arch/x86/kernel/module.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*  Kernel module help for x86.
     Copyright (C) 2001 Rusty Russell.

 */

 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

 #include <linux/moduleloader.h>
 #include <linux/elf.h>
 #include <linux/vmalloc.h>
 #include <linux/fs.h>
 #include <linux/string.h>
 #include <linux/kernel.h>
 #include <linux/kasan.h>
 #include <linux/bug.h>
 #include <linux/mm.h>
 #include <linux/gfp.h>
 #include <linux/jump_label.h>
 #include <linux/random.h>
 #include <linux/memory.h>

 #include <asm/text-patching.h>
 #include <asm/page.h>
 #include <asm/setup.h>
 #include <asm/unwind.h>

 #if 0
 #define DEBUGP(fmt, ...)				\
 	printk(KERN_DEBUG fmt, ##__VA_ARGS__)
 #else
 #define DEBUGP(fmt, ...)				\
 do {							\
 	if (0)						\
 		printk(KERN_DEBUG fmt, ##__VA_ARGS__);	\
 } while (0)
 #endif

 #ifdef CONFIG_X86_32
 int apply_relocate(Elf32_Shdr *sechdrs,
 		   const char *strtab,
 		   unsigned int symindex,
 		   unsigned int relsec,
 		   struct module *me)
 {
 	unsigned int i;
 	Elf32_Rel *rel = (void *)sechdrs[relsec].sh_addr;
 	Elf32_Sym *sym;
 	uint32_t *location;

 	DEBUGP("Applying relocate section %u to %u\n",
 	       relsec, sechdrs[relsec].sh_info);
 	for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
 		/* This is where to make the change */
 		location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 			+ rel[i].r_offset;
 		/* This is the symbol it is referring to.  Note that all
 		   undefined symbols have been resolved.  */
 		sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
 			+ ELF32_R_SYM(rel[i].r_info);

 		switch (ELF32_R_TYPE(rel[i].r_info)) {
 		case R_386_32:
 			/* We add the value into the location given */
 			*location += sym->st_value;
 			break;
 		case R_386_PC32:
 		case R_386_PLT32:
 			/* Add the value, subtract its position */
 			*location += sym->st_value - (uint32_t)location;
 			break;
 		default:
 			pr_err("%s: Unknown relocation: %u\n",
 			       me->name, ELF32_R_TYPE(rel[i].r_info));
 			return -ENOEXEC;
 		}
 	}
 	return 0;
 }
 #else /*X86_64*/
 static int __write_relocate_add(Elf64_Shdr *sechdrs,
 		   const char *strtab,
 		   unsigned int symindex,
 		   unsigned int relsec,
 		   struct module *me,
 		   void *(*write)(void *dest, const void *src, size_t len),
 		   bool apply)
 {
 	unsigned int i;
 	Elf64_Rela *rel = (void *)sechdrs[relsec].sh_addr;
 	Elf64_Sym *sym;
 	void *loc;
 	u64 val;
 	u64 zero = 0ULL;

 	DEBUGP("%s relocate section %u to %u\n",
 	       apply ? "Applying" : "Clearing",
 	       relsec, sechdrs[relsec].sh_info);
 	for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
 		size_t size;

 		/* This is where to make the change */
 		loc = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 			+ rel[i].r_offset;

 		/* This is the symbol it is referring to.  Note that all
 		   undefined symbols have been resolved.  */
 		sym = (Elf64_Sym *)sechdrs[symindex].sh_addr
 			+ ELF64_R_SYM(rel[i].r_info);

 		DEBUGP("type %d st_value %Lx r_addend %Lx loc %Lx\n",
 		       (int)ELF64_R_TYPE(rel[i].r_info),
 		       sym->st_value, rel[i].r_addend, (u64)loc);

 		val = sym->st_value + rel[i].r_addend;

