x86/kprobes: Fix crash when probing CS CALL instructionsgrafted

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) <mhiramat@kernel.org>
Signed-off-by: Jinke Han <jinkehan@didiglobal.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000

1 files changed, 370 insertions, 0 deletions

diff --git a/drivers/regulator/mp886x.c b/drivers/regulator/mp886x.c
new file mode 100644
index 000000000..e0b62bc02
--- /dev/null
+++ b/drivers/regulator/mp886x.c
@@ -0,0 +1,370 @@
+// SPDX-License-Identifier: GPL-2.0
+//
+// MP8867/MP8869 regulator driver
+//
+// Copyright (C) 2020 Synaptics Incorporated
+//
+// Author: Jisheng Zhang <jszhang@kernel.org>
+
+#include <linux/gpio/consumer.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/regmap.h>
+#include <linux/regulator/driver.h>
+#include <linux/regulator/of_regulator.h>
+
+#define MP886X_VSEL		0x00
+#define  MP886X_V_BOOT		(1 << 7)
+#define MP886X_SYSCNTLREG1	0x01
+#define  MP886X_MODE		(1 << 0)
+#define  MP886X_SLEW_SHIFT	3
+#define  MP886X_SLEW_MASK	(0x7 << MP886X_SLEW_SHIFT)
+#define  MP886X_GO		(1 << 6)
+#define  MP886X_EN		(1 << 7)
+#define MP8869_SYSCNTLREG2	0x02
+
+struct mp886x_cfg_info {
+	const struct regulator_ops *rops;
+	const unsigned int slew_rates[8];
+	const int switch_freq[4];
+	const u8 fs_reg;
+	const u8 fs_shift;
+};
+
+struct mp886x_device_info {
+	struct device *dev;
+	struct regulator_desc desc;
+	struct regulator_init_data *regulator;
+	struct gpio_desc *en_gpio;
+	const struct mp886x_cfg_info *ci;
+	u32 r[2];
+	unsigned int sel;
+};
+
+static void mp886x_set_switch_freq(struct mp886x_device_info *di,
+				   struct regmap *regmap,
+				   u32 freq)
+{
+	const struct mp886x_cfg_info *ci = di->ci;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(ci->switch_freq); i++) {
+		if (freq == ci->switch_freq[i]) {
+			regmap_update_bits(regmap, ci->fs_reg,
+				  0x3 << ci->fs_shift, i << ci->fs_shift);
+			return;
+		}
+	}
+
+	dev_err(di->dev, "invalid frequency %d\n", freq);
+}
+
+static int mp886x_set_mode(struct regulator_dev *rdev, unsigned int mode)
+{
+	switch (mode) {
+	case REGULATOR_MODE_FAST:
+		regmap_update_bits(rdev->regmap, MP886X_SYSCNTLREG1,
+				   MP886X_MODE, MP886X_MODE);
+		break;
+	case REGULATOR_MODE_NORMAL:
+		regmap_update_bits(rdev->regmap, MP886X_SYSCNTLREG1,
+				   MP886X_MODE, 0);
+		break;
+	default:
+		return -EINVAL;
+	}
+	return 0;
+}
+
+static unsigned int mp886x_get_mode(struct regulator_dev *rdev)
+{
+	u32 val;
+	int ret;
+
+	ret = regmap_read(rdev->regmap, MP886X_SYSCNTLREG1, &val);
+	if (ret < 0)
+		return ret;
+	if (val & MP886X_MODE)
+		return REGULATOR_MODE_FAST;
+	else
+		return REGULATOR_MODE_NORMAL;
+}
+
+static int mp8869_set_voltage_sel(struct regulator_dev *rdev, unsigned int sel)
+{
+	int ret;
+
+	ret = regmap_update_bits(rdev->regmap, MP886X_SYSCNTLREG1,
+				 MP886X_GO, MP886X_GO);
+	if (ret < 0)
+		return ret;
+
+	sel <<= ffs(rdev->desc->vsel_mask) - 1;
+	return regmap_update_bits(rdev->regmap, rdev->desc->vsel_reg,
+				  MP886X_V_BOOT | rdev->desc->vsel_mask, sel);
+}
+
+static inline unsigned int mp8869_scale(unsigned int uv, u32 r1, u32 r2)
+{
+	u32 tmp = uv * r1 / r2;
+
+	return uv + tmp;
+}
+
+static int mp8869_get_voltage_sel(struct regulator_dev *rdev)
+{
