From a5f7a5bb3b7f28ba7e4fa246775b29a0e5537255 Mon Sep 17 00:00:00 2001 From: Jinke Han Date: Tue, 8 Sep 2026 15:37:42 +0800 Subject: x86/kprobes: Fix crash when probing CS CALL instructions When using eBPF to probe CS CALL instructions within a function, a crash can be triggered. The eBPF tool probes offset 257 of the __hrtimer_run_queues() function: <__hrtimer_run_queues+249>: nopl 0x0(%rax,%rax,1) <__hrtimer_run_queues+254>: mov %r14,%rdi <__hrtimer_run_queues+257>: cs call <__x86_indirect_thunk_r12> <__hrtimer_run_queues+263>: mov %eax,%r12d <__hrtimer_run_queues+266>: xchg %ax,%ax <__hrtimer_run_queues+268>: mov %r13,%rdi Which triggers this crash: BUG: unable to handle page fault for address: 00000000000f41c9 #PF: supervisor write access in kernel mode #PF: error_code(0x0002) - not-present page PGD 0 P4D 0 Oops: 0002 [#1] SMP NOPTI CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: P RIP: 0010:__hrtimer_run_queues+0x106/0x230 Note that __hrtimer_run_queues+0x106 is __hrtimer_run_queues+262, which is at the 6th byte of the above CS CALL instruction. Since the CS CALL instruction occupies 6 bytes, the exception occurred in the middle of that call instruction. The root cause is that when using eBPF tools to probe in the middle of a function, a kprobe with INT3 is used as the underlying implementation. During single-step emulation of the original CALL instruction, int3_emulate_call() assumes that the probed CALL instruction is 5 bytes long. However, the actual CS-prefixed CALL instruction occupies 6 bytes, so it constructs an incorrect exception return address. When the CPU returns from the kprobe handler, the next instruction to be executed is at the address of the last byte of that CS CALL instruction. Coincidentally, starting from that address, the CPU fetches and decodes a completely different instruction, which ultimately triggers a kernel crash. Fix the issue by using the actual instruction length obtained from the instruction decoder when constructing the exception return address, rather than relying on the hardcoded CALL_INSN_SIZE macro. [ mingo: Refined the changelog ] Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step") Suggested-by: Masami Hiramatsu (Google) Signed-off-by: Jinke Han Signed-off-by: Ingo Molnar Reviewed-by: Masami Hiramatsu (Google) Acked-by: Yafang Shao Acked-by: Borislav Petkov Cc: Peter Zijlstra Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000 --- drivers/mfd/ntxec.c | 270 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 270 insertions(+) create mode 100644 drivers/mfd/ntxec.c (limited to 'drivers/mfd/ntxec.c') diff --git a/drivers/mfd/ntxec.c b/drivers/mfd/ntxec.c new file mode 100644 index 000000000..08c68de0f --- /dev/null +++ b/drivers/mfd/ntxec.c @@ -0,0 +1,270 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * The Netronix embedded controller is a microcontroller found in some + * e-book readers designed by the original design manufacturer Netronix, Inc. + * It contains RTC, battery monitoring, system power management, and PWM + * functionality. + * + * This driver implements register access, version detection, and system + * power-off/reset. + * + * Copyright 2020 Jonathan Neuschäfer + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#define NTXEC_REG_VERSION 0x00 +#define NTXEC_REG_POWEROFF 0x50 +#define NTXEC_REG_POWERKEEP 0x70 +#define NTXEC_REG_RESET 0x90 + +#define NTXEC_POWEROFF_VALUE 0x0100 +#define NTXEC_POWERKEEP_VALUE 0x0800 +#define NTXEC_RESET_VALUE 0xff00 + +static struct i2c_client *poweroff_restart_client; + +static void ntxec_poweroff(void) +{ + int res; + u8 buf[3] = { NTXEC_REG_POWEROFF }; + struct i2c_msg msgs[] = { + { + .addr = poweroff_restart_client->addr, + .flags = 0, + .len = sizeof(buf), + .buf = buf, + }, + }; + + put_unaligned_be16(NTXEC_POWEROFF_VALUE, buf + 1); + + res = i2c_transfer(poweroff_restart_client->adapter, msgs, ARRAY_SIZE(msgs)); + if (res < 0) + dev_warn(&poweroff_restart_client->dev, + "Failed to power off (err = %d)\n", res); + + /* + * The time from the register write until the host CPU is powered off + * has been observed to be about 2.5 to 3 seconds. Sleep long enough to + * safely avoid returning from the poweroff handler. + */ + msleep(5000); +} + +static int ntxec_restart(struct notifier_block *nb, + unsigned long action, void *data) +{ + int res; + u8 buf[3] = { NTXEC_REG_RESET }; + /* + * NOTE: The lower half of the reset value is not sent, because sending + * it causes an I2C error. (The reset handler in the downstream driver + * does send the full two-byte value, but doesn't check the result). + */ + struct i2c_msg msgs[] = { + { + .addr = poweroff_restart_client->addr, + .flags = 0, + .len = sizeof(buf) - 1, + .buf = buf, + }, + }; + + put_unaligned_be16(NTXEC_RESET_VALUE, buf + 1); + + res = i2c_transfer(poweroff_restart_client->adapter, msgs, ARRAY_SIZE(msgs)); + if (res < 0) + dev_warn(&poweroff_restart_client->dev, + "Failed to restart (err = %d)\n", res); + + return NOTIFY_DONE; +} + +static struct notifier_block ntxec_restart_handler = { + .notifier_call = ntxec_restart, + .priority = 128, +}; + +static int regmap_ignore_write(void *context, + unsigned int reg, unsigned int val) + +{ + struct regmap *regmap = context; + + regmap_write(regmap, reg, val); + + return 0; +} + +static int regmap_wrap_read(void *context, unsigned int reg, + unsigned int *val) +{ + struct regmap *regmap = context; + + return regmap_read(regmap, reg, val); +} + +/* + * Some firmware versions do not ack written data, add a wrapper. It + * is used to stack another regmap on top. + */ +static const struct regmap_config regmap_config_noack = { + .name = "ntxec_noack", + .reg_bits = 8, + .val_bits = 16, + .cache_type = REGCACHE_NONE, + .reg_write = regmap_ignore_write, + .reg_read = regmap_wrap_read +}; + +static const struct regmap_config regmap_config = { + .name = "ntxec", + .reg_bits = 8, + .val_bits = 16, + .cache_type = REGCACHE_NONE, + .val_format_endian = REGMAP_ENDIAN_BIG, +}; + +static const struct mfd_cell ntxec_subdev[] = { + { .name = "ntxec-rtc" }, + { .name = "ntxec-pwm" }, +}; + +static const struct mfd_cell ntxec_subdev_pwm[] = { + { .name = "ntxec-pwm" }, +}; + +static int ntxec_probe(struct i2c_client *client) +{ + struct ntxec *ec; + unsigned int version; + int res; + const struct mfd_cell *subdevs; + size_t n_subdevs; + + ec = devm_kmalloc(&client->dev, sizeof(*ec), GFP_KERNEL); + if (!ec) + return -ENOMEM; + + ec->dev = &client->dev; + + ec->regmap = devm_regmap_init_i2c(client, ®map_config); + if (IS_ERR(ec->regmap)) { + dev_err(ec->dev, "Failed to set up regmap for device\n"); + return PTR_ERR(ec->regmap); + } + + /* Determine the firmware version */ + res = regmap_read(ec->regmap, NTXEC_REG_VERSION, &version); + if (res < 0) { + dev_err(ec->dev, "Failed to read firmware version number\n"); + return res; + } + + /* Bail out if we encounter an unknown firmware version */ + switch (version) { + case NTXEC_VERSION_KOBO_AURA: + case NTXEC_VERSION_TOLINO_VISION: + subdevs = ntxec_subdev; + n_subdevs = ARRAY_SIZE(ntxec_subdev); + break; + case NTXEC_VERSION_TOLINO_SHINE2: + subdevs = ntxec_subdev_pwm; + n_subdevs = ARRAY_SIZE(ntxec_subdev_pwm); + /* Another regmap stacked on top of the other */ + ec->regmap = devm_regmap_init(ec->dev, NULL, + ec->regmap, + ®map_config_noack); + if (IS_ERR(ec->regmap)) + return PTR_ERR(ec->regmap); + break; + default: + dev_err(ec->dev, + "Netronix embedded controller version %04x is not supported.\n", + version); + return -ENODEV; + } + + dev_info(ec->dev, + "Netronix embedded controller version %04x detected.\n", version); + + if (of_device_is_system_power_controller(ec->dev->of_node)) { + /* + * Set the 'powerkeep' bit. This is necessary on some boards + * in order to keep the system running. + */ + res = regmap_write(ec->regmap, NTXEC_REG_POWERKEEP, + NTXEC_POWERKEEP_VALUE); + if (res < 0) + return res; + + if (poweroff_restart_client) + /* + * Another instance of the driver already took + * poweroff/restart duties. + */ + dev_err(ec->dev, "poweroff_restart_client already assigned\n"); + else + poweroff_restart_client = client; + + if (pm_power_off) + /* Another driver already registered a poweroff handler. */ + dev_err(ec->dev, "pm_power_off already assigned\n"); + else + pm_power_off = ntxec_poweroff; + + res = register_restart_handler(&ntxec_restart_handler); + if (res) + dev_err(ec->dev, + "Failed to register restart handler: %d\n", res); + } + + i2c_set_clientdata(client, ec); + + res = devm_mfd_add_devices(ec->dev, PLATFORM_DEVID_NONE, + subdevs, n_subdevs, NULL, 0, NULL); + if (res) + dev_err(ec->dev, "Failed to add subdevices: %d\n", res); + + return res; +} + +static void ntxec_remove(struct i2c_client *client) +{ + if (client == poweroff_restart_client) { + poweroff_restart_client = NULL; + pm_power_off = NULL; + unregister_restart_handler(&ntxec_restart_handler); + } +} + +static const struct of_device_id of_ntxec_match_table[] = { + { .compatible = "netronix,ntxec", }, + {} +}; +MODULE_DEVICE_TABLE(of, of_ntxec_match_table); + +static struct i2c_driver ntxec_driver = { + .driver = { + .name = "ntxec", + .of_match_table = of_ntxec_match_table, + }, + .probe = ntxec_probe, + .remove = ntxec_remove, +}; +module_i2c_driver(ntxec_driver); + +MODULE_AUTHOR("Jonathan Neuschäfer "); +MODULE_DESCRIPTION("Core driver for Netronix EC"); +MODULE_LICENSE("GPL"); -- cgit v1.3.1