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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 | // SPDX-License-Identifier: GPL-2.0 #include <linux/buildid.h> #include <linux/elf.h> #include <linux/pagemap.h> #define BUILD_ID 3 /* * Parse build id from the note segment. This logic can be shared between * 32-bit and 64-bit system, because Elf32_Nhdr and Elf64_Nhdr are * identical. */ static inline int parse_build_id(void *page_addr, unsigned char *build_id, __u32 *size, void *note_start, Elf32_Word note_size) { Elf32_Word note_offs = 0, new_offs; /* check for overflow */ if (note_start < page_addr || note_start + note_size < note_start) return -EINVAL; /* only supports note that fits in the first page */ if (note_start + note_size > page_addr + PAGE_SIZE) return -EINVAL; while (note_offs + sizeof(Elf32_Nhdr) < note_size) { Elf32_Nhdr *nhdr = (Elf32_Nhdr *)(note_start + note_offs); if (nhdr->n_type == BUILD_ID && nhdr->n_namesz == sizeof("GNU") && nhdr->n_descsz > 0 && nhdr->n_descsz <= BUILD_ID_SIZE_MAX) { memcpy(build_id, note_start + note_offs + ALIGN(sizeof("GNU"), 4) + sizeof(Elf32_Nhdr), nhdr->n_descsz); memset(build_id + nhdr->n_descsz, 0, BUILD_ID_SIZE_MAX - nhdr->n_descsz); if (size) *size = nhdr->n_descsz; return 0; } new_offs = note_offs + sizeof(Elf32_Nhdr) + ALIGN(nhdr->n_namesz, 4) + ALIGN(nhdr->n_descsz, 4); if (new_offs <= note_offs) /* overflow */ break; note_offs = new_offs; } return -EINVAL; } /* Parse build ID from 32-bit ELF */ static int get_build_id_32(void *page_addr, unsigned char *build_id, __u32 *size) { Elf32_Ehdr *ehdr = (Elf32_Ehdr *)page_addr; Elf32_Phdr *phdr; int i; /* only supports phdr that fits in one page */ if (ehdr->e_phnum > (PAGE_SIZE - sizeof(Elf32_Ehdr)) / sizeof(Elf32_Phdr)) return -EINVAL; phdr = (Elf32_Phdr *)(page_addr + sizeof(Elf32_Ehdr)); for (i = 0; i < ehdr->e_phnum; ++i) { if (phdr[i].p_type == PT_NOTE && !parse_build_id(page_addr, build_id, size, page_addr + phdr[i].p_offset, phdr[i].p_filesz)) return 0; } return -EINVAL; } /* Parse build ID from 64-bit ELF */ static int get_build_id_64(void *page_addr, unsigned char *build_id, __u32 *size) { Elf64_Ehdr *ehdr = (Elf64_Ehdr *)page_addr; Elf64_Phdr *phdr; int i; /* only supports phdr that fits in one page */ if (ehdr->e_phnum > (PAGE_SIZE - sizeof(Elf64_Ehdr)) / sizeof(Elf64_Phdr)) return -EINVAL; phdr = (Elf64_Phdr *)(page_addr + sizeof(Elf64_Ehdr)); for (i = 0; i < ehdr->e_phnum; ++i) { if (phdr[i].p_type == PT_NOTE && !parse_build_id(page_addr, build_id, size, page_addr + phdr[i].p_offset, phdr[i].p_filesz)) return 0; } return -EINVAL; } /* * Parse build ID of ELF file mapped to vma * @vma: vma object * @build_id: buffer to store build id, at least BUILD_ID_SIZE long * @size: returns actual build id size in case of success * * Returns 0 on success, otherwise error (< 0). */ int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id, __u32 *size) { Elf32_Ehdr *ehdr; struct page *page; void *page_addr; int ret; /* only works for page backed storage */ if (!vma->vm_file) return -EINVAL; page = find_get_page(vma->vm_file->f_mapping, 0); if (!page) return -EFAULT; /* page not mapped */ ret = -EINVAL; page_addr = kmap_atomic(page); ehdr = (Elf32_Ehdr *)page_addr; /* compare magic x7f "ELF" */ if (memcmp(ehdr->e_ident, ELFMAG, SELFMAG) != 0) goto out; /* only support executable file and shared object file */ if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN) goto out; if (ehdr->e_ident[EI_CLASS] == ELFCLASS32) ret = get_build_id_32(page_addr, build_id, size); else if (ehdr->e_ident[EI_CLASS] == ELFCLASS64) ret = get_build_id_64(page_addr, build_id, size); out: kunmap_atomic(page_addr); put_page(page); return ret; } |