 		switch (ELF64_R_TYPE(rel[i].r_info)) {
 		case R_X86_64_NONE:
 			continue;  /* nothing to write */
 		case R_X86_64_64:
 			size = 8;
 			break;
 		case R_X86_64_32:
 			if (val != *(u32 *)&val)
 				goto overflow;
 			size = 4;
 			break;
 		case R_X86_64_32S:
 			if ((s64)val != *(s32 *)&val)
 				goto overflow;
 			size = 4;
 			break;
 		case R_X86_64_PC32:
 		case R_X86_64_PLT32:
 			val -= (u64)loc;
 			size = 4;
 			break;
 		case R_X86_64_PC64:
 			val -= (u64)loc;
 			size = 8;
 			break;
 		default:
 			pr_err("%s: Unknown rela relocation: %llu\n",
 			       me->name, ELF64_R_TYPE(rel[i].r_info));
 			return -ENOEXEC;
 		}

 		if (apply) {
 			if (memcmp(loc, &zero, size)) {
 				pr_err("x86/modules: Invalid relocation target, existing value is nonzero for type %d, loc %p, val %Lx\n",
 				       (int)ELF64_R_TYPE(rel[i].r_info), loc, val);
 				return -ENOEXEC;
 			}
 			write(loc, &val, size);
 		} else {
 			if (memcmp(loc, &val, size)) {
 				pr_warn("x86/modules: Invalid relocation target, existing value does not match expected value for type %d, loc %p, val %Lx\n",
 					(int)ELF64_R_TYPE(rel[i].r_info), loc, val);
 				return -ENOEXEC;
 			}
 			write(loc, &zero, size);
 		}
 	}
 	return 0;

 overflow:
 	pr_err("overflow in relocation type %d val %Lx\n",
 	       (int)ELF64_R_TYPE(rel[i].r_info), val);
 	pr_err("`%s' likely not compiled with -mcmodel=kernel\n",
 	       me->name);
 	return -ENOEXEC;
 }

 static int write_relocate_add(Elf64_Shdr *sechdrs,
 			      const char *strtab,
 			      unsigned int symindex,
 			      unsigned int relsec,
 			      struct module *me,
 			      bool apply)
 {
 	int ret;
 	bool early = me->state == MODULE_STATE_UNFORMED;
 	void *(*write)(void *, const void *, size_t) = memcpy;

 	if (!early) {
 		write = text_poke;
 		mutex_lock(&text_mutex);
 	}

 	ret = __write_relocate_add(sechdrs, strtab, symindex, relsec, me,
 				   write, apply);

 	if (!early) {
 		text_poke_sync();
 		mutex_unlock(&text_mutex);
 	}

 	return ret;
 }

 int apply_relocate_add(Elf64_Shdr *sechdrs,
 		   const char *strtab,
 		   unsigned int symindex,
 		   unsigned int relsec,
 		   struct module *me)
 {
 	return write_relocate_add(sechdrs, strtab, symindex, relsec, me, true);
 }

 #ifdef CONFIG_LIVEPATCH
 void clear_relocate_add(Elf64_Shdr *sechdrs,
 			const char *strtab,
 			unsigned int symindex,
 			unsigned int relsec,
 			struct module *me)
 {
 	write_relocate_add(sechdrs, strtab, symindex, relsec, me, false);
 }
 #endif

 #endif

 int module_finalize(const Elf_Ehdr *hdr,
 		    const Elf_Shdr *sechdrs,
 		    struct module *me)
 {
 	const Elf_Shdr *s, *alt = NULL, *locks = NULL,
 		*orc = NULL, *orc_ip = NULL,
 		*retpolines = NULL, *returns = NULL, *ibt_endbr = NULL,
 		*calls = NULL, *cfi = NULL;
 	char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;

 	for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
 		if (!strcmp(".altinstructions", secstrings + s->sh_name))
 			alt = s;
 		if (!strcmp(".smp_locks", secstrings + s->sh_name))
 			locks = s;
 		if (!strcmp(".orc_unwind", secstrings + s->sh_name))
 			orc = s;
 		if (!strcmp(".orc_unwind_ip", secstrings + s->sh_name))
 			orc_ip = s;
 		if (!strcmp(".retpoline_sites", secstrings + s->sh_name))
 			retpolines = s;
 		if (!strcmp(".return_sites", secstrings + s->sh_name))
 			returns = s;
 		if (!strcmp(".call_sites", secstrings + s->sh_name))
 			calls = s;
 		if (!strcmp(".cfi_sites", secstrings + s->sh_name))
 			cfi = s;
 		if (!strcmp(".ibt_endbr_seal", secstrings + s->sh_name))
 			ibt_endbr = s;
 	}

