tools/objtool/klp-post-link.c

Source file repositories/reference/linux-study-clean/tools/objtool/klp-post-link.c

File Facts

System
Linux kernel
Corpus path
tools/objtool/klp-post-link.c
Extension
.c
Size
4323 bytes
Lines
169
Domain
Support Tooling And Documentation
Bucket
tools
Inferred role
Support Tooling And Documentation: implementation source
Status
source implementation candidate

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Dependency Surface

Detected Declarations

Annotated Snippet

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;

Annotation

Implementation Notes