1 ========================= 1 =========================
2 GCC plugin infrastructure 2 GCC plugin infrastructure
3 ========================= 3 =========================
4 4
5 5
6 Introduction 6 Introduction
7 ============ 7 ============
8 8
9 GCC plugins are loadable modules that provide 9 GCC plugins are loadable modules that provide extra features to the
10 compiler [1]_. They are useful for runtime ins 10 compiler [1]_. They are useful for runtime instrumentation and static analysis.
11 We can analyse, change and add further code du 11 We can analyse, change and add further code during compilation via
12 callbacks [2]_, GIMPLE [3]_, IPA [4]_ and RTL 12 callbacks [2]_, GIMPLE [3]_, IPA [4]_ and RTL passes [5]_.
13 13
14 The GCC plugin infrastructure of the kernel su 14 The GCC plugin infrastructure of the kernel supports building out-of-tree
15 modules, cross-compilation and building in a s 15 modules, cross-compilation and building in a separate directory.
16 Plugin source files have to be compilable by a 16 Plugin source files have to be compilable by a C++ compiler.
17 17
18 Currently the GCC plugin infrastructure suppor 18 Currently the GCC plugin infrastructure supports only some architectures.
19 Grep "select HAVE_GCC_PLUGINS" to find out whi 19 Grep "select HAVE_GCC_PLUGINS" to find out which architectures support
20 GCC plugins. 20 GCC plugins.
21 21
22 This infrastructure was ported from grsecurity 22 This infrastructure was ported from grsecurity [6]_ and PaX [7]_.
23 23
24 -- 24 --
25 25
26 .. [1] https://gcc.gnu.org/onlinedocs/gccint/P 26 .. [1] https://gcc.gnu.org/onlinedocs/gccint/Plugins.html
27 .. [2] https://gcc.gnu.org/onlinedocs/gccint/P 27 .. [2] https://gcc.gnu.org/onlinedocs/gccint/Plugin-API.html#Plugin-API
28 .. [3] https://gcc.gnu.org/onlinedocs/gccint/G 28 .. [3] https://gcc.gnu.org/onlinedocs/gccint/GIMPLE.html
29 .. [4] https://gcc.gnu.org/onlinedocs/gccint/I 29 .. [4] https://gcc.gnu.org/onlinedocs/gccint/IPA.html
30 .. [5] https://gcc.gnu.org/onlinedocs/gccint/R 30 .. [5] https://gcc.gnu.org/onlinedocs/gccint/RTL.html
31 .. [6] https://grsecurity.net/ 31 .. [6] https://grsecurity.net/
32 .. [7] https://pax.grsecurity.net/ 32 .. [7] https://pax.grsecurity.net/
33 33
34 34
35 Purpose <<
36 ======= <<
37 <<
38 GCC plugins are designed to provide a place to <<
39 compiler features that are neither in GCC nor <<
40 their utility is proven, the goal is to upstre <<
41 (and Clang), and then to finally remove them f <<
42 feature is available in all supported versions <<
43 <<
44 Specifically, new plugins should implement onl <<
45 upstream compiler support (in either GCC or Cl <<
46 <<
47 When a feature exists in Clang but not GCC, ef <<
48 bring the feature to upstream GCC (rather than <<
49 GCC plugin), so the entire ecosystem can benef <<
50 <<
51 Similarly, even if a feature provided by a GCC <<
52 in Clang, but the feature is proven to be usef <<
53 to upstream the feature to GCC (and Clang). <<
54 <<
55 After a feature is available in upstream GCC, <<
56 unbuildable for the corresponding GCC version <<
57 kernel-supported versions of GCC provide the f <<
58 be removed from the kernel. <<
59 <<
60 <<
61 Files 35 Files
62 ===== 36 =====
63 37
64 **$(src)/scripts/gcc-plugins** 38 **$(src)/scripts/gcc-plugins**
65 39
66 This is the directory of the GCC plugi 40 This is the directory of the GCC plugins.
67 41
68 **$(src)/scripts/gcc-plugins/gcc-common.h** 42 **$(src)/scripts/gcc-plugins/gcc-common.h**
