1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Symbols calculate_checksums() must not give an entry of their own.
4 *
5 * Three kinds are skipped, for two different reasons:
6 *
7 * zero-length there is nothing to hash, and an entry keyed on the
8 * symbol's address would collide with whatever really lives
9 * there.
10 * alias a second name for an address already checksummed.
11 * cold part hashed as part of its parent, which func_for_each_insn()
12 * walks into, so a separate entry would double-count it.
13 *
14 * An entry per address is the invariant: .discard.sym_checksum is looked up by
15 * the address a relocation points at, so two entries for one address make the
16 * lookup ambiguous and one of the two checksums unreachable.
17 */
18
19 static const char __modinfo[]
20 __attribute__((section(".modinfo"), used, aligned(1))) = "\0name=vmlinux";
21
22 /* Zero-length: an object symbol of size 0, in a section of its own. */
23 extern char empty_marker[];
24 __asm__(".pushsection .data.empty_marker,\"aw\",@progbits\n"
25 ".globl empty_marker\n"
26 ".type empty_marker, @object\n"
27 "empty_marker:\n"
28 ".size empty_marker, 0\n"
29 ".popsection\n");
30
31 int real_function(int x);
real_function(int x)32 int real_function(int x)
33 {
34 #ifdef PATCHED
35 return x + 2;
36 #else
37 return x + 1;
38 #endif
39 }
40
41 /* Alias: a second name for real_function's address. */
42 int alias_function(int x) __attribute__((alias("real_function")));
43
target(int x)44 int target(int x)
45 {
46 return real_function(x) + alias_function(x) + (int)(long)empty_marker;
47 }
48