Commit 9a479f76 authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

objtool: Add --cfi to generate the .cfi_sites section 



Add the location of all __cfi_##name symbols (as generated by kCFI) to
a section such that we might re-write things at kernel boot.

Notably; boot time re-hashing and FineIBT are the intended use of
this.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20221027092842.568039454@infradead.org
parent b341b20d

tools/objtool/builtin-check.c

+1 −0
Original line number Diff line number Diff line
@@ -80,6 +80,7 @@ const struct option check_options[] = { 
	OPT_BOOLEAN('s', "stackval", &opts.stackval, "validate frame pointer rules"),

	OPT_BOOLEAN('t', "static-call", &opts.static_call, "annotate static calls"),

	OPT_BOOLEAN('u', "uaccess", &opts.uaccess, "validate uaccess rules for SMAP"),

	OPT_BOOLEAN(0  , "cfi", &opts.cfi, "annotate kernel control flow integrity (kCFI) function preambles"),

	OPT_CALLBACK_OPTARG(0, "dump", NULL, NULL, "orc", "dump metadata", parse_dump),



	OPT_GROUP("Options:"),

tools/objtool/check.c

+69 −0
Original line number Diff line number Diff line
@@ -861,6 +861,68 @@ static int create_ibt_endbr_seal_sections(struct objtool_file *file) 
	return 0;

}



static int create_cfi_sections(struct objtool_file *file)

{

	struct section *sec, *s;

	struct symbol *sym;

	unsigned int *loc;

	int idx;



	sec = find_section_by_name(file->elf, ".cfi_sites");

	if (sec) {

		INIT_LIST_HEAD(&file->call_list);

		WARN("file already has .cfi_sites section, skipping");

		return 0;

	}



	idx = 0;

	for_each_sec(file, s) {

		if (!s->text)

			continue;



		list_for_each_entry(sym, &s->symbol_list, list) {

			if (sym->type != STT_FUNC)

				continue;



			if (strncmp(sym->name, "__cfi_", 6))

				continue;



			idx++;

		}

	}



	sec = elf_create_section(file->elf, ".cfi_sites", 0, sizeof(unsigned int), idx);

	if (!sec)

		return -1;



	idx = 0;

	for_each_sec(file, s) {

		if (!s->text)

			continue;



		list_for_each_entry(sym, &s->symbol_list, list) {

			if (sym->type != STT_FUNC)

				continue;



			if (strncmp(sym->name, "__cfi_", 6))

				continue;



			loc = (unsigned int *)sec->data->d_buf + idx;

			memset(loc, 0, sizeof(unsigned int));



			if (elf_add_reloc_to_insn(file->elf, sec,

						  idx * sizeof(unsigned int),

						  R_X86_64_PC32,

						  s, sym->offset))

				return -1;



			idx++;

		}

	}



	return 0;

}



static int create_mcount_loc_sections(struct objtool_file *file)

{

	struct section *sec;
@@ -4430,6 +4492,13 @@ int check(struct objtool_file *file) 
		warnings += ret;

	}



	if (opts.cfi) {

		ret = create_cfi_sections(file);

		if (ret < 0)

			goto out;

		warnings += ret;

	}



	if (opts.rethunk) {

		ret = create_return_sites_sections(file);

		if (ret < 0)

tools/objtool/include/objtool/builtin.h

+1 −0
Original line number Diff line number Diff line
@@ -27,6 +27,7 @@ struct opts { 
	bool static_call;

	bool uaccess;

	int prefix;

	bool cfi;



	/* options: */

	bool backtrace;