static inline void print_ip_sym(unsigned long ip)
{
printk("[<%px>] %pS\n", (void *) ip, (void *) ip);
}
然后我们就可以看到类似如下的内核log：
1 /*
2 * Show a '%p' thing. A kernel extension is that the '%p' is followed
3 * by an extra set of alphanumeric characters that are extended format
4 * specifiers.
5 *
6 * Please update scripts/checkpatch.pl when adding/removing conversion
7 * characters. (Search for "check for vsprintf extension").
8 *
9 * Right now we handle:
10 *
11 * - 'F' For symbolic function descriptor pointers with offset
12 * - 'f' For simple symbolic function names without offset
13 * - 'S' For symbolic direct pointers with offset
14 * - 's' For symbolic direct pointers without offset
15 * - '[FfSs]R' as above with __builtin_extract_return_addr() translation
16 * - 'B' For backtraced symbolic direct pointers with offset
17 * - 'R' For decoded struct resource, e.g., [mem 0x0-0x1f 64bit pref]
18 * - 'r' For raw struct resource, e.g., [mem 0x0-0x1f flags 0x201]
19 * - 'b[l]' For a bitmap, the number of bits is determined by the field
20 * width which must be explicitly specified either as part of the
21 * format string '%32b[l]' or through '%*b[l]', [l] selects
22 * range-list format instead of hex format
23 * - 'M' For a 6-byte MAC address, it prints the address in the
24 * usual colon-separated hex notation
25 * - 'm' For a 6-byte MAC address, it prints the hex address without colons
26 * - 'MF' For a 6-byte MAC FDDI address, it prints the address
27 * with a dash-separated hex notation
28 * - '[mM]R' For a 6-byte MAC address, Reverse order (Bluetooth)
29 * - 'I' [46] for IPv4/IPv6 addresses printed in the usual way
30 * IPv4 uses dot-separated decimal without leading 0's (1.2.3.4)
31 * IPv6 uses colon separated network-order 16 bit hex with leading 0's
32 * [S][pfs]
33 * Generic IPv4/IPv6 address (struct sockaddr *) that falls back to
34 * [4] or [6] and is able to print port [p], flowinfo [f], scope [s]
35 * - 'i' [46] for 'raw' IPv4/IPv6 addresses
36 * IPv6 omits the colons (01020304...0f)
37 * IPv4 uses dot-separated decimal with leading 0's (010.123.045.006)
38 * [S][pfs]
39 * Generic IPv4/IPv6 address (struct sockaddr *) that falls back to
40 * [4] or [6] and is able to print port [p], flowinfo [f], scope [s]
41 * - '[Ii][4S][hnbl]' IPv4 addresses in host, network, big or little endian order
42 * - 'I[6S]c' for IPv6 addresses printed as specified by
43 * http://tools.ietf.org/html/rfc5952
44 * - 'E[achnops]' For an escaped buffer, where rules are defined by combination
45 * of the following flags (see string_escape_mem() for the
46 * details):
47 * a - ESCAPE_ANY
48 * c - ESCAPE_SPECIAL
49 * h - ESCAPE_HEX
50 * n - ESCAPE_NULL
51 * o - ESCAPE_OCTAL
52 * p - ESCAPE_NP
53 * s - ESCAPE_SPACE
54 * By default ESCAPE_ANY_NP is used.
55 * - 'U' For a 16 byte UUID/GUID, it prints the UUID/GUID in the form
56 * "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
57 * Options for %pU are:
58 * b big endian lower case hex (default)
59 * B big endian UPPER case hex
60 * l little endian lower case hex
61 * L little endian UPPER case hex
62 * big endian output byte order is:
63 * [0][1][2][3]-[4][5]-[6][7]-[8][9]-[10][11][12][13][14][15]
64 * little endian output byte order is:
65 * [3][2][1][0]-[5][4]-[7][6]-[8][9]-[10][11][12][13][14][15]
66 * - 'V' For a struct va_format which contains a format string * and va_list *,
67 * call vsnprintf(->format, *->va_list).
68 * Implements a "recursive vsnprintf".
69 * Do not use this feature without some mechanism to verify the
70 * correctness of the format string and va_list arguments.
71 * - 'K' For a kernel pointer that should be hidden from unprivileged users
72 * - 'NF' For a netdev_features_t
73 * - 'h[CDN]' For a variable-length buffer, it prints it as a hex string with
74 * a certain separator (' ' by default):
75 * C colon
76 * D dash
77 * N no separator
78 * The maximum supported length is 64 bytes of the input. Consider
79 * to use print_hex_dump() for the larger input.
