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, 324 insertions, 0 deletions

diff --git a/drivers/soc/mediatek/mtk-devapc.c b/drivers/soc/mediatek/mtk-devapc.c
new file mode 100644
index 000000000..f54c96613
--- /dev/null
+++ b/drivers/soc/mediatek/mtk-devapc.c
@@ -0,0 +1,324 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2020 MediaTek Inc.
+ */
+
+#include <linux/clk.h>
+#include <linux/interrupt.h>
+#include <linux/iopoll.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/of.h>
+#include <linux/of_irq.h>
+#include <linux/of_address.h>
+
+#define VIO_MOD_TO_REG_IND(m)	((m) / 32)
+#define VIO_MOD_TO_REG_OFF(m)	((m) % 32)
+
+struct mtk_devapc_vio_dbgs {
+	union {
+		u32 vio_dbg0;
+		struct {
+			u32 mstid:16;
+			u32 dmnid:6;
+			u32 vio_w:1;
+			u32 vio_r:1;
+			u32 addr_h:4;
+			u32 resv:4;
+		} dbg0_bits;
+	};
+
+	u32 vio_dbg1;
+};
+
+struct mtk_devapc_regs_ofs {
+	/* reg offset */
+	u32 vio_mask_offset;
+	u32 vio_sta_offset;
+	u32 vio_dbg0_offset;
+	u32 vio_dbg1_offset;
+	u32 apc_con_offset;
+	u32 vio_shift_sta_offset;
+	u32 vio_shift_sel_offset;
+	u32 vio_shift_con_offset;
+};
+
+struct mtk_devapc_data {
+	/* numbers of violation index */
+	u32 vio_idx_num;
+	const struct mtk_devapc_regs_ofs *regs_ofs;
+};
+
+struct mtk_devapc_context {
+	struct device *dev;
+	void __iomem *infra_base;
+	struct clk *infra_clk;
+	const struct mtk_devapc_data *data;
+};
+
+static void clear_vio_status(struct mtk_devapc_context *ctx)
+{
+	void __iomem *reg;
+	int i;
+
+	reg = ctx->infra_base + ctx->data->regs_ofs->vio_sta_offset;
+
+	for (i = 0; i < VIO_MOD_TO_REG_IND(ctx->data->vio_idx_num) - 1; i++)
+		writel(GENMASK(31, 0), reg + 4 * i);
+
+	writel(GENMASK(VIO_MOD_TO_REG_OFF(ctx->data->vio_idx_num) - 1, 0),
+	       reg + 4 * i);
+}
+
+static void mask_module_irq(struct mtk_devapc_context *ctx, bool mask)
+{
+	void __iomem *reg;
+	u32 val;
+	int i;
+
+	reg = ctx->infra_base + ctx->data->regs_ofs->vio_mask_offset;
+
+	if (mask)
+		val = GENMASK(31, 0);
+	else
+		val = 0;
+
+	for (i = 0; i < VIO_MOD_TO_REG_IND(ctx->data->vio_idx_num) - 1; i++)
+		writel(val, reg + 4 * i);
+
+	val = readl(reg + 4 * i);
+	if (mask)
+		val |= GENMASK(VIO_MOD_TO_REG_OFF(ctx->data->vio_idx_num) - 1,
+			       0);
+	else
+		val &= ~GENMASK(VIO_MOD_TO_REG_OFF(ctx->data->vio_idx_num) - 1,
+				0);
+
+	writel(val, reg + 4 * i);
+}
+
+#define PHY_DEVAPC_TIMEOUT	0x10000
+
+/*
+ * devapc_sync_vio_dbg - do "shift" mechansim" to get full violation information.
+ *                       shift mechanism is depends on devapc hardware design.
+ *                       Mediatek devapc set multiple slaves as a group.
+ *                       When violation is triggered, violation info is kept
+ *                       inside devapc hardware.
+ *                       Driver should do shift mechansim to sync full violation
+ *                       info to VIO_DBGs registers.
