - Remove 4s sleep in netpoll if carrier is instantly detected on
     boot.

   - Add configurable limit of MDB entries per port, and port-vlan.

   - Continue populating drop reasons throughout the stack.

   - Retire a handful of legacy Qdiscs and classifiers.

  Protocols:

   - Support IPv4 big TCP (TSO frames larger than 64kB).

   - Add IP_LOCAL_PORT_RANGE socket option, to control local port range
     on socket by socket basis.

   - Track and report in procfs number of MPTCP sockets used.

   - Support mixing IPv4 and IPv6 flows in the in-kernel MPTCP path
     manager.

   - IPv6: don't check net.ipv6.route.max_size and rely on garbage
     collection to free memory (similarly to IPv4).

   - Support Penultimate Segment Pop (PSP) flavor in SRv6 (RFC8986).

   - ICMP: add per-rate limit counters.

   - Add support for user scanning requests in ieee802154.

   - Remove static WEP support.

   - Support minimal Wi-Fi 7 Extremely High Throughput (EHT) rate
     reporting.

   - WiFi 7 EHT channel puncturing support (client & AP).

  BPF:

   - Add a rbtree data structure following the "next-gen data structure"
     precedent set by recently added linked list, that is, by using
     kfunc + kptr instead of adding a new BPF map type.

   - Expose XDP hints via kfuncs with initial support for RX hash and
     timestamp metadata.

   - Add BPF_F_NO_TUNNEL_KEY extension to bpf_skb_set_tunnel_key to
     better support decap on GRE tunnel devices not operating in collect
     metadata.

   - Improve x86 JIT's codegen for PROBE_MEM runtime error checks.

   - Remove the need for trace_printk_lock for bpf_trace_printk and
     bpf_trace_vprintk helpers.

   - Extend libbpf's bpf_tracing.h support for tracing arguments of
     kprobes/uprobes and syscall as a special case.

   - Significantly reduce the search time for module symbols by
     livepatch and BPF.

   - Enable cpumasks to be used as kptrs, which is useful for tracing
     programs tracking which tasks end up running on which CPUs in
     different time intervals.

   - Add support for BPF trampoline on s390x and riscv64.

   - Add capability to export the XDP features supported by the NIC.

   - Add __bpf_kfunc tag for marking kernel functions as kfuncs.

   - Add cgroup.memory=nobpf kernel parameter option to disable BPF
     memory accounting for container environments.

  Netfilter:

   - Remove the CLUSTERIP target. It has been marked as obsolete for
     years, and we still have WARN splats wrt races of the out-of-band
     /proc interface installed by this target.

   - Add 'destroy' commands to nf_tables. They are identical to the
     existing 'delete' commands, but do not return an error if the
     referenced object (set, chain, rule...) did not exist.

  Driver API:

   - Improve cpumask_local_spread() locality to help NICs set the right
     IRQ affinity on AMD platforms.

   - Separate C22 and C45 MDIO bus transactions more clearly.

   - Introduce new DCB table to control DSCP rewrite on egress.

   - Support configuration of Physical Layer Collision Avoidance (PLCA)
     Reconciliation Sublayer (RS) (802.3cg-2019). Modern version of
     shared medium Ethernet.

   - Support for MAC Merge layer (IEEE 802.3-2018 clause 99). Allowing
     preemption of low priority frames by high priority frames.

   - Add support for controlling MACSec offload using netlink SET.

   - Rework devlink instance refcounts to allow registration and
     de-registration under the instance lock. Split the code into
     multiple files, drop some of the unnecessarily granular locks and
     factor out common parts of netlink operation handling.

   - Add TX frame aggregation parameters (for USB drivers).

   - Add a new attr TCA_EXT_WARN_MSG to report TC (offload) warning
     messages with notifications for debug.

   - Allow offloading of UDP NEW connections via act_ct.

   - Add support for per action HW stats in TC.

