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9a0b5817ad
Implement SMP alternatives, i.e. switching at runtime between different code versions for UP and SMP. The code can patch both SMP->UP and UP->SMP. The UP->SMP case is useful for CPU hotplug. With CONFIG_CPU_HOTPLUG enabled the code switches to UP at boot time and when the number of CPUs goes down to 1, and switches to SMP when the number of CPUs goes up to 2. Without CONFIG_CPU_HOTPLUG or on non-SMP-capable systems the code is patched once at boot time (if needed) and the tables are released afterwards. The changes in detail: * The current alternatives bits are moved to a separate file, the SMP alternatives code is added there. * The patch adds some new elf sections to the kernel: .smp_altinstructions like .altinstructions, also contains a list of alt_instr structs. .smp_altinstr_replacement like .altinstr_replacement, but also has some space to save original instruction before replaving it. .smp_locks list of pointers to lock prefixes which can be nop'ed out on UP. The first two are used to replace more complex instruction sequences such as spinlocks and semaphores. It would be possible to deal with the lock prefixes with that as well, but by handling them as special case the table sizes become much smaller. * The sections are page-aligned and padded up to page size, so they can be free if they are not needed. * Splitted the code to release init pages to a separate function and use it to release the elf sections if they are unused. Signed-off-by: Gerd Hoffmann <kraxel@suse.de> Signed-off-by: Chuck Ebbert <76306.1226@compuserve.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
141 lines
3.8 KiB
C
141 lines
3.8 KiB
C
/* Kernel module help for i386.
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Copyright (C) 2001 Rusty Russell.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#include <linux/moduleloader.h>
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#include <linux/elf.h>
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#include <linux/vmalloc.h>
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#include <linux/fs.h>
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#include <linux/string.h>
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#include <linux/kernel.h>
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#if 0
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#define DEBUGP printk
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#else
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#define DEBUGP(fmt...)
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#endif
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void *module_alloc(unsigned long size)
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{
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if (size == 0)
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return NULL;
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return vmalloc_exec(size);
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}
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/* Free memory returned from module_alloc */
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void module_free(struct module *mod, void *module_region)
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{
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vfree(module_region);
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/* FIXME: If module_region == mod->init_region, trim exception
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table entries. */
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}
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/* We don't need anything special. */
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int module_frob_arch_sections(Elf_Ehdr *hdr,
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Elf_Shdr *sechdrs,
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char *secstrings,
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struct module *mod)
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{
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return 0;
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}
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int apply_relocate(Elf32_Shdr *sechdrs,
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const char *strtab,
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unsigned int symindex,
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unsigned int relsec,
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struct module *me)
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{
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unsigned int i;
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Elf32_Rel *rel = (void *)sechdrs[relsec].sh_addr;
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Elf32_Sym *sym;
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uint32_t *location;
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DEBUGP("Applying relocate section %u to %u\n", relsec,
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sechdrs[relsec].sh_info);
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for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
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/* This is where to make the change */
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location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
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+ rel[i].r_offset;
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/* This is the symbol it is referring to. Note that all
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undefined symbols have been resolved. */
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sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
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+ ELF32_R_SYM(rel[i].r_info);
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switch (ELF32_R_TYPE(rel[i].r_info)) {
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case R_386_32:
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/* We add the value into the location given */
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*location += sym->st_value;
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break;
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case R_386_PC32:
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/* Add the value, subtract its postition */
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*location += sym->st_value - (uint32_t)location;
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break;
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default:
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printk(KERN_ERR "module %s: Unknown relocation: %u\n",
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me->name, ELF32_R_TYPE(rel[i].r_info));
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return -ENOEXEC;
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}
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}
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return 0;
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}
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int apply_relocate_add(Elf32_Shdr *sechdrs,
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const char *strtab,
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unsigned int symindex,
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unsigned int relsec,
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struct module *me)
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{
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printk(KERN_ERR "module %s: ADD RELOCATION unsupported\n",
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me->name);
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return -ENOEXEC;
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}
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int module_finalize(const Elf_Ehdr *hdr,
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const Elf_Shdr *sechdrs,
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struct module *me)
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{
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const Elf_Shdr *s, *text = NULL, *alt = NULL, *locks = NULL;
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char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
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for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
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if (!strcmp(".text", secstrings + s->sh_name))
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text = s;
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if (!strcmp(".altinstructions", secstrings + s->sh_name))
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alt = s;
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if (!strcmp(".smp_locks", secstrings + s->sh_name))
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locks= s;
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}
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if (alt) {
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/* patch .altinstructions */
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void *aseg = (void *)alt->sh_addr;
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apply_alternatives(aseg, aseg + alt->sh_size);
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}
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if (locks && text) {
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void *lseg = (void *)locks->sh_addr;
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void *tseg = (void *)text->sh_addr;
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alternatives_smp_module_add(me, me->name,
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lseg, lseg + locks->sh_size,
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tseg, tseg + text->sh_size);
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}
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return 0;
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}
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void module_arch_cleanup(struct module *mod)
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{
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alternatives_smp_module_del(mod);
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}
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