linux/arch/arm/kernel/module-plts.c
Rusty Russell 7523e4dc50 module: use a structure to encapsulate layout.
Makes it easier to handle init vs core cleanly, though the change is
fairly invasive across random architectures.

It simplifies the rbtree code immediately, however, while keeping the
core data together in the same cachline (now iff the rbtree code is
enabled).

Acked-by: Peter Zijlstra <peterz@infradead.org>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
2015-12-04 22:46:25 +01:00

183 lines
4.9 KiB
C

/*
* Copyright (C) 2014 Linaro Ltd. <ard.biesheuvel@linaro.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/elf.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <asm/cache.h>
#include <asm/opcodes.h>
#define PLT_ENT_STRIDE L1_CACHE_BYTES
#define PLT_ENT_COUNT (PLT_ENT_STRIDE / sizeof(u32))
#define PLT_ENT_SIZE (sizeof(struct plt_entries) / PLT_ENT_COUNT)
#ifdef CONFIG_THUMB2_KERNEL
#define PLT_ENT_LDR __opcode_to_mem_thumb32(0xf8dff000 | \
(PLT_ENT_STRIDE - 4))
#else
#define PLT_ENT_LDR __opcode_to_mem_arm(0xe59ff000 | \
(PLT_ENT_STRIDE - 8))
#endif
struct plt_entries {
u32 ldr[PLT_ENT_COUNT];
u32 lit[PLT_ENT_COUNT];
};
static bool in_init(const struct module *mod, u32 addr)
{
return addr - (u32)mod->init_layout.base < mod->init_layout.size;
}
u32 get_module_plt(struct module *mod, unsigned long loc, Elf32_Addr val)
{
struct plt_entries *plt, *plt_end;
int c, *count;
if (in_init(mod, loc)) {
plt = (void *)mod->arch.init_plt->sh_addr;
plt_end = (void *)plt + mod->arch.init_plt->sh_size;
count = &mod->arch.init_plt_count;
} else {
plt = (void *)mod->arch.core_plt->sh_addr;
plt_end = (void *)plt + mod->arch.core_plt->sh_size;
count = &mod->arch.core_plt_count;
}
/* Look for an existing entry pointing to 'val' */
for (c = *count; plt < plt_end; c -= PLT_ENT_COUNT, plt++) {
int i;
if (!c) {
/* Populate a new set of entries */
*plt = (struct plt_entries){
{ [0 ... PLT_ENT_COUNT - 1] = PLT_ENT_LDR, },
{ val, }
};
++*count;
return (u32)plt->ldr;
}
for (i = 0; i < PLT_ENT_COUNT; i++) {
if (!plt->lit[i]) {
plt->lit[i] = val;
++*count;
}
if (plt->lit[i] == val)
return (u32)&plt->ldr[i];
}
}
BUG();
}
static int duplicate_rel(Elf32_Addr base, const Elf32_Rel *rel, int num,
u32 mask)
{
u32 *loc1, *loc2;
int i;
for (i = 0; i < num; i++) {
if (rel[i].r_info != rel[num].r_info)
continue;
/*
* Identical relocation types against identical symbols can
* still result in different PLT entries if the addend in the
* place is different. So resolve the target of the relocation
* to compare the values.
*/
loc1 = (u32 *)(base + rel[i].r_offset);
loc2 = (u32 *)(base + rel[num].r_offset);
if (((*loc1 ^ *loc2) & mask) == 0)
return 1;
}
return 0;
}
/* Count how many PLT entries we may need */
static unsigned int count_plts(Elf32_Addr base, const Elf32_Rel *rel, int num)
{
unsigned int ret = 0;
int i;
/*
* Sure, this is order(n^2), but it's usually short, and not
* time critical
*/
for (i = 0; i < num; i++)
switch (ELF32_R_TYPE(rel[i].r_info)) {
case R_ARM_CALL:
case R_ARM_PC24:
case R_ARM_JUMP24:
if (!duplicate_rel(base, rel, i,
__opcode_to_mem_arm(0x00ffffff)))
ret++;
break;
#ifdef CONFIG_THUMB2_KERNEL
case R_ARM_THM_CALL:
case R_ARM_THM_JUMP24:
if (!duplicate_rel(base, rel, i,
__opcode_to_mem_thumb32(0x07ff2fff)))
ret++;
#endif
}
return ret;
}
int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
char *secstrings, struct module *mod)
{
unsigned long core_plts = 0, init_plts = 0;
Elf32_Shdr *s, *sechdrs_end = sechdrs + ehdr->e_shnum;
/*
* To store the PLTs, we expand the .text section for core module code
* and the .init.text section for initialization code.
*/
for (s = sechdrs; s < sechdrs_end; ++s)
if (strcmp(".core.plt", secstrings + s->sh_name) == 0)
mod->arch.core_plt = s;
else if (strcmp(".init.plt", secstrings + s->sh_name) == 0)
mod->arch.init_plt = s;
if (!mod->arch.core_plt || !mod->arch.init_plt) {
pr_err("%s: sections missing\n", mod->name);
return -ENOEXEC;
}
for (s = sechdrs + 1; s < sechdrs_end; ++s) {
const Elf32_Rel *rels = (void *)ehdr + s->sh_offset;
int numrels = s->sh_size / sizeof(Elf32_Rel);
Elf32_Shdr *dstsec = sechdrs + s->sh_info;
if (s->sh_type != SHT_REL)
continue;
if (strstr(secstrings + s->sh_name, ".init"))
init_plts += count_plts(dstsec->sh_addr, rels, numrels);
else
core_plts += count_plts(dstsec->sh_addr, rels, numrels);
}
mod->arch.core_plt->sh_type = SHT_NOBITS;
mod->arch.core_plt->sh_flags = SHF_EXECINSTR | SHF_ALLOC;
mod->arch.core_plt->sh_addralign = L1_CACHE_BYTES;
mod->arch.core_plt->sh_size = round_up(core_plts * PLT_ENT_SIZE,
sizeof(struct plt_entries));
mod->arch.core_plt_count = 0;
mod->arch.init_plt->sh_type = SHT_NOBITS;
mod->arch.init_plt->sh_flags = SHF_EXECINSTR | SHF_ALLOC;
mod->arch.init_plt->sh_addralign = L1_CACHE_BYTES;
mod->arch.init_plt->sh_size = round_up(init_plts * PLT_ENT_SIZE,
sizeof(struct plt_entries));
mod->arch.init_plt_count = 0;
pr_debug("%s: core.plt=%x, init.plt=%x\n", __func__,
mod->arch.core_plt->sh_size, mod->arch.init_plt->sh_size);
return 0;
}