   - Support hardware miss to TC action (continue processing in SW from
     a specific point in the action chain).

   - Warn if old Wireless Extension user space interface is used with
     modern cfg80211/mac80211 drivers. Do not support Wireless
     Extensions for Wi-Fi 7 devices at all. Everyone should switch to
     using nl80211 interface instead.

   - Improve the CAN bit timing configuration. Use extack to return
     error messages directly to user space, update the SJW handling,
     including the definition of a new default value that will benefit
     CAN-FD controllers, by increasing their oscillator tolerance.

  New hardware / drivers:

   - Ethernet:
      - nVidia BlueField-3 support (control traffic driver)
      - Ethernet support for imx93 SoCs
      - Motorcomm yt8531 gigabit Ethernet PHY
      - onsemi NCN26000 10BASE-T1S PHY (with support for PLCA)
      - Microchip LAN8841 PHY (incl. cable diagnostics and PTP)
      - Amlogic gxl MDIO mux

   - WiFi:
      - RealTek RTL8188EU (rtl8xxxu)
      - Qualcomm Wi-Fi 7 devices (ath12k)

   - CAN:
      - Renesas R-Car V4H

  Drivers:

   - Bluetooth:
      - Set Per Platform Antenna Gain (PPAG) for Intel controllers.

   - Ethernet NICs:
      - Intel (1G, igc):
         - support TSN / Qbv / packet scheduling features of i226 model
      - Intel (100G, ice):
         - use GNSS subsystem instead of TTY
         - multi-buffer XDP support
         - extend support for GPIO pins to E823 devices
      - nVidia/Mellanox:
         - update the shared buffer configuration on PFC commands
         - implement PTP adjphase function for HW offset control
         - TC support for Geneve and GRE with VF tunnel offload
         - more efficient crypto key management method
         - multi-port eswitch support
      - Netronome/Corigine:
         - add DCB IEEE support
         - support IPsec offloading for NFP3800
      - Freescale/NXP (enetc):
         - support XDP_REDIRECT for XDP non-linear buffers
         - improve reconfig, avoid link flap and waiting for idle
         - support MAC Merge layer
      - Other NICs:
         - sfc/ef100: add basic devlink support for ef100
         - ionic: rx_push mode operation (writing descriptors via MMIO)
         - bnxt: use the auxiliary bus abstraction for RDMA
         - r8169: disable ASPM and reset bus in case of tx timeout
         - cpsw: support QSGMII mode for J721e CPSW9G
         - cpts: support pulse-per-second output
         - ngbe: add an mdio bus driver
         - usbnet: optimize usbnet_bh() by avoiding unnecessary queuing
         - r8152: handle devices with FW with NCM support
         - amd-xgbe: support 10Mbps, 2.5GbE speeds and rx-adaptation
         - virtio-net: support multi buffer XDP
         - virtio/vsock: replace virtio_vsock_pkt with sk_buff
         - tsnep: XDP support

   - Ethernet high-speed switches:
      - nVidia/Mellanox (mlxsw):
         - add support for latency TLV (in FW control messages)
      - Microchip (sparx5):
         - separate explicit and implicit traffic forwarding rules, make
           the implicit rules always active
         - add support for egress DSCP rewrite
         - IS0 VCAP support (Ingress Classification)
         - IS2 VCAP filters (protos, L3 addrs, L4 ports, flags, ToS
           etc.)
         - ES2 VCAP support (Egress Access Control)
         - support for Per-Stream Filtering and Policing (802.1Q,
           8.6.5.1)

   - Ethernet embedded switches:
      - Marvell (mv88e6xxx):
         - add MAB (port auth) offload support
         - enable PTP receive for mv88e6390
      - NXP (ocelot):
         - support MAC Merge layer
         - support for the the vsc7512 internal copper phys
      - Microchip:
         - lan9303: convert to PHYLINK
         - lan966x: support TC flower filter statistics
         - lan937x: PTP support for KSZ9563/KSZ8563 and LAN937x
         - lan937x: support Credit Based Shaper configuration
         - ksz9477: support Energy Efficient Ethernet
      - other:
         - qca8k: convert to regmap read/write API, use bulk operations
         - rswitch: Improve TX timestamp accuracy

   - Intel WiFi (iwlwifi):
      - EHT (Wi-Fi 7) rate reporting
      - STEP equalizer support: transfer some STEP (connection to radio
        on platforms with integrated wifi) related parameters from the
        BIOS to the firmware.

