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aec0be2d6e
Stack traces that happen from function tracing check if the address on the stack is a __kernel_text_address(). That is, is the address kernel code. This calls core_kernel_text() which returns true if the address is part of the builtin kernel code. It also calls is_module_text_address() which returns true if the address belongs to module code. But what is missing is ftrace dynamically allocated trampolines. These trampolines are allocated for individual ftrace_ops that call the ftrace_ops callback functions directly. But if they do a stack trace, the code checking the stack wont detect them as they are neither core kernel code nor module address space. Adding another field to ftrace_ops that also stores the size of the trampoline assigned to it we can create a new function called is_ftrace_trampoline() that returns true if the address is a dynamically allocate ftrace trampoline. Note, it ignores trampolines that are not dynamically allocated as they will return true with the core_kernel_text() function. Link: http://lkml.kernel.org/r/20141119034829.497125839@goodmis.org Cc: Ingo Molnar <mingo@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Acked-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
145 lines
4.0 KiB
C
145 lines
4.0 KiB
C
/* Rewritten by Rusty Russell, on the backs of many others...
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Copyright (C) 2001 Rusty Russell, 2002 Rusty Russell IBM.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#include <linux/ftrace.h>
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#include <linux/memory.h>
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#include <linux/module.h>
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#include <linux/ftrace.h>
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#include <linux/mutex.h>
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#include <linux/init.h>
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#include <asm/sections.h>
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#include <asm/uaccess.h>
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/*
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* mutex protecting text section modification (dynamic code patching).
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* some users need to sleep (allocating memory...) while they hold this lock.
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*
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* NOT exported to modules - patching kernel text is a really delicate matter.
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*/
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DEFINE_MUTEX(text_mutex);
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extern struct exception_table_entry __start___ex_table[];
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extern struct exception_table_entry __stop___ex_table[];
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/* Cleared by build time tools if the table is already sorted. */
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u32 __initdata __visible main_extable_sort_needed = 1;
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/* Sort the kernel's built-in exception table */
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void __init sort_main_extable(void)
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{
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if (main_extable_sort_needed && __stop___ex_table > __start___ex_table) {
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pr_notice("Sorting __ex_table...\n");
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sort_extable(__start___ex_table, __stop___ex_table);
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}
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}
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/* Given an address, look for it in the exception tables. */
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const struct exception_table_entry *search_exception_tables(unsigned long addr)
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{
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const struct exception_table_entry *e;
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e = search_extable(__start___ex_table, __stop___ex_table-1, addr);
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if (!e)
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e = search_module_extables(addr);
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return e;
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}
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static inline int init_kernel_text(unsigned long addr)
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{
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if (addr >= (unsigned long)_sinittext &&
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addr < (unsigned long)_einittext)
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return 1;
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return 0;
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}
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int core_kernel_text(unsigned long addr)
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{
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if (addr >= (unsigned long)_stext &&
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addr < (unsigned long)_etext)
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return 1;
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if (system_state == SYSTEM_BOOTING &&
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init_kernel_text(addr))
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return 1;
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return 0;
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}
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/**
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* core_kernel_data - tell if addr points to kernel data
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* @addr: address to test
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*
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* Returns true if @addr passed in is from the core kernel data
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* section.
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*
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* Note: On some archs it may return true for core RODATA, and false
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* for others. But will always be true for core RW data.
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*/
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int core_kernel_data(unsigned long addr)
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{
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if (addr >= (unsigned long)_sdata &&
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addr < (unsigned long)_edata)
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return 1;
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return 0;
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}
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int __kernel_text_address(unsigned long addr)
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{
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if (core_kernel_text(addr))
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return 1;
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if (is_module_text_address(addr))
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return 1;
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if (is_ftrace_trampoline(addr))
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return 1;
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/*
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* There might be init symbols in saved stacktraces.
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* Give those symbols a chance to be printed in
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* backtraces (such as lockdep traces).
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*
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* Since we are after the module-symbols check, there's
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* no danger of address overlap:
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*/
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if (init_kernel_text(addr))
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return 1;
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return 0;
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}
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int kernel_text_address(unsigned long addr)
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{
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if (core_kernel_text(addr))
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return 1;
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if (is_module_text_address(addr))
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return 1;
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return is_ftrace_trampoline(addr);
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}
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/*
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* On some architectures (PPC64, IA64) function pointers
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* are actually only tokens to some data that then holds the
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* real function address. As a result, to find if a function
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* pointer is part of the kernel text, we need to do some
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* special dereferencing first.
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*/
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int func_ptr_is_kernel_text(void *ptr)
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{
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unsigned long addr;
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addr = (unsigned long) dereference_function_descriptor(ptr);
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if (core_kernel_text(addr))
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return 1;
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return is_module_text_address(addr);
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}
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