modpost.c

/* Postprocess module symbol versions
 *
 * Copyright 2003       Kai Germaschewski
 * Copyright 2002-2004  Rusty Russell, IBM Corporation
 * Copyright 2006       Sam Ravnborg
 * Based in part on module-init-tools/depmod.c,file2alias
 *
 * This software may be used and distributed according to the terms
 * of the GNU General Public License, incorporated herein by reference.
 *
 * Usage: modpost vmlinux module1.o module2.o ...
 */

#include <ctype.h>
#include "modpost.h"
#include "../../include/linux/license.h"

/* Are we using CONFIG_MODVERSIONS? */
int modversions = 0;
/* Warn about undefined symbols? (do so if we have vmlinux) */
int have_vmlinux = 0;
/* Is CONFIG_MODULE_SRCVERSION_ALL set? */
static int all_versions = 0;
/* If we are modposting external module set to 1 */
static int external_module = 0;
/* Only warn about unresolved symbols */
static int warn_unresolved = 0;
/* How a symbol is exported */
enum export {
	export_plain,      export_unused,     export_gpl,
	export_unused_gpl, export_gpl_future, export_unknown
};

void fatal(const char *fmt, ...)
{
	va_list arglist;

	fprintf(stderr, "FATAL: ");

	va_start(arglist, fmt);
	vfprintf(stderr, fmt, arglist);
	va_end(arglist);

	exit(1);
}

void warn(const char *fmt, ...)
{
	va_list arglist;

	fprintf(stderr, "WARNING: ");

	va_start(arglist, fmt);
	vfprintf(stderr, fmt, arglist);
	va_end(arglist);
}

void merror(const char *fmt, ...)
{
	va_list arglist;

	fprintf(stderr, "ERROR: ");

	va_start(arglist, fmt);
	vfprintf(stderr, fmt, arglist);
	va_end(arglist);
}

static int is_vmlinux(const char *modname)
{
	const char *myname;

	if ((myname = strrchr(modname, '/')))
		myname++;
	else
		myname = modname;

	return strcmp(myname, "vmlinux") == 0;
}

void *do_nofail(void *ptr, const char *expr)
{
	if (!ptr) {
		fatal("modpost: Memory allocation failure: %s.\n", expr);
	}
	return ptr;
}

/* A list of all modules we processed */

static struct module *modules;

static struct module *find_module(char *modname)
{
	struct module *mod;

	for (mod = modules; mod; mod = mod->next)
		if (strcmp(mod->name, modname) == 0)
			break;
	return mod;
}

static struct module *new_module(char *modname)
{
	struct module *mod;
	char *p, *s;

	mod = NOFAIL(malloc(sizeof(*mod)));
	memset(mod, 0, sizeof(*mod));
	p = NOFAIL(strdup(modname));

	/* strip trailing .o */
	if ((s = strrchr(p, '.')) != NULL)
		if (strcmp(s, ".o") == 0)
			*s = '\0';

	/* add to list */
	mod->name = p;
	mod->gpl_compatible = -1;
	mod->next = modules;
	modules = mod;

	return mod;
}

/* A hash of all exported symbols,
 * struct symbol is also used for lists of unresolved symbols */

#define SYMBOL_HASH_SIZE 1024

struct symbol {
	struct symbol *next;
	struct module *module;
	unsigned int crc;
	int crc_valid;
	unsigned int weak:1;
	unsigned int vmlinux:1;    /* 1 if symbol is defined in vmlinux */
	unsigned int kernel:1;     /* 1 if symbol is from kernel
				    *  (only for external modules) **/
	unsigned int preloaded:1;  /* 1 if symbol from Module.symvers */
	enum export  export;       /* Type of export */
	char name[0];
};

static struct symbol *symbolhash[SYMBOL_HASH_SIZE];

/* This is based on the hash agorithm from gdbm, via tdb */
static inline unsigned int tdb_hash(const char *name)
{
	unsigned value;	/* Used to compute the hash value.  */
	unsigned   i;	/* Used to cycle through random values. */