   - Qualcomm 802.11ax WiFi (ath11k):
      - IPQ5018 support
      - Fine Timing Measurement (FTM) responder role support
      - channel 177 support

   - MediaTek WiFi (mt76):
      - per-PHY LED support
      - mt7996: EHT (Wi-Fi 7) support
      - Wireless Ethernet Dispatch (WED) reset support
      - switch to using page pool allocator

   - RealTek WiFi (rtw89):
      - support new version of Bluetooth co-existance

   - Mobile:
      - rmnet: support TX aggregation"

* tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (1872 commits)
  page_pool: add a comment explaining the fragment counter usage
  net: ethtool: fix __ethtool_dev_mm_supported() implementation
  ethtool: pse-pd: Fix double word in comments
  xsk: add linux/vmalloc.h to xsk.c
  sefltests: netdevsim: wait for devlink instance after netns removal
  selftest: fib_tests: Always cleanup before exit
  net/mlx5e: Align IPsec ASO result memory to be as required by hardware
  net/mlx5e: TC, Set CT miss to the specific ct action instance
  net/mlx5e: Rename CHAIN_TO_REG to MAPPED_OBJ_TO_REG
  net/mlx5: Refactor tc miss handling to a single function
  net/mlx5: Kconfig: Make tc offload depend on tc skb extension
  net/sched: flower: Support hardware miss to tc action
  net/sched: flower: Move filter handle initialization earlier
  net/sched: cls_api: Support hardware miss to tc action
  net/sched: Rename user cookie and act cookie
  sfc: fix builds without CONFIG_RTC_LIB
  sfc: clean up some inconsistent indentings
  net/mlx4_en: Introduce flexible array to silence overflow warning
  net: lan966x: Fix possible deadlock inside PTP
  net/ulp: Remove redundant ->clone() test in inet_clone_ulp().
  ...

