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, 202 insertions, 0 deletions

diff --git a/drivers/phy/mediatek/phy-mtk-dp.c b/drivers/phy/mediatek/phy-mtk-dp.c
new file mode 100644
index 000000000..d7024a144
--- /dev/null
+++ b/drivers/phy/mediatek/phy-mtk-dp.c
@@ -0,0 +1,202 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * MediaTek DisplayPort PHY driver
+ *
+ * Copyright (c) 2022, BayLibre Inc.
+ * Copyright (c) 2022, MediaTek Inc.
+ */
+
+#include <linux/delay.h>
+#include <linux/io.h>
+#include <linux/mfd/syscon.h>
+#include <linux/of.h>
+#include <linux/phy/phy.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+
+#define PHY_OFFSET			0x1000
+
+#define MTK_DP_PHY_DIG_PLL_CTL_1	(PHY_OFFSET + 0x14)
+#define TPLL_SSC_EN			BIT(3)
+
+#define MTK_DP_PHY_DIG_BIT_RATE		(PHY_OFFSET + 0x3C)
+#define BIT_RATE_RBR			0
+#define BIT_RATE_HBR			1
+#define BIT_RATE_HBR2			2
+#define BIT_RATE_HBR3			3
+
+#define MTK_DP_PHY_DIG_SW_RST		(PHY_OFFSET + 0x38)
+#define DP_GLB_SW_RST_PHYD		BIT(0)
+
+#define MTK_DP_LANE0_DRIVING_PARAM_3		(PHY_OFFSET + 0x138)
+#define MTK_DP_LANE1_DRIVING_PARAM_3		(PHY_OFFSET + 0x238)
+#define MTK_DP_LANE2_DRIVING_PARAM_3		(PHY_OFFSET + 0x338)
+#define MTK_DP_LANE3_DRIVING_PARAM_3		(PHY_OFFSET + 0x438)
+#define XTP_LN_TX_LCTXC0_SW0_PRE0_DEFAULT	BIT(4)
+#define XTP_LN_TX_LCTXC0_SW0_PRE1_DEFAULT	(BIT(10) | BIT(12))
+#define XTP_LN_TX_LCTXC0_SW0_PRE2_DEFAULT	GENMASK(20, 19)
+#define XTP_LN_TX_LCTXC0_SW0_PRE3_DEFAULT	GENMASK(29, 29)
+#define DRIVING_PARAM_3_DEFAULT	(XTP_LN_TX_LCTXC0_SW0_PRE0_DEFAULT | \
+				 XTP_LN_TX_LCTXC0_SW0_PRE1_DEFAULT | \
+				 XTP_LN_TX_LCTXC0_SW0_PRE2_DEFAULT | \
+				 XTP_LN_TX_LCTXC0_SW0_PRE3_DEFAULT)
+
+#define XTP_LN_TX_LCTXC0_SW1_PRE0_DEFAULT	GENMASK(4, 3)
+#define XTP_LN_TX_LCTXC0_SW1_PRE1_DEFAULT	GENMASK(12, 9)
+#define XTP_LN_TX_LCTXC0_SW1_PRE2_DEFAULT	(BIT(18) | BIT(21))
+#define XTP_LN_TX_LCTXC0_SW2_PRE0_DEFAULT	GENMASK(29, 29)
+#define DRIVING_PARAM_4_DEFAULT	(XTP_LN_TX_LCTXC0_SW1_PRE0_DEFAULT | \
+				 XTP_LN_TX_LCTXC0_SW1_PRE1_DEFAULT | \
+				 XTP_LN_TX_LCTXC0_SW1_PRE2_DEFAULT | \
+				 XTP_LN_TX_LCTXC0_SW2_PRE0_DEFAULT)
+
+#define XTP_LN_TX_LCTXC0_SW2_PRE1_DEFAULT	(BIT(3) | BIT(5))
+#define XTP_LN_TX_LCTXC0_SW3_PRE0_DEFAULT	GENMASK(13, 12)
+#define DRIVING_PARAM_5_DEFAULT	(XTP_LN_TX_LCTXC0_SW2_PRE1_DEFAULT | \
+				 XTP_LN_TX_LCTXC0_SW3_PRE0_DEFAULT)
+
+#define XTP_LN_TX_LCTXCP1_SW0_PRE0_DEFAULT	0
+#define XTP_LN_TX_LCTXCP1_SW0_PRE1_DEFAULT	GENMASK(10, 10)
+#define XTP_LN_TX_LCTXCP1_SW0_PRE2_DEFAULT	GENMASK(19, 19)
+#define XTP_LN_TX_LCTXCP1_SW0_PRE3_DEFAULT	GENMASK(28, 28)
+#define DRIVING_PARAM_6_DEFAULT	(XTP_LN_TX_LCTXCP1_SW0_PRE0_DEFAULT | \
+				 XTP_LN_TX_LCTXCP1_SW0_PRE1_DEFAULT | \
+				 XTP_LN_TX_LCTXCP1_SW0_PRE2_DEFAULT | \
+				 XTP_LN_TX_LCTXCP1_SW0_PRE3_DEFAULT)
+
+#define XTP_LN_TX_LCTXCP1_SW1_PRE0_DEFAULT	0
+#define XTP_LN_TX_LCTXCP1_SW1_PRE1_DEFAULT	GENMASK(10, 9)
+#define XTP_LN_TX_LCTXCP1_SW1_PRE2_DEFAULT	GENMASK(19, 18)
+#define XTP_LN_TX_LCTXCP1_SW2_PRE0_DEFAULT	0
+#define DRIVING_PARAM_7_DEFAULT	(XTP_LN_TX_LCTXCP1_SW1_PRE0_DEFAULT | \
+				 XTP_LN_TX_LCTXCP1_SW1_PRE1_DEFAULT | \
+				 XTP_LN_TX_LCTXCP1_SW1_PRE2_DEFAULT | \
+				 XTP_LN_TX_LCTXCP1_SW2_PRE0_DEFAULT)
+
+#define XTP_LN_TX_LCTXCP1_SW2_PRE1_DEFAULT	GENMASK(3, 3)
