/* * Copyright (C) 2014 Linaro Ltd. <ard.biesheuvel@linaro.org> * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. */ #include <linux/elf.h>#include <linux/kernel.h>#include <linux/module.h> #include <asm/cache.h>#include <asm/opcodes.h> #define PLT_ENT_STRIDE		L1_CACHE_BYTES#define PLT_ENT_COUNT		(PLT_ENT_STRIDE / sizeof(u32))#define PLT_ENT_SIZE		(sizeof(struct plt_entries) / PLT_ENT_COUNT) #ifdef CONFIG_THUMB2_KERNEL#define PLT_ENT_LDR		__opcode_to_mem_thumb32(0xf8dff000 | \							(PLT_ENT_STRIDE - 4))#else#define PLT_ENT_LDR		__opcode_to_mem_arm(0xe59ff000 | \						    (PLT_ENT_STRIDE - 8))#endif struct plt_entries {	u32	ldr[PLT_ENT_COUNT];	u32	lit[PLT_ENT_COUNT];}; static bool in_init(const struct module *mod, u32 addr){	return addr - (u32)mod->module_init < mod->init_size;} u32 get_module_plt(struct module *mod, unsigned long loc, Elf32_Addr val){	struct plt_entries *plt, *plt_end;	int c, *count; 	if (in_init(mod, loc)) {		plt = (void *)mod->arch.init_plt->sh_addr;		plt_end = (void *)plt + mod->arch.init_plt->sh_size;		count = &mod->arch.init_plt_count;	} else {		plt = (void *)mod->arch.core_plt->sh_addr;		plt_end = (void *)plt + mod->arch.core_plt->sh_size;		count = &mod->arch.core_plt_count;	} 	/* Look for an existing entry pointing to 'val' */	for (c = *count; plt < plt_end; c -= PLT_ENT_COUNT, plt++) {		int i; 		if (!c) {			/* Populate a new set of entries */			*plt = (struct plt_entries){				{ [0 ... PLT_ENT_COUNT - 1] = PLT_ENT_LDR, },				{ val, }			};			++*count;			return (u32)plt->ldr;		}		for (i = 0; i < PLT_ENT_COUNT; i++) {			if (!plt->lit[i]) {				plt->lit[i] = val;				++*count;			}			if (plt->lit[i] == val)				return (u32)&plt->ldr[i];		}	}	BUG();} static int duplicate_rel(Elf32_Addr base, const Elf32_Rel *rel, int num,			   u32 mask){	u32 *loc1, *loc2;	int i; 	for (i = 0; i < num; i++) {		if (rel[i].r_info != rel[num].r_info)			continue; 		/*		 * Identical relocation types against identical symbols can		 * still result in different PLT entries if the addend in the		 * place is different. So resolve the target of the relocation		 * to compare the values.		 */		loc1 = (u32 *)(base + rel[i].r_offset);		loc2 = (u32 *)(base + rel[num].r_offset);		if (((*loc1 ^ *loc2) & mask) == 0)			return 1;	}	return 0;} /* Count how many PLT entries we may need */static unsigned int count_plts(Elf32_Addr base, const Elf32_Rel *rel, int num){	unsigned int ret = 0;	int i; 	/*	 * Sure, this is order(n^2), but it's usually short, and not	 * time critical	 */	for (i = 0; i < num; i++)		switch (ELF32_R_TYPE(rel[i].r_info)) {		case R_ARM_CALL:		case R_ARM_PC24:		case R_ARM_JUMP24:			if (!duplicate_rel(base, rel, i,					   __opcode_to_mem_arm(0x00ffffff)))				ret++;			break;#ifdef CONFIG_THUMB2_KERNEL		case R_ARM_THM_CALL:		case R_ARM_THM_JUMP24:			if (!duplicate_rel(base, rel, i,					   __opcode_to_mem_thumb32(0x07ff2fff)))				ret++;#endif		}	return ret;} int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,			      char *secstrings, struct module *mod){	unsigned long core_plts = 0, init_plts = 0;	Elf32_Shdr *s, *sechdrs_end = sechdrs + ehdr->e_shnum; 	/*	 * To store the PLTs, we expand the .text section for core module code	 * and the .init.text section for initialization code.	 */	for (s = sechdrs; s < sechdrs_end; ++s)		if (strcmp(".core.plt", secstrings + s->sh_name) == 0)			mod->arch.core_plt = s;		else if (strcmp(".init.plt", secstrings + s->sh_name) == 0)			mod->arch.init_plt = s; 	if (!mod->arch.core_plt || !mod->arch.init_plt) {		pr_err("%s: sections missing\n", mod->name);		return -ENOEXEC;	} 	for (s = sechdrs + 1; s < sechdrs_end; ++s) {		const Elf32_Rel *rels = (void *)ehdr + s->sh_offset;		int numrels = s->sh_size / sizeof(Elf32_Rel);		Elf32_Shdr *dstsec = sechdrs + s->sh_info; 		if (s->sh_type != SHT_REL)			continue; 		if (strstr(secstrings + s->sh_name, ".init"))			init_plts += count_plts(dstsec->sh_addr, rels, numrels);		else			core_plts += count_plts(dstsec->sh_addr, rels, numrels);	} 	mod->arch.core_plt->sh_type = SHT_NOBITS;	mod->arch.core_plt->sh_flags = SHF_EXECINSTR | SHF_ALLOC;	mod->arch.core_plt->sh_addralign = L1_CACHE_BYTES;	mod->arch.core_plt->sh_size = round_up(core_plts * PLT_ENT_SIZE,					       sizeof(struct plt_entries));	mod->arch.core_plt_count = 0; 	mod->arch.init_plt->sh_type = SHT_NOBITS;	mod->arch.init_plt->sh_flags = SHF_EXECINSTR | SHF_ALLOC;	mod->arch.init_plt->sh_addralign = L1_CACHE_BYTES;	mod->arch.init_plt->sh_size = round_up(init_plts * PLT_ENT_SIZE,					       sizeof(struct plt_entries));	mod->arch.init_plt_count = 0;	pr_debug("%s: core.plt=%x, init.plt=%x\n", __func__,		 mod->arch.core_plt->sh_size, mod->arch.init_plt->sh_size);	return 0;}