1 files changed, 630 insertions, 0 deletions

diff --git a/drivers/tty/serial/kgdboc.c b/drivers/tty/serial/kgdboc.c
new file mode 100644
index 000000000..7ce7bb164
--- /dev/null
+++ b/drivers/tty/serial/kgdboc.c
@@ -0,0 +1,630 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Based on the same principle as kgdboe using the NETPOLL api, this
+ * driver uses a console polling api to implement a gdb serial inteface
+ * which is multiplexed on a console port.
+ *
+ * Maintainer: Jason Wessel <jason.wessel@windriver.com>
+ *
+ * 2007-2008 (c) Jason Wessel - Wind River Systems, Inc.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/ctype.h>
+#include <linux/kgdb.h>
+#include <linux/kdb.h>
+#include <linux/tty.h>
+#include <linux/console.h>
+#include <linux/vt_kern.h>
+#include <linux/input.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/serial_core.h>
+
+#define MAX_CONFIG_LEN		40
+
+static struct kgdb_io		kgdboc_io_ops;
+
+/* -1 = init not run yet, 0 = unconfigured, 1 = configured. */
+static int configured		= -1;
+static DEFINE_MUTEX(config_mutex);
+
+static char config[MAX_CONFIG_LEN];
+static struct kparam_string kps = {
+	.string			= config,
+	.maxlen			= MAX_CONFIG_LEN,
+};
+
+static int kgdboc_use_kms;  /* 1 if we use kernel mode switching */
+static struct tty_driver	*kgdb_tty_driver;
+static int			kgdb_tty_line;
+
+static struct platform_device *kgdboc_pdev;
+
+#if IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE)
+static struct kgdb_io		kgdboc_earlycon_io_ops;
+static int                      (*earlycon_orig_exit)(struct console *con);
+#endif /* IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE) */
+
+#ifdef CONFIG_KDB_KEYBOARD
+static int kgdboc_reset_connect(struct input_handler *handler,
+				struct input_dev *dev,
+				const struct input_device_id *id)
+{
+	input_reset_device(dev);
+
+	/* Return an error - we do not want to bind, just to reset */
+	return -ENODEV;
+}
+
+static void kgdboc_reset_disconnect(struct input_handle *handle)
+{
+	/* We do not expect anyone to actually bind to us */
+	BUG();
+}
+
+static const struct input_device_id kgdboc_reset_ids[] = {
+	{
+		.flags = INPUT_DEVICE_ID_MATCH_EVBIT,
+		.evbit = { BIT_MASK(EV_KEY) },
+	},
+	{ }
+};
+
+static struct input_handler kgdboc_reset_handler = {
+	.connect	= kgdboc_reset_connect,
+	.disconnect	= kgdboc_reset_disconnect,
+	.name		= "kgdboc_reset",
+	.id_table	= kgdboc_reset_ids,
+};
+
+static DEFINE_MUTEX(kgdboc_reset_mutex);
+
+static void kgdboc_restore_input_helper(struct work_struct *dummy)
+{
+	/*
+	 * We need to take a mutex to prevent several instances of
+	 * this work running on different CPUs so they don't try
+	 * to register again already registered handler.
+	 */
+	mutex_lock(&kgdboc_reset_mutex);
+
+	if (input_register_handler(&kgdboc_reset_handler) == 0)
+		input_unregister_handler(&kgdboc_reset_handler);
+
+	mutex_unlock(&kgdboc_reset_mutex);
+}
+
+static DECLARE_WORK(kgdboc_restore_input_work, kgdboc_restore_input_helper);
+
+static void kgdboc_restore_input(void)
+{
+	if (likely(system_state == SYSTEM_RUNNING))
+		schedule_work(&kgdboc_restore_input_work);
+}
+
+static int kgdboc_register_kbd(char **cptr)
+{
+	if (strncmp(*cptr, "kbd", 3) == 0 ||
+		strncmp(*cptr, "kdb", 3) == 0) {
+		if (kdb_poll_idx < KDB_POLL_FUNC_MAX) {
+			kdb_poll_funcs[kdb_poll_idx] = kdb_get_kbd_char;
