linux/arch/powerpc/kernel/module_32.c
Emil Medve eda09fbdcd [POWERPC] Optimize counting distinct entries in the relocation sections
When a module has relocation sections with tens of thousands of
entries, counting the distinct/unique entries only (i.e. no
duplicates) at load time can take tens of seconds and up to minutes.
The sore point is the count_relocs() function which is called as part
of the architecture specific module loading processing path:

	-> load_module()			generic
	   -> module_frob_arch_sections()	arch specific
	      -> get_plt_size()		32-bit
	      -> get_stubs_size()	64-bit
		 -> count_relocs()

Here count_relocs is being called to find out how many distinct
targets of R_PPC_REL24 relocations there are, since each distinct
target needs a PLT entry or a stub created for it.

The previous counting algorithm has O(n^2) complexity.  Basically two
solutions were proposed on the e-mail list: a hash based approach and
a sort based approach.

The hash based approach is the fastest (O(n)) but the has it needs
additional memory and for certain corner cases it could take lots of
memory due to the degeneration of the hash.  One such proposal was
submitted here:

http://ozlabs.org/pipermail/linuxppc-dev/2007-June/037641.html

The sort based approach is slower (O(n * log n + n)) but if the
sorting is done "in place" it doesn't need additional memory.
This has O(n + n * log n) complexity with no additional memory
requirements.

This commit implements the in-place sort option.

Signed-off-by: Emil Medve <Emilian.Medve@Freescale.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
2007-12-21 15:05:58 +11:00

383 lines
10 KiB
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>
#include <linux/bug.h>
#include <linux/sort.h>
#include "setup.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, 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;
}
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] == 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_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;
}
}
return 0;
}
static const Elf_Shdr *find_section(const Elf_Ehdr *hdr,
const Elf_Shdr *sechdrs,
const char *name)
{
char *secstrings;
unsigned int i;
secstrings = (char *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
for (i = 1; i < hdr->e_shnum; i++)
if (strcmp(secstrings+sechdrs[i].sh_name, name) == 0)
return &sechdrs[i];
return NULL;
}
int module_finalize(const Elf_Ehdr *hdr,
const Elf_Shdr *sechdrs,
struct module *me)
{
const Elf_Shdr *sect;
int err;
err = module_bug_finalize(hdr, sechdrs, me);
if (err) /* never true, currently */
return err;
/* Apply feature fixups */
sect = find_section(hdr, sechdrs, "__ftr_fixup");
if (sect != NULL)
do_feature_fixups(cur_cpu_spec->cpu_features,
(void *)sect->sh_addr,
(void *)sect->sh_addr + sect->sh_size);
return 0;
}
void module_arch_cleanup(struct module *mod)
{
module_bug_cleanup(mod);
}
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;
}