	/* Set the initial value from the key size. */
	for (value = 0x238F13AF * strlen(name), i=0; name[i]; i++)
		value = (value + (((unsigned char *)name)[i] << (i*5 % 24)));

	return (1103515243 * value + 12345);
}

/**
 * Allocate a new symbols for use in the hash of exported symbols or
 * the list of unresolved symbols per module
 **/
static struct symbol *alloc_symbol(const char *name, unsigned int weak,
				   struct symbol *next)
{
	struct symbol *s = NOFAIL(malloc(sizeof(*s) + strlen(name) + 1));

	memset(s, 0, sizeof(*s));
	strcpy(s->name, name);
	s->weak = weak;
	s->next = next;
	return s;
}

/* For the hash of exported symbols */
static struct symbol *new_symbol(const char *name, struct module *module,
				 enum export export)
{
	unsigned int hash;
	struct symbol *new;

	hash = tdb_hash(name) % SYMBOL_HASH_SIZE;
	new = symbolhash[hash] = alloc_symbol(name, 0, symbolhash[hash]);
	new->module = module;
	new->export = export;
	return new;
}

static struct symbol *find_symbol(const char *name)
{
	struct symbol *s;

	/* For our purposes, .foo matches foo.  PPC64 needs this. */
	if (name[0] == '.')
		name++;

	for (s = symbolhash[tdb_hash(name) % SYMBOL_HASH_SIZE]; s; s=s->next) {
		if (strcmp(s->name, name) == 0)
			return s;
	}
	return NULL;
}

static struct {
	const char *str;
	enum export export;
} export_list[] = {
	{ .str = "EXPORT_SYMBOL",            .export = export_plain },
	{ .str = "EXPORT_UNUSED_SYMBOL",     .export = export_unused },
	{ .str = "EXPORT_SYMBOL_GPL",        .export = export_gpl },
	{ .str = "EXPORT_UNUSED_SYMBOL_GPL", .export = export_unused_gpl },
	{ .str = "EXPORT_SYMBOL_GPL_FUTURE", .export = export_gpl_future },
	{ .str = "(unknown)",                .export = export_unknown },
};


static const char *export_str(enum export ex)
{
	return export_list[ex].str;
}

static enum export export_no(const char * s)
{
	int i;
	if (!s)
		return export_unknown;
	for (i = 0; export_list[i].export != export_unknown; i++) {
		if (strcmp(export_list[i].str, s) == 0)
			return export_list[i].export;
	}
	return export_unknown;
}

static enum export export_from_sec(struct elf_info *elf, Elf_Section sec)
{
	if (sec == elf->export_sec)
		return export_plain;
	else if (sec == elf->export_unused_sec)
		return export_unused;
	else if (sec == elf->export_gpl_sec)
		return export_gpl;
	else if (sec == elf->export_unused_gpl_sec)
		return export_unused_gpl;
	else if (sec == elf->export_gpl_future_sec)
		return export_gpl_future;
	else
		return export_unknown;
}

/**
 * Add an exported symbol - it may have already been added without a
 * CRC, in this case just update the CRC
 **/
static struct symbol *sym_add_exported(const char *name, struct module *mod,
				       enum export export)
{
	struct symbol *s = find_symbol(name);

	if (!s) {
		s = new_symbol(name, mod, export);
	} else {
		if (!s->preloaded) {
			warn("%s: '%s' exported twice. Previous export "
			     "was in %s%s\n", mod->name, name,
			     s->module->name,
			     is_vmlinux(s->module->name) ?"":".ko");
		}
	}
	s->preloaded = 0;
	s->vmlinux   = is_vmlinux(mod->name);
	s->kernel    = 0;
	s->export    = export;
	return s;
}

static void sym_update_crc(const char *name, struct module *mod,
			   unsigned int crc, enum export export)
{
	struct symbol *s = find_symbol(name);

	if (!s)
		s = new_symbol(name, mod, export);
	s->crc = crc;
	s->crc_valid = 1;
}

void *grab_file(const char *filename, unsigned long *size)
{
	struct stat st;
	void *map;
	int fd;

	fd = open(filename, O_RDONLY);
	if (fd < 0 || fstat(fd, &st) != 0)
		return NULL;

