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linux/arch/alpha/kernel/module.c
Chaskiel Grundman 69ac59647e [PATCH] alpha: process_reloc_for_got confuses r_offset and r_addend 
arch/alpha/kernel/module.c:process_reloc_for_got(), which figures out how big
the .got section for a module should be, appears to be confusing r_offset (the
file offset that the relocation needs to be applied to) with r_addend (the
offset of the relocation's actual target address from the address of the
relocation's symbol).  Because of this, one .got entry is allocated for each
relocation instead of one each unique symbol/addend.

In the module I am working with, this causes the .got section to be almost 10
times larger than it needs to be (75544 bytes instead of 7608 bytes).  As the
.got is accessed with global-pointer-relative instructions, it needs to be
within the 64k gp "zone", and a 75544 byte .got clearly does not fit.  The
result of this is that relocation overflows are detected during module load
and the load is aborted.

Change struct got_entry/process_reloc_for_got to fix this.

Acked-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-09-09 13:57:30 -07:00

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/* Kernel module help for Alpha.
Copyright (C) 2002 Richard Henderson.
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/moduleloader.h>
#include <linux/elf.h>
#include <linux/vmalloc.h>
#include <linux/fs.h>
#include <linux/string.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#if 0
#define DEBUGP printk
#else
#define DEBUGP(fmt...)
#endif
void *
module_alloc(unsigned long size)
{
if (size == 0)
return NULL;
return vmalloc(size);
}
void
module_free(struct module *mod, void *module_region)
{
vfree(module_region);
}
/* Allocate the GOT at the end of the core sections. */
struct got_entry {
struct got_entry *next;
Elf64_Sxword r_addend;
int got_offset;
};
static inline void
process_reloc_for_got(Elf64_Rela *rela,
struct got_entry *chains, Elf64_Xword *poffset)
{
unsigned long r_sym = ELF64_R_SYM (rela->r_info);
unsigned long r_type = ELF64_R_TYPE (rela->r_info);
Elf64_Sxword r_addend = rela->r_addend;
struct got_entry *g;
if (r_type != R_ALPHA_LITERAL)
return;
for (g = chains + r_sym; g ; g = g->next)
if (g->r_addend == r_addend) {
if (g->got_offset == 0) {
g->got_offset = *poffset;
*poffset += 8;
}
goto found_entry;
}
g = kmalloc (sizeof (*g), GFP_KERNEL);
g->next = chains[r_sym].next;
g->r_addend = r_addend;
g->got_offset = *poffset;
*poffset += 8;
chains[r_sym].next = g;
found_entry:
/* Trick: most of the ELF64_R_TYPE field is unused. There are
42 valid relocation types, and a 32-bit field. Co-opt the
bits above 256 to store the got offset for this reloc. */
rela->r_info |= g->got_offset << 8;
}
int
module_frob_arch_sections(Elf64_Ehdr *hdr, Elf64_Shdr *sechdrs,
char *secstrings, struct module *me)
{
struct got_entry *chains;
Elf64_Rela *rela;
Elf64_Shdr *esechdrs, *symtab, *s, *got;
unsigned long nsyms, nrela, i;
esechdrs = sechdrs + hdr->e_shnum;
symtab = got = NULL;
/* Find out how large the symbol table is. Allocate one got_entry
head per symbol. Normally this will be enough, but not always.
We'll chain different offsets for the symbol down each head. */
for (s = sechdrs; s < esechdrs; ++s)
if (s->sh_type == SHT_SYMTAB)
symtab = s;
else if (!strcmp(".got", secstrings + s->sh_name)) {
got = s;
me->arch.gotsecindex = s - sechdrs;
}
if (!symtab) {
printk(KERN_ERR "module %s: no symbol table\n", me->name);
return -ENOEXEC;
}
if (!got) {
printk(KERN_ERR "module %s: no got section\n", me->name);
return -ENOEXEC;
}
nsyms = symtab->sh_size / sizeof(Elf64_Sym);
