linux/arch/x86/vdso/vdso2c.h

/*
 * This file is included twice from vdso2c.c.  It generates code for 32-bit
 * and 64-bit vDSOs.  We need both for 64-bit builds, since 32-bit vDSOs
 * are built for 32-bit userspace.
 */

static int GOFUNC(void *addr, size_t len, FILE *outfile, const char *name)
{
	int found_load = 0;
	unsigned long load_size = -1;  /* Work around bogus warning */
	unsigned long data_size;
	Elf_Ehdr *hdr = (Elf_Ehdr *)addr;
	int i;
	unsigned long j;
	Elf_Shdr *symtab_hdr = NULL, *strtab_hdr, *secstrings_hdr,
		*alt_sec = NULL;
	Elf_Dyn *dyn = 0, *dyn_end = 0;
	const char *secstrings;
	uint64_t syms[NSYMS] = {};

	Elf_Phdr *pt = (Elf_Phdr *)(addr + hdr->e_phoff);

	/* Walk the segment table. */
	for (i = 0; i < hdr->e_phnum; i++) {
		if (pt[i].p_type == PT_LOAD) {
			if (found_load)
				fail("multiple PT_LOAD segs\n");

			if (pt[i].p_offset != 0 || pt[i].p_vaddr != 0)
				fail("PT_LOAD in wrong place\n");

			if (pt[i].p_memsz != pt[i].p_filesz)
				fail("cannot handle memsz != filesz\n");

			load_size = pt[i].p_memsz;
			found_load = 1;
		} else if (pt[i].p_type == PT_DYNAMIC) {
			dyn = addr + pt[i].p_offset;
			dyn_end = addr + pt[i].p_offset + pt[i].p_memsz;
		}
	}
	if (!found_load)
		fail("no PT_LOAD seg\n");
	data_size = (load_size + 4095) / 4096 * 4096;

	/* Walk the dynamic table */
	for (i = 0; dyn + i < dyn_end && dyn[i].d_tag != DT_NULL; i++) {
		if (dyn[i].d_tag == DT_REL || dyn[i].d_tag == DT_RELSZ ||
		    dyn[i].d_tag == DT_RELENT || dyn[i].d_tag == DT_TEXTREL)
			fail("vdso image contains dynamic relocations\n");
	}

	/* Walk the section table */
	secstrings_hdr = addr + hdr->e_shoff + hdr->e_shentsize*hdr->e_shstrndx;
	secstrings = addr + secstrings_hdr->sh_offset;
	for (i = 0; i < hdr->e_shnum; i++) {
		Elf_Shdr *sh = addr + hdr->e_shoff + hdr->e_shentsize * i;
		if (sh->sh_type == SHT_SYMTAB)
			symtab_hdr = sh;

		if (!strcmp(secstrings + sh->sh_name, ".altinstructions"))
			alt_sec = sh;
	}

	if (!symtab_hdr) {
		fail("no symbol table\n");
		return 1;
	}

	strtab_hdr = addr + hdr->e_shoff +
		hdr->e_shentsize * symtab_hdr->sh_link;

	/* Walk the symbol table */
	for (i = 0; i < symtab_hdr->sh_size / symtab_hdr->sh_entsize; i++) {
		int k;
		Elf_Sym *sym = addr + symtab_hdr->sh_offset +
			symtab_hdr->sh_entsize * i;
		const char *name = addr + strtab_hdr->sh_offset + sym->st_name;
		for (k = 0; k < NSYMS; k++) {
			if (!strcmp(name, required_syms[k])) {
				if (syms[k]) {
					fail("duplicate symbol %s\n",
					     required_syms[k]);
				}
				syms[k] = sym->st_value;
			}
		}
	}

	/* Validate mapping addresses. */
	for (i = 0; i < sizeof(special_pages) / sizeof(special_pages[0]); i++) {
		if (!syms[i])
			continue;  /* The mapping isn't used; ignore it. */

		if (syms[i] % 4096)
			fail("%s must be a multiple of 4096\n",
			     required_syms[i]);
		if (syms[i] < data_size)
			fail("%s must be after the text mapping\n",
			     required_syms[i]);
		if (syms[sym_end_mapping] < syms[i] + 4096)
			fail("%s overruns end_mapping\n", required_syms[i]);
	}
	if (syms[sym_end_mapping] % 4096)
		fail("end_mapping must be a multiple of 4096\n");

	/* Remove sections. */
	hdr->e_shoff = 0;
	hdr->e_shentsize = 0;
	hdr->e_shnum = 0;
	hdr->e_shstrndx = SHN_UNDEF;

	if (!name) {
		fwrite(addr, load_size, 1, outfile);
		return 0;
	}

	fprintf(outfile, "/* AUTOMATICALLY GENERATED -- DO NOT EDIT */\n\n");
	fprintf(outfile, "#include <linux/linkage.h>\n");
	fprintf(outfile, "#include <asm/page_types.h>\n");
	fprintf(outfile, "#include <asm/vdso.h>\n");
	fprintf(outfile, "\n");
	fprintf(outfile,
		"static unsigned char raw_data[%lu] __page_aligned_data = {",
		data_size);
	for (j = 0; j < load_size; j++) {
		if (j % 10 == 0)
			fprintf(outfile, "\n\t");
		fprintf(outfile, "0x%02X, ", (int)((unsigned char *)addr)[j]);
	}
	fprintf(outfile, "\n};\n\n");

	fprintf(outfile, "static struct page *pages[%lu];\n\n",
		data_size / 4096);

	fprintf(outfile, "const struct vdso_image %s = {\n", name);
	fprintf(outfile, "\t.data = raw_data,\n");
	fprintf(outfile, "\t.size = %lu,\n", data_size);
	fprintf(outfile, "\t.pages = pages,\n");
	if (alt_sec) {
		fprintf(outfile, "\t.alt = %lu,\n",
			(unsigned long)alt_sec->sh_offset);
		fprintf(outfile, "\t.alt_len = %lu,\n",
			(unsigned long)alt_sec->sh_size);
	}
	for (i = 0; i < NSYMS; i++) {
		if (syms[i])
			fprintf(outfile, "\t.sym_%s = 0x%" PRIx64 ",\n",
				required_syms[i], syms[i]);
	}
	fprintf(outfile, "};\n");

	return 0;
}