	*size = st.st_size;
	map = mmap(NULL, *size, PROT_READ|PROT_WRITE, MAP_PRIVATE, fd, 0);
	close(fd);

	if (map == MAP_FAILED)
		return NULL;
	return map;
}

/**
  * Return a copy of the next line in a mmap'ed file.
  * spaces in the beginning of the line is trimmed away.
  * Return a pointer to a static buffer.
  **/
char* get_next_line(unsigned long *pos, void *file, unsigned long size)
{
	static char line[4096];
	int skip = 1;
	size_t len = 0;
	signed char *p = (signed char *)file + *pos;
	char *s = line;

	for (; *pos < size ; (*pos)++)
	{
		if (skip && isspace(*p)) {
			p++;
			continue;
		}
		skip = 0;
		if (*p != '\n' && (*pos < size)) {
			len++;
			*s++ = *p++;
			if (len > 4095)
				break; /* Too long, stop */
		} else {
			/* End of string */
			*s = '\0';
			return line;
		}
	}
	/* End of buffer */
	return NULL;
}

void release_file(void *file, unsigned long size)
{
	munmap(file, size);
}

static int parse_elf(struct elf_info *info, const char *filename)
{
	unsigned int i;
	Elf_Ehdr *hdr;
	Elf_Shdr *sechdrs;
	Elf_Sym  *sym;

	hdr = grab_file(filename, &info->size);
	if (!hdr) {
		perror(filename);
		exit(1);
	}
	info->hdr = hdr;
	if (info->size < sizeof(*hdr)) {
		/* file too small, assume this is an empty .o file */
		return 0;
	}
	/* Is this a valid ELF file? */
	if ((hdr->e_ident[EI_MAG0] != ELFMAG0) ||
	    (hdr->e_ident[EI_MAG1] != ELFMAG1) ||
	    (hdr->e_ident[EI_MAG2] != ELFMAG2) ||
	    (hdr->e_ident[EI_MAG3] != ELFMAG3)) {
		/* Not an ELF file - silently ignore it */
		return 0;
	}
	/* Fix endianness in ELF header */
	hdr->e_shoff    = TO_NATIVE(hdr->e_shoff);
	hdr->e_shstrndx = TO_NATIVE(hdr->e_shstrndx);
	hdr->e_shnum    = TO_NATIVE(hdr->e_shnum);
	hdr->e_machine  = TO_NATIVE(hdr->e_machine);
	sechdrs = (void *)hdr + hdr->e_shoff;
	info->sechdrs = sechdrs;

	/* Fix endianness in section headers */
	for (i = 0; i < hdr->e_shnum; i++) {
		sechdrs[i].sh_type   = TO_NATIVE(sechdrs[i].sh_type);
		sechdrs[i].sh_offset = TO_NATIVE(sechdrs[i].sh_offset);
		sechdrs[i].sh_size   = TO_NATIVE(sechdrs[i].sh_size);
		sechdrs[i].sh_link   = TO_NATIVE(sechdrs[i].sh_link);
		sechdrs[i].sh_name   = TO_NATIVE(sechdrs[i].sh_name);
	}
	/* Find symbol table. */
	for (i = 1; i < hdr->e_shnum; i++) {
		const char *secstrings
			= (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
		const char *secname;

		if (sechdrs[i].sh_offset > info->size) {
			fatal("%s is truncated. sechdrs[i].sh_offset=%u > sizeof(*hrd)=%ul\n", filename, (unsigned int)sechdrs[i].sh_offset, sizeof(*hdr));
			return 0;
		}
		secname = secstrings + sechdrs[i].sh_name;
		if (strcmp(secname, ".modinfo") == 0) {
			info->modinfo = (void *)hdr + sechdrs[i].sh_offset;
			info->modinfo_len = sechdrs[i].sh_size;
		} else if (strcmp(secname, "__ksymtab") == 0)
			info->export_sec = i;
		else if (strcmp(secname, "__ksymtab_unused") == 0)
			info->export_unused_sec = i;
		else if (strcmp(secname, "__ksymtab_gpl") == 0)
			info->export_gpl_sec = i;
		else if (strcmp(secname, "__ksymtab_unused_gpl") == 0)
			info->export_unused_gpl_sec = i;
		else if (strcmp(secname, "__ksymtab_gpl_future") == 0)
			info->export_gpl_future_sec = i;