80 * - 'a[pd]' For address types [p] phys_addr_t, [d] dma_addr_t and derivatives
81 * (default assumed to be phys_addr_t, passed by reference)
82 * - 'd[234]' For a dentry name (optionally 2-4 last components)
83 * - 'D[234]' Same as 'd' but for a struct file
84 * - 'g' For block_device name (gendisk + partition number)
85 * - 'C' For a clock, it prints the name (Common Clock Framework) or address
86 * (legacy clock framework) of the clock
87 * - 'Cn' For a clock, it prints the name (Common Clock Framework) or address
88 * (legacy clock framework) of the clock
89 * - 'Cr' For a clock, it prints the current rate of the clock
90 * - 'G' For flags to be printed as a collection of symbolic strings that would
91 * construct the specific value. Supported flags given by option:
92 * p page flags (see struct page) given as pointer to unsigned long
93 * g gfp flags (GFP_* and __GFP_*) given as pointer to gfp_t
94 * v vma flags (VM_*) given as pointer to unsigned long
95 * - 'O' For a kobject based struct. Must be one of the following:
96 * - 'OF[fnpPcCF]' For a device tree object
97 * Without any optional arguments prints the full_name
98 * f device node full_name
99 * n device node name
100 * p device node phandle
101 * P device node path spec (name + @unit)
102 * F device node flags
103 * c major compatible string
104 * C full compatible string
105 *
106 * ** Please update also Documentation/printk-formats.txt when making changes **
107 *
108 * Note: The difference between 'S' and 'F' is that on ia64 and ppc64
109 * function pointers are really function descriptors, which contain a
110 * pointer to the real address.
111 */
112 static noinline_for_stack
113 char *pointer(const char *fmt, char *buf, char *end, void *ptr,
114 struct printf_spec spec)
115 {
116 const int default_width = 2 * sizeof(void *);
117
118 if (!ptr && *fmt != 'K') {
119 /*
120 * Print (null) with the same width as a pointer so it makes
121 * tabular output look nice.
122 */
123 if (spec.field_width == -1)
124 spec.field_width = default_width;
125 return string(buf, end, "(null)", spec);
126 }
127
128 switch (*fmt) {
129 case 'F':
130 case 'f':
131 ptr = dereference_function_descriptor(ptr);
132 /* Fallthrough */
133 case 'S':
134 case 's':
135 case 'B':
136 return symbol_string(buf, end, ptr, spec, fmt);
137 case 'R':
138 case 'r':
139 return resource_string(buf, end, ptr, spec, fmt);
140 case 'h':
141 return hex_string(buf, end, ptr, spec, fmt);
142 case 'b':
143 switch (fmt[1]) {
144 case 'l':
145 return bitmap_list_string(buf, end, ptr, spec, fmt);
146 default:
147 return bitmap_string(buf, end, ptr, spec, fmt);
148 }
149 case 'M': /* Colon separated: 00:01:02:03:04:05 */
150 case 'm': /* Contiguous: 000102030405 */
151 /* [mM]F (FDDI) */
152 /* [mM]R (Reverse order; Bluetooth) */
153 return mac_address_string(buf, end, ptr, spec, fmt);
154 case 'I': /* Formatted IP supported
155 * 4: 1.2.3.4
156 * 6: 0001:0203:...:0708
157 * 6c: 1::708 or 1::1.2.3.4
158 */
159 case 'i': /* Contiguous:
160 * 4: 001.002.003.004
161 * 6: 000102...0f
162 */
163 switch (fmt[1]) {
164 case '6':
165 return ip6_addr_string(buf, end, ptr, spec, fmt);
166 case '4':
167 return ip4_addr_string(buf, end, ptr, spec, fmt);
168 case 'S': {
169 const union {
170 struct sockaddr raw;
171 struct sockaddr_in v4;
172 struct sockaddr_in6 v6;
173 } *sa = ptr;
174
175 switch (sa->raw.sa_family) {
176 case AF_INET:
177 return ip4_addr_string_sa(buf, end, &sa->v4, spec, fmt);
178 case AF_INET6:
179 return ip6_addr_string_sa(buf, end, &sa->v6, spec, fmt);
180 default:
181 return string(buf, end, "(invalid address)", spec);
182 }}
183 }
184 break;
185 case 'E':
186 return escaped_string(buf, end, ptr, spec, fmt);
187 case 'U':
188 return uuid_string(buf, end, ptr, spec, fmt);
189 case 'V':
190 {
191 va_list va;
192
193 va_copy(va, *((struct va_format *)ptr)->va);
194 buf += vsnprintf(buf, end > buf ? end - buf : 0,
195 ((struct va_format *)ptr)->fmt, va);
196 va_end(va);
197 return buf;
198 }
199 case 'K':
200 switch (kptr_restrict) {
201 case 0:
202 /* Always print %pK values */
203 break;
204 case 1: {
205 const struct cred *cred;
206
207 /*
208 * kptr_restrict==1 cannot be used in IRQ context
209 * because its test for CAP_SYSLOG would be meaningless.
