// SPDX-License-Identifier: GPL-2.0-or-later /* Rewritten by Rusty Russell, on the backs of many others... Copyright (C) 2001 Rusty Russell, 2002 Rusty Russell IBM. */ #include <linux/ftrace.h> #include <linux/memory.h> #include <linux/extable.h> #include <linux/module.h> #include <linux/mutex.h> #include <linux/init.h> #include <linux/kprobes.h> #include <linux/filter.h> #include <asm/sections.h> #include <linux/uaccess.h> /* * mutex protecting text section modification (dynamic code patching). * some users need to sleep (allocating memory...) while they hold this lock. * * Note: Also protects SMP-alternatives modification on x86. * * NOT exported to modules - patching kernel text is a really delicate matter. */ DEFINE_MUTEX(text_mutex); extern struct exception_table_entry __start___ex_table[]; extern struct exception_table_entry __stop___ex_table[]; /* Cleared by build time tools if the table is already sorted. */ u32 __initdata __visible main_extable_sort_needed = 1; /* Sort the kernel's built-in exception table */ void __init sort_main_extable(void) { if (main_extable_sort_needed && &__stop___ex_table > &__start___ex_table) { pr_notice("Sorting __ex_table...\n"); sort_extable(__start___ex_table, __stop___ex_table); } } /* Given an address, look for it in the kernel exception table */ const struct exception_table_entry *search_kernel_exception_table(unsigned long addr) { return search_extable(__start___ex_table, __stop___ex_table - __start___ex_table, addr); } /* Given an address, look for it in the exception tables. */ const struct exception_table_entry *search_exception_tables(unsigned long addr) { const struct exception_table_entry *e; e = search_kernel_exception_table(addr); if (!e) e = search_module_extables(addr); if (!e) e = search_bpf_extables(addr); return e; } int init_kernel_text(unsigned long addr) { if (addr >= (unsigned long)_sinittext && addr < (unsigned long)_einittext) return 1; return 0; } int notrace core_kernel_text(unsigned long addr) { if (addr >= (unsigned long)_stext && addr < (unsigned long)_etext) return 1; if (system_state < SYSTEM_RUNNING && init_kernel_text(addr)) return 1; return 0; } /** * core_kernel_data - tell if addr points to kernel data * @addr: address to test * * Returns true if @addr passed in is from the core kernel data * section. * * Note: On some archs it may return true for core RODATA, and false * for others. But will always be true for core RW data. */ int core_kernel_data(unsigned long addr) { if (addr >= (unsigned long)_sdata && addr < (unsigned long)_edata) return 1; return 0; } int __kernel_text_address(unsigned long addr) { if (kernel_text_address(addr)) return 1; /* * There might be init symbols in saved stacktraces. * Give those symbols a chance to be printed in * backtraces (such as lockdep traces). * * Since we are after the module-symbols check, there's * no danger of address overlap: */ if (init_kernel_text(addr)) return 1; return 0; } int kernel_text_address(unsigned long addr) { bool no_rcu; int ret = 1; if (core_kernel_text(addr)) return 1; /* * If a stack dump happens while RCU is not watching, then * RCU needs to be notified that it requires to start * watching again. This can happen either by tracing that * triggers a stack trace, or a WARN() that happens during * coming back from idle, or cpu on or offlining. * * is_module_text_address() as well as the kprobe slots, * is_bpf_text_address() and is_bpf_image_address require * RCU to be watching. */ no_rcu = !rcu_is_watching(); /* Treat this like an NMI as it can happen anywhere */ if (no_rcu) rcu_nmi_enter(); if (is_module_text_address(addr)) goto out; if (is_ftrace_trampoline(addr)) goto out; if (is_kprobe_optinsn_slot(addr) || is_kprobe_insn_slot(addr)) goto out; if (is_bpf_text_address(addr)) goto out; ret = 0; out: if (no_rcu) rcu_nmi_exit(); return ret; } /* * On some architectures (PPC64, IA64) function pointers * are actually only tokens to some data that then holds the * real function address. As a result, to find if a function * pointer is part of the kernel text, we need to do some * special dereferencing first. */ int func_ptr_is_kernel_text(void *ptr) { unsigned long addr; addr = (unsigned long) dereference_function_descriptor(ptr); if (core_kernel_text(addr)) return 1; return is_module_text_address(addr); }