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1 #ifndef _LINUX_ELFNOTE_H |
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2 #define _LINUX_ELFNOTE_H |
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3 /* |
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4 * Helper macros to generate ELF Note structures, which are put into a |
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5 * PT_NOTE segment of the final vmlinux image. These are useful for |
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6 * including name-value pairs of metadata into the kernel binary (or |
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7 * modules?) for use by external programs. |
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8 * |
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9 * Each note has three parts: a name, a type and a desc. The name is |
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10 * intended to distinguish the note's originator, so it would be a |
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11 * company, project, subsystem, etc; it must be in a suitable form for |
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12 * use in a section name. The type is an integer which is used to tag |
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13 * the data, and is considered to be within the "name" namespace (so |
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14 * "FooCo"'s type 42 is distinct from "BarProj"'s type 42). The |
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15 * "desc" field is the actual data. There are no constraints on the |
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16 * desc field's contents, though typically they're fairly small. |
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17 * |
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18 * All notes from a given NAME are put into a section named |
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19 * .note.NAME. When the kernel image is finally linked, all the notes |
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20 * are packed into a single .notes section, which is mapped into the |
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21 * PT_NOTE segment. Because notes for a given name are grouped into |
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22 * the same section, they'll all be adjacent the output file. |
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23 * |
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24 * This file defines macros for both C and assembler use. Their |
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25 * syntax is slightly different, but they're semantically similar. |
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26 * |
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27 * See the ELF specification for more detail about ELF notes. |
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28 */ |
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29 |
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30 #ifdef __ASSEMBLER__ |
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31 /* |
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32 * Generate a structure with the same shape as Elf{32,64}_Nhdr (which |
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33 * turn out to be the same size and shape), followed by the name and |
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34 * desc data with appropriate padding. The 'desctype' argument is the |
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35 * assembler pseudo op defining the type of the data e.g. .asciz while |
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36 * 'descdata' is the data itself e.g. "hello, world". |
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37 * |
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38 * e.g. ELFNOTE(XYZCo, 42, .asciz, "forty-two") |
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39 * ELFNOTE(XYZCo, 12, .long, 0xdeadbeef) |
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40 */ |
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41 #define ELFNOTE_START(name, type, flags) \ |
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42 .pushsection .note.name, flags,@note ; \ |
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43 .balign 4 ; \ |
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44 .long 2f - 1f /* namesz */ ; \ |
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45 .long 4484f - 3f /* descsz */ ; \ |
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46 .long type ; \ |
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47 1:.asciz #name ; \ |
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48 2:.balign 4 ; \ |
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49 3: |
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50 |
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51 #define ELFNOTE_END \ |
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52 4484:.balign 4 ; \ |
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53 .popsection ; |
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54 |
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55 #define ELFNOTE(name, type, desc) \ |
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56 ELFNOTE_START(name, type, "") \ |
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57 desc ; \ |
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58 ELFNOTE_END |
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59 |
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60 #else /* !__ASSEMBLER__ */ |
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61 #include <linux/elf.h> |
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62 /* |
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63 * Use an anonymous structure which matches the shape of |
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64 * Elf{32,64}_Nhdr, but includes the name and desc data. The size and |
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65 * type of name and desc depend on the macro arguments. "name" must |
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66 * be a literal string, and "desc" must be passed by value. You may |
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67 * only define one note per line, since __LINE__ is used to generate |
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68 * unique symbols. |
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69 */ |
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70 #define _ELFNOTE_PASTE(a,b) a##b |
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71 #define _ELFNOTE(size, name, unique, type, desc) \ |
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72 static const struct { \ |
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73 struct elf##size##_note _nhdr; \ |
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74 unsigned char _name[sizeof(name)] \ |
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75 __attribute__((aligned(sizeof(Elf##size##_Word)))); \ |
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76 typeof(desc) _desc \ |
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77 __attribute__((aligned(sizeof(Elf##size##_Word)))); \ |
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78 } _ELFNOTE_PASTE(_note_, unique) \ |
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79 __used \ |
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80 __attribute__((section(".note." name), \ |
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81 aligned(sizeof(Elf##size##_Word)), \ |
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82 unused)) = { \ |
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83 { \ |
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84 sizeof(name), \ |
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85 sizeof(desc), \ |
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86 type, \ |
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87 }, \ |
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88 name, \ |
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89 desc \ |
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90 } |
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91 #define ELFNOTE(size, name, type, desc) \ |
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92 _ELFNOTE(size, name, __LINE__, type, desc) |
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93 |
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94 #define ELFNOTE32(name, type, desc) ELFNOTE(32, name, type, desc) |
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95 #define ELFNOTE64(name, type, desc) ELFNOTE(64, name, type, desc) |
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96 #endif /* __ASSEMBLER__ */ |
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97 |
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98 #endif /* _LINUX_ELFNOTE_H */ |