// SPDX-License-Identifier: GPL-2.0-or-later/* * Copyright (C) 2015 Josh Poimboeuf <jpoimboe@redhat.com> */ /* * This file reads all the special sections which have alternate instructions * which can be patched in or redirected to at runtime. */ #include <stdlib.h>#include <string.h> #include <arch/special.h>#include <objtool/builtin.h>#include <objtool/special.h>#include <objtool/warn.h> struct special_entry {	const char *sec;	bool group, jump_or_nop;	unsigned char size, orig, new;	unsigned char orig_len, new_len; /* group only */	unsigned char feature; /* ALTERNATIVE macro CPU feature */	unsigned char key; /* jump_label key */}; static const struct special_entry entries[] = {	{		.sec = ".altinstructions",		.group = true,		.size = ALT_ENTRY_SIZE,		.orig = ALT_ORIG_OFFSET,		.orig_len = ALT_ORIG_LEN_OFFSET,		.new = ALT_NEW_OFFSET,		.new_len = ALT_NEW_LEN_OFFSET,		.feature = ALT_FEATURE_OFFSET,	},	{		.sec = "__jump_table",		.jump_or_nop = true,		.size = JUMP_ENTRY_SIZE,		.orig = JUMP_ORIG_OFFSET,		.new = JUMP_NEW_OFFSET,		.key = JUMP_KEY_OFFSET,	},	{		.sec = "__ex_table",		.size = EX_ENTRY_SIZE,		.orig = EX_ORIG_OFFSET,		.new = EX_NEW_OFFSET,	},	{},}; void __weak arch_handle_alternative(struct special_alt *alt){} static void reloc_to_sec_off(struct reloc *reloc, struct section **sec,			     unsigned long *off){	*sec = reloc->sym->sec;	*off = reloc->sym->offset + reloc_addend(reloc);} static int get_alt_entry(struct elf *elf, const struct special_entry *entry,			 struct section *sec, int idx,			 struct special_alt *alt){	struct reloc *orig_reloc, *new_reloc;	unsigned long offset; 	offset = idx * entry->size; 	alt->group = entry->group;	alt->jump_or_nop = entry->jump_or_nop; 	if (alt->group) {		alt->orig_len = *(unsigned char *)(sec->data->d_buf + offset +						   entry->orig_len);		alt->new_len = *(unsigned char *)(sec->data->d_buf + offset +						  entry->new_len);		alt->feature = *(unsigned int *)(sec->data->d_buf + offset +						 entry->feature);	} 	orig_reloc = find_reloc_by_dest(elf, sec, offset + entry->orig);	if (!orig_reloc) {		ERROR_FUNC(sec, offset + entry->orig, "can't find orig reloc");		return -1;	} 	reloc_to_sec_off(orig_reloc, &alt->orig_sec, &alt->orig_off); 	arch_handle_alternative(alt); 	if (!entry->group || alt->new_len) {		new_reloc = find_reloc_by_dest(elf, sec, offset + entry->new);		if (!new_reloc) {			ERROR_FUNC(sec, offset + entry->new, "can't find new reloc");			return -1;		} 		reloc_to_sec_off(new_reloc, &alt->new_sec, &alt->new_off); 		/* _ASM_EXTABLE_EX hack */		if (alt->new_off >= 0x7ffffff0)			alt->new_off -= 0x7ffffff0;	} 	if (entry->key) {		struct reloc *key_reloc; 		key_reloc = find_reloc_by_dest(elf, sec, offset + entry->key);		if (!key_reloc) {			ERROR_FUNC(sec, offset + entry->key, "can't find key reloc");			return -1;		}		alt->key_addend = reloc_addend(key_reloc);	} 	return 0;} /* * Read all the special sections and create a list of special_alt structs which * describe all the alternate instructions which can be patched in or * redirected to at runtime. */int special_get_alts(struct elf *elf, struct list_head *alts){	const struct special_entry *entry;	struct section *sec;	unsigned int nr_entries;	struct special_alt *alt;	int idx; 	INIT_LIST_HEAD(alts); 	for (entry = entries; entry->sec; entry++) {		sec = find_section_by_name(elf, entry->sec);		if (!sec)			continue; 		if (sec_size(sec) % entry->size != 0) {			ERROR("%s size not a multiple of %d", sec->name, entry->size);			return -1;		} 		nr_entries = sec_size(sec) / entry->size; 		for (idx = 0; idx < nr_entries; idx++) {			alt = malloc(sizeof(*alt));			if (!alt) {				ERROR_GLIBC("malloc failed");				return -1;			}			memset(alt, 0, sizeof(*alt)); 			if (get_alt_entry(elf, entry, sec, idx, alt))				return -1; 			list_add_tail(&alt->list, alts);		}	} 	return 0;}