1 files changed, 175 insertions, 0 deletions
diff --git a/kernel/extable.c b/kernel/extable.c
new file mode 100644
index 000000000..b0ea5eb0c
--- /dev/null
+++ b/kernel/extable.c
@@ -0,0 +1,175 @@
+// 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);
+}