+			kdb_poll_idx++;
+			if (cptr[0][3] == ',')
+				*cptr += 4;
+			else
+				return 1;
+		}
+	}
+	return 0;
+}
+
+static void kgdboc_unregister_kbd(void)
+{
+	int i;
+
+	for (i = 0; i < kdb_poll_idx; i++) {
+		if (kdb_poll_funcs[i] == kdb_get_kbd_char) {
+			kdb_poll_idx--;
+			kdb_poll_funcs[i] = kdb_poll_funcs[kdb_poll_idx];
+			kdb_poll_funcs[kdb_poll_idx] = NULL;
+			i--;
+		}
+	}
+	flush_work(&kgdboc_restore_input_work);
+}
+#else /* ! CONFIG_KDB_KEYBOARD */
+#define kgdboc_register_kbd(x) 0
+#define kgdboc_unregister_kbd()
+#define kgdboc_restore_input()
+#endif /* ! CONFIG_KDB_KEYBOARD */
+
+#if IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE)
+static void cleanup_earlycon(void)
+{
+	if (kgdboc_earlycon_io_ops.cons)
+		kgdb_unregister_io_module(&kgdboc_earlycon_io_ops);
+}
+#else /* !IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE) */
+static inline void cleanup_earlycon(void) { }
+#endif /* !IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE) */
+
+static void cleanup_kgdboc(void)
+{
+	cleanup_earlycon();
+
+	if (configured != 1)
+		return;
+
+	if (kgdb_unregister_nmi_console())
+		return;
+	kgdboc_unregister_kbd();
+	kgdb_unregister_io_module(&kgdboc_io_ops);
+}
+
+static int configure_kgdboc(void)
+{
+	struct tty_driver *p;
+	int tty_line = 0;
+	int err = -ENODEV;
+	char *cptr = config;
+	struct console *cons;
+	int cookie;
+
+	if (!strlen(config) || isspace(config[0])) {
+		err = 0;
+		goto noconfig;
+	}
+
+	kgdboc_io_ops.cons = NULL;
+	kgdb_tty_driver = NULL;
+
+	kgdboc_use_kms = 0;
+	if (strncmp(cptr, "kms,", 4) == 0) {
+		cptr += 4;
+		kgdboc_use_kms = 1;
+	}
+
+	if (kgdboc_register_kbd(&cptr))
+		goto do_register;
+
+	p = tty_find_polling_driver(cptr, &tty_line);
+	if (!p)
+		goto noconfig;
+
+	/*
+	 * Take console_lock to serialize device() callback with
+	 * other console operations. For example, fg_console is
+	 * modified under console_lock when switching vt.
+	 */
+	console_lock();
+
+	cookie = console_srcu_read_lock();
+	for_each_console_srcu(cons) {
+		int idx;
+		if (cons->device && cons->device(cons, &idx) == p &&
+		    idx == tty_line) {
+			kgdboc_io_ops.cons = cons;
+			break;
+		}
+	}
+	console_srcu_read_unlock(cookie);
+
+	console_unlock();
+
+	kgdb_tty_driver = p;
+	kgdb_tty_line = tty_line;
+
+do_register:
+	err = kgdb_register_io_module(&kgdboc_io_ops);
+	if (err)
+		goto noconfig;
+
+	err = kgdb_register_nmi_console();
+	if (err)
+		goto nmi_con_failed;
+
+	configured = 1;
+
+	return 0;
+
+nmi_con_failed:
+	kgdb_unregister_io_module(&kgdboc_io_ops);
+noconfig:
+	kgdboc_unregister_kbd();
+	configured = 0;
+
+	return err;
+}
+
+static int kgdboc_probe(struct platform_device *pdev)
+{
+	int ret = 0;
+
+	mutex_lock(&config_mutex);
+	if (configured != 1) {
+		ret = configure_kgdboc();
+
+		/* Convert "no device" to "defer" so we'll keep trying */
+		if (ret == -ENODEV)
+			ret = -EPROBE_DEFER;
+	}
+	mutex_unlock(&config_mutex);
+
+	return ret;
+}
+
+static struct platform_driver kgdboc_platform_driver = {
+	.probe = kgdboc_probe,
+	.driver = {
+		.name = "kgdboc",
+		.suppress_bind_attrs = true,
+	},
+};
+
+static int __init init_kgdboc(void)
+{
+	int ret;
+
+	/*
+	 * kgdboc is a little bit of an odd "platform_driver".  It can be
+	 * up and running long before the platform_driver object is