		if (sechdrs[i].sh_type != SHT_SYMTAB)
			continue;

		info->symtab_start = (void *)hdr + sechdrs[i].sh_offset;
		info->symtab_stop  = (void *)hdr + sechdrs[i].sh_offset
			                         + sechdrs[i].sh_size;
		info->strtab       = (void *)hdr +
			             sechdrs[sechdrs[i].sh_link].sh_offset;
	}
	if (!info->symtab_start) {
		fatal("%s has no symtab?\n", filename);
	}
	/* Fix endianness in symbols */
	for (sym = info->symtab_start; sym < info->symtab_stop; sym++) {
		sym->st_shndx = TO_NATIVE(sym->st_shndx);
		sym->st_name  = TO_NATIVE(sym->st_name);
		sym->st_value = TO_NATIVE(sym->st_value);
		sym->st_size  = TO_NATIVE(sym->st_size);
	}
	return 1;
}

static void parse_elf_finish(struct elf_info *info)
{
	release_file(info->hdr, info->size);
}

#define CRC_PFX     MODULE_SYMBOL_PREFIX "__crc_"
#define KSYMTAB_PFX MODULE_SYMBOL_PREFIX "__ksymtab_"

static void handle_modversions(struct module *mod, struct elf_info *info,
			       Elf_Sym *sym, const char *symname)
{
	unsigned int crc;
	enum export export = export_from_sec(info, sym->st_shndx);

	switch (sym->st_shndx) {
	case SHN_COMMON:
		warn("\"%s\" [%s] is COMMON symbol\n", symname, mod->name);
		break;
	case SHN_ABS:
		/* CRC'd symbol */
		if (memcmp(symname, CRC_PFX, strlen(CRC_PFX)) == 0) {
			crc = (unsigned int) sym->st_value;
			sym_update_crc(symname + strlen(CRC_PFX), mod, crc,
					export);
		}
		break;
	case SHN_UNDEF:
		/* undefined symbol */
		if (ELF_ST_BIND(sym->st_info) != STB_GLOBAL &&
		    ELF_ST_BIND(sym->st_info) != STB_WEAK)
			break;
		/* ignore global offset table */
		if (strcmp(symname, "_GLOBAL_OFFSET_TABLE_") == 0)
			break;
		/* ignore __this_module, it will be resolved shortly */
		if (strcmp(symname, MODULE_SYMBOL_PREFIX "__this_module") == 0)
			break;
/* cope with newer glibc (2.3.4 or higher) STT_ definition in elf.h */
#if defined(STT_REGISTER) || defined(STT_SPARC_REGISTER)
/* add compatibility with older glibc */
#ifndef STT_SPARC_REGISTER
#define STT_SPARC_REGISTER STT_REGISTER
#endif
		if (info->hdr->e_machine == EM_SPARC ||
		    info->hdr->e_machine == EM_SPARCV9) {
			/* Ignore register directives. */
			if (ELF_ST_TYPE(sym->st_info) == STT_SPARC_REGISTER)
				break;
			if (symname[0] == '.') {
				char *munged = strdup(symname);
				munged[0] = '_';
				munged[1] = toupper(munged[1]);
				symname = munged;
			}
		}
#endif

		if (memcmp(symname, MODULE_SYMBOL_PREFIX,
			   strlen(MODULE_SYMBOL_PREFIX)) == 0)
			mod->unres = alloc_symbol(symname +
						  strlen(MODULE_SYMBOL_PREFIX),
						  ELF_ST_BIND(sym->st_info) == STB_WEAK,
						  mod->unres);
		break;
	default:
		/* All exported symbols */
		if (memcmp(symname, KSYMTAB_PFX, strlen(KSYMTAB_PFX)) == 0) {
			sym_add_exported(symname + strlen(KSYMTAB_PFX), mod,
					export);
		}
		if (strcmp(symname, MODULE_SYMBOL_PREFIX "init_module") == 0)
			mod->has_init = 1;
		if (strcmp(symname, MODULE_SYMBOL_PREFIX "cleanup_module") == 0)
			mod->has_cleanup = 1;
		break;
	}
}

