Commit 0d83da43 authored by Josh Poimboeuf's avatar Josh Poimboeuf
Browse files

objtool/klp: Add --checksum option to generate per-function checksums 



In preparation for the objtool klp diff subcommand, add a command-line
option to generate a unique checksum for each function.  This will
enable detection of functions which have changed between two versions of
an object file.

Acked-by: default avatarPetr Mladek <pmladek@suse.com>
Tested-by: default avatarJoe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@kernel.org>
parent f6b740ef

tools/objtool/Makefile

+24 −14
Original line number Diff line number Diff line
@@ -2,6 +2,27 @@ 
include ../scripts/Makefile.include

include ../scripts/Makefile.arch



ifeq ($(SRCARCH),x86)

	BUILD_ORC    := y

	ARCH_HAS_KLP := y

endif



ifeq ($(SRCARCH),loongarch)

	BUILD_ORC	   := y

endif



ifeq ($(ARCH_HAS_KLP),y)

	HAVE_XXHASH = $(shell echo "int main() {}" | \

		      $(HOSTCC) -xc - -o /dev/null -lxxhash 2> /dev/null && echo y || echo n)

	ifeq ($(HAVE_XXHASH),y)

		LIBXXHASH_CFLAGS := $(shell $(HOSTPKG_CONFIG) libxxhash --cflags 2>/dev/null) \

				    -DBUILD_KLP

		LIBXXHASH_LIBS   := $(shell $(HOSTPKG_CONFIG) libxxhash --libs 2>/dev/null || echo -lxxhash)

	endif

endif



export BUILD_ORC



ifeq ($(srctree),)

srctree := $(patsubst %/,%,$(dir $(CURDIR)))

srctree := $(patsubst %/,%,$(dir $(srctree)))
@@ -36,10 +57,10 @@ INCLUDES := -I$(srctree)/tools/include \ 
	    -I$(srctree)/tools/objtool/arch/$(SRCARCH)/include \

	    -I$(LIBSUBCMD_OUTPUT)/include



OBJTOOL_CFLAGS  := -std=gnu11 -fomit-frame-pointer -O2 -g \

		   $(WARNINGS) $(INCLUDES) $(LIBELF_FLAGS) $(HOSTCFLAGS)

OBJTOOL_CFLAGS  := -std=gnu11 -fomit-frame-pointer -O2 -g $(WARNINGS)	\

		   $(INCLUDES) $(LIBELF_FLAGS) $(LIBXXHASH_CFLAGS) $(HOSTCFLAGS)



OBJTOOL_LDFLAGS := $(LIBSUBCMD) $(LIBELF_LIBS) $(HOSTLDFLAGS)

OBJTOOL_LDFLAGS := $(LIBSUBCMD) $(LIBELF_LIBS) $(LIBXXHASH_LIBS) $(HOSTLDFLAGS)



# Allow old libelf to be used:

elfshdr := $(shell echo '$(pound)include <libelf.h>' | $(HOSTCC) $(OBJTOOL_CFLAGS) -x c -E - 2>/dev/null | grep elf_getshdr)
@@ -51,17 +72,6 @@ HOST_OVERRIDES := CC="$(HOSTCC)" LD="$(HOSTLD)" AR="$(HOSTAR)" 
AWK = awk

MKDIR = mkdir



BUILD_ORC := n



ifeq ($(SRCARCH),x86)

	BUILD_ORC := y

endif



ifeq ($(SRCARCH),loongarch)

	BUILD_ORC := y

endif



export BUILD_ORC

export srctree OUTPUT CFLAGS SRCARCH AWK

include $(srctree)/tools/build/Makefile.include

tools/objtool/builtin-check.c

+10 −1
Original line number Diff line number Diff line
@@ -73,6 +73,7 @@ static int parse_hacks(const struct option *opt, const char *str, int unset) 


static const struct option check_options[] = {

	OPT_GROUP("Actions:"),

	OPT_BOOLEAN(0,		 "checksum", &opts.checksum, "generate per-function checksums"),

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

	OPT_CALLBACK_OPTARG('h', "hacks", NULL, NULL, "jump_label,noinstr,skylake", "patch toolchain bugs/limitations", parse_hacks),

	OPT_BOOLEAN('i',	 "ibt", &opts.ibt, "validate and annotate IBT"),
@@ -160,7 +161,15 @@ static bool opts_valid(void) 
		return false;

	}



	if (opts.hack_jump_label	||

#ifndef BUILD_KLP

	if (opts.checksum) {

		ERROR("--checksum not supported; install xxhash-devel and recompile");

		return false;

	}

#endif



	if (opts.checksum		||

	    opts.hack_jump_label	||

	    opts.hack_noinstr		||

	    opts.ibt			||

	    opts.mcount			||

tools/objtool/check.c

+136 −5
Original line number Diff line number Diff line
@@ -14,6 +14,7 @@ 
#include <objtool/check.h>