+	 * created and thus doesn't actually store anything in it.  There's
+	 * only one instance of kgdb so anything is stored as global state.
+	 * The platform_driver is only created so that we can leverage the
+	 * kernel's mechanisms (like -EPROBE_DEFER) to call us when our
+	 * underlying tty is ready.  Here we init our platform driver and
+	 * then create the single kgdboc instance.
+	 */
+	ret = platform_driver_register(&kgdboc_platform_driver);
+	if (ret)
+		return ret;
+
+	kgdboc_pdev = platform_device_alloc("kgdboc", PLATFORM_DEVID_NONE);
+	if (!kgdboc_pdev) {
+		ret = -ENOMEM;
+		goto err_did_register;
+	}
+
+	ret = platform_device_add(kgdboc_pdev);
+	if (!ret)
+		return 0;
+
+	platform_device_put(kgdboc_pdev);
+
+err_did_register:
+	platform_driver_unregister(&kgdboc_platform_driver);
+	return ret;
+}
+
+static void exit_kgdboc(void)
+{
+	mutex_lock(&config_mutex);
+	cleanup_kgdboc();
+	mutex_unlock(&config_mutex);
+
+	platform_device_unregister(kgdboc_pdev);
+	platform_driver_unregister(&kgdboc_platform_driver);
+}
+
+static int kgdboc_get_char(void)
+{
+	if (!kgdb_tty_driver)
+		return -1;
+	return kgdb_tty_driver->ops->poll_get_char(kgdb_tty_driver,
+						kgdb_tty_line);
+}
+
+static void kgdboc_put_char(u8 chr)
+{
+	if (!kgdb_tty_driver)
+		return;
+	kgdb_tty_driver->ops->poll_put_char(kgdb_tty_driver,
+					kgdb_tty_line, chr);
+}
+
+static int param_set_kgdboc_var(const char *kmessage,
+				const struct kernel_param *kp)
+{
+	size_t len = strlen(kmessage);
+	int ret = 0;
+
+	if (len >= MAX_CONFIG_LEN) {
+		pr_err("config string too long\n");
+		return -ENOSPC;
+	}
+
+	if (kgdb_connected) {
+		pr_err("Cannot reconfigure while KGDB is connected.\n");
+		return -EBUSY;
+	}
+
+	mutex_lock(&config_mutex);
+
+	strcpy(config, kmessage);
+	/* Chop out \n char as a result of echo */
+	if (len && config[len - 1] == '\n')
+		config[len - 1] = '\0';
+
+	if (configured == 1)
+		cleanup_kgdboc();
+
+	/*
+	 * Configure with the new params as long as init already ran.
+	 * Note that we can get called before init if someone loads us
+	 * with "modprobe kgdboc kgdboc=..." or if they happen to use
+	 * the odd syntax of "kgdboc.kgdboc=..." on the kernel command.
+	 */
+	if (configured >= 0)
+		ret = configure_kgdboc();
+
+	/*
+	 * If we couldn't configure then clear out the config.  Note that
+	 * specifying an invalid config on the kernel command line vs.
+	 * through sysfs have slightly different behaviors.  If we fail
+	 * to configure what was specified on the kernel command line
+	 * we'll leave it in the 'config' and return -EPROBE_DEFER from
+	 * our probe.  When specified through sysfs userspace is
+	 * responsible for loading the tty driver before setting up.
+	 */
+	if (ret)
+		config[0] = '\0';
+
+	mutex_unlock(&config_mutex);
+
+	return ret;
+}
+
+static int dbg_restore_graphics;
+
+static void kgdboc_pre_exp_handler(void)
+{
+	if (!dbg_restore_graphics && kgdboc_use_kms) {
+		dbg_restore_graphics = 1;
+		con_debug_enter(vc_cons[fg_console].d);
+	}
+	/* Increment the module count when the debugger is active */
+	if (!kgdb_connected)
+		try_module_get(THIS_MODULE);
+}
+
+static void kgdboc_post_exp_handler(void)
+{
+	/* decrement the module count when the debugger detaches */
+	if (!kgdb_connected)
+		module_put(THIS_MODULE);
+	if (kgdboc_use_kms && dbg_restore_graphics) {
