diff options
Diffstat (limited to 'kernel/extable.c')
| -rw-r--r-- | kernel/extable.c | 170 |
1 files changed, 170 insertions, 0 deletions
diff --git a/kernel/extable.c b/kernel/extable.c new file mode 100644 index 0000000000..71f482581c --- /dev/null +++ b/kernel/extable.c @@ -0,0 +1,170 @@ +// 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/elf.h> +#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 notrace core_kernel_text(unsigned long addr) +{ + if (is_kernel_text(addr)) + return 1; + + if (system_state < SYSTEM_FREEING_INITMEM && + is_kernel_inittext(addr)) + 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 (is_kernel_inittext(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) + ct_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) + ct_nmi_exit(); + + return ret; +} + +/* + * On some architectures (PPC64, IA64, PARISC) 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. + */ +#ifdef CONFIG_HAVE_FUNCTION_DESCRIPTORS +void *dereference_function_descriptor(void *ptr) +{ + func_desc_t *desc = ptr; + void *p; + + if (!get_kernel_nofault(p, (void *)&desc->addr)) + ptr = p; + return ptr; +} +EXPORT_SYMBOL_GPL(dereference_function_descriptor); + +void *dereference_kernel_function_descriptor(void *ptr) +{ + if (ptr < (void *)__start_opd || ptr >= (void *)__end_opd) + return ptr; + + return dereference_function_descriptor(ptr); +} +#endif + +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); +} |