210 */
211 if (in_irq() || in_serving_softirq() || in_nmi()) {
212 if (spec.field_width == -1)
213 spec.field_width = default_width;
214 return string(buf, end, "pK-error", spec);
215 }
216
217 /*
218 * Only print the real pointer value if the current
219 * process has CAP_SYSLOG and is running with the
220 * same credentials it started with. This is because
221 * access to files is checked at open() time, but %pK
222 * checks permission at read() time. We don't want to
223 * leak pointer values if a binary opens a file using
224 * %pK and then elevates privileges before reading it.
225 */
226 cred = current_cred();
227 if (!has_capability_noaudit(current, CAP_SYSLOG) ||
228 !uid_eq(cred->euid, cred->uid) ||
229 !gid_eq(cred->egid, cred->gid))
230 ptr = NULL;
231 break;
232 }
233 case 2:
234 default:
235 /* Always print 0's for %pK */
236 ptr = NULL;
237 break;
238 }
239 break;
240
241 case 'N':
242 return netdev_bits(buf, end, ptr, fmt);
243 case 'a':
244 return address_val(buf, end, ptr, fmt);
245 case 'd':
246 return dentry_name(buf, end, ptr, spec, fmt);
247 case 'C':
248 return clock(buf, end, ptr, spec, fmt);
249 case 'D':
250 return dentry_name(buf, end,
251 ((const struct file *)ptr)->f_path.dentry,
252 spec, fmt);
253 #ifdef CONFIG_BLOCK
254 case 'g':
255 return bdev_name(buf, end, ptr, spec, fmt);
256 #endif
257
258 case 'G':
259 return flags_string(buf, end, ptr, fmt);
260 case 'O':
261 switch (fmt[1]) {
262 case 'F':
263 return device_node_string(buf, end, ptr, spec, fmt + 1);
264 }
265 }
266 spec.flags |= SMALL;
267 if (spec.field_width == -1) {
268 spec.field_width = default_width;
269 spec.flags |= ZEROPAD;
270 }
271 spec.base = 16;
272
273 return number(buf, end, (unsigned long) ptr, spec);
274 }
第136行， symbol_string(buf, end, ptr, spec, fmt);
1 static noinline_for_stack
2 char *symbol_string(char *buf, char *end, void *ptr,
3 struct printf_spec spec, const char *fmt)
4 {
5 unsigned long value;
6 #ifdef CONFIG_KALLSYMS
7 char sym[KSYM_SYMBOL_LEN];
8 #endif
9
10 if (fmt[1] == 'R')
11 ptr = __builtin_extract_return_addr(ptr);
12 value = (unsigned long)ptr;
13
14 #ifdef CONFIG_KALLSYMS
15 if (*fmt == 'B')
16 sprint_backtrace(sym, value);
17 else if (*fmt != 'f' && *fmt != 's')
18 sprint_symbol(sym, value);
19 else
20 sprint_symbol_no_offset(sym, value);
21
22 return string(buf, end, sym, spec);
23 #else
24 return special_hex_number(buf, end, value, sizeof(void *));
25 #endif
26 }
第20行：sprint_symbol_no_offset
1 /**
2 * sprint_symbol_no_offset - Look up a kernel symbol and return it in a text buffer
3 * @buffer: buffer to be stored
4 * @address: address to lookup
5 *
6 * This function looks up a kernel symbol with @address and stores its name
7 * and module name to @buffer if possible. If no symbol was found, just saves
8 * its @address as is.
9 *
10 * This function returns the number of bytes stored in @buffer.
11 */
12 int sprint_symbol_no_offset(char *buffer, unsigned long address)
13 {
14 return __sprint_symbol(buffer, address, 0, 0);
15 }
完。