+#define XTP_LN_TX_LCTXCP1_SW3_PRE0_DEFAULT	0
+#define DRIVING_PARAM_8_DEFAULT	(XTP_LN_TX_LCTXCP1_SW2_PRE1_DEFAULT | \
+				 XTP_LN_TX_LCTXCP1_SW3_PRE0_DEFAULT)
+
+struct mtk_dp_phy {
+	struct regmap *regs;
+};
+
+static int mtk_dp_phy_init(struct phy *phy)
+{
+	struct mtk_dp_phy *dp_phy = phy_get_drvdata(phy);
+	static const u32 driving_params[] = {
+		DRIVING_PARAM_3_DEFAULT,
+		DRIVING_PARAM_4_DEFAULT,
+		DRIVING_PARAM_5_DEFAULT,
+		DRIVING_PARAM_6_DEFAULT,
+		DRIVING_PARAM_7_DEFAULT,
+		DRIVING_PARAM_8_DEFAULT
+	};
+
+	regmap_bulk_write(dp_phy->regs, MTK_DP_LANE0_DRIVING_PARAM_3,
+			  driving_params, ARRAY_SIZE(driving_params));
+	regmap_bulk_write(dp_phy->regs, MTK_DP_LANE1_DRIVING_PARAM_3,
+			  driving_params, ARRAY_SIZE(driving_params));
+	regmap_bulk_write(dp_phy->regs, MTK_DP_LANE2_DRIVING_PARAM_3,
+			  driving_params, ARRAY_SIZE(driving_params));
+	regmap_bulk_write(dp_phy->regs, MTK_DP_LANE3_DRIVING_PARAM_3,
+			  driving_params, ARRAY_SIZE(driving_params));
+
+	return 0;
+}
+
+static int mtk_dp_phy_configure(struct phy *phy, union phy_configure_opts *opts)
+{
+	struct mtk_dp_phy *dp_phy = phy_get_drvdata(phy);
+	u32 val;
+
+	if (opts->dp.set_rate) {
+		switch (opts->dp.link_rate) {
+		default:
+			dev_err(&phy->dev,
+				"Implementation error, unknown linkrate %x\n",
+				opts->dp.link_rate);
+			return -EINVAL;
+		case 1620:
+			val = BIT_RATE_RBR;
+			break;
+		case 2700:
+			val = BIT_RATE_HBR;
+			break;
+		case 5400:
+			val = BIT_RATE_HBR2;
+			break;
+		case 8100:
+			val = BIT_RATE_HBR3;
+			break;
+		}
+		regmap_write(dp_phy->regs, MTK_DP_PHY_DIG_BIT_RATE, val);
+	}
+
+	regmap_update_bits(dp_phy->regs, MTK_DP_PHY_DIG_PLL_CTL_1,
+			   TPLL_SSC_EN, opts->dp.ssc ? TPLL_SSC_EN : 0);
+
+	return 0;
+}
+
+static int mtk_dp_phy_reset(struct phy *phy)
+{
+	struct mtk_dp_phy *dp_phy = phy_get_drvdata(phy);
+
+	regmap_update_bits(dp_phy->regs, MTK_DP_PHY_DIG_SW_RST,
+			   DP_GLB_SW_RST_PHYD, 0);
+	usleep_range(50, 200);
+	regmap_update_bits(dp_phy->regs, MTK_DP_PHY_DIG_SW_RST,
+			   DP_GLB_SW_RST_PHYD, 1);
+
+	return 0;
+}
+
+static const struct phy_ops mtk_dp_phy_dev_ops = {
+	.init = mtk_dp_phy_init,
+	.configure = mtk_dp_phy_configure,
+	.reset = mtk_dp_phy_reset,
+	.owner = THIS_MODULE,
+};
+
+static int mtk_dp_phy_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct mtk_dp_phy *dp_phy;
+	struct phy *phy;
+	struct regmap *regs;
+
+	regs = *(struct regmap **)dev->platform_data;
+	if (!regs)
+		return dev_err_probe(dev, -EINVAL,
+				     "No data passed, requires struct regmap**\n");
+
+	dp_phy = devm_kzalloc(dev, sizeof(*dp_phy), GFP_KERNEL);
+	if (!dp_phy)
+		return -ENOMEM;
+
+	dp_phy->regs = regs;
+	phy = devm_phy_create(dev, NULL, &mtk_dp_phy_dev_ops);
+	if (IS_ERR(phy))
+		return dev_err_probe(dev, PTR_ERR(phy),
+				     "Failed to create DP PHY\n");
+
+	phy_set_drvdata(phy, dp_phy);
+	if (!dev->of_node)
+		phy_create_lookup(phy, "dp", dev_name(dev));
+
+	return 0;
+}
+
+static struct platform_driver mtk_dp_phy_driver = {
+	.probe = mtk_dp_phy_probe,
+	.driver = {
+		.name = "mediatek-dp-phy",
+	},
+};
+module_platform_driver(mtk_dp_phy_driver);
+
+MODULE_AUTHOR("Markus Schneider-Pargmann <msp@baylibre.com>");
+MODULE_DESCRIPTION("MediaTek DP PHY Driver");
+MODULE_LICENSE("GPL");