Re: [PATCH v2 2/3] extable: verify address is read-only

From: kbuild test robot
Date: Sat Feb 18 2017 - 01:51:01 EST

Hi Eddie,

[auto build test WARNING on linus/master]
[also build test WARNING on v4.10-rc8 next-20170217]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url: https://github.com/0day-ci/linux/commits/Eddie-Kovsky/provide-check-for-ro_after_init-memory-sections/20170218-141040
config: x86_64-randconfig-x008-201707 (attached as .config)
compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901
reproduce:
# save the attached .config to linux build tree
make ARCH=x86_64

All warnings (new ones prefixed by >>):

In file included from include/linux/trace_clock.h:12:0,
from include/linux/ftrace.h:9,
from kernel/extable.c:18:
kernel/extable.c: In function 'kernel_ro_address':
kernel/extable.c:168:6: error: implicit declaration of function 'is_module_ro_address' [-Werror=implicit-function-declaration]
if (is_module_ro_address(addr))
^
include/linux/compiler.h:149:30: note: in definition of macro '__trace_if'
if (__builtin_constant_p(!!(cond)) ? !!(cond) : \
^~~~
>> kernel/extable.c:168:2: note: in expansion of macro 'if'
if (is_module_ro_address(addr))
^~
cc1: some warnings being treated as errors

vim +/if +168 kernel/extable.c

12 GNU General Public License for more details.
13
14 You should have received a copy of the GNU General Public License
15 along with this program; if not, write to the Free Software
16 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
17 */
> 18 #include <linux/ftrace.h>
19 #include <linux/memory.h>
20 #include <linux/module.h>
21 #include <linux/mutex.h>
22 #include <linux/init.h>
23
24 #include <asm/sections.h>
25 #include <linux/uaccess.h>
26
27 /*
28 * mutex protecting text section modification (dynamic code patching).
29 * some users need to sleep (allocating memory...) while they hold this lock.
30 *
31 * NOT exported to modules - patching kernel text is a really delicate matter.
32 */
33 DEFINE_MUTEX(text_mutex);
34
35 extern struct exception_table_entry __start___ex_table[];
36 extern struct exception_table_entry __stop___ex_table[];
37
38 /* Cleared by build time tools if the table is already sorted. */
39 u32 __initdata __visible main_extable_sort_needed = 1;
40
41 /* Sort the kernel's built-in exception table */
42 void __init sort_main_extable(void)
43 {
44 if (main_extable_sort_needed && __stop___ex_table > __start___ex_table) {
45 pr_notice("Sorting __ex_table...\n");
46 sort_extable(__start___ex_table, __stop___ex_table);
47 }
48 }
49
50 /* Given an address, look for it in the exception tables. */
51 const struct exception_table_entry *search_exception_tables(unsigned long addr)
52 {
53 const struct exception_table_entry *e;
54
55 e = search_extable(__start___ex_table, __stop___ex_table-1, addr);
56 if (!e)
57 e = search_module_extables(addr);
58 return e;
59 }
60
61 static inline int init_kernel_text(unsigned long addr)
62 {
63 if (addr >= (unsigned long)_sinittext &&
64 addr < (unsigned long)_einittext)
65 return 1;
66 return 0;
67 }
68
69 int core_kernel_text(unsigned long addr)
70 {
71 if (addr >= (unsigned long)_stext &&
72 addr < (unsigned long)_etext)
73 return 1;
74
75 if (system_state == SYSTEM_BOOTING &&
76 init_kernel_text(addr))
77 return 1;
78 return 0;
79 }
80
81 /**
82 * core_kernel_data - tell if addr points to kernel data
83 * @addr: address to test
84 *
85 * Returns true if @addr passed in is from the core kernel data
86 * section.
87 *
88 * Note: On some archs it may return true for core RODATA, and false
89 * for others. But will always be true for core RW data.
90 */
91 int core_kernel_data(unsigned long addr)
92 {
93 if (addr >= (unsigned long)_sdata &&
94 addr < (unsigned long)_edata)
95 return 1;
96 return 0;
97 }
98
99 int __kernel_text_address(unsigned long addr)
100 {
101 if (core_kernel_text(addr))
102 return 1;
103 if (is_module_text_address(addr))
104 return 1;
105 if (is_ftrace_trampoline(addr))
106 return 1;
107 /*
108 * There might be init symbols in saved stacktraces.
109 * Give those symbols a chance to be printed in
110 * backtraces (such as lockdep traces).
111 *
112 * Since we are after the module-symbols check, there's
113 * no danger of address overlap:
114 */
115 if (init_kernel_text(addr))
116 return 1;
117 return 0;
118 }
119
120 int kernel_text_address(unsigned long addr)
121 {
122 if (core_kernel_text(addr))
123 return 1;
124 if (is_module_text_address(addr))
125 return 1;
126 return is_ftrace_trampoline(addr);
127 }
128
129 /*
130 * On some architectures (PPC64, IA64) function pointers
131 * are actually only tokens to some data that then holds the
132 * real function address. As a result, to find if a function
133 * pointer is part of the kernel text, we need to do some
134 * special dereferencing first.
135 */
136 int func_ptr_is_kernel_text(void *ptr)
137 {
138 unsigned long addr;
139 addr = (unsigned long) dereference_function_descriptor(ptr);
140 if (core_kernel_text(addr))
141 return 1;
142 return is_module_text_address(addr);
143 }
144
145 /**
146 * core_kernel_ro_data - Verify address points to read-only section
147 * @addr: address to test
148 *
149 */
150 int core_kernel_ro_data(unsigned long addr)
151 {
152 if (addr >= (unsigned long)__start_rodata &&
153 addr < (unsigned long)__end_rodata)
154 return 1;
155
156 if (addr >= (unsigned long)__start_data_ro_after_init &&
157 addr < (unsigned long)__end_data_ro_after_init)
158 return 1;
159
160 return 0;
161 }
162
163 /* Verify that address is const or ro_after_init. */
164 int kernel_ro_address(unsigned long addr)
165 {
166 if (core_kernel_ro_data(addr))
167 return 1;
> 168 if (is_module_ro_address(addr))
169 return 1;
170
171 return 0;

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