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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169// SPDX-License-Identifier: GPL-2.0-or-later/* * Read the intermediate KLP reloc/symbol representations created by klp diff * and convert them to the proper format required by livepatch. This needs to * run last to avoid linker wreckage. Linkers don't tend to handle the "two * rela sections for a single base section" case very well, nor do they like * SHN_LIVEPATCH. * * This is the final tool in the livepatch module generation pipeline: * * kernel builds -> objtool klp diff -> module link -> objtool klp post-link */
#include <fcntl.h>#include <gelf.h>#include <objtool/objtool.h>#include <objtool/warn.h>#include <objtool/klp.h>#include <objtool/util.h>#include <linux/livepatch_external.h>
static int fix_klp_relocs(struct elf *elf){ struct section *symtab, *klp_relocs;
klp_relocs = find_section_by_name(elf, KLP_RELOCS_SEC); if (!klp_relocs) return 0;
symtab = find_section_by_name(elf, ".symtab"); if (!symtab) { ERROR("missing .symtab"); return -1; }
for (int i = 0; i < sec_size(klp_relocs) / sizeof(struct klp_reloc); i++) { struct klp_reloc *klp_reloc; unsigned long klp_reloc_off; struct section *sec, *tmp, *klp_rsec; unsigned long offset; struct reloc *reloc; char sym_modname[64]; char rsec_name[SEC_NAME_LEN]; u64 addend; struct symbol *sym, *klp_sym;
klp_reloc_off = i * sizeof(*klp_reloc); klp_reloc = klp_relocs->data->d_buf + klp_reloc_off;
/* * Read __klp_relocs[i]: */
/* klp_reloc.sec_offset */ reloc = find_reloc_by_dest(elf, klp_relocs, klp_reloc_off + offsetof(struct klp_reloc, offset)); if (!reloc) { ERROR("malformed " KLP_RELOCS_SEC " section"); return -1; }
sec = reloc->sym->sec; offset = reloc_addend(reloc);
/* klp_reloc.sym */ reloc = find_reloc_by_dest(elf, klp_relocs, klp_reloc_off + offsetof(struct klp_reloc, sym)); if (!reloc) { ERROR("malformed " KLP_RELOCS_SEC " section"); return -1; }
klp_sym = reloc->sym; addend = reloc_addend(reloc);
/* symbol format: .klp.sym.modname.sym_name,sympos */ if (sscanf(klp_sym->name + strlen(KLP_SYM_PREFIX), "%55[^.]", sym_modname) != 1) ERROR("can't find modname in klp symbol '%s'", klp_sym->name);
/* * Create the KLP rela: */
/* section format: .klp.rela.sec_objname.section_name */ if (snprintf_check(rsec_name, SEC_NAME_LEN, KLP_RELOC_SEC_PREFIX "%s.%s", sym_modname, sec->name)) return -1;
klp_rsec = find_section_by_name(elf, rsec_name); if (!klp_rsec) { klp_rsec = elf_create_section(elf, rsec_name, 0, elf_rela_size(elf), SHT_RELA, elf_addr_size(elf), SHF_ALLOC | SHF_INFO_LINK | SHF_RELA_LIVEPATCH); if (!klp_rsec) return -1;
klp_rsec->sh.sh_link = symtab->idx; klp_rsec->sh.sh_info = sec->idx; klp_rsec->base = sec; }
tmp = sec->rsec; sec->rsec = klp_rsec; if (!elf_create_reloc(elf, sec, offset, klp_sym, addend, klp_reloc->type)) return -1; sec->rsec = tmp;
/* * Fix up the corresponding KLP symbol: */
klp_sym->sym.st_shndx = SHN_LIVEPATCH; if (!gelf_update_sym(symtab->data, klp_sym->idx, &klp_sym->sym)) { ERROR_ELF("gelf_update_sym"); return -1; }
/* * Disable the original non-KLP reloc by converting it to R_*_NONE: */
reloc = find_reloc_by_dest(elf, sec, offset); sym = reloc->sym; sym->sym.st_shndx = SHN_LIVEPATCH; set_reloc_type(elf, reloc, 0); if (!gelf_update_sym(symtab->data, sym->idx, &sym->sym)) { ERROR_ELF("gelf_update_sym"); return -1; } }
return 0;}
/* * This runs on the livepatch module after all other linking has been done. It * converts the intermediate __klp_relocs section into proper KLP relocs to be * processed by livepatch. This needs to run last to avoid linker wreckage. * Linkers don't tend to handle the "two rela sections for a single base * section" case very well, nor do they appreciate SHN_LIVEPATCH. */int cmd_klp_post_link(int argc, const char **argv){ struct elf *elf;
argc--; argv++;
if (argc != 1) { fprintf(stderr, "%d\n", argc); fprintf(stderr, "usage: objtool link <file.ko>\n"); return -1; }
elf = elf_open_read(argv[0], O_RDWR); if (!elf) return -1;
if (fix_klp_relocs(elf)) return -1;
if (elf_write(elf)) return -1;
return elf_close(elf);}