Commit 164c9201 authored by Josh Poimboeuf's avatar Josh Poimboeuf
Browse files

objtool: Add base objtool support for livepatch modules 



In preparation for klp-build, enable "classic" objtool to work on
livepatch modules:

  - Avoid duplicate symbol/section warnings for prefix symbols and the
    .static_call_sites and __mcount_loc sections which may have already
    been extracted by klp diff.

  - Add __klp_funcs to the IBT function pointer section whitelist.

  - Prevent KLP symbols from getting incorrectly classified as cold
    subfunctions.

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 2058f6d1

tools/objtool/check.c

+47 −5
Original line number Diff line number Diff line
@@ -3,6 +3,7 @@ 
 * Copyright (C) 2015-2017 Josh Poimboeuf <jpoimboe@redhat.com>

 */



#define _GNU_SOURCE /* memmem() */

#include <string.h>

#include <stdlib.h>

#include <inttypes.h>
@@ -611,6 +612,20 @@ static int init_pv_ops(struct objtool_file *file) 
	return 0;

}



static bool is_livepatch_module(struct objtool_file *file)

{

	struct section *sec;



	if (!opts.module)

		return false;



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

	if (!sec)

		return false;



	return memmem(sec->data->d_buf, sec_size(sec), "\0livepatch=Y", 12);

}



static int create_static_call_sections(struct objtool_file *file)

{

	struct static_call_site *site;
@@ -622,7 +637,14 @@ static int create_static_call_sections(struct objtool_file *file) 


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

	if (sec) {

		/*

		 * Livepatch modules may have already extracted the static call

		 * site entries to take advantage of vmlinux static call

		 * privileges.

		 */

		if (!file->klp)

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



		return 0;

	}
@@ -666,7 +688,7 @@ static int create_static_call_sections(struct objtool_file *file) 


		key_sym = find_symbol_by_name(file->elf, tmp);

		if (!key_sym) {

			if (!opts.module) {

			if (!opts.module || file->klp) {

				ERROR("static_call: can't find static_call_key symbol: %s", tmp);

				return -1;

			}
@@ -885,7 +907,13 @@ static int create_mcount_loc_sections(struct objtool_file *file) 


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

	if (sec) {

		/*

		 * Livepatch modules have already extracted their __mcount_loc

		 * entries to cover the !CONFIG_FTRACE_MCOUNT_USE_OBJTOOL case.

		 */

		if (!file->klp)

			WARN("file already has __mcount_loc section, skipping");



		return 0;

	}
@@ -2569,6 +2597,8 @@ static bool validate_branch_enabled(void) 


static int decode_sections(struct objtool_file *file)

{

	file->klp = is_livepatch_module(file);



	mark_rodata(file);



	if (init_pv_ops(file))
@@ -4244,6 +4274,9 @@ static bool ignore_unreachable_insn(struct objtool_file *file, struct instructio 
 *   - compiler cloned functions (*.cold, *.part0, etc)

 *   - asm functions created with inline asm or without SYM_FUNC_START()

 *

 * Also, the function may already have a prefix from a previous objtool run

 * (livepatch extracted functions, or manually running objtool multiple times).

 *

 * So return 0 if the NOPs are missing or the function already has a prefix

 * symbol.

 */
@@ -4266,6 +4299,14 @@ static int create_prefix_symbol(struct objtool_file *file, struct symbol *func) 
	if (snprintf_check(name, SYM_NAME_LEN, "__pfx_%s", func->name))

		return -1;



	if (file->klp) {

		struct symbol *pfx;



		pfx = find_symbol_by_offset(func->sec, func->offset - opts.prefix);

		if (pfx && is_prefix_func(pfx) && !strcmp(pfx->name, name))

			return 0;

	}



	insn = find_insn(file, func->sec, func->offset);

	if (!insn) {

		WARN("%s: can't find starting instruction", func->name);
@@ -4618,6 +4659,7 @@ static int validate_ibt(struct objtool_file *file) 
		    !strncmp(sec->name, ".debug", 6)			||

		    !strcmp(sec->name, ".altinstructions")		||

		    !strcmp(sec->name, ".ibt_endbr_seal")		||

		    !strcmp(sec->name, ".kcfi_traps")			||

		    !strcmp(sec->name, ".orc_unwind_ip")		||

		    !strcmp(sec->name, ".retpoline_sites")		||

		    !strcmp(sec->name, ".smp_locks")			||
@@ -4627,12 +4669,12 @@ static int validate_ibt(struct objtool_file *file) 
		    !strcmp(sec->name, "__bug_table")			||

		    !strcmp(sec->name, "__ex_table")			||

		    !strcmp(sec->name, "__jump_table")			||

		    !strcmp(sec->name, "__klp_funcs")			||

		    !strcmp(sec->name, "__mcount_loc")			||

		    !strcmp(sec->name, ".kcfi_traps")			||

		    !strcmp(sec->name, ".llvm.call-graph-profile")	||

		    !strcmp(sec->name, ".llvm_bb_addr_map")		||

		    !strcmp(sec->name, "__tracepoints")			||

		    strstr(sec->name, "__patchable_function_entries"))

		    !strcmp(sec->name, "__patchable_function_entries"))

			continue;



		for_each_reloc(sec->rsec, reloc)

tools/objtool/elf.c

+4 −1
Original line number Diff line number Diff line
@@ -499,7 +499,10 @@ static int elf_add_symbol(struct elf *elf, struct symbol *sym) 
	     strstarts(sym->name, "__pi___cfi_")))

		sym->prefix = 1;



	if (is_func_sym(sym) && strstr(sym->name, ".cold"))

	if (strstarts(sym->name, ".klp.sym"))

		sym->klp = 1;



	if (!sym->klp && is_func_sym(sym) && strstr(sym->name, ".cold"))

		sym->cold = 1;

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

tools/objtool/include/objtool/elf.h

+1 −0
Original line number Diff line number Diff line
@@ -88,6 +88,7 @@ struct symbol { 
	u8 debug_checksum    : 1;

	u8 changed	     : 1;

	u8 included	     : 1;

	u8 klp		     : 1;

	struct list_head pv_target;

	struct reloc *relocs;

	struct section *group_sec;

tools/objtool/include/objtool/objtool.h

+1 −1
Original line number Diff line number Diff line
@@ -28,7 +28,7 @@ struct objtool_file { 
	struct list_head mcount_loc_list;

	struct list_head endbr_list;

	struct list_head call_list;

	bool ignore_unreachables, hints, rodata;

	bool ignore_unreachables, hints, rodata, klp;



	unsigned int nr_endbr;

	unsigned int nr_endbr_int;