+	struct mp886x_device_info *di = rdev_get_drvdata(rdev);
+	int ret, uv;
+	unsigned int val;
+	bool fbloop;
+
+	ret = regmap_read(rdev->regmap, rdev->desc->vsel_reg, &val);
+	if (ret)
+		return ret;
+
+	fbloop = val & MP886X_V_BOOT;
+	if (fbloop) {
+		uv = rdev->desc->min_uV;
+		uv = mp8869_scale(uv, di->r[0], di->r[1]);
+		return regulator_map_voltage_linear(rdev, uv, uv);
+	}
+
+	val &= rdev->desc->vsel_mask;
+	val >>= ffs(rdev->desc->vsel_mask) - 1;
+
+	return val;
+}
+
+static const struct regulator_ops mp8869_regulator_ops = {
+	.set_voltage_sel = mp8869_set_voltage_sel,
+	.get_voltage_sel = mp8869_get_voltage_sel,
+	.set_voltage_time_sel = regulator_set_voltage_time_sel,
+	.map_voltage = regulator_map_voltage_linear,
+	.list_voltage = regulator_list_voltage_linear,
+	.enable = regulator_enable_regmap,
+	.disable = regulator_disable_regmap,
+	.is_enabled = regulator_is_enabled_regmap,
+	.set_mode = mp886x_set_mode,
+	.get_mode = mp886x_get_mode,
+	.set_ramp_delay = regulator_set_ramp_delay_regmap,
+};
+
+static const struct mp886x_cfg_info mp8869_ci = {
+	.rops = &mp8869_regulator_ops,
+	.slew_rates = {
+		40000,
+		30000,
+		20000,
+		10000,
+		5000,
+		2500,
+		1250,
+		625,
+	},
+	.switch_freq = {
+		500000,
+		750000,
+		1000000,
+		1250000,
+	},
+	.fs_reg = MP8869_SYSCNTLREG2,
+	.fs_shift = 4,
+};
+
+static int mp8867_set_voltage_sel(struct regulator_dev *rdev, unsigned int sel)
+{
+	struct mp886x_device_info *di = rdev_get_drvdata(rdev);
+	int ret, delta;
+
+	ret = mp8869_set_voltage_sel(rdev, sel);
+	if (ret < 0)
+		return ret;
+
+	delta = di->sel - sel;
+	if (abs(delta) <= 5)
+		ret = regmap_update_bits(rdev->regmap, MP886X_SYSCNTLREG1,
+					 MP886X_GO, 0);
+	di->sel = sel;
+
+	return ret;
+}
+
+static int mp8867_get_voltage_sel(struct regulator_dev *rdev)
+{
+	struct mp886x_device_info *di = rdev_get_drvdata(rdev);
+	int ret, uv;
+	unsigned int val;
+	bool fbloop;
+
+	ret = regmap_read(rdev->regmap, rdev->desc->vsel_reg, &val);
+	if (ret)
+		return ret;
+
+	fbloop = val & MP886X_V_BOOT;
+
+	val &= rdev->desc->vsel_mask;
+	val >>= ffs(rdev->desc->vsel_mask) - 1;
+
+	if (fbloop) {
+		uv = regulator_list_voltage_linear(rdev, val);
+		uv = mp8869_scale(uv, di->r[0], di->r[1]);
+		return regulator_map_voltage_linear(rdev, uv, uv);
+	}
+
+	return val;
+}
+
+static const struct regulator_ops mp8867_regulator_ops = {
+	.set_voltage_sel = mp8867_set_voltage_sel,
+	.get_voltage_sel = mp8867_get_voltage_sel,
+	.set_voltage_time_sel = regulator_set_voltage_time_sel,
+	.map_voltage = regulator_map_voltage_linear,
+	.list_voltage = regulator_list_voltage_linear,
+	.enable = regulator_enable_regmap,
+	.disable = regulator_disable_regmap,
+	.is_enabled = regulator_is_enabled_regmap,
+	.set_mode = mp886x_set_mode,
+	.get_mode = mp886x_get_mode,
+	.set_ramp_delay = regulator_set_ramp_delay_regmap,
+};
+
+static const struct mp886x_cfg_info mp8867_ci = {
+	.rops = &mp8867_regulator_ops,
+	.slew_rates = {
+		64000,
+		32000,
+		16000,
+		8000,
+		4000,
+		2000,
+		1000,
+		500,
+	},
+	.switch_freq = {
+		500000,
+		750000,
+		1000000,
+		1500000,
+	},
+	.fs_reg = MP886X_SYSCNTLREG1,
+	.fs_shift = 1,
+};
+
+static int mp886x_regulator_register(struct mp886x_device_info *di,