+		dbg_restore_graphics = 0;
+		con_debug_leave();
+	}
+	kgdboc_restore_input();
+}
+
+static struct kgdb_io kgdboc_io_ops = {
+	.name			= "kgdboc",
+	.read_char		= kgdboc_get_char,
+	.write_char		= kgdboc_put_char,
+	.pre_exception		= kgdboc_pre_exp_handler,
+	.post_exception		= kgdboc_post_exp_handler,
+};
+
+#if IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE)
+static int kgdboc_option_setup(char *opt)
+{
+	if (!opt) {
+		pr_err("config string not provided\n");
+		return 1;
+	}
+
+	if (strlen(opt) >= MAX_CONFIG_LEN) {
+		pr_err("config string too long\n");
+		return 1;
+	}
+	strcpy(config, opt);
+
+	return 1;
+}
+
+__setup("kgdboc=", kgdboc_option_setup);
+
+
+/* This is only available if kgdboc is a built in for early debugging */
+static int __init kgdboc_early_init(char *opt)
+{
+	kgdboc_option_setup(opt);
+	configure_kgdboc();
+	return 0;
+}
+
+early_param("ekgdboc", kgdboc_early_init);
+
+static int kgdboc_earlycon_get_char(void)
+{
+	char c;
+
+	if (!kgdboc_earlycon_io_ops.cons->read(kgdboc_earlycon_io_ops.cons,
+					       &c, 1))
+		return NO_POLL_CHAR;
+
+	return c;
+}
+
+static void kgdboc_earlycon_put_char(u8 chr)
+{
+	kgdboc_earlycon_io_ops.cons->write(kgdboc_earlycon_io_ops.cons, &chr,
+					   1);
+}
+
+static void kgdboc_earlycon_pre_exp_handler(void)
+{
+	struct console *con;
+	static bool already_warned;
+	int cookie;
+
+	if (already_warned)
+		return;
+
+	/*
+	 * When the first normal console comes up the kernel will take all
+	 * the boot consoles out of the list.  Really, we should stop using
+	 * the boot console when it does that but until a TTY is registered
+	 * we have no other choice so we keep using it.  Since not all
+	 * serial drivers might be OK with this, print a warning once per
+	 * boot if we detect this case.
+	 */
+	cookie = console_srcu_read_lock();
+	for_each_console_srcu(con) {
+		if (con == kgdboc_earlycon_io_ops.cons)
+			break;
+	}
+	console_srcu_read_unlock(cookie);
+	if (con)
+		return;
+
+	already_warned = true;
+	pr_warn("kgdboc_earlycon is still using bootconsole\n");
+}
+
+static int kgdboc_earlycon_deferred_exit(struct console *con)
+{
+	/*
+	 * If we get here it means the boot console is going away but we
+	 * don't yet have a suitable replacement.  Don't pass through to
+	 * the original exit routine.  We'll call it later in our deinit()
+	 * function.  For now, restore the original exit() function pointer
+	 * as a sentinal that we've hit this point.
+	 */
+	con->exit = earlycon_orig_exit;
+
+	return 0;
+}
+
+static void kgdboc_earlycon_deinit(void)
+{
+	if (!kgdboc_earlycon_io_ops.cons)
+		return;
+
+	if (kgdboc_earlycon_io_ops.cons->exit == kgdboc_earlycon_deferred_exit)
+		/*
+		 * kgdboc_earlycon is exiting but original boot console exit
+		 * was never called (AKA kgdboc_earlycon_deferred_exit()
+		 * didn't ever run).  Undo our trap.
+		 */
+		kgdboc_earlycon_io_ops.cons->exit = earlycon_orig_exit;
+	else if (kgdboc_earlycon_io_ops.cons->exit)
+		/*
+		 * We skipped calling the exit() routine so we could try to
+		 * keep using the boot console even after it went away.  We're
+		 * finally done so call the function now.
+		 */
+		kgdboc_earlycon_io_ops.cons->exit(kgdboc_earlycon_io_ops.cons);
+
+	kgdboc_earlycon_io_ops.cons = NULL;
+}
+
+static struct kgdb_io kgdboc_earlycon_io_ops = {
