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

3 files changed, 229 insertions, 0 deletions

diff --git a/drivers/phy/axiado/Kconfig b/drivers/phy/axiado/Kconfig
new file mode 100644
index 000000000..d159e0345
--- /dev/null
+++ b/drivers/phy/axiado/Kconfig
@@ -0,0 +1,11 @@
+#
+# PHY drivers for Axiado platforms
+#
+
+config PHY_AX3000_EMMC
+	tristate "Axiado eMMC PHY driver"
+	depends on OF && (ARCH_AXIADO || COMPILE_TEST)
+	select GENERIC_PHY
+	help
+	  Enables this to support for the AX3000 EMMC PHY driver.
+	  If unsure, say N.
diff --git a/drivers/phy/axiado/Makefile b/drivers/phy/axiado/Makefile
new file mode 100644
index 000000000..1e2b1ba01
--- /dev/null
+++ b/drivers/phy/axiado/Makefile
@@ -0,0 +1 @@
+obj-$(CONFIG_PHY_AX3000_EMMC)		+= phy-axiado-emmc.o
diff --git a/drivers/phy/axiado/phy-axiado-emmc.c b/drivers/phy/axiado/phy-axiado-emmc.c
new file mode 100644
index 000000000..e0e217477
--- /dev/null
+++ b/drivers/phy/axiado/phy-axiado-emmc.c
@@ -0,0 +1,217 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Axiado eMMC PHY driver
+ *
+ * Copyright (C) 2017 Arasan Chip Systems Inc.
+ * Copyright (C) 2022-2026 Axiado Corporation (or its affiliates).
+ *
+ * Based on Arasan Driver (sdhci-pci-arasan.c)
+ * sdhci-pci-arasan.c - Driver for Arasan PCI Controller with integrated phy.
+ */
+#include <linux/bitfield.h>
+#include <linux/delay.h>
+#include <linux/io.h>
+#include <linux/iopoll.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/phy/phy.h>
+#include <linux/platform_device.h>
+
+/* Arasan eMMC 5.1 - PHY configuration registers */
+#define CAP_REG_IN_S1_MSB		0x04
+#define PHY_CTRL_1			0x38
+#define PHY_CTRL_2			0x3c
+#define PHY_CTRL_3			0x40
+#define STATUS				0x50
+
+#define DLL_ENBL	BIT(26)
+#define RTRIM_EN	BIT(21)
+#define PDB_ENBL	BIT(23)
+#define RETB_ENBL	BIT(1)
+
+#define REN_STRB	BIT(27)
+#define REN_CMD_EN	GENMASK(20, 12)
+
+/* Pull-UP Enable on CMD Line */
+#define PU_CMD_EN	GENMASK(11, 3)
+
+/* Selection value for the optimum delay from 1-32 output tap lines */
+#define OTAP_DLY	0x02
+/* DLL charge pump current trim default [1000] */
+#define DLL_TRM_ICP	0x08
+/* Select the frequency range of DLL Operation */
+#define FRQ_SEL	0x01
+
+#define OTAP_SEL_MASK		GENMASK(10, 7)
+#define DLL_TRM_MASK		GENMASK(25, 22)
+#define DLL_FRQSEL_MASK		GENMASK(27, 25)
+
+#define OTAP_SEL(x)		(FIELD_PREP(OTAP_SEL_MASK, x) | OTAPDLY_EN)
+#define DLL_TRM(x)		(FIELD_PREP(DLL_TRM_MASK, x) | DLL_ENBL)
+#define DLL_FRQSEL(x)	FIELD_PREP(DLL_FRQSEL_MASK, x)
+
+#define OTAPDLY_EN	BIT(11)
+
+#define SEL_DLY_RXCLK	BIT(18)
+#define SEL_DLY_TXCLK	BIT(19)
+
+#define CALDONE_MASK	0x40
+#define DLL_RDY_MASK	0x1
+#define MAX_CLK_BUF0	BIT(20)
+#define MAX_CLK_BUF1	BIT(21)
+#define MAX_CLK_BUF2	BIT(22)
+
+#define CLK_MULTIPLIER	0xc008e
+#define POLL_TIMEOUT_MS	3000
+#define POLL_DELAY_US	100
+
+struct axiado_emmc_phy {
+	void __iomem *reg_base;
+	struct device *dev;
+};
+
+static int axiado_emmc_phy_init(struct phy *phy)
+{
+	struct axiado_emmc_phy *ax_phy = phy_get_drvdata(phy);
+	struct device *dev = ax_phy->dev;
+	u32 val;
+	int ret;
+
+	val = readl(ax_phy->reg_base + PHY_CTRL_1);
+	writel(val | RETB_ENBL | RTRIM_EN, ax_phy->reg_base + PHY_CTRL_1);
+
+	val = readl(ax_phy->reg_base + PHY_CTRL_3);
+	writel(val | PDB_ENBL, ax_phy->reg_base + PHY_CTRL_3);
+
+	ret = readl_poll_timeout(ax_phy->reg_base + STATUS, val,
+				 val & CALDONE_MASK, POLL_DELAY_US,
+				 POLL_TIMEOUT_MS * 1000);
+	if (ret) {
+		dev_err(dev, "PHY calibration timeout\n");
+		return ret;
+	}
+