 	if (retpolines || cfi) {
 		void *rseg = NULL, *cseg = NULL;
 		unsigned int rsize = 0, csize = 0;

 		if (retpolines) {
 			rseg = (void *)retpolines->sh_addr;
 			rsize = retpolines->sh_size;
 		}

 		if (cfi) {
 			cseg = (void *)cfi->sh_addr;
 			csize = cfi->sh_size;
 		}

 		apply_fineibt(rseg, rseg + rsize, cseg, cseg + csize);
 	}
 	if (retpolines) {
 		void *rseg = (void *)retpolines->sh_addr;
 		apply_retpolines(rseg, rseg + retpolines->sh_size);
 	}
 	if (returns) {
 		void *rseg = (void *)returns->sh_addr;
 		apply_returns(rseg, rseg + returns->sh_size);
 	}
 	if (alt) {
 		/* patch .altinstructions */
 		void *aseg = (void *)alt->sh_addr;
 		apply_alternatives(aseg, aseg + alt->sh_size);
 	}
 	if (calls || alt) {
 		struct callthunk_sites cs = {};

 		if (calls) {
 			cs.call_start = (void *)calls->sh_addr;
 			cs.call_end = (void *)calls->sh_addr + calls->sh_size;
 		}

 		if (alt) {
 			cs.alt_start = (void *)alt->sh_addr;
 			cs.alt_end = (void *)alt->sh_addr + alt->sh_size;
 		}

 		callthunks_patch_module_calls(&cs, me);
 	}
 	if (ibt_endbr) {
 		void *iseg = (void *)ibt_endbr->sh_addr;
 		apply_seal_endbr(iseg, iseg + ibt_endbr->sh_size);
 	}
 	if (locks) {
 		void *lseg = (void *)locks->sh_addr;
 		void *text = me->mem[MOD_TEXT].base;
 		void *text_end = text + me->mem[MOD_TEXT].size;
 		alternatives_smp_module_add(me, me->name,
 					    lseg, lseg + locks->sh_size,
 					    text, text_end);
 	}

 	if (orc && orc_ip)
 		unwind_module_init(me, (void *)orc_ip->sh_addr, orc_ip->sh_size,
 				   (void *)orc->sh_addr, orc->sh_size);

 	return 0;
 }

 void module_arch_cleanup(struct module *mod)
 {
 	alternatives_smp_module_del(mod);
 }
	// SPDX-License-Identifier: GPL-2.0-or-later
	/* Kernel module help for x86.
	Copyright (C) 2001 Rusty Russell.

	*/

	#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

	#include <linux/moduleloader.h>
	#include <linux/elf.h>
	#include <linux/vmalloc.h>
	#include <linux/fs.h>
	#include <linux/string.h>
	#include <linux/kernel.h>
	#include <linux/kasan.h>
	#include <linux/bug.h>
	#include <linux/mm.h>
	#include <linux/gfp.h>
	#include <linux/jump_label.h>
	#include <linux/random.h>
	#include <linux/memory.h>

	#include <asm/text-patching.h>
	#include <asm/page.h>
	#include <asm/setup.h>
	#include <asm/unwind.h>

	#if 0
	#define DEBUGP(fmt, ...) \
	printk(KERN_DEBUG fmt, ##__VA_ARGS__)
	#else
	#define DEBUGP(fmt, ...) \
	do { \
	if (0) \
	printk(KERN_DEBUG fmt, ##__VA_ARGS__); \
	} while (0)
	#endif

	#ifdef CONFIG_X86_32
	int apply_relocate(Elf32_Shdr *sechdrs,
	const char *strtab,
	unsigned int symindex,
	unsigned int relsec,
	struct module *me)
	{
	unsigned int i;
	Elf32_Rel rel = (void )sechdrs[relsec].sh_addr;
	Elf32_Sym *sym;
	uint32_t *location;