+	.name			= "kgdboc_earlycon",
+	.read_char		= kgdboc_earlycon_get_char,
+	.write_char		= kgdboc_earlycon_put_char,
+	.pre_exception		= kgdboc_earlycon_pre_exp_handler,
+	.deinit			= kgdboc_earlycon_deinit,
+};
+
+#define MAX_CONSOLE_NAME_LEN (sizeof((struct console *) 0)->name)
+static char kgdboc_earlycon_param[MAX_CONSOLE_NAME_LEN] __initdata;
+static bool kgdboc_earlycon_late_enable __initdata;
+
+static int __init kgdboc_earlycon_init(char *opt)
+{
+	struct console *con;
+
+	kdb_init(KDB_INIT_EARLY);
+
+	/*
+	 * Look for a matching console, or if the name was left blank just
+	 * pick the first one we find.
+	 */
+
+	/*
+	 * Hold the console_list_lock to guarantee that no consoles are
+	 * unregistered until the kgdboc_earlycon setup is complete.
+	 * Trapping the exit() callback relies on exit() not being
+	 * called until the trap is setup. This also allows safe
+	 * traversal of the console list and race-free reading of @flags.
+	 */
+	console_list_lock();
+	for_each_console(con) {
+		if (con->write && con->read &&
+		    (con->flags & (CON_BOOT | CON_ENABLED)) &&
+		    (!opt || !opt[0] || strcmp(con->name, opt) == 0))
+			break;
+	}
+
+	if (!con) {
+		/*
+		 * Both earlycon and kgdboc_earlycon are initialized during
+		 * early parameter parsing. We cannot guarantee earlycon gets
+		 * in first and, in any case, on ACPI systems earlycon may
+		 * defer its own initialization (usually to somewhere within
+		 * setup_arch() ). To cope with either of these situations
+		 * we can defer our own initialization to a little later in
+		 * the boot.
+		 */
+		if (!kgdboc_earlycon_late_enable) {
+			pr_info("No suitable earlycon yet, will try later\n");
+			if (opt)
+				strscpy(kgdboc_earlycon_param, opt,
+					sizeof(kgdboc_earlycon_param));
+			kgdboc_earlycon_late_enable = true;
+		} else {
+			pr_info("Couldn't find kgdb earlycon\n");
+		}
+		goto unlock;
+	}
+
+	kgdboc_earlycon_io_ops.cons = con;
+	pr_info("Going to register kgdb with earlycon '%s'\n", con->name);
+	if (kgdb_register_io_module(&kgdboc_earlycon_io_ops) != 0) {
+		kgdboc_earlycon_io_ops.cons = NULL;
+		pr_info("Failed to register kgdb with earlycon\n");
+	} else {
+		/* Trap exit so we can keep earlycon longer if needed. */
+		earlycon_orig_exit = con->exit;
+		con->exit = kgdboc_earlycon_deferred_exit;
+	}
+
+unlock:
+	console_list_unlock();
+
+	/* Non-zero means malformed option so we always return zero */
+	return 0;
+}
+
+early_param("kgdboc_earlycon", kgdboc_earlycon_init);
+
+/*
+ * This is only intended for the late adoption of an early console.
+ *
+ * It is not a reliable way to adopt regular consoles because we can not
+ * control what order console initcalls are made and, in any case, many
+ * regular consoles are registered much later in the boot process than
+ * the console initcalls!
+ */
+static int __init kgdboc_earlycon_late_init(void)
+{
+	if (kgdboc_earlycon_late_enable)
+		kgdboc_earlycon_init(kgdboc_earlycon_param);
+	return 0;
+}
+console_initcall(kgdboc_earlycon_late_init);
+
+#endif /* IS_BUILTIN(CONFIG_KGDB_SERIAL_CONSOLE) */
+
+module_init(init_kgdboc);
+module_exit(exit_kgdboc);
+module_param_call(kgdboc, param_set_kgdboc_var, param_get_string, &kps, 0644);
+MODULE_PARM_DESC(kgdboc, "<serial_device>[,baud]");
+MODULE_DESCRIPTION("KGDB Console TTY Driver");
+MODULE_LICENSE("GPL");