69 43
70 This is a compatibility header for GCC 44 This is a compatibility header for GCC plugins.
71 It should be always included instead o 45 It should be always included instead of individual gcc headers.
72 46
73 **$(src)/scripts/gcc-plugins/gcc-generate-gimp 47 **$(src)/scripts/gcc-plugins/gcc-generate-gimple-pass.h,
74 $(src)/scripts/gcc-plugins/gcc-generate-ipa-pa 48 $(src)/scripts/gcc-plugins/gcc-generate-ipa-pass.h,
75 $(src)/scripts/gcc-plugins/gcc-generate-simple 49 $(src)/scripts/gcc-plugins/gcc-generate-simple_ipa-pass.h,
76 $(src)/scripts/gcc-plugins/gcc-generate-rtl-pa 50 $(src)/scripts/gcc-plugins/gcc-generate-rtl-pass.h**
77 51
78 These headers automatically generate t 52 These headers automatically generate the registration structures for
79 GIMPLE, SIMPLE_IPA, IPA and RTL passes 53 GIMPLE, SIMPLE_IPA, IPA and RTL passes.
80 They should be preferred to creating t 54 They should be preferred to creating the structures by hand.
81 55
82 56
83 Usage 57 Usage
84 ===== 58 =====
85 59
86 You must install the gcc plugin headers for yo 60 You must install the gcc plugin headers for your gcc version,
87 e.g., on Ubuntu for gcc-10:: 61 e.g., on Ubuntu for gcc-10::
88 62
89 apt-get install gcc-10-plugin-dev 63 apt-get install gcc-10-plugin-dev
90 64
91 Or on Fedora:: 65 Or on Fedora::
92 66
93 dnf install gcc-plugin-devel libmpc-de !! 67 dnf install gcc-plugin-devel
94 <<
95 Or on Fedora when using cross-compilers that i <<
96 <<
97 dnf install libmpc-devel <<
98 68
99 Enable the GCC plugin infrastructure and some 69 Enable the GCC plugin infrastructure and some plugin(s) you want to use
100 in the kernel config:: 70 in the kernel config::
101 71
102 CONFIG_GCC_PLUGINS=y 72 CONFIG_GCC_PLUGINS=y
>> 73 CONFIG_GCC_PLUGIN_CYC_COMPLEXITY=y
103 CONFIG_GCC_PLUGIN_LATENT_ENTROPY=y 74 CONFIG_GCC_PLUGIN_LATENT_ENTROPY=y
104 ... 75 ...
105 76
106 Run gcc (native or cross-compiler) to ensure p <<
107 <<
108 gcc -print-file-name=plugin <<
109 CROSS_COMPILE=arm-linux-gnu- ${CROSS_C <<
110 <<
111 The word "plugin" means they are not detected: <<
112 <<
113 plugin <<
114 <<
115 A full path means they are detected:: <<
116 <<
117 /usr/lib/gcc/x86_64-redhat-linux/12/plu <<
118 <<
119 To compile the minimum tool set including the 77 To compile the minimum tool set including the plugin(s)::
120 78
121 make scripts 79 make scripts
122 80
123 or just run the kernel make and compile the wh 81 or just run the kernel make and compile the whole kernel with
124 the cyclomatic complexity GCC plugin. 82 the cyclomatic complexity GCC plugin.
125 83
126 84
127 4. How to add a new GCC plugin 85 4. How to add a new GCC plugin
128 ============================== 86 ==============================
129 87
130 The GCC plugins are in scripts/gcc-plugins/. Y 88 The GCC plugins are in scripts/gcc-plugins/. You need to put plugin source files
131 right under scripts/gcc-plugins/. Creating sub 89 right under scripts/gcc-plugins/. Creating subdirectories is not supported.
132 It must be added to scripts/gcc-plugins/Makefi 90 It must be added to scripts/gcc-plugins/Makefile, scripts/Makefile.gcc-plugins
133 and a relevant Kconfig file. 91 and a relevant Kconfig file.
>> 92 See the cyc_complexity_plugin.c (CONFIG_GCC_PLUGIN_CYC_COMPLEXITY) GCC plugin.
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