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/auxdisplay/max6959.c | 190 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 190 insertions(+) create mode 100644 drivers/auxdisplay/max6959.c (limited to 'drivers/auxdisplay/max6959.c') diff --git a/drivers/auxdisplay/max6959.c b/drivers/auxdisplay/max6959.c new file mode 100644 index 000000000..888788a1f --- /dev/null +++ b/drivers/auxdisplay/max6959.c @@ -0,0 +1,190 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * MAX6958/6959 7-segment LED display controller + * Datasheet: + * https://www.analog.com/media/en/technical-documentation/data-sheets/MAX6958-MAX6959.pdf + * + * Copyright (c) 2024, Intel Corporation. + * Author: Andy Shevchenko + */ +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include + +#include "line-display.h" + +/* Registers */ +#define REG_DECODE_MODE 0x01 +#define REG_INTENSITY 0x02 +#define REG_SCAN_LIMIT 0x03 +#define REG_CONFIGURATION 0x04 +#define REG_CONFIGURATION_S_BIT BIT(0) + +#define REG_DIGIT(x) (0x20 + (x)) +#define REG_DIGIT0 0x20 +#define REG_DIGIT1 0x21 +#define REG_DIGIT2 0x22 +#define REG_DIGIT3 0x23 + +#define REG_SEGMENTS 0x24 +#define REG_MAX REG_SEGMENTS + +struct max6959_priv { + struct linedisp linedisp; + struct delayed_work work; + struct regmap *regmap; +}; + +static void max6959_disp_update(struct work_struct *work) +{ + struct max6959_priv *priv = container_of(work, struct max6959_priv, work.work); + struct linedisp *linedisp = &priv->linedisp; + struct linedisp_map *map = linedisp->map; + char *s = linedisp->buf; + u8 buf[4]; + + /* Map segments according to datasheet */ + buf[0] = bitrev8(map_to_seg7(&map->map.seg7, *s++)) >> 1; + buf[1] = bitrev8(map_to_seg7(&map->map.seg7, *s++)) >> 1; + buf[2] = bitrev8(map_to_seg7(&map->map.seg7, *s++)) >> 1; + buf[3] = bitrev8(map_to_seg7(&map->map.seg7, *s++)) >> 1; + + regmap_bulk_write(priv->regmap, REG_DIGIT(0), buf, ARRAY_SIZE(buf)); +} + +static int max6959_linedisp_get_map_type(struct linedisp *linedisp) +{ + struct max6959_priv *priv = container_of(linedisp, struct max6959_priv, linedisp); + + INIT_DELAYED_WORK(&priv->work, max6959_disp_update); + return LINEDISP_MAP_SEG7; +} + +static void max6959_linedisp_update(struct linedisp *linedisp) +{ + struct max6959_priv *priv = container_of(linedisp, struct max6959_priv, linedisp); + + schedule_delayed_work(&priv->work, 0); +} + +static const struct linedisp_ops max6959_linedisp_ops = { + .get_map_type = max6959_linedisp_get_map_type, + .update = max6959_linedisp_update, +}; + +static int max6959_enable(struct max6959_priv *priv, bool enable) +{ + return regmap_assign_bits(priv->regmap, REG_CONFIGURATION, REG_CONFIGURATION_S_BIT, enable); +} + +static void max6959_power_off(void *priv) +{ + max6959_enable(priv, false); +} + +static int max6959_power_on(struct max6959_priv *priv) +{ + struct device *dev = regmap_get_device(priv->regmap); + int ret; + + ret = max6959_enable(priv, true); + if (ret) + return ret; + + return devm_add_action_or_reset(dev, max6959_power_off, priv); +} + +static const struct regmap_config max6959_regmap_config = { + .reg_bits = 8, + .val_bits = 8, + + .max_register = REG_MAX, + .cache_type = REGCACHE_MAPLE, +}; + +static int max6959_i2c_probe(struct i2c_client *client) +{ + struct device *dev = &client->dev; + struct max6959_priv *priv; + int ret; + + priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL); + if (!priv) + return -ENOMEM; + + priv->regmap = devm_regmap_init_i2c(client, &max6959_regmap_config); + if (IS_ERR(priv->regmap)) + return PTR_ERR(priv->regmap); + + ret = max6959_power_on(priv); + if (ret) + return ret; + + ret = linedisp_register(&priv->linedisp, dev, 4, &max6959_linedisp_ops); + if (ret) + return ret; + + i2c_set_clientdata(client, priv); + + return 0; +} + +static void max6959_i2c_remove(struct i2c_client *client) +{ + struct max6959_priv *priv = i2c_get_clientdata(client); + + cancel_delayed_work_sync(&priv->work); + linedisp_unregister(&priv->linedisp); +} + +static int max6959_suspend(struct device *dev) +{ + return max6959_enable(dev_get_drvdata(dev), false); +} + +static int max6959_resume(struct device *dev) +{ + return max6959_enable(dev_get_drvdata(dev), true); +} + +static DEFINE_SIMPLE_DEV_PM_OPS(max6959_pm_ops, max6959_suspend, max6959_resume); + +static const struct i2c_device_id max6959_i2c_id[] = { + { "max6959" }, + { } +}; +MODULE_DEVICE_TABLE(i2c, max6959_i2c_id); + +static const struct of_device_id max6959_of_table[] = { + { .compatible = "maxim,max6959" }, + { } +}; +MODULE_DEVICE_TABLE(of, max6959_of_table); + +static struct i2c_driver max6959_i2c_driver = { + .driver = { + .name = "max6959", + .pm = pm_sleep_ptr(&max6959_pm_ops), + .of_match_table = max6959_of_table, + }, + .probe = max6959_i2c_probe, + .remove = max6959_i2c_remove, + .id_table = max6959_i2c_id, +}; +module_i2c_driver(max6959_i2c_driver); + +MODULE_DESCRIPTION("MAX6958/6959 7-segment LED controller"); +MODULE_AUTHOR("Andy Shevchenko "); +MODULE_LICENSE("GPL"); +MODULE_IMPORT_NS("LINEDISP"); -- cgit v1.3.1