+ *
+ */
+static int devapc_sync_vio_dbg(struct mtk_devapc_context *ctx)
+{
+	void __iomem *pd_vio_shift_sta_reg;
+	void __iomem *pd_vio_shift_sel_reg;
+	void __iomem *pd_vio_shift_con_reg;
+	int min_shift_group;
+	int ret;
+	u32 val;
+
+	pd_vio_shift_sta_reg = ctx->infra_base +
+			       ctx->data->regs_ofs->vio_shift_sta_offset;
+	pd_vio_shift_sel_reg = ctx->infra_base +
+			       ctx->data->regs_ofs->vio_shift_sel_offset;
+	pd_vio_shift_con_reg = ctx->infra_base +
+			       ctx->data->regs_ofs->vio_shift_con_offset;
+
+	/* Find the minimum shift group which has violation */
+	val = readl(pd_vio_shift_sta_reg);
+	if (!val)
+		return false;
+
+	min_shift_group = __ffs(val);
+
+	/* Assign the group to sync */
+	writel(0x1 << min_shift_group, pd_vio_shift_sel_reg);
+
+	/* Start syncing */
+	writel(0x1, pd_vio_shift_con_reg);
+
+	ret = readl_poll_timeout(pd_vio_shift_con_reg, val, val == 0x3, 0,
+				 PHY_DEVAPC_TIMEOUT);
+	if (ret) {
+		dev_err(ctx->dev, "%s: Shift violation info failed\n", __func__);
+		return false;
+	}
+
+	/* Stop syncing */
+	writel(0x0, pd_vio_shift_con_reg);
+
+	/* Write clear */
+	writel(0x1 << min_shift_group, pd_vio_shift_sta_reg);
+
+	return true;
+}
+
+/*
+ * devapc_extract_vio_dbg - extract full violation information after doing
+ *                          shift mechanism.
+ */
+static void devapc_extract_vio_dbg(struct mtk_devapc_context *ctx)
+{
+	struct mtk_devapc_vio_dbgs vio_dbgs;
+	void __iomem *vio_dbg0_reg;
+	void __iomem *vio_dbg1_reg;
+
+	vio_dbg0_reg = ctx->infra_base + ctx->data->regs_ofs->vio_dbg0_offset;
+	vio_dbg1_reg = ctx->infra_base + ctx->data->regs_ofs->vio_dbg1_offset;
+
+	vio_dbgs.vio_dbg0 = readl(vio_dbg0_reg);
+	vio_dbgs.vio_dbg1 = readl(vio_dbg1_reg);
+
+	/* Print violation information */
+	if (vio_dbgs.dbg0_bits.vio_w)
+		dev_info(ctx->dev, "Write Violation\n");
+	else if (vio_dbgs.dbg0_bits.vio_r)
+		dev_info(ctx->dev, "Read Violation\n");
+
+	dev_info(ctx->dev, "Bus ID:0x%x, Dom ID:0x%x, Vio Addr:0x%x\n",
+		 vio_dbgs.dbg0_bits.mstid, vio_dbgs.dbg0_bits.dmnid,
+		 vio_dbgs.vio_dbg1);
+}
+
+/*
+ * devapc_violation_irq - the devapc Interrupt Service Routine (ISR) will dump
+ *                        violation information including which master violates
+ *                        access slave.
+ */
+static irqreturn_t devapc_violation_irq(int irq_number, void *data)
+{
+	struct mtk_devapc_context *ctx = data;
+
+	while (devapc_sync_vio_dbg(ctx))
+		devapc_extract_vio_dbg(ctx);
+
+	clear_vio_status(ctx);
+
+	return IRQ_HANDLED;
+}
+
+/*
+ * start_devapc - unmask slave's irq to start receiving devapc violation.
+ */
+static void start_devapc(struct mtk_devapc_context *ctx)
+{
+	writel(BIT(31), ctx->infra_base + ctx->data->regs_ofs->apc_con_offset);
+
+	mask_module_irq(ctx, false);
+}
+
+/*
+ * stop_devapc - mask slave's irq to stop service.
