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/acpi/nvs.c | 213 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 213 insertions(+) create mode 100644 drivers/acpi/nvs.c (limited to 'drivers/acpi/nvs.c') diff --git a/drivers/acpi/nvs.c b/drivers/acpi/nvs.c new file mode 100644 index 000000000..12aee4102 --- /dev/null +++ b/drivers/acpi/nvs.c @@ -0,0 +1,213 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * nvs.c - Routines for saving and restoring ACPI NVS memory region + * + * Copyright (C) 2008-2011 Rafael J. Wysocki , Novell Inc. + */ + +#define pr_fmt(fmt) "ACPI: PM: " fmt + +#include +#include +#include +#include +#include +#include + +#include "internal.h" + +/* ACPI NVS regions, APEI may use it */ + +struct nvs_region { + __u64 phys_start; + __u64 size; + struct list_head node; +}; + +static LIST_HEAD(nvs_region_list); + +#ifdef CONFIG_ACPI_SLEEP +static int suspend_nvs_register(unsigned long start, unsigned long size); +#else +static inline int suspend_nvs_register(unsigned long a, unsigned long b) +{ + return 0; +} +#endif + +int acpi_nvs_register(__u64 start, __u64 size) +{ + struct nvs_region *region; + + region = kmalloc_obj(*region); + if (!region) + return -ENOMEM; + region->phys_start = start; + region->size = size; + list_add_tail(®ion->node, &nvs_region_list); + + return suspend_nvs_register(start, size); +} + +int acpi_nvs_for_each_region(int (*func)(__u64 start, __u64 size, void *data), + void *data) +{ + int rc; + struct nvs_region *region; + + list_for_each_entry(region, &nvs_region_list, node) { + rc = func(region->phys_start, region->size, data); + if (rc) + return rc; + } + + return 0; +} + + +#ifdef CONFIG_ACPI_SLEEP +/* + * Platforms, like ACPI, may want us to save some memory used by them during + * suspend and to restore the contents of this memory during the subsequent + * resume. The code below implements a mechanism allowing us to do that. + */ + +struct nvs_page { + unsigned long phys_start; + unsigned int size; + void *kaddr; + void *data; + bool unmap; + struct list_head node; +}; + +static LIST_HEAD(nvs_list); + +/** + * suspend_nvs_register - register platform NVS memory region to save + * @start: Physical address of the region. + * @size: Size of the region. + * + * The NVS region need not be page-aligned (both ends) and we arrange + * things so that the data from page-aligned addresses in this region will + * be copied into separate RAM pages. + */ +static int suspend_nvs_register(unsigned long start, unsigned long size) +{ + struct nvs_page *entry, *next; + + pr_info("Registering ACPI NVS region [mem %#010lx-%#010lx] (%ld bytes)\n", + start, start + size - 1, size); + + while (size > 0) { + unsigned int nr_bytes; + + entry = kzalloc_obj(struct nvs_page); + if (!entry) + goto Error; + + list_add_tail(&entry->node, &nvs_list); + entry->phys_start = start; + nr_bytes = PAGE_SIZE - (start & ~PAGE_MASK); + entry->size = (size < nr_bytes) ? size : nr_bytes; + + start += entry->size; + size -= entry->size; + } + return 0; + + Error: + list_for_each_entry_safe(entry, next, &nvs_list, node) { + list_del(&entry->node); + kfree(entry); + } + return -ENOMEM; +} + +/** + * suspend_nvs_free - free data pages allocated for saving NVS regions + */ +void suspend_nvs_free(void) +{ + struct nvs_page *entry; + + list_for_each_entry(entry, &nvs_list, node) + if (entry->data) { + kfree(entry->data); + entry->data = NULL; + if (entry->kaddr) { + if (entry->unmap) { + iounmap(entry->kaddr); + entry->unmap = false; + } else { + acpi_os_unmap_iomem(entry->kaddr, + entry->size); + } + entry->kaddr = NULL; + } + } +} + +/** + * suspend_nvs_alloc - allocate memory necessary for saving NVS regions + */ +int suspend_nvs_alloc(void) +{ + struct nvs_page *entry; + + list_for_each_entry(entry, &nvs_list, node) { + entry->data = kmalloc(PAGE_SIZE, GFP_KERNEL); + if (!entry->data) { + suspend_nvs_free(); + return -ENOMEM; + } + } + return 0; +} + +/** + * suspend_nvs_save - save NVS memory regions + */ +int suspend_nvs_save(void) +{ + struct nvs_page *entry; + + pr_info("Saving platform NVS memory\n"); + + list_for_each_entry(entry, &nvs_list, node) + if (entry->data) { + unsigned long phys = entry->phys_start; + unsigned int size = entry->size; + + entry->kaddr = acpi_os_get_iomem(phys, size); + if (!entry->kaddr) { + entry->kaddr = acpi_os_ioremap(phys, size); + entry->unmap = !!entry->kaddr; + } + if (!entry->kaddr) { + suspend_nvs_free(); + return -ENOMEM; + } + memcpy(entry->data, entry->kaddr, entry->size); + } + + return 0; +} + +/** + * suspend_nvs_restore - restore NVS memory regions + * + * This function is going to be called with interrupts disabled, so it + * cannot iounmap the virtual addresses used to access the NVS region. + */ +void suspend_nvs_restore(void) +{ + struct nvs_page *entry; + + pr_info("Restoring platform NVS memory\n"); + + list_for_each_entry(entry, &nvs_list, node) + if (entry->data) + memcpy(entry->kaddr, entry->data, entry->size); +} +#endif -- cgit v1.3.1