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/nvmem/microchip-otpc.c | 289 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 289 insertions(+) create mode 100644 drivers/nvmem/microchip-otpc.c (limited to 'drivers/nvmem/microchip-otpc.c') diff --git a/drivers/nvmem/microchip-otpc.c b/drivers/nvmem/microchip-otpc.c new file mode 100644 index 000000000..df979e854 --- /dev/null +++ b/drivers/nvmem/microchip-otpc.c @@ -0,0 +1,289 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * OTP Memory controller + * + * Copyright (C) 2022 Microchip Technology Inc. and its subsidiaries + * + * Author: Claudiu Beznea + */ + +#include +#include +#include +#include +#include +#include + +#define MCHP_OTPC_CR (0x0) +#define MCHP_OTPC_CR_READ BIT(6) +#define MCHP_OTPC_MR (0x4) +#define MCHP_OTPC_MR_ADDR GENMASK(31, 16) +#define MCHP_OTPC_AR (0x8) +#define MCHP_OTPC_SR (0xc) +#define MCHP_OTPC_SR_READ BIT(6) +#define MCHP_OTPC_HR (0x20) +#define MCHP_OTPC_HR_SIZE GENMASK(15, 8) +#define MCHP_OTPC_DR (0x24) + +#define MCHP_OTPC_NAME "mchp-otpc" +#define MCHP_OTPC_SIZE (11 * 1024) + +/** + * struct mchp_otpc - OTPC private data structure + * @base: base address + * @dev: struct device pointer + * @packets: list of packets in OTP memory + * @npackets: number of packets in OTP memory + */ +struct mchp_otpc { + void __iomem *base; + struct device *dev; + struct list_head packets; + u32 npackets; +}; + +/** + * struct mchp_otpc_packet - OTPC packet data structure + * @list: list head + * @id: packet ID + * @offset: packet offset (in words) in OTP memory + */ +struct mchp_otpc_packet { + struct list_head list; + u32 id; + u32 offset; +}; + +static struct mchp_otpc_packet *mchp_otpc_id_to_packet(struct mchp_otpc *otpc, + u32 id) +{ + struct mchp_otpc_packet *packet; + + if (id >= otpc->npackets) + return NULL; + + list_for_each_entry(packet, &otpc->packets, list) { + if (packet->id == id) + return packet; + } + + return NULL; +} + +static int mchp_otpc_prepare_read(struct mchp_otpc *otpc, + unsigned int offset) +{ + u32 tmp; + + /* Set address. */ + tmp = readl_relaxed(otpc->base + MCHP_OTPC_MR); + tmp &= ~MCHP_OTPC_MR_ADDR; + tmp |= FIELD_PREP(MCHP_OTPC_MR_ADDR, offset); + writel_relaxed(tmp, otpc->base + MCHP_OTPC_MR); + + /* Set read. */ + tmp = readl_relaxed(otpc->base + MCHP_OTPC_CR); + tmp |= MCHP_OTPC_CR_READ; + writel_relaxed(tmp, otpc->base + MCHP_OTPC_CR); + + /* Wait for packet to be transferred into temporary buffers. */ + return read_poll_timeout(readl_relaxed, tmp, !(tmp & MCHP_OTPC_SR_READ), + 10000, 2000, false, otpc->base + MCHP_OTPC_SR); +} + +/* + * OTPC memory is organized into packets. Each packets contains a header and + * a payload. Header is 4 bytes long and contains the size of the payload. + * Payload size varies. The memory footprint is something as follows: + * + * Memory offset Memory footprint Packet ID + * ------------- ---------------- --------- + * + * 0x0 +------------+ <-- packet 0 + * | header 0 | + * 0x4 +------------+ + * | payload 0 | + * . . + * . ... . + * . . + * offset1 +------------+ <-- packet 1 + * | header 1 | + * offset1 + 0x4 +------------+ + * | payload 1 | + * . . + * . ... . + * . . + * offset2 +------------+ <-- packet 2 + * . . + * . ... . + * . . + * offsetN +------------+ <-- packet N + * | header N | + * offsetN + 0x4 +------------+ + * | payload N | + * . . + * . ... . + * . . + * +------------+ + * + * where offset1, offset2, offsetN depends on the size of payload 0, payload 1, + * payload N-1. + * + * The access to memory is done on a per packet basis: the control registers + * need to be updated with an offset address (within a packet range) and the + * data registers will be update by controller with information contained by + * that packet. E.g. if control registers are updated with any address within + * the range [offset1, offset2) the data registers are updated by controller + * with packet 1. Header data is accessible though MCHP_OTPC_HR