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/rtc/rtc-sd2405al.c | 229 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 229 insertions(+) create mode 100644 drivers/rtc/rtc-sd2405al.c (limited to 'drivers/rtc/rtc-sd2405al.c') diff --git a/drivers/rtc/rtc-sd2405al.c b/drivers/rtc/rtc-sd2405al.c new file mode 100644 index 000000000..7982a910a --- /dev/null +++ b/drivers/rtc/rtc-sd2405al.c @@ -0,0 +1,229 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * RTC driver for the SD2405AL Real-Time Clock + * + * Datasheet: + * https://image.dfrobot.com/image/data/TOY0021/SD2405AL%20datasheet%20(Angelo%20v0.1).pdf + * + * I2C slave address: 0x32 + * + * Copyright (C) 2024-2025 Tóth János + */ + +#include +#include +#include +#include + +/* Real time clock registers */ +#define SD2405AL_REG_T_SEC 0x00 +#define SD2405AL_REG_T_MIN 0x01 +#define SD2405AL_REG_T_HOUR 0x02 +# define SD2405AL_BIT_12H_PM BIT(5) +# define SD2405AL_BIT_24H BIT(7) +#define SD2405AL_REG_T_WEEK 0x03 +#define SD2405AL_REG_T_DAY 0x04 +#define SD2405AL_REG_T_MON 0x05 +#define SD2405AL_REG_T_YEAR 0x06 + +#define SD2405AL_NUM_T_REGS (SD2405AL_REG_T_YEAR - SD2405AL_REG_T_SEC + 1) + +/* Control registers */ +#define SD2405AL_REG_CTR1 0x0F +# define SD2405AL_BIT_WRTC2 BIT(2) +# define SD2405AL_BIT_WRTC3 BIT(7) +#define SD2405AL_REG_CTR2 0x10 +# define SD2405AL_BIT_WRTC1 BIT(7) +#define SD2405AL_REG_CTR3 0x11 +#define SD2405AL_REG_TTF 0x12 +#define SD2405AL_REG_CNTDWN 0x13 + +/* General RAM */ +#define SD2405AL_REG_M_START 0x14 +#define SD2405AL_REG_M_END 0x1F + +struct sd2405al { + struct device *dev; + struct regmap *regmap; +}; + +static int sd2405al_enable_reg_write(struct sd2405al *sd2405al) +{ + int ret; + + /* order of writes is important */ + ret = regmap_update_bits(sd2405al->regmap, SD2405AL_REG_CTR2, + SD2405AL_BIT_WRTC1, SD2405AL_BIT_WRTC1); + if (ret < 0) + return ret; + + ret = regmap_update_bits(sd2405al->regmap, SD2405AL_REG_CTR1, + SD2405AL_BIT_WRTC2 | SD2405AL_BIT_WRTC3, + SD2405AL_BIT_WRTC2 | SD2405AL_BIT_WRTC3); + if (ret < 0) + return ret; + + return 0; +} + +static int sd2405al_disable_reg_write(struct sd2405al *sd2405al) +{ + int ret; + + /* order of writes is important */ + ret = regmap_update_bits(sd2405al->regmap, SD2405AL_REG_CTR1, + SD2405AL_BIT_WRTC2 | SD2405AL_BIT_WRTC3, 0x00); + if (ret < 0) + return ret; + + ret = regmap_update_bits(sd2405al->regmap, SD2405AL_REG_CTR2, + SD2405AL_BIT_WRTC1, 0x00); + if (ret < 0) + return ret; + + return 0; +} + +static int sd2405al_read_time(struct device *dev, struct rtc_time *time) +{ + u8 data[SD2405AL_NUM_T_REGS] = { 0 }; + struct sd2405al *sd2405al = dev_get_drvdata(dev); + int ret; + + ret = regmap_bulk_read(sd2405al->regmap, SD2405AL_REG_T_SEC, data, + SD2405AL_NUM_T_REGS); + if (ret < 0) + return ret; + + time->tm_sec = bcd2bin(data[SD2405AL_REG_T_SEC] & 0x7F); + time->tm_min = bcd2bin(data[SD2405AL_REG_T_MIN] & 0x7F); + + if (data[SD2405AL_REG_T_HOUR] & SD2405AL_BIT_24H) + time->tm_hour = bcd2bin(data[SD2405AL_REG_T_HOUR] & 0x3F); + else + if (data[SD2405AL_REG_T_HOUR] & SD2405AL_BIT_12H_PM) + time->tm_hour = bcd2bin(data[SD2405AL_REG_T_HOUR] + & 0x1F) + 12; + else /* 12 hour mode, AM */ + time->tm_hour = bcd2bin(data[SD2405AL_REG_T_HOUR] + & 0x1F); + + time->tm_wday = bcd2bin(data[SD2405AL_REG_T_WEEK] & 0x07); + time->tm_mday = bcd2bin(data[SD2405AL_REG_T_DAY] & 0x3F); + time->tm_mon = bcd2bin(data[SD2405AL_REG_T_MON] & 0x1F) - 1; + time->tm_year = bcd2bin(data[SD2405AL_REG_T_YEAR]) + 100; + + dev_dbg(sd2405al->dev, "read time: %ptR (%d)\n", time, time->tm_wday); + + return 0; +} + +static int sd2405al_set_time(struct device *dev, struct rtc_time *time) +{ + u8 data[SD2405AL_NUM_T_REGS]; + struct sd2405al *sd2405al = dev_get_drvdata(dev); + int ret; + + data[SD2405AL_REG_T_SEC] = bin2bcd(time->tm_sec); + data[SD2405AL_REG_T_MIN] = bin2bcd(time->tm_min); + data[SD2405AL_REG_T_HOUR] = bin2bcd(time->tm_hour) | SD2405AL_BIT_24H; + data[SD2405AL_REG_T_DAY] = bin2bcd(time->tm_mday); + data[SD2405AL_REG_T_WEEK] = bin2bcd(time->tm_wday); + data[SD2405AL_REG_T_MON] = bin2bcd(time->tm_mon) + 1; + data[SD2405AL_REG_T_YEAR] = bin2bcd(time->tm_year - 100); + + ret = sd2405al_enable_reg_write(sd2405al); + if (ret < 0) + return ret; + + ret = regmap_bulk_write(sd2405al->regmap, SD2405AL_REG_T_SEC, data, + SD2405AL_NUM_T_REGS); + if (ret < 0) + return ret; + + ret = regmap_write(sd2405al->regmap, SD2405AL_REG_TTF, 0x00); + if (ret < 0) + return ret; + + ret = sd2405al_disable_reg_write(sd2405al); + if (ret < 0) + return ret; + + dev_dbg(sd2405al->dev, "set time: %ptR (%d)\n", time, time->tm_wday); + + return 0; +} + +static const struct rtc_class_ops sd2405al_rtc_ops = { + .read_time = sd2405al_read_time, + .set_time = sd2405al_set_time, +}; + +static const struct regmap_config sd2405al_regmap_conf = { + .reg_bits = 8, + .val_bits = 8, + .max_register = SD2405AL_REG_M_END, +}; + +static int sd2405al_probe(struct i2c_client *client) +{ + struct sd2405al *sd2405al; + struct rtc_device *rtc; + int ret; + + if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) + return -ENODEV; + + sd2405al = devm_kzalloc(&client->dev, sizeof(*sd2405al), GFP_KERNEL); + if (!sd2405al) + return -ENOMEM; + + sd2405al->dev = &client->dev; + + sd2405al->regmap = devm_regmap_init_i2c(client, &sd2405al_regmap_conf); + if (IS_ERR(sd2405al->regmap)) + return PTR_ERR(sd2405al->regmap); + + rtc = devm_rtc_allocate_device(&client->dev); + if (IS_ERR(rtc)) + return PTR_ERR(rtc); + + rtc->ops = &sd2405al_rtc_ops; + rtc->range_min = RTC_TIMESTAMP_BEGIN_2000; + rtc->range_max = RTC_TIMESTAMP_END_2099; + + dev_set_drvdata(&client->dev, sd2405al); + + ret = devm_rtc_register_device(rtc); + if (ret < 0) + return ret; + + return 0; +} + +static const struct i2c_device_id sd2405al_id[] = { + { .name = "sd2405al" }, + { /* sentinel */ } +}; +MODULE_DEVICE_TABLE(i2c, sd2405al_id); + +static const __maybe_unused struct of_device_id sd2405al_of_match[] = { + { .compatible = "dfrobot,sd2405al" }, + { /* sentinel */ } +}; +MODULE_DEVICE_TABLE(of, sd2405al_of_match); + +static struct i2c_driver sd2405al_driver = { + .driver = { + .name = "sd2405al", + .of_match_table = of_match_ptr(sd2405al_of_match), + }, + .probe = sd2405al_probe, + .id_table = sd2405al_id, +}; + +module_i2c_driver(sd2405al_driver); + +MODULE_AUTHOR("Tóth János "); +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("SD2405AL RTC driver"); -- cgit v1.3.1