/**
 * Parse tag=value strings from .modinfo section
 **/
static char *next_string(char *string, unsigned long *secsize)
{
	/* Skip non-zero chars */
	while (string[0]) {
		string++;
		if ((*secsize)-- <= 1)
			return NULL;
	}

	/* Skip any zero padding. */
	while (!string[0]) {
		string++;
		if ((*secsize)-- <= 1)
			return NULL;
	}
	return string;
}

static char *get_next_modinfo(void *modinfo, unsigned long modinfo_len,
			      const char *tag, char *info)
{
	char *p;
	unsigned int taglen = strlen(tag);
	unsigned long size = modinfo_len;

	if (info) {
		size -= info - (char *)modinfo;
		modinfo = next_string(info, &size);
	}

	for (p = modinfo; p; p = next_string(p, &size)) {
		if (strncmp(p, tag, taglen) == 0 && p[taglen] == '=')
			return p + taglen + 1;
	}
	return NULL;
}

static char *get_modinfo(void *modinfo, unsigned long modinfo_len,
			 const char *tag)

{
	return get_next_modinfo(modinfo, modinfo_len, tag, NULL);
}

/**
 * Test if string s ends in string sub
 * return 0 if match
 **/
static int strrcmp(const char *s, const char *sub)
{
        int slen, sublen;

	if (!s || !sub)
		return 1;

	slen = strlen(s);
        sublen = strlen(sub);

	if ((slen == 0) || (sublen == 0))
		return 1;

        if (sublen > slen)
                return 1;

        return memcmp(s + slen - sublen, sub, sublen);
}

/**
 * Whitelist to allow certain references to pass with no warning.
 * Pattern 1:
 *   If a module parameter is declared __initdata and permissions=0
 *   then this is legal despite the warning generated.
 *   We cannot see value of permissions here, so just ignore
 *   this pattern.
 *   The pattern is identified by:
 *   tosec   = .init.data
 *   fromsec = .data*
 *   atsym   =__param*
 *
 * Pattern 2:
 *   Many drivers utilise a *driver container with references to
 *   add, remove, probe functions etc.
 *   These functions may often be marked __init and we do not want to
 *   warn here.
 *   the pattern is identified by:
 *   tosec   = .init.text | .exit.text | .init.data
 *   fromsec = .data
 *   atsym = *driver, *_template, *_sht, *_ops, *_probe, *probe_one, *_console
 *
 * Pattern 3:
 *   Whitelist all references from .pci_fixup* section to .init.text
 *   This is part of the PCI init when built-in
 *
 * Pattern 4:
 *   Whitelist all refereces from .text.head to .init.data
 *   Whitelist all refereces from .text.head to .init.text
 *
 * Pattern 5:
 *   Some symbols belong to init section but still it is ok to reference
 *   these from non-init sections as these symbols don't have any memory
 *   allocated for them and symbol address and value are same. So even
 *   if init section is freed, its ok to reference those symbols.
 *   For ex. symbols marking the init section boundaries.
 *   This pattern is identified by
 *   refsymname = __init_begin, _sinittext, _einittext
 *
 * Pattern 6:
 *   During the early init phase we have references from .init.text to
 *   .text we have an intended section mismatch - do not warn about it.
 *   See kernel_init() in init/main.c
 *   tosec   = .init.text
 *   fromsec = .text
 *   atsym = kernel_init
 *
 * Pattern 7:
 *  Logos used in drivers/video/logo reside in __initdata but the
 *  funtion that references them are EXPORT_SYMBOL() so cannot be
 *  marker __init. So we whitelist them here.
 *  The pattern is:
 *  tosec      = .init.data
 *  fromsec    = .text*
 *  refsymname = logo_
 *
 * Pattern 8:
 *  Symbols contained in .paravirtprobe may safely reference .init.text.
 *  The pattern is:
 *  tosec   = .init.text
 *  fromsec  = .paravirtprobe
 *
 * Pattern 9:
 *  Some of functions are common code between boot time and hotplug
 *  time. The bootmem allocater is called only boot time in its
 *  functions. So it's ok to reference.
 *  tosec    = .init.text
 *
 * Pattern 10:
 *  ia64 has machvec table for each platform. It is mixture of function
 *  pointer of .init.text and .text.
 *  fromsec  = .machvec
 **/
static int secref_whitelist(const char *modname, const char *tosec,
			    const char *fromsec, const char *atsym,
			    const char *refsymname)
{
	int f1 = 1, f2 = 1;
	const char **s;
	const char *pat2sym[] = {
		"driver",
		"_template", /* scsi uses *_template a lot */
		"_sht",      /* scsi also used *_sht to some extent */
		"_ops",
		"_probe",
		"_probe_one",
		"_console",
		"apic_es7000",
		NULL
	};