	DEBUGP("Applying relocate section %u to %u\n",
	relsec, sechdrs[relsec].sh_info);
	for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
	/* This is where to make the change */
	location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
	+ rel[i].r_offset;
	/* This is the symbol it is referring to. Note that all
	undefined symbols have been resolved. */
	sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
	+ ELF32_R_SYM(rel[i].r_info);

	switch (ELF32_R_TYPE(rel[i].r_info)) {
	case R_386_32:
	/* We add the value into the location given */
	*location += sym->st_value;
	break;
	case R_386_PC32:
	case R_386_PLT32:
	/* Add the value, subtract its position */
	*location += sym->st_value - (uint32_t)location;
	break;
	default:
	pr_err("%s: Unknown relocation: %u\n",
	me->name, ELF32_R_TYPE(rel[i].r_info));
	return -ENOEXEC;
	}
	}
	return 0;
	}
	#else /X86_64/
	static int __write_relocate_add(Elf64_Shdr *sechdrs,
	const char *strtab,
	unsigned int symindex,
	unsigned int relsec,
	struct module *me,
	void (write)(void dest, const void src, size_t len),
	bool apply)
	{
	unsigned int i;
	Elf64_Rela rel = (void )sechdrs[relsec].sh_addr;
	Elf64_Sym *sym;
	void *loc;
	u64 val;
	u64 zero = 0ULL;

	DEBUGP("%s relocate section %u to %u\n",
	apply ? "Applying" : "Clearing",
	relsec, sechdrs[relsec].sh_info);
	for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
	size_t size;

	/* This is where to make the change */
	loc = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
	+ rel[i].r_offset;

	/* This is the symbol it is referring to. Note that all
	undefined symbols have been resolved. */
	sym = (Elf64_Sym *)sechdrs[symindex].sh_addr
	+ ELF64_R_SYM(rel[i].r_info);

	DEBUGP("type %d st_value %Lx r_addend %Lx loc %Lx\n",
	(int)ELF64_R_TYPE(rel[i].r_info),
	sym->st_value, rel[i].r_addend, (u64)loc);

	val = sym->st_value + rel[i].r_addend;

	switch (ELF64_R_TYPE(rel[i].r_info)) {
	case R_X86_64_NONE:
	continue; /* nothing to write */
	case R_X86_64_64:
	size = 8;
	break;
	case R_X86_64_32:
	if (val != (u32 )&val)
	goto overflow;
	size = 4;
	break;
	case R_X86_64_32S:
	if ((s64)val != (s32 )&val)
	goto overflow;
	size = 4;
	break;
	case R_X86_64_PC32:
	case R_X86_64_PLT32:
	val -= (u64)loc;
	size = 4;
	break;
	case R_X86_64_PC64:
	val -= (u64)loc;
	size = 8;
	break;
	default:
	pr_err("%s: Unknown rela relocation: %llu\n",
	me->name, ELF64_R_TYPE(rel[i].r_info));
	return -ENOEXEC;
	}

	if (apply) {
	if (memcmp(loc, &zero, size)) {
	pr_err("x86/modules: Invalid relocation target, existing value is nonzero for type %d, loc %p, val %Lx\n",
	(int)ELF64_R_TYPE(rel[i].r_info), loc, val);
	return -ENOEXEC;
	}
	write(loc, &val, size);
	} else {
	if (memcmp(loc, &val, size)) {
	pr_warn("x86/modules: Invalid relocation target, existing value does not match expected value for type %d, loc %p, val %Lx\n",
	(int)ELF64_R_TYPE(rel[i].r_info), loc, val);
	return -ENOEXEC;
	}
	write(loc, &zero, size);
	}
	}
	return 0;

	overflow:
	pr_err("overflow in relocation type %d val %Lx\n",
	(int)ELF64_R_TYPE(rel[i].r_info), val);
	pr_err("`%s' likely not compiled with -mcmodel=kernel\n",
	me->name);
	return -ENOEXEC;
	}

	static int write_relocate_add(Elf64_Shdr *sechdrs,
	const char *strtab,
	unsigned int symindex,
	unsigned int relsec,
	struct module *me,
	bool apply)
	{
	int ret;
	bool early = me->state == MODULE_STATE_UNFORMED;
	void (write)(void , const void , size_t) = memcpy;

	if (!early) {
	write = text_poke;
	mutex_lock(&text_mutex);
	}

	ret = __write_relocate_add(sechdrs, strtab, symindex, relsec, me,
	write, apply);

	if (!early) {
	text_poke_sync();
	mutex_unlock(&text_mutex);
	}

	return ret;
	}

	int apply_relocate_add(Elf64_Shdr *sechdrs,
	const char *strtab,
	unsigned int symindex,
	unsigned int relsec,
	struct module *me)
	{
	return write_relocate_add(sechdrs, strtab, symindex, relsec, me, true);
	}

