arch/ppc/kernel/module.c

/*  Kernel module help for PPC.
    Copyright (C) 2001 Rusty Russell.

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/
#include <linux/module.h>
#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/cache.h>

#if 0
#define DEBUGP printk
#else
#define DEBUGP(fmt , ...)
#endif

LIST_HEAD(module_bug_list);

void *module_alloc(unsigned long size)
{
	if (size == 0)
		return NULL;
	return vmalloc(size);
}

/* Free memory returned from module_alloc */
void module_free(struct module *mod, void *module_region)
{
	vfree(module_region);
	/* FIXME: If module_region == mod->init_region, trim exception
           table entries. */
}

/* Count how many different relocations (different symbol, different
   addend) */
static unsigned int count_relocs(const Elf32_Rela *rela, unsigned int num)
{
	unsigned int i, j, ret = 0;

	/* Sure, this is order(n^2), but it's usually short, and not
           time critical */
	for (i = 0; i < num; i++) {
		for (j = 0; j < i; j++) {
			/* If this addend appeared before, it's
                           already been counted */
			if (ELF32_R_SYM(rela[i].r_info)
			    == ELF32_R_SYM(rela[j].r_info)
			    && rela[i].r_addend == rela[j].r_addend)
				break;
		}
		if (j == i) ret++;
	}
	return ret;
}

/* Get the potential trampolines size required of the init and
   non-init sections */
static unsigned long get_plt_size(const Elf32_Ehdr *hdr,
				  const Elf32_Shdr *sechdrs,
				  const char *secstrings,
				  int is_init)
{
	unsigned long ret = 0;
	unsigned i;

	/* Everything marked ALLOC (this includes the exported
           symbols) */
	for (i = 1; i < hdr->e_shnum; i++) {
		/* If it's called *.init*, and we're not init, we're
                   not interested */
		if ((strstr(secstrings + sechdrs[i].sh_name, ".init") != 0)
		    != is_init)
			continue;

		/* We don't want to look at debug sections. */
		if (strstr(secstrings + sechdrs[i].sh_name, ".debug") != 0)
			continue;

		if (sechdrs[i].sh_type == SHT_RELA) {
			DEBUGP("Found relocations in section %u\n", i);
			DEBUGP("Ptr: %p.  Number: %u\n",
			       (void *)hdr + sechdrs[i].sh_offset,
			       sechdrs[i].sh_size / sizeof(Elf32_Rela));
			ret += count_relocs((void *)hdr
					     + sechdrs[i].sh_offset,
					     sechdrs[i].sh_size
					     / sizeof(Elf32_Rela))
				* sizeof(struct ppc_plt_entry);
		}
	}

	return ret;
}

int module_frob_arch_sections(Elf32_Ehdr *hdr,
			      Elf32_Shdr *sechdrs,
			      char *secstrings,
			      struct module *me)
{
	unsigned int i;

	/* Find .plt and .init.plt sections */
	for (i = 0; i < hdr->e_shnum; i++) {
		if (strcmp(secstrings + sechdrs[i].sh_name, ".init.plt") == 0)
			me->arch.init_plt_section = i;
		else if (strcmp(secstrings + sechdrs[i].sh_name, ".plt") == 0)
			me->arch.core_plt_section = i;
	}
	if (!me->arch.core_plt_section || !me->arch.init_plt_section) {
		printk("Module doesn't contain .plt or .init.plt sections.\n");
		return -ENOEXEC;
	}

	/* Override their sizes */
	sechdrs[me->arch.core_plt_section].sh_size
		= get_plt_size(hdr, sechdrs, secstrings, 0);
	sechdrs[me->arch.init_plt_section].sh_size
		= get_plt_size(hdr, sechdrs, secstrings, 1);
	return 0;
}

int apply_relocate(Elf32_Shdr *sechdrs,
		   const char *strtab,
		   unsigned int symindex,
		   unsigned int relsec,
		   struct module *module)
{
	printk(KERN_ERR "%s: Non-ADD RELOCATION unsupported\n",
	       module->name);
	return -ENOEXEC;
}

static inline int entry_matches(struct ppc_plt_entry *entry, Elf32_Addr val)
{
	if (entry->jump[0] == 0x3d600000 + ((val + 0x8000) >> 16)
	    && entry->jump[1] == 0x396b0000 + (val & 0xffff))
		return 1;
	return 0;
}

/* Set up a trampoline in the PLT to bounce us to the distant function */
static uint32_t do_plt_call(void *location,
			    Elf32_Addr val,
			    Elf32_Shdr *sechdrs,
			    struct module *mod)
{
	struct ppc_plt_entry *entry;

	DEBUGP("Doing plt for call to 0x%x at 0x%x\n", val, (unsigned int)location);
	/* Init, or core PLT? */
	if (location >= mod->module_core
	    && location < mod->module_core + mod->core_size)
		entry = (void *)sechdrs[mod->arch.core_plt_section].sh_addr;
	else
		entry = (void *)sechdrs[mod->arch.init_plt_section].sh_addr;