	const char *pat3refsym[] = {
		"__init_begin",
		"_sinittext",
		"_einittext",
		NULL
	};

	const char *pat4sym[] = {
		"sparse_index_alloc",
		"zone_wait_table_init",
		NULL
	};

	/* Check for pattern 1 */
	if (strcmp(tosec, ".init.data") != 0)
		f1 = 0;
	if (strncmp(fromsec, ".data", strlen(".data")) != 0)
		f1 = 0;
	if (strncmp(atsym, "__param", strlen("__param")) != 0)
		f1 = 0;

	if (f1)
		return f1;

	/* Check for pattern 2 */
	if ((strcmp(tosec, ".init.text") != 0) &&
	    (strcmp(tosec, ".exit.text") != 0) &&
	    (strcmp(tosec, ".init.data") != 0))
		f2 = 0;
	if (strcmp(fromsec, ".data") != 0)
		f2 = 0;

	for (s = pat2sym; *s; s++)
		if (strrcmp(atsym, *s) == 0)
			f1 = 1;
	if (f1 && f2)
		return 1;

	/* Check for pattern 3 */
	if ((strncmp(fromsec, ".pci_fixup", strlen(".pci_fixup")) == 0) &&
	    (strcmp(tosec, ".init.text") == 0))
	return 1;

	/* Check for pattern 4 */
	if ((strcmp(fromsec, ".text.head") == 0) &&
		((strcmp(tosec, ".init.data") == 0) ||
		(strcmp(tosec, ".init.text") == 0)))
	return 1;

	/* Check for pattern 5 */
	for (s = pat3refsym; *s; s++)
		if (strcmp(refsymname, *s) == 0)
			return 1;

	/* Check for pattern 6 */
	if ((strcmp(tosec, ".init.text") == 0) &&
	    (strcmp(fromsec, ".text") == 0) &&
	    (strcmp(refsymname, "kernel_init") == 0))
		return 1;

	/* Check for pattern 7 */
	if ((strcmp(tosec, ".init.data") == 0) &&
	    (strncmp(fromsec, ".text", strlen(".text")) == 0) &&
	    (strncmp(refsymname, "logo_", strlen("logo_")) == 0))
		return 1;

	/* Check for pattern 8 */
	if ((strcmp(tosec, ".init.text") == 0) &&
	    (strcmp(fromsec, ".paravirtprobe") == 0))
		return 1;

	/* Check for pattern 9 */
	if ((strcmp(tosec, ".init.text") == 0) &&
	    (strcmp(fromsec, ".text") == 0))
		for (s = pat4sym; *s; s++)
			if (strcmp(atsym, *s) == 0)
				return 1;

	/* Check for pattern 10 */
	if (strcmp(fromsec, ".machvec") == 0)
		return 1;

	return 0;
}

/**
 * Find symbol based on relocation record info.
 * In some cases the symbol supplied is a valid symbol so
 * return refsym. If st_name != 0 we assume this is a valid symbol.
 * In other cases the symbol needs to be looked up in the symbol table
 * based on section and address.
 *  **/
static Elf_Sym *find_elf_symbol(struct elf_info *elf, Elf_Addr addr,
				Elf_Sym *relsym)
{
	Elf_Sym *sym;

	if (relsym->st_name != 0)
		return relsym;
	for (sym = elf->symtab_start; sym < elf->symtab_stop; sym++) {
		if (sym->st_shndx != relsym->st_shndx)
			continue;
		if (sym->st_value == addr)
			return sym;
	}
	return NULL;
}

static inline int is_arm_mapping_symbol(const char *str)
{
	return str[0] == '$' && strchr("atd", str[1])
	       && (str[2] == '\0' || str[2] == '.');
}