	#ifdef CONFIG_LIVEPATCH
	void clear_relocate_add(Elf64_Shdr *sechdrs,
	const char *strtab,
	unsigned int symindex,
	unsigned int relsec,
	struct module *me)
	{
	write_relocate_add(sechdrs, strtab, symindex, relsec, me, false);
	}
	#endif

	#endif

	int module_finalize(const Elf_Ehdr *hdr,
	const Elf_Shdr *sechdrs,
	struct module *me)
	{
	const Elf_Shdr s, alt = NULL, *locks = NULL,
	orc = NULL, orc_ip = NULL,
	retpolines = NULL, returns = NULL, *ibt_endbr = NULL,
	calls = NULL, cfi = NULL;
	char secstrings = (void )hdr + sechdrs[hdr->e_shstrndx].sh_offset;

	for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
	if (!strcmp(".altinstructions", secstrings + s->sh_name))
	alt = s;
	if (!strcmp(".smp_locks", secstrings + s->sh_name))
	locks = s;
	if (!strcmp(".orc_unwind", secstrings + s->sh_name))
	orc = s;
	if (!strcmp(".orc_unwind_ip", secstrings + s->sh_name))
	orc_ip = s;
	if (!strcmp(".retpoline_sites", secstrings + s->sh_name))
	retpolines = s;
	if (!strcmp(".return_sites", secstrings + s->sh_name))
	returns = s;
	if (!strcmp(".call_sites", secstrings + s->sh_name))
	calls = s;
	if (!strcmp(".cfi_sites", secstrings + s->sh_name))
	cfi = s;
	if (!strcmp(".ibt_endbr_seal", secstrings + s->sh_name))
	ibt_endbr = s;
	}

	if (retpolines \|\| cfi) {
	void rseg = NULL, cseg = NULL;
	unsigned int rsize = 0, csize = 0;

	if (retpolines) {
	rseg = (void *)retpolines->sh_addr;
	rsize = retpolines->sh_size;
	}

	if (cfi) {
	cseg = (void *)cfi->sh_addr;
	csize = cfi->sh_size;
	}

	apply_fineibt(rseg, rseg + rsize, cseg, cseg + csize);
	}
	if (retpolines) {
	void rseg = (void )retpolines->sh_addr;
	apply_retpolines(rseg, rseg + retpolines->sh_size);
	}
	if (returns) {
	void rseg = (void )returns->sh_addr;
	apply_returns(rseg, rseg + returns->sh_size);
	}
	if (alt) {
	/* patch .altinstructions */
	void aseg = (void )alt->sh_addr;
	apply_alternatives(aseg, aseg + alt->sh_size);
	}
	if (calls \|\| alt) {
	struct callthunk_sites cs = {};

	if (calls) {
	cs.call_start = (void *)calls->sh_addr;
	cs.call_end = (void *)calls->sh_addr + calls->sh_size;
	}

	if (alt) {
	cs.alt_start = (void *)alt->sh_addr;
	cs.alt_end = (void *)alt->sh_addr + alt->sh_size;
	}

	callthunks_patch_module_calls(&cs, me);
	}
	if (ibt_endbr) {
	void iseg = (void )ibt_endbr->sh_addr;
	apply_seal_endbr(iseg, iseg + ibt_endbr->sh_size);
	}
	if (locks) {
	void lseg = (void )locks->sh_addr;
	void *text = me->mem[MOD_TEXT].base;
	void *text_end = text + me->mem[MOD_TEXT].size;
	alternatives_smp_module_add(me, me->name,
	lseg, lseg + locks->sh_size,
	text, text_end);
	}

	if (orc && orc_ip)
	unwind_module_init(me, (void *)orc_ip->sh_addr, orc_ip->sh_size,
	(void *)orc->sh_addr, orc->sh_size);

	return 0;
	}

	void module_arch_cleanup(struct module *mod)
	{
	alternatives_smp_module_del(mod);
	}