+				     struct regulator_config *config)
+{
+	struct regulator_desc *rdesc = &di->desc;
+	struct regulator_dev *rdev;
+
+	rdesc->name = "mp886x-reg";
+	rdesc->supply_name = "vin";
+	rdesc->ops = di->ci->rops;
+	rdesc->type = REGULATOR_VOLTAGE;
+	rdesc->n_voltages = 128;
+	rdesc->enable_reg = MP886X_SYSCNTLREG1;
+	rdesc->enable_mask = MP886X_EN;
+	rdesc->min_uV = 600000;
+	rdesc->uV_step = 10000;
+	rdesc->vsel_reg = MP886X_VSEL;
+	rdesc->vsel_mask = 0x3f;
+	rdesc->ramp_reg = MP886X_SYSCNTLREG1;
+	rdesc->ramp_mask = MP886X_SLEW_MASK;
+	rdesc->ramp_delay_table = di->ci->slew_rates;
+	rdesc->n_ramp_values = ARRAY_SIZE(di->ci->slew_rates);
+	rdesc->owner = THIS_MODULE;
+
+	rdev = devm_regulator_register(di->dev, &di->desc, config);
+	if (IS_ERR(rdev))
+		return PTR_ERR(rdev);
+	di->sel = rdesc->ops->get_voltage_sel(rdev);
+	return 0;
+}
+
+static const struct regmap_config mp886x_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+};
+
+static int mp886x_i2c_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	struct device_node *np = dev->of_node;
+	struct mp886x_device_info *di;
+	struct regulator_config config = { };
+	struct regmap *regmap;
+	u32 freq;
+	int ret;
+
+	di = devm_kzalloc(dev, sizeof(struct mp886x_device_info), GFP_KERNEL);
+	if (!di)
+		return -ENOMEM;
+
+	di->regulator = of_get_regulator_init_data(dev, np, &di->desc);
+	if (!di->regulator) {
+		dev_err(dev, "Platform data not found!\n");
+		return -EINVAL;
+	}
+
+	ret = of_property_read_u32_array(np, "mps,fb-voltage-divider",
+					 di->r, 2);
+	if (ret)
+		return ret;
+
+	di->en_gpio = devm_gpiod_get(dev, "enable", GPIOD_OUT_HIGH);
+	if (IS_ERR(di->en_gpio))
+		return PTR_ERR(di->en_gpio);
+
+	di->ci = i2c_get_match_data(client);
+	di->dev = dev;
+
+	regmap = devm_regmap_init_i2c(client, &mp886x_regmap_config);
+	if (IS_ERR(regmap)) {
+		dev_err(dev, "Failed to allocate regmap!\n");
+		return PTR_ERR(regmap);
+	}
+	i2c_set_clientdata(client, di);
+
+	config.dev = di->dev;
+	config.init_data = di->regulator;
+	config.regmap = regmap;
+	config.driver_data = di;
+	config.of_node = np;
+
+	if (!of_property_read_u32(np, "mps,switch-frequency-hz", &freq))
+		mp886x_set_switch_freq(di, regmap, freq);
+
+	ret = mp886x_regulator_register(di, &config);
+	if (ret < 0)
+		dev_err(dev, "Failed to register regulator!\n");
+	return ret;
+}
+
+static const struct of_device_id mp886x_dt_ids[] = {
+	{ .compatible = "mps,mp8867", .data = &mp8867_ci },
+	{ .compatible = "mps,mp8869", .data = &mp8869_ci },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, mp886x_dt_ids);
+
+static const struct i2c_device_id mp886x_id[] = {
+	{ .name = "mp8867", .driver_data = (kernel_ulong_t)&mp8867_ci },
+	{ .name = "mp8869", .driver_data = (kernel_ulong_t)&mp8869_ci },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, mp886x_id);
+
+static struct i2c_driver mp886x_regulator_driver = {
+	.driver = {
+		.name = "mp886x-regulator",
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+		.of_match_table = mp886x_dt_ids,
+	},
+	.probe = mp886x_i2c_probe,
+	.id_table = mp886x_id,
+};
+module_i2c_driver(mp886x_regulator_driver);
+
+MODULE_AUTHOR("Jisheng Zhang <jszhang@kernel.org>");
+MODULE_DESCRIPTION("MP886x regulator driver");
+MODULE_LICENSE("GPL v2");