text: /*  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/ftrace.h>
  #include <linux/cache.h>
  #include <linux/bug.h>
  #include <linux/sort.h>
  
  #include "setup.h"
  
  #if 0
  #define DEBUGP printk
  #else
  #define DEBUGP(fmt , ...)
  #endif
  
  /* Count how many different relocations (different symbol, different
     addend) */
  static unsigned int count_relocs(const Elf32_Rela *rela, unsigned int num)
  {
  	unsigned int i, r_info, r_addend, _count_relocs;
  
  	_count_relocs = 0;
  	r_info = 0;
  	r_addend = 0;
  	for (i = 0; i < num; i++)
  		/* Only count 24-bit relocs, others don't need stubs */
  		if (ELF32_R_TYPE(rela[i].r_info) == R_PPC_REL24 &&
  		    (r_info != ELF32_R_SYM(rela[i].r_info) ||
  		     r_addend != rela[i].r_addend)) {
  			_count_relocs++;
  			r_info = ELF32_R_SYM(rela[i].r_info);
  			r_addend = rela[i].r_addend;
  		}
  
  #ifdef CONFIG_DYNAMIC_FTRACE
  	_count_relocs++;	/* add one for ftrace_caller */
  #endif
  	return _count_relocs;
  }
  
  static int relacmp(const void *_x, const void *_y)
  {
  	const Elf32_Rela *x, *y;
  
  	y = (Elf32_Rela *)_x;
  	x = (Elf32_Rela *)_y;
  
  	/* Compare the entire r_info (as opposed to ELF32_R_SYM(r_info) only) to
  	 * make the comparison cheaper/faster. It won't affect the sorting or
  	 * the counting algorithms' performance
  	 */
  	if (x->r_info < y->r_info)
  		return -1;
  	else if (x->r_info > y->r_info)
  		return 1;
  	else if (x->r_addend < y->r_addend)
  		return -1;
  	else if (x->r_addend > y->r_addend)
  		return 1;
  	else
  		return 0;
  }
  
  static void relaswap(void *_x, void *_y, int size)
  {
  	uint32_t *x, *y, tmp;
  	int i;
  
  	y = (uint32_t *)_x;
  	x = (uint32_t *)_y;
  
  	for (i = 0; i < sizeof(Elf32_Rela) / sizeof(uint32_t); i++) {
  		tmp = x[i];
  		x[i] = y[i];
  		y[i] = tmp;
  	}
  }
  
  /* 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));
  
  			/* Sort the relocation information based on a symbol and
  			 * addend key. This is a stable O(n*log n) complexity
  			 * alogrithm but it will reduce the complexity of
  			 * count_relocs() to linear complexity O(n)
  			 */
  			sort((void *)hdr + sechdrs[i].sh_offset,
  			     sechdrs[i].sh_size / sizeof(Elf32_Rela),
  			     sizeof(Elf32_Rela), relacmp, relaswap);
  
  			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] == 0x3d800000 + ((val + 0x8000) >> 16)
  	    && entry->jump[1] == 0x398c0000 + (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++;
  	}
  
  	entry->jump[0] = 0x3d800000+((val+0x8000)>>16); /* lis r12,sym@ha */
  	entry->jump[1] = 0x398c0000 + (val&0xffff);     /* addi r12,r12,sym@l*/
  	entry->jump[2] = 0x7d8903a6;                    /* mtctr r12 */
  	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_HI:
  			/* Higher half of the symbol */
  			*(uint16_t *)location = (value >> 16);
  			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;
  		}
  	}
  #ifdef CONFIG_DYNAMIC_FTRACE
  	module->arch.tramp =
  		do_plt_call(module->module_core,
  			    (unsigned long)ftrace_caller,
  			    sechdrs, module);
  #endif
  	return 0;
  }
  