+ */
+static void stop_devapc(struct mtk_devapc_context *ctx)
+{
+	mask_module_irq(ctx, true);
+
+	writel(BIT(2), ctx->infra_base + ctx->data->regs_ofs->apc_con_offset);
+}
+
+static const struct mtk_devapc_regs_ofs devapc_regs_ofs_mt6779 = {
+	.vio_mask_offset = 0x0,
+	.vio_sta_offset = 0x400,
+	.vio_dbg0_offset = 0x900,
+	.vio_dbg1_offset = 0x904,
+	.apc_con_offset = 0xF00,
+	.vio_shift_sta_offset = 0xF10,
+	.vio_shift_sel_offset = 0xF14,
+	.vio_shift_con_offset = 0xF20,
+};
+
+static const struct mtk_devapc_data devapc_mt6779 = {
+	.vio_idx_num = 511,
+	.regs_ofs = &devapc_regs_ofs_mt6779,
+};
+
+static const struct mtk_devapc_data devapc_mt8186 = {
+	.vio_idx_num = 519,
+	.regs_ofs = &devapc_regs_ofs_mt6779,
+};
+
+static const struct of_device_id mtk_devapc_dt_match[] = {
+	{
+		.compatible = "mediatek,mt6779-devapc",
+		.data = &devapc_mt6779,
+	}, {
+		.compatible = "mediatek,mt8186-devapc",
+		.data = &devapc_mt8186,
+	}, {
+	},
+};
+MODULE_DEVICE_TABLE(of, mtk_devapc_dt_match);
+
+static int mtk_devapc_probe(struct platform_device *pdev)
+{
+	struct device_node *node = pdev->dev.of_node;
+	struct mtk_devapc_context *ctx;
+	u32 devapc_irq;
+	int ret;
+
+	if (IS_ERR(node))
+		return -ENODEV;
+
+	ctx = devm_kzalloc(&pdev->dev, sizeof(*ctx), GFP_KERNEL);
+	if (!ctx)
+		return -ENOMEM;
+
+	ctx->data = of_device_get_match_data(&pdev->dev);
+	ctx->dev = &pdev->dev;
+
+	ctx->infra_base = of_iomap(node, 0);
+	if (!ctx->infra_base)
+		return -EINVAL;
+
+	devapc_irq = irq_of_parse_and_map(node, 0);
+	if (!devapc_irq) {
+		ret = -EINVAL;
+		goto err;
+	}
+
+	ctx->infra_clk = devm_clk_get_enabled(&pdev->dev, "devapc-infra-clock");
+	if (IS_ERR(ctx->infra_clk)) {
+		ret = -EINVAL;
+		goto err;
+	}
+
+	ret = devm_request_irq(&pdev->dev, devapc_irq, devapc_violation_irq,
+			       IRQF_TRIGGER_NONE, "devapc", ctx);
+	if (ret)
+		goto err;
+
+	platform_set_drvdata(pdev, ctx);
+
+	start_devapc(ctx);
+
+	return 0;
+
+err:
+	iounmap(ctx->infra_base);
+	return ret;
+}
+
+static void mtk_devapc_remove(struct platform_device *pdev)
+{
+	struct mtk_devapc_context *ctx = platform_get_drvdata(pdev);
+
+	stop_devapc(ctx);
+	iounmap(ctx->infra_base);
+}
+
+static struct platform_driver mtk_devapc_driver = {
+	.probe = mtk_devapc_probe,
+	.remove = mtk_devapc_remove,
+	.driver = {
+		.name = "mtk-devapc",
+		.of_match_table = mtk_devapc_dt_match,
+	},
+};
+
+module_platform_driver(mtk_devapc_driver);
+
+MODULE_DESCRIPTION("Mediatek Device APC Driver");
+MODULE_AUTHOR("Neal Liu <neal.liu@mediatek.com>");
+MODULE_LICENSE("GPL");