/* 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;
}