#include <objtool/special.h>

#include <objtool/warn.h>

#include <objtool/checksum.h>



#include <linux/objtool_types.h>

#include <linux/hashtable.h>
@@ -971,6 +972,59 @@ static int create_direct_call_sections(struct objtool_file *file) 
	return 0;

}



#ifdef BUILD_KLP

static int create_sym_checksum_section(struct objtool_file *file)

{

	struct section *sec;

	struct symbol *sym;

	unsigned int idx = 0;

	struct sym_checksum *checksum;

	size_t entsize = sizeof(struct sym_checksum);



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

	if (sec) {

		if (!opts.dryrun)

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



		return 0;

	}



	for_each_sym(file->elf, sym)

		if (sym->csum.checksum)

			idx++;



	if (!idx)

		return 0;



	sec = elf_create_section_pair(file->elf, ".discard.sym_checksum", entsize,

				      idx, idx);

	if (!sec)

		return -1;



	idx = 0;

	for_each_sym(file->elf, sym) {

		if (!sym->csum.checksum)

			continue;



		if (!elf_init_reloc(file->elf, sec->rsec, idx, idx * entsize,

				    sym, 0, R_TEXT64))

			return -1;



		checksum = (struct sym_checksum *)sec->data->d_buf + idx;

		checksum->addr = 0; /* reloc */

		checksum->checksum = sym->csum.checksum;



		mark_sec_changed(file->elf, sec, true);



		idx++;

	}



	return 0;

}

#else

static int create_sym_checksum_section(struct objtool_file *file) { return -EINVAL; }

#endif



/*

 * Warnings shouldn't be reported for ignored functions.

 */
@@ -1748,6 +1802,7 @@ static int handle_group_alt(struct objtool_file *file, 
		nop->type = INSN_NOP;

		nop->sym = orig_insn->sym;

		nop->alt_group = new_alt_group;

		nop->fake = 1;

	}



	if (!special_alt->new_len) {
@@ -2517,6 +2572,14 @@ static void mark_holes(struct objtool_file *file) 
	}

}



static bool validate_branch_enabled(void)

{

	return opts.stackval ||

	       opts.orc ||

	       opts.uaccess ||

	       opts.checksum;

}



static int decode_sections(struct objtool_file *file)

{

	mark_rodata(file);
@@ -2545,8 +2608,7 @@ static int decode_sections(struct objtool_file *file) 
	 * Must be before add_jump_destinations(), which depends on 'func'

	 * being set for alternatives, to enable proper sibling call detection.

	 */

	if (opts.stackval || opts.orc || opts.uaccess || opts.noinstr ||

	    opts.hack_jump_label) {

	if (validate_branch_enabled() || opts.noinstr || opts.hack_jump_label) {

		if (add_special_section_alts(file))

			return -1;

	}
@@ -3518,6 +3580,50 @@ static bool skip_alt_group(struct instruction *insn) 
	return alt_insn->type == INSN_CLAC || alt_insn->type == INSN_STAC;

}



static void checksum_update_insn(struct objtool_file *file, struct symbol *func,

				 struct instruction *insn)

{

	struct reloc *reloc = insn_reloc(file, insn);

	unsigned long offset;

	struct symbol *sym;



	if (insn->fake)

		return;



	checksum_update(func, insn, insn->sec->data->d_buf + insn->offset, insn->len);



	if (!reloc) {

		struct symbol *call_dest = insn_call_dest(insn);



		if (call_dest)

			checksum_update(func, insn, call_dest->demangled_name,

					strlen(call_dest->demangled_name));

		return;

	}



	sym = reloc->sym;

	offset = arch_insn_adjusted_addend(insn, reloc);



	if (is_string_sec(sym->sec)) {

		char *str;



		str = sym->sec->data->d_buf + sym->offset + offset;

		checksum_update(func, insn, str, strlen(str));

		return;

	}



	if (is_sec_sym(sym)) {

		sym = find_symbol_containing(reloc->sym->sec, offset);

		if (!sym)

			return;



		offset -= sym->offset;

	}



	checksum_update(func, insn, sym->demangled_name, strlen(sym->demangled_name));

	checksum_update(func, insn, &offset, sizeof(offset));

}



/*

 * Follow the branch starting at the given instruction, and recursively follow

 * any other branches (jumps).  Meanwhile, track the frame pointer state at
@@ -3538,6 +3644,9 @@ static int validate_branch(struct objtool_file *file, struct symbol *func, 
	while (1) {

		next_insn = next_insn_to_validate(file, insn);



		if (opts.checksum && func && insn->sec)

			checksum_update_insn(file, func, insn);



		if (func && insn_func(insn) && func != insn_func(insn)->pfunc) {

			/* Ignore KCFI type preambles, which always fall through */

			if (is_prefix_func(func))
@@ -3787,7 +3896,13 @@ static int validate_unwind_hint(struct objtool_file *file, 
				  struct insn_state *state)