	/* Find this entry, or if that fails, the next avail. entry */
	while (entry->jump[0]) {
		if (entry_matches(entry, val)) return (uint32_t)entry;
		entry++;
	}

	/* Stolen from Paul Mackerras as well... */
	entry->jump[0] = 0x3d600000+((val+0x8000)>>16);	/* lis r11,sym@ha */
	entry->jump[1] = 0x396b0000 + (val&0xffff);	/* addi r11,r11,sym@l*/
	entry->jump[2] = 0x7d6903a6;			/* mtctr r11 */
	entry->jump[3] = 0x4e800420;			/* bctr */

	DEBUGP("Initialized plt for 0x%x at %p\n", val, entry);
	return (uint32_t)entry;
}

int apply_relocate_add(Elf32_Shdr *sechdrs,
		       const char *strtab,
		       unsigned int symindex,
		       unsigned int relsec,
		       struct module *module)
{
	unsigned int i;
	Elf32_Rela *rela = (void *)sechdrs[relsec].sh_addr;
	Elf32_Sym *sym;
	uint32_t *location;
	uint32_t value;

	DEBUGP("Applying ADD relocate section %u to %u\n", relsec,
	       sechdrs[relsec].sh_info);
	for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rela); i++) {
		/* This is where to make the change */
		location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
			+ rela[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(rela[i].r_info);
		/* `Everything is relative'. */
		value = sym->st_value + rela[i].r_addend;

		switch (ELF32_R_TYPE(rela[i].r_info)) {
		case R_PPC_ADDR32:
			/* Simply set it */
			*(uint32_t *)location = value;
			break;

		case R_PPC_ADDR16_LO:
			/* Low half of the symbol */
			*(uint16_t *)location = value;
			break;
		
		case R_PPC_ADDR16_HA:
			/* Sign-adjusted lower 16 bits: PPC ELF ABI says:
			   (((x >> 16) + ((x & 0x8000) ? 1 : 0))) & 0xFFFF.
			   This is the same, only sane.
			 */
			*(uint16_t *)location = (value + 0x8000) >> 16;
			break;

		case R_PPC_REL24:
			if ((int)(value - (uint32_t)location) < -0x02000000
			    || (int)(value - (uint32_t)location) >= 0x02000000)
				value = do_plt_call(location, value,
						    sechdrs, module);

			/* Only replace bits 2 through 26 */
			DEBUGP("REL24 value = %08X. location = %08X\n",
			       value, (uint32_t)location);
			DEBUGP("Location before: %08X.\n",
			       *(uint32_t *)location);
			*(uint32_t *)location
				= (*(uint32_t *)location & ~0x03fffffc)
				| ((value - (uint32_t)location)
				   & 0x03fffffc);
			DEBUGP("Location after: %08X.\n",
			       *(uint32_t *)location);
			DEBUGP("ie. jump to %08X+%08X = %08X\n",
			       *(uint32_t *)location & 0x03fffffc,
			       (uint32_t)location,
			       (*(uint32_t *)location & 0x03fffffc)
			       + (uint32_t)location);
			break;

		case R_PPC_REL32:
			/* 32-bit relative jump. */
			*(uint32_t *)location = value - (uint32_t)location;
			break;

		default:
			printk("%s: unknown ADD relocation: %u\n",
			       module->name,
			       ELF32_R_TYPE(rela[i].r_info));
			return -ENOEXEC;
		}
	}
	return 0;
}

int module_finalize(const Elf_Ehdr *hdr,
		    const Elf_Shdr *sechdrs,
		    struct module *me)
{
	char *secstrings;
	unsigned int i;

	me->arch.bug_table = NULL;
	me->arch.num_bugs = 0;

	/* Find the __bug_table section, if present */
	secstrings = (char *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
	for (i = 1; i < hdr->e_shnum; i++) {
		if (strcmp(secstrings+sechdrs[i].sh_name, "__bug_table"))
			continue;
		me->arch.bug_table = (void *) sechdrs[i].sh_addr;
		me->arch.num_bugs = sechdrs[i].sh_size / sizeof(struct bug_entry);
		break;
	}

	/*
	 * Strictly speaking this should have a spinlock to protect against
	 * traversals, but since we only traverse on BUG()s, a spinlock
	 * could potentially lead to deadlock and thus be counter-productive.
	 */
	list_add(&me->arch.bug_list, &module_bug_list);

	return 0;
}

void module_arch_cleanup(struct module *mod)
{
	list_del(&mod->arch.bug_list);
}

struct bug_entry *module_find_bug(unsigned long bugaddr)
{
	struct mod_arch_specific *mod;
	unsigned int i;
	struct bug_entry *bug;

	list_for_each_entry(mod, &module_bug_list, bug_list) {
		bug = mod->bug_table;
		for (i = 0; i < mod->num_bugs; ++i, ++bug)
			if (bugaddr == bug->bug_addr)
				return bug;
	}
	return NULL;
}