arch/x86/kernel/module.c

Source file repositories/reference/linux-study-clean/arch/x86/kernel/module.c

File Facts

System
Linux kernel
Corpus path
arch/x86/kernel/module.c
Extension
.c
Size
8217 bytes
Lines
324
Domain
Architecture Layer
Bucket
arch/x86
Inferred role
Architecture Layer: exported/initcall integration point
Status
integration implementation candidate

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

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 sec %u, idx %u, type %d, loc %lx, val %llx\n",

Annotation

Implementation Notes