Commit | Line | Data |
---|---|---|
a6576540 MD |
1 | /* SPDX-License-Identifier: (GPL-2.0-only OR LGPL-2.1-only) |
2 | * | |
3 | * wrapper/kallsyms.c | |
4 | * | |
5 | * Wrapper around kallsyms. Using kprobes to get its address when available. | |
6 | * | |
7 | * Can we mainline LTTng already so we don't have to waste our time doing this | |
8 | * kind of hack ? | |
9 | * | |
10 | * Copyright (C) 2020 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> | |
11 | */ | |
12 | ||
13 | #include <linux/kprobes.h> | |
14 | #include <linux/module.h> | |
15 | #include <wrapper/kallsyms.h> | |
16 | ||
5f4c791e | 17 | #if (LTTNG_LINUX_VERSION_CODE >= LTTNG_KERNEL_VERSION(5,7,0)) |
a6576540 MD |
18 | |
19 | #ifndef CONFIG_KPROBES | |
20 | # error "LTTng-modules requires CONFIG_KPROBES on kernels >= 5.7.0" | |
21 | #endif | |
22 | ||
928a843e MJ |
23 | #ifdef LTTNG_CONFIG_PPC64_ELF_ABI_V1 |
24 | #if (LTTNG_LINUX_VERSION_CODE >= LTTNG_KERNEL_VERSION(5,18,0)) | |
25 | #include <asm/elf.h> | |
26 | ||
27 | #define LTTNG_FUNC_DESC_TYPE struct func_desc | |
28 | #define LTTNG_FUNC_DESC_ADDR_NAME addr | |
29 | ||
30 | #else | |
31 | ||
32 | #include <asm/types.h> | |
33 | ||
34 | #define LTTNG_FUNC_DESC_TYPE func_descr_t | |
35 | #define LTTNG_FUNC_DESC_ADDR_NAME entry | |
36 | #endif | |
37 | ||
38 | static | |
39 | LTTNG_FUNC_DESC_TYPE kallsyms_lookup_name_func_desc; | |
40 | #endif | |
41 | ||
a6576540 MD |
42 | static |
43 | unsigned long (*kallsyms_lookup_name_sym)(const char *name); | |
44 | ||
45 | static | |
46 | int dummy_kprobe_handler(struct kprobe *p, struct pt_regs *regs) | |
47 | { | |
48 | return 0; | |
49 | } | |
50 | ||
51 | static | |
52 | unsigned long do_get_kallsyms(void) | |
53 | { | |
54 | struct kprobe probe; | |
55 | int ret; | |
56 | unsigned long addr; | |
57 | ||
58 | memset(&probe, 0, sizeof(probe)); | |
59 | probe.pre_handler = dummy_kprobe_handler; | |
60 | probe.symbol_name = "kallsyms_lookup_name"; | |
62b81e88 | 61 | #ifdef LTTNG_CONFIG_PPC64_ELF_ABI_V2 |
480cce43 HZ |
62 | /* |
63 | * With powerpc64 ABIv2, we need the global entry point of | |
64 | * kallsyms_lookup_name to call it later, while kprobe_register would | |
65 | * automatically adjust the global entry point to the local entry point, | |
66 | * when a kprobe was registered at a function entry. So we add 4 bytes | |
67 | * which is the length of one instruction to kallsyms_lookup_name to | |
68 | * avoid the adjustment. | |
69 | */ | |
70 | probe.offset = 4; | |
71 | #endif | |
a6576540 MD |
72 | ret = register_kprobe(&probe); |
73 | if (ret) | |
74 | return 0; | |
62b81e88 | 75 | #ifdef LTTNG_CONFIG_PPC64_ELF_ABI_V2 |
480cce43 HZ |
76 | /* Substract 4 bytes to get what we originally want */ |
77 | addr = (unsigned long)(((char *)probe.addr) - 4); | |
928a843e MJ |
78 | #elif defined(LTTNG_CONFIG_PPC64_ELF_ABI_V1) |
79 | /* | |
80 | * Build a function descriptor from the address of | |
81 | * 'kallsyms_lookup_name' returned by kprobe and the toc of | |
82 | * 'sprint_symbol' which is in the same compile unit and exported. I | |
83 | * hate this on so many levels but it works. | |
84 | */ | |
85 | kallsyms_lookup_name_func_desc.LTTNG_FUNC_DESC_ADDR_NAME = (unsigned long) probe.addr; | |
86 | kallsyms_lookup_name_func_desc.toc = ((LTTNG_FUNC_DESC_TYPE *) &sprint_symbol)->toc; | |
87 | addr = (unsigned long) &kallsyms_lookup_name_func_desc; | |
480cce43 | 88 | #else |
a6576540 | 89 | addr = (unsigned long)probe.addr; |
480cce43 | 90 | #endif |
a6576540 MD |
91 | #ifdef CONFIG_ARM |
92 | #ifdef CONFIG_THUMB2_KERNEL | |
93 | if (addr) | |
94 | addr |= 1; /* set bit 0 in address for thumb mode */ | |
95 | #endif | |
96 | #endif | |
97 | unregister_kprobe(&probe); | |
98 | return addr; | |
99 | } | |
100 | ||
101 | unsigned long wrapper_kallsyms_lookup_name(const char *name) | |
102 | { | |
103 | if (!kallsyms_lookup_name_sym) { | |
104 | kallsyms_lookup_name_sym = (void *)do_get_kallsyms(); | |
105 | } | |
106 | if (kallsyms_lookup_name_sym) | |
107 | return kallsyms_lookup_name_sym(name); | |
108 | else { | |
5a15f70c | 109 | printk_once(KERN_WARNING "LTTng: requires kallsyms_lookup_name\n"); |
a6576540 MD |
110 | return 0; |
111 | } | |
112 | } | |
113 | EXPORT_SYMBOL_GPL(wrapper_kallsyms_lookup_name); | |
114 | ||
115 | #endif | |
26f03ad4 L |
116 | |
117 | #ifdef CONFIG_ANDROID | |
118 | MODULE_IMPORT_NS(VFS_internal_I_am_really_a_filesystem_and_am_NOT_a_driver); | |
119 | #endif |