/*
 * If there's no name there, ignore it; likewise, ignore it if it's
 * one of the magic symbols emitted used by current ARM tools.
 *
 * Otherwise if find_symbols_between() returns those symbols, they'll
 * fail the whitelist tests and cause lots of false alarms ... fixable
 * only by merging __exit and __init sections into __text, bloating
 * the kernel (which is especially evil on embedded platforms).
 */
static inline int is_valid_name(struct elf_info *elf, Elf_Sym *sym)
{
	const char *name = elf->strtab + sym->st_name;

	if (!name || !strlen(name))
		return 0;
	return !is_arm_mapping_symbol(name);
}

/*
 * Find symbols before or equal addr and after addr - in the section sec.
 * If we find two symbols with equal offset prefer one with a valid name.
 * The ELF format may have a better way to detect what type of symbol
 * it is, but this works for now.
 **/
static void find_symbols_between(struct elf_info *elf, Elf_Addr addr,
				 const char *sec,
			         Elf_Sym **before, Elf_Sym **after)
{
	Elf_Sym *sym;
	Elf_Ehdr *hdr = elf->hdr;
	Elf_Addr beforediff = ~0;
	Elf_Addr afterdiff = ~0;
	const char *secstrings = (void *)hdr +
				 elf->sechdrs[hdr->e_shstrndx].sh_offset;

	*before = NULL;
	*after = NULL;

	for (sym = elf->symtab_start; sym < elf->symtab_stop; sym++) {
		const char *symsec;

		if (sym->st_shndx >= SHN_LORESERVE)
			continue;
		symsec = secstrings + elf->sechdrs[sym->st_shndx].sh_name;
		if (strcmp(symsec, sec) != 0)
			continue;
		if (!is_valid_name(elf, sym))
			continue;
		if (sym->st_value <= addr) {
			if ((addr - sym->st_value) < beforediff) {
				beforediff = addr - sym->st_value;
				*before = sym;
			}
			else if ((addr - sym->st_value) == beforediff) {
				*before = sym;
			}
		}
		else
		{
			if ((sym->st_value - addr) < afterdiff) {
				afterdiff = sym->st_value - addr;
				*after = sym;
			}
			else if ((sym->st_value - addr) == afterdiff) {
				*after = sym;
			}
		}
	}
}

/**
 * Print a warning about a section mismatch.
 * Try to find symbols near it so user can find it.
 * Check whitelist before warning - it may be a false positive.
 **/
static void warn_sec_mismatch(const char *modname, const char *fromsec,
			      struct elf_info *elf, Elf_Sym *sym, Elf_Rela r)
{
	const char *refsymname = "";
	Elf_Sym *before, *after;
	Elf_Sym *refsym;
	Elf_Ehdr *hdr = elf->hdr;
	Elf_Shdr *sechdrs = elf->sechdrs;
	const char *secstrings = (void *)hdr +
				 sechdrs[hdr->e_shstrndx].sh_offset;
	const char *secname = secstrings + sechdrs[sym->st_shndx].sh_name;

	find_symbols_between(elf, r.r_offset, fromsec, &before, &after);

	refsym = find_elf_symbol(elf, r.r_addend, sym);
	if (refsym && strlen(elf->strtab + refsym->st_name))
		refsymname = elf->strtab + refsym->st_name;

	/* check whitelist - we may ignore it */
	if (before &&
	    secref_whitelist(modname, secname, fromsec,
			     elf->strtab + before->st_name, refsymname))
		return;

	if (before && after) {
		warn("%s - Section mismatch: reference to %s:%s from %s "
		     "between '%s' (at offset 0x%llx) and '%s'\n",
		     modname, secname, refsymname, fromsec,
		     elf->strtab + before->st_name,
		     (long long)r.r_offset,
		     elf->strtab + after->st_name);
	} else if (before) {
		warn("%s - Section mismatch: reference to %s:%s from %s "
		     "after '%s' (at offset 0x%llx)\n",
		     modname, secname, refsymname, fromsec,
		     elf->strtab + before->st_name,
		     (long long)r.r_offset);
	} else if (after) {
		warn("%s - Section mismatch: reference to %s:%s from %s "
		     "before '%s' (at offset -0x%llx)\n",
		     modname, secname, refsymname, fromsec,
		     elf->strtab + after->st_name,
		     (long long)r.r_offset);
	} else {
		warn("%s - Section mismatch: reference to %s:%s from %s "
		     "(offset 0x%llx)\n",
		     modname, secname, fromsec, refsymname,
		     (long long)r.r_offset);
	}
}

