metag: Module support

Signed-off-by: James Hogan <james.hogan@imgtec.com>

arch/metag/include/asm/module.h

+#ifndef _ASM_METAG_MODULE_H
+#define _ASM_METAG_MODULE_H
+
+#include <asm-generic/module.h>
+
+struct metag_plt_entry {
+	/* Indirect jump instruction sequence. */
+	unsigned long tramp[2];
+};
+
+struct mod_arch_specific {
+	/* Indices of PLT sections within module. */
+	unsigned int core_plt_section, init_plt_section;
+};
+
+#if defined CONFIG_METAG_META12
+#define MODULE_PROC_FAMILY "META 1.2 "
+#elif defined CONFIG_METAG_META21
+#define MODULE_PROC_FAMILY "META 2.1 "
+#else
+#define MODULE_PROC_FAMILY ""
+#endif
+
+#ifdef CONFIG_4KSTACKS
+#define MODULE_STACKSIZE "4KSTACKS "
+#else
+#define MODULE_STACKSIZE ""
+#endif
+
+#define MODULE_ARCH_VERMAGIC MODULE_PROC_FAMILY MODULE_STACKSIZE
+
+#ifdef MODULE
+asm(".section .plt,\"ax\",@progbits; .balign 8; .previous");
+asm(".section .init.plt,\"ax\",@progbits; .balign 8; .previous");
+#endif
+
+#endif /* _ASM_METAG_MODULE_H */

arch/metag/kernel/module.c

+/*  Kernel module help for Meta.
+
+    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.
+*/
+#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/sort.h>
+
+#include <asm/unaligned.h>
+
+/* 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 relbranch relocs, others don't need stubs */
+		if (ELF32_R_TYPE(rela[i].r_info) == R_METAG_RELBRANCH &&
+		    (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;
+		}
+
+	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") != NULL)
+		    != is_init)
+			continue;
+
+		/* We don't want to look at debug sections. */
+		if (strstr(secstrings + sechdrs[i].sh_name, ".debug") != NULL)
+			continue;
+
+		if (sechdrs[i].sh_type == SHT_RELA) {
+			pr_debug("Found relocations in section %u\n", i);
+			pr_debug("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 metag_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) {
+		pr_err("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.core_plt_section].sh_type = SHT_NOBITS;
+	sechdrs[me->arch.init_plt_section].sh_size
+		= get_plt_size(hdr, sechdrs, secstrings, 1);
+	sechdrs[me->arch.init_plt_section].sh_type = SHT_NOBITS;
+	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 metag_plt_entry *entry;
+	/* Instructions used to do the indirect jump.  */
+	uint32_t tramp[2];
+
+	/* We have to trash a register, so we assume that any control
+	   transfer more than 21-bits away must be a function call
+	   (so we can use a call-clobbered register).  */
+
+	/* MOVT D0Re0,#HI(v) */
+	tramp[0] = 0x02000005 | (((val & 0xffff0000) >> 16) << 3);
+	/* JUMP D0Re0,#LO(v) */
+	tramp[1] = 0xac000001 | ((val & 0x0000ffff) << 3);
+
+	/* 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->tramp[0])
+		if (entry->tramp[0] == tramp[0] && entry->tramp[1] == tramp[1])
+			return (uint32_t)entry;
+		else
+			entry++;
+
+	entry->tramp[0] = tramp[0];
+	entry->tramp[1] = tramp[1];
+
+	return (uint32_t)entry;
+}
+
+int apply_relocate_add(Elf32_Shdr *sechdrs,
+		   const char *strtab,
+		   unsigned int symindex,
+		   unsigned int relsec,
+		   struct module *me)
+{
+	unsigned int i;
+	Elf32_Rela *rel = (void *)sechdrs[relsec].sh_addr;
+	Elf32_Sym *sym;
+	Elf32_Addr relocation;
+	uint32_t *location;
+	int32_t value;
+
+	pr_debug("Applying relocate section %u to %u\n", relsec,
+		 sechdrs[relsec].sh_info);
+	for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
+		/* This is where to make the change */
+		location = (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 = (Elf32_Sym *)sechdrs[symindex].sh_addr
+			+ ELF32_R_SYM(rel[i].r_info);
+		relocation = sym->st_value + rel[i].r_addend;
+
+		switch (ELF32_R_TYPE(rel[i].r_info)) {
+		case R_METAG_NONE:
+			break;
+		case R_METAG_HIADDR16:
+			relocation >>= 16;
+		case R_METAG_LOADDR16:
+			*location = (*location & 0xfff80007) |
+				((relocation & 0xffff) << 3);
+			break;
+		case R_METAG_ADDR32:
+			/*
+			 * Packed data structures may cause a misaligned
+			 * R_METAG_ADDR32 to be emitted.
+			 */
+			put_unaligned(relocation, location);
+			break;
+		case R_METAG_GETSETOFF:
+			*location += ((relocation & 0xfff) << 7);
+			break;
+		case R_METAG_RELBRANCH:
+			if (*location & (0x7ffff << 5)) {
+				pr_err("bad relbranch relocation\n");
+				break;
+			}
+
+			/* This jump is too big for the offset slot. Build
+			 * a PLT to jump through to get to where we want to go.
+			 * NB: 21bit check - not scaled to 19bit yet
+			 */
+			if (((int32_t)(relocation -
+				       (uint32_t)location) > 0xfffff) ||
+			    ((int32_t)(relocation -
+				       (uint32_t)location) < -0xfffff)) {
+				relocation = do_plt_call(location, relocation,
+							 sechdrs, me);
+			}
+
+			value = relocation - (uint32_t)location;
+
+			/* branch instruction aligned */
+			value /= 4;
+
+			if ((value > 0x7ffff) || (value < -0x7ffff)) {
+				/*
+				 * this should have been caught by the code
+				 * above!
+				 */
+				pr_err("overflow of relbranch reloc\n");
+			}
+
+			*location = (*location & (~(0x7ffff << 5))) |
+				((value & 0x7ffff) << 5);
+			break;
+
+		default:
+			pr_err("module %s: Unknown relocation: %u\n",
+			       me->name, ELF32_R_TYPE(rel[i].r_info));
+			return -ENOEXEC;
+		}
+	}
+	return 0;
+}