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/input/touchscreen/raspberrypi-ts.c | 226 +++++++++++++++++++++++++++++ 1 file changed, 226 insertions(+) create mode 100644 drivers/input/touchscreen/raspberrypi-ts.c (limited to 'drivers/input/touchscreen/raspberrypi-ts.c') diff --git a/drivers/input/touchscreen/raspberrypi-ts.c b/drivers/input/touchscreen/raspberrypi-ts.c new file mode 100644 index 000000000..841d39a44 --- /dev/null +++ b/drivers/input/touchscreen/raspberrypi-ts.c @@ -0,0 +1,226 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Raspberry Pi firmware based touchscreen driver + * + * Copyright (C) 2015, 2017 Raspberry Pi + * Copyright (C) 2018 Nicolas Saenz Julienne + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#define RPI_TS_DEFAULT_WIDTH 800 +#define RPI_TS_DEFAULT_HEIGHT 480 + +#define RPI_TS_MAX_SUPPORTED_POINTS 10 + +#define RPI_TS_FTS_TOUCH_DOWN 0 +#define RPI_TS_FTS_TOUCH_CONTACT 2 + +#define RPI_TS_POLL_INTERVAL 17 /* 60fps */ + +#define RPI_TS_NPOINTS_REG_INVALIDATE 99 + +struct rpi_ts { + struct platform_device *pdev; + struct input_dev *input; + struct touchscreen_properties prop; + + void __iomem *fw_regs_va; + dma_addr_t fw_regs_phys; + + int known_ids; +}; + +struct rpi_ts_regs { + u8 device_mode; + u8 gesture_id; + u8 num_points; + struct rpi_ts_touch { + u8 xh; + u8 xl; + u8 yh; + u8 yl; + u8 pressure; /* Not supported */ + u8 area; /* Not supported */ + } point[RPI_TS_MAX_SUPPORTED_POINTS]; +}; + +static void rpi_ts_poll(struct input_dev *input) +{ + struct rpi_ts *ts = input_get_drvdata(input); + struct rpi_ts_regs regs; + int modified_ids = 0; + long released_ids; + int event_type; + int touchid; + int x, y; + int i; + + memcpy_fromio(®s, ts->fw_regs_va, sizeof(regs)); + /* + * We poll the memory based register copy of the touchscreen chip using + * the number of points register to know whether the copy has been + * updated (we write 99 to the memory copy, the GPU will write between + * 0 - 10 points) + */ + iowrite8(RPI_TS_NPOINTS_REG_INVALIDATE, + ts->fw_regs_va + offsetof(struct rpi_ts_regs, num_points)); + + if (regs.num_points == RPI_TS_NPOINTS_REG_INVALIDATE || + (regs.num_points == 0 && ts->known_ids == 0)) + return; + + for (i = 0; i < regs.num_points; i++) { + x = (((int)regs.point[i].xh & 0xf) << 8) + regs.point[i].xl; + y = (((int)regs.point[i].yh & 0xf) << 8) + regs.point[i].yl; + touchid = (regs.point[i].yh >> 4) & 0xf; + event_type = (regs.point[i].xh >> 6) & 0x03; + + modified_ids |= BIT(touchid); + + if (event_type == RPI_TS_FTS_TOUCH_DOWN || + event_type == RPI_TS_FTS_TOUCH_CONTACT) { + input_mt_slot(input, touchid); + input_mt_report_slot_state(input, MT_TOOL_FINGER, 1); + touchscreen_report_pos(input, &ts->prop, x, y, true); + } + } + + released_ids = ts->known_ids & ~modified_ids; + for_each_set_bit(i, &released_ids, RPI_TS_MAX_SUPPORTED_POINTS) { + input_mt_slot(input, i); + input_mt_report_slot_inactive(input); + modified_ids &= ~(BIT(i)); + } + ts->known_ids = modified_ids; + + input_mt_sync_frame(input); + input_sync(input); +} + +static void rpi_ts_dma_cleanup(void *data) +{ + struct rpi_ts *ts = data; + struct device *dev = &ts->pdev->dev; + + dma_free_coherent(dev, PAGE_SIZE, ts->fw_regs_va, ts->fw_regs_phys); +} + +static int rpi_ts_probe(struct platform_device *pdev) +{ + struct device *dev = &pdev->dev; + struct device_node *np = dev->of_node; + struct input_dev *input; + struct rpi_firmware *fw; + struct rpi_ts *ts; + u32 touchbuf; + int error; + + struct device_node *fw_node __free(device_node) = of_get_parent(np); + if (!fw_node) { + dev_err(dev, "Missing firmware node\n"); + return -ENOENT; + } + + fw = devm_rpi_firmware_get(&pdev->dev, fw_node); + if (!fw) + return -EPROBE_DEFER; + + ts = devm_kzalloc(dev, sizeof(*ts), GFP_KERNEL); + if (!ts) + return -ENOMEM; + ts->pdev = pdev; + + ts->fw_regs_va = dma_alloc_coherent(dev, PAGE_SIZE, &ts->fw_regs_phys, + GFP_KERNEL); + if (!ts->fw_regs_va) { + dev_err(dev, "failed to dma_alloc_coherent\n"); + return -ENOMEM; + } + + error = devm_add_action_or_reset(dev, rpi_ts_dma_cleanup, ts); + if (error) { + dev_err(dev, "failed to devm_add_action_or_reset, %d\n", error); + return error; + } + + touchbuf = (u32)ts->fw_regs_phys; + error = rpi_firmware_property(fw, RPI_FIRMWARE_FRAMEBUFFER_SET_TOUCHBUF, + &touchbuf, sizeof(touchbuf)); + if (error || touchbuf != 0) { + dev_warn(dev, "Failed to set touchbuf, %d\n", error); + return error; + } + + input = devm_input_allocate_device(dev); + if (!input) { + dev_err(dev, "Failed to allocate input device\n"); + return -ENOMEM; + } + + ts->input = input; + input_set_drvdata(input, ts); + + input->name = "raspberrypi-ts"; + input->id.bustype = BUS_HOST; + + input_set_abs_params(input, ABS_MT_POSITION_X, 0, + RPI_TS_DEFAULT_WIDTH, 0, 0); + input_set_abs_params(input, ABS_MT_POSITION_Y, 0, + RPI_TS_DEFAULT_HEIGHT, 0, 0); + touchscreen_parse_properties(input, true, &ts->prop); + + error = input_mt_init_slots(input, RPI_TS_MAX_SUPPORTED_POINTS, + INPUT_MT_DIRECT); + if (error) { + dev_err(dev, "could not init mt slots, %d\n", error); + return error; + } + + error = input_setup_polling(input, rpi_ts_poll); + if (error) { + dev_err(dev, "could not set up polling mode, %d\n", error); + return error; + } + + input_set_poll_interval(input, RPI_TS_POLL_INTERVAL); + + error = input_register_device(input); + if (error) { + dev_err(dev, "could not register input device, %d\n", error); + return error; + } + + return 0; +} + +static const struct of_device_id rpi_ts_match[] = { + { .compatible = "raspberrypi,firmware-ts", }, + {}, +}; +MODULE_DEVICE_TABLE(of, rpi_ts_match); + +static struct platform_driver rpi_ts_driver = { + .driver = { + .name = "raspberrypi-ts", + .of_match_table = rpi_ts_match, + }, + .probe = rpi_ts_probe, +}; +module_platform_driver(rpi_ts_driver); + +MODULE_AUTHOR("Gordon Hollingworth"); +MODULE_AUTHOR("Nicolas Saenz Julienne "); +MODULE_DESCRIPTION("Raspberry Pi firmware based touchscreen driver"); +MODULE_LICENSE("GPL v2"); -- cgit v1.3.1