+	val = readl(ax_phy->reg_base + PHY_CTRL_1);
+	writel(val | REN_CMD_EN | PU_CMD_EN, ax_phy->reg_base + PHY_CTRL_1);
+
+	val = readl(ax_phy->reg_base + PHY_CTRL_2);
+	writel(val | REN_STRB, ax_phy->reg_base + PHY_CTRL_2);
+
+	val = readl(ax_phy->reg_base + PHY_CTRL_3);
+	writel(val | MAX_CLK_BUF0 | MAX_CLK_BUF1 | MAX_CLK_BUF2,
+	       ax_phy->reg_base + PHY_CTRL_3);
+
+	writel(CLK_MULTIPLIER, ax_phy->reg_base + CAP_REG_IN_S1_MSB);
+
+	val = readl(ax_phy->reg_base + PHY_CTRL_3);
+	writel(val | SEL_DLY_RXCLK | SEL_DLY_TXCLK,
+	       ax_phy->reg_base + PHY_CTRL_3);
+
+	return 0;
+}
+
+static int axiado_emmc_phy_power_on(struct phy *phy)
+{
+	struct axiado_emmc_phy *ax_phy = phy_get_drvdata(phy);
+	struct device *dev = ax_phy->dev;
+	u32 val;
+	int ret;
+
+	val = readl(ax_phy->reg_base + PHY_CTRL_1);
+	writel(val | RETB_ENBL, ax_phy->reg_base + PHY_CTRL_1);
+
+	val = readl(ax_phy->reg_base + PHY_CTRL_3);
+	writel(val | PDB_ENBL, ax_phy->reg_base + PHY_CTRL_3);
+
+	val = readl(ax_phy->reg_base + PHY_CTRL_2);
+	writel(val | OTAP_SEL(OTAP_DLY), ax_phy->reg_base + PHY_CTRL_2);
+
+	val = readl(ax_phy->reg_base + PHY_CTRL_1);
+	writel(val | DLL_TRM(DLL_TRM_ICP), ax_phy->reg_base + PHY_CTRL_1);
+
+	val = readl(ax_phy->reg_base + PHY_CTRL_3);
+	writel(val | DLL_FRQSEL(FRQ_SEL), ax_phy->reg_base + PHY_CTRL_3);
+
+	ret = read_poll_timeout(readl, val, val & DLL_RDY_MASK, POLL_DELAY_US,
+				POLL_TIMEOUT_MS * 1000, false,
+				ax_phy->reg_base + STATUS);
+	if (ret) {
+		dev_err(dev, "DLL ready timeout\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static int axiado_emmc_phy_power_off(struct phy *phy)
+{
+	struct axiado_emmc_phy *ax_phy = phy_get_drvdata(phy);
+	u32 val;
+
+	val = readl(ax_phy->reg_base + PHY_CTRL_1);
+	val &= ~(DLL_TRM_MASK | DLL_ENBL);
+	writel(val, ax_phy->reg_base + PHY_CTRL_1);
+
+	val = readl(ax_phy->reg_base + PHY_CTRL_3);
+	val &= ~(DLL_FRQSEL_MASK | PDB_ENBL);
+	writel(val, ax_phy->reg_base + PHY_CTRL_3);
+
+	return 0;
+}
+
+static const struct phy_ops axiado_emmc_phy_ops = {
+	.init = axiado_emmc_phy_init,
+	.power_on = axiado_emmc_phy_power_on,
+	.power_off = axiado_emmc_phy_power_off,
+	.owner = THIS_MODULE,
+};
+
+static const struct of_device_id axiado_emmc_phy_of_match[] = {
+	{ .compatible = "axiado,ax3000-emmc-phy" },
+	{ /* sentinel */ },
+};
+MODULE_DEVICE_TABLE(of, axiado_emmc_phy_of_match);
+
+static int axiado_emmc_phy_probe(struct platform_device *pdev)
+{
+	struct axiado_emmc_phy *ax_phy;
+	struct phy_provider *phy_provider;
+	struct device *dev = &pdev->dev;
+	struct phy *generic_phy;
+
+	if (!dev->of_node)
+		return -ENODEV;
+
+	ax_phy = devm_kzalloc(dev, sizeof(*ax_phy), GFP_KERNEL);
+	if (!ax_phy)
+		return -ENOMEM;
+
+	ax_phy->reg_base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(ax_phy->reg_base))
+		return PTR_ERR(ax_phy->reg_base);
+
+	ax_phy->dev = dev;
+
+	generic_phy = devm_phy_create(dev, dev->of_node, &axiado_emmc_phy_ops);
+	if (IS_ERR(generic_phy))
+		return dev_err_probe(dev, PTR_ERR(generic_phy),
+				     "failed to create PHY\n");
+
+	phy_set_drvdata(generic_phy, ax_phy);
+	phy_provider = devm_of_phy_provider_register(dev, of_phy_simple_xlate);
+
+	return PTR_ERR_OR_ZERO(phy_provider);
+}
+
+static struct platform_driver axiado_emmc_phy_driver = {
+	.probe = axiado_emmc_phy_probe,
+	.driver = {
+		.name = "axiado-emmc-phy",
+		.of_match_table = axiado_emmc_phy_of_match,
+	},
+};
+module_platform_driver(axiado_emmc_phy_driver);
+
+MODULE_DESCRIPTION("AX3000 eMMC PHY Driver");
+MODULE_AUTHOR("Axiado Corporation");
+MODULE_LICENSE("GPL");