/**
 * A module includes a number of sections that are discarded
 * either when loaded or when used as built-in.
 * For loaded modules all functions marked __init and all data
 * marked __initdata will be discarded when the module has been intialized.
 * Likewise for modules used built-in the sections marked __exit
 * are discarded because __exit marked function are supposed to be called
 * only when a moduel is unloaded which never happes for built-in modules.
 * The check_sec_ref() function traverses all relocation records
 * to find all references to a section that reference a section that will
 * be discarded and warns about it.
 **/
static void check_sec_ref(struct module *mod, const char *modname,
			  struct elf_info *elf,
			  int section(const char*),
			  int section_ref_ok(const char *))
{
	int i;
	Elf_Sym  *sym;
	Elf_Ehdr *hdr = elf->hdr;
	Elf_Shdr *sechdrs = elf->sechdrs;
	const char *secstrings = (void *)hdr +
				 sechdrs[hdr->e_shstrndx].sh_offset;

	/* Walk through all sections */
	for (i = 0; i < hdr->e_shnum; i++) {
		const char *name = secstrings + sechdrs[i].sh_name;
		const char *secname;
		Elf_Rela r;
		unsigned int r_sym;
		/* We want to process only relocation sections and not .init */
		if (sechdrs[i].sh_type == SHT_RELA) {
			Elf_Rela *rela;
			Elf_Rela *start = (void *)hdr + sechdrs[i].sh_offset;
			Elf_Rela *stop  = (void*)start + sechdrs[i].sh_size;
			name += strlen(".rela");
			if (section_ref_ok(name))
				continue;

			for (rela = start; rela < stop; rela++) {
				r.r_offset = TO_NATIVE(rela->r_offset);
#if KERNEL_ELFCLASS == ELFCLASS64
				if (hdr->e_machine == EM_MIPS) {
					r_sym = ELF64_MIPS_R_SYM(rela->r_info);
					r_sym = TO_NATIVE(r_sym);
				} else {
					r.r_info = TO_NATIVE(rela->r_info);
					r_sym = ELF_R_SYM(r.r_info);
				}
#else
				r.r_info = TO_NATIVE(rela->r_info);
				r_sym = ELF_R_SYM(r.r_info);
#endif
				r.r_addend = TO_NATIVE(rela->r_addend);
				sym = elf->symtab_start + r_sym;
				/* Skip special sections */
				if (sym->st_shndx >= SHN_LORESERVE)
					continue;

				secname = secstrings +
					sechdrs[sym->st_shndx].sh_name;
				if (section(secname))
					warn_sec_mismatch(modname, name,
							  elf, sym, r);
			}
		} else if (sechdrs[i].sh_type == SHT_REL) {
			Elf_Rel *rel;
			Elf_Rel *start = (void *)hdr + sechdrs[i].sh_offset;
			Elf_Rel *stop  = (void*)start + sechdrs[i].sh_size;
			name += strlen(".rel");
			if (section_ref_ok(name))
				continue;

			for (rel = start; rel < stop; rel++) {
				r.r_offset = TO_NATIVE(rel->r_offset);
#if KERNEL_ELFCLASS == ELFCLASS64
				if (hdr->e_machine == EM_MIPS) {
					r_sym = ELF64_MIPS_R_SYM(rel->r_info);
					r_sym = TO_NATIVE(r_sym);
				} else {
					r.r_info = TO_NATIVE(rel->r_info);
					r_sym = ELF_R_SYM(r.r_info);
				}
#else
				r.r_info = TO_NATIVE(rel->r_info);
				r_sym = ELF_R_SYM(r.r_info);
#endif