register. + * Payload data is accessible though MCHP_OTPC_DR and MCHP_OTPC_AR registers. + * There is no direct mapping b/w the offset requested by software and the + * offset returned by hardware. + * + * For this, the read function will return the first requested bytes in the + * packet. The user will have to be aware of the memory footprint before doing + * the read request. + */ +static int mchp_otpc_read(void *priv, unsigned int off, void *val, + size_t bytes) +{ + struct mchp_otpc *otpc = priv; + struct mchp_otpc_packet *packet; + u32 *buf = val; + u32 offset; + size_t len = 0; + int ret, payload_size; + + /* + * We reach this point with off being multiple of stride = 4 to + * be able to cross the subsystem. Inside the driver we use continuous + * unsigned integer numbers for packet id, thus divide off by 4 + * before passing it to mchp_otpc_id_to_packet(). + */ + packet = mchp_otpc_id_to_packet(otpc, off / 4); + if (!packet) + return -EINVAL; + offset = packet->offset; + + while (len < bytes) { + ret = mchp_otpc_prepare_read(otpc, offset); + if (ret) + return ret; + + /* Read and save header content. */ + *buf++ = readl_relaxed(otpc->base + MCHP_OTPC_HR); + len += sizeof(*buf); + offset++; + if (len >= bytes) + break; + + /* Read and save payload content. */ + payload_size = FIELD_GET(MCHP_OTPC_HR_SIZE, *(buf - 1)); + writel_relaxed(0UL, otpc->base + MCHP_OTPC_AR); + do { + *buf++ = readl_relaxed(otpc->base + MCHP_OTPC_DR); + len += sizeof(*buf); + offset++; + payload_size--; + } while (payload_size >= 0 && len < bytes); + } + + return 0; +} + +static int mchp_otpc_init_packets_list(struct mchp_otpc *otpc, u32 *size) +{ + struct mchp_otpc_packet *packet; + u32 word, word_pos = 0, id = 0, npackets = 0, payload_size; + int ret; + + INIT_LIST_HEAD(&otpc->packets); + *size = 0; + + while (*size < MCHP_OTPC_SIZE) { + ret = mchp_otpc_prepare_read(otpc, word_pos); + if (ret) + return ret; + + word = readl_relaxed(otpc->base + MCHP_OTPC_HR); + payload_size = FIELD_GET(MCHP_OTPC_HR_SIZE, word); + if (!payload_size) + break; + + packet = devm_kzalloc(otpc->dev, sizeof(*packet), GFP_KERNEL); + if (!packet) + return -ENOMEM; + + packet->id = id++; + packet->offset = word_pos; + INIT_LIST_HEAD(&packet->list); + list_add_tail(&packet->list, &otpc->packets); + + /* Count size by adding header and paload sizes. */ + *size += 4 * (payload_size + 1); + /* Next word: this packet (header, payload) position + 1. */ + word_pos += payload_size + 2; + + npackets++; + } + + otpc->npackets = npackets; + + return 0; +} + +static struct nvmem_config mchp_nvmem_config = { + .name = MCHP_OTPC_NAME, + .type = NVMEM_TYPE_OTP, + .read_only = true, + .word_size = 4, + .stride = 4, + .reg_read = mchp_otpc_read, +}; + +static int mchp_otpc_probe(struct platform_device *pdev) +{ + struct nvmem_device *nvmem; + struct mchp_otpc *otpc; + u32 size; + int ret; + + otpc = devm_kzalloc(&pdev->dev, sizeof(*otpc), GFP_KERNEL); + if (!otpc) + return -ENOMEM; + + otpc->base = devm_platform_ioremap_resource(pdev, 0); + if (IS_ERR(otpc->base)) + return PTR_ERR(otpc->base); + + otpc->dev = &pdev->dev; + ret = mchp_otpc_init_packets_list(otpc, &size); + if (ret) + return ret; + + mchp_nvmem_config.dev = otpc->dev; + mchp_nvmem_config.add_legacy_fixed_of_cells = true; + mchp_nvmem_config.size = size; + mchp_nvmem_config.priv = otpc; + nvmem = devm_nvmem_register(&pdev->dev, &mchp_nvmem_config); + + return PTR_ERR_OR_ZERO(nvmem); +} + +static const struct of_device_id __maybe_unused mchp_otpc_ids[] = { + { .compatible = "microchip,sama7g5-otpc", }, + { }, +}; +MODULE_DEVICE_TABLE(of, mchp_otpc_ids); + +static struct platform_driver mchp_otpc_driver = { + .probe = mchp_otpc_probe, + .driver = { + .name = MCHP_OTPC_NAME, + .of_match_table = of_match_ptr(mchp_otpc_ids), + }, +}; +module_platform_driver(mchp_otpc_driver); + +MODULE_AUTHOR("Claudiu Beznea "); +MODULE_DESCRIPTION("Microchip SAMA7G5 OTPC driver"); +MODULE_LICENSE("GPL"); -- cgit v1.3.1