{

	if (insn->hint && !insn->visited) {

		int ret = validate_branch(file, insn_func(insn), insn, *state);

		struct symbol *func = insn_func(insn);

		int ret;



		if (opts.checksum)

			checksum_init(func);



		ret = validate_branch(file, func, insn, *state);

		if (ret)

			BT_INSN(insn, "<=== (hint)");

		return ret;
@@ -4166,6 +4281,7 @@ static int validate_symbol(struct objtool_file *file, struct section *sec, 
			   struct symbol *sym, struct insn_state *state)

{

	struct instruction *insn;

	struct symbol *func;

	int ret;



	if (!sym->len) {
@@ -4183,9 +4299,18 @@ static int validate_symbol(struct objtool_file *file, struct section *sec, 
	if (opts.uaccess)

		state->uaccess = sym->uaccess_safe;



	ret = validate_branch(file, insn_func(insn), insn, *state);

	func = insn_func(insn);



	if (opts.checksum)

		checksum_init(func);



	ret = validate_branch(file, func, insn, *state);

	if (ret)

		BT_INSN(insn, "<=== (sym)");



	if (opts.checksum)

		checksum_finish(func);



	return ret;

}
@@ -4703,7 +4828,7 @@ int check(struct objtool_file *file) 
	if (opts.retpoline)

		warnings += validate_retpoline(file);



	if (opts.stackval || opts.orc || opts.uaccess) {

	if (validate_branch_enabled()) {

		int w = 0;



		w += validate_functions(file);
@@ -4782,6 +4907,12 @@ int check(struct objtool_file *file) 
	if (opts.noabs)

		warnings += check_abs_references(file);



	if (opts.checksum) {

		ret = create_sym_checksum_section(file);

		if (ret)

			goto out;

	}



	if (opts.orc && nr_insns) {

		ret = orc_create(file);

		if (ret)

tools/objtool/elf.c

+43 −3
Original line number Diff line number Diff line
@@ -17,6 +17,7 @@ 
#include <unistd.h>

#include <errno.h>

#include <libgen.h>

#include <ctype.h>

#include <linux/interval_tree_generic.h>

#include <objtool/builtin.h>

#include <objtool/elf.h>
@@ -412,7 +413,38 @@ static int read_sections(struct elf *elf) 
	return 0;

}



static void elf_add_symbol(struct elf *elf, struct symbol *sym)

static const char *demangle_name(struct symbol *sym)

{

	char *str;



	if (!is_local_sym(sym))

		return sym->name;



	if (!is_func_sym(sym) && !is_object_sym(sym))

		return sym->name;



	if (!strstarts(sym->name, "__UNIQUE_ID_") && !strchr(sym->name, '.'))

		return sym->name;



	str = strdup(sym->name);

	if (!str) {

		ERROR_GLIBC("strdup");

		return NULL;

	}



	for (int i = strlen(str) - 1; i >= 0; i--) {

		char c = str[i];



		if (!isdigit(c) && c != '.') {

			str[i + 1] = '\0';

			break;

		}

	};



	return str;

}



static int elf_add_symbol(struct elf *elf, struct symbol *sym)

{

	struct list_head *entry;

	struct rb_node *pnode;
@@ -456,6 +488,12 @@ static void elf_add_symbol(struct elf *elf, struct symbol *sym) 
	if (is_func_sym(sym) && strstr(sym->name, ".cold"))

		sym->cold = 1;

	sym->pfunc = sym->cfunc = sym;



	sym->demangled_name = demangle_name(sym);

	if (!sym->demangled_name)

		return -1;



	return 0;

}



static int read_symbols(struct elf *elf)
@@ -529,7 +567,8 @@ static int read_symbols(struct elf *elf) 
		} else

			sym->sec = find_section_by_index(elf, 0);



		elf_add_symbol(elf, sym);

		if (elf_add_symbol(elf, sym))

			return -1;

	}



	if (opts.stats) {
@@ -867,7 +906,8 @@ struct symbol *elf_create_symbol(struct elf *elf, const char *name, 
		mark_sec_changed(elf, symtab_shndx, true);

	}



	elf_add_symbol(elf, sym);

	if (elf_add_symbol(elf, sym))

		return NULL;



	return sym;

}

tools/objtool/include/objtool/builtin.h

+3 −2
Original line number Diff line number Diff line
@@ -9,12 +9,15 @@ 


struct opts {

	/* actions: */

	bool cfi;

	bool checksum;

	bool dump_orc;

	bool hack_jump_label;

	bool hack_noinstr;

	bool hack_skylake;

	bool ibt;

	bool mcount;

	bool noabs;

	bool noinstr;

	bool orc;

	bool retpoline;
@@ -25,8 +28,6 @@ struct opts { 
	bool static_call;

	bool uaccess;

	int prefix;

	bool cfi;

	bool noabs;



	/* options: */

	bool backtrace;