// 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);}