chains = kmalloc(nsyms * sizeof(struct got_entry), GFP_KERNEL);
memset(chains, 0, nsyms * sizeof(struct got_entry));
got->sh_size = 0;
got->sh_addralign = 8;
got->sh_type = SHT_NOBITS;
/* Examine all LITERAL relocations to find out what GOT entries
are required. This sizes the GOT section as well. */
for (s = sechdrs; s < esechdrs; ++s)
if (s->sh_type == SHT_RELA) {
nrela = s->sh_size / sizeof(Elf64_Rela);
rela = (void *)hdr + s->sh_offset;
for (i = 0; i < nrela; ++i)
process_reloc_for_got(rela+i, chains,
&got->sh_size);
}
/* Free the memory we allocated. */
for (i = 0; i < nsyms; ++i) {
struct got_entry *g, *n;
for (g = chains[i].next; g ; g = n) {
n = g->next;
kfree(g);
}
}
kfree(chains);
return 0;
}
int
apply_relocate(Elf64_Shdr *sechdrs, const char *strtab, unsigned int symindex,
unsigned int relsec, struct module *me)
{
printk(KERN_ERR "module %s: REL relocation unsupported\n", me->name);
return -ENOEXEC;
}
int
apply_relocate_add(Elf64_Shdr *sechdrs, const char *strtab,
unsigned int symindex, unsigned int relsec,
struct module *me)
{
Elf64_Rela *rela = (void *)sechdrs[relsec].sh_addr;
unsigned long i, n = sechdrs[relsec].sh_size / sizeof(*rela);
Elf64_Sym *symtab, *sym;
void *base, *location;
unsigned long got, gp;
DEBUGP("Applying relocate section %u to %u\n", relsec,
sechdrs[relsec].sh_info);
base = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr;
symtab = (Elf64_Sym *)sechdrs[symindex].sh_addr;
/* The small sections were sorted to the end of the segment.
The following should definitely cover them. */
gp = (u64)me->module_core + me->core_size - 0x8000;
got = sechdrs[me->arch.gotsecindex].sh_addr;
for (i = 0; i < n; i++) {
unsigned long r_sym = ELF64_R_SYM (rela[i].r_info);
unsigned long r_type = ELF64_R_TYPE (rela[i].r_info);
unsigned long r_got_offset = r_type >> 8;
unsigned long value, hi, lo;
r_type &= 0xff;
/* This is where to make the change. */
location = base + rela[i].r_offset;
/* This is the symbol it is referring to. Note that all
unresolved symbols have been resolved. */
sym = symtab + r_sym;
value = sym->st_value + rela[i].r_addend;
switch (r_type) {
case R_ALPHA_NONE:
break;
case R_ALPHA_REFQUAD:
/* BUG() can produce misaligned relocations. */
((u32 *)location)[0] = value;
((u32 *)location)[1] = value >> 32;
break;
case R_ALPHA_GPREL32:
value -= gp;
if ((int)value != value)
goto reloc_overflow;
*(u32 *)location = value;
break;
case R_ALPHA_LITERAL:
hi = got + r_got_offset;
lo = hi - gp;
if ((short)lo != lo)
goto reloc_overflow;
*(u16 *)location = lo;
*(u64 *)hi = value;
break;
case R_ALPHA_LITUSE:
break;
case R_ALPHA_GPDISP:
value = gp - (u64)location;
lo = (short)value;
hi = (int)(value - lo);
if (hi + lo != value)
goto reloc_overflow;
*(u16 *)location = hi >> 16;
*(u16 *)(location + rela[i].r_addend) = lo;
break;
case R_ALPHA_BRSGP:
/* BRSGP is only allowed to bind to local symbols.
If the section is undef, this means that the
value was resolved from somewhere else. */
if (sym->st_shndx == SHN_UNDEF)
goto reloc_overflow;
if ((sym->st_other & STO_ALPHA_STD_GPLOAD) ==
STO_ALPHA_STD_GPLOAD)
/* Omit the prologue. */
value += 8;
/* FALLTHRU */
case R_ALPHA_BRADDR:
value -= (u64)location + 4;
if (value & 3)
goto reloc_overflow;
value = (long)value >> 2;
if (value + (1<<21) >= 1<<22)
goto reloc_overflow;
value &= 0x1fffff;
value |= *(u32 *)location & ~0x1fffff;
*(u32 *)location = value;
break;
case R_ALPHA_HINT:
break;
case R_ALPHA_SREL32:
value -= (u64)location;
if ((int)value != value)
goto reloc_overflow;
*(u32 *)location = value;
break;
case R_ALPHA_SREL64:
value -= (u64)location;
*(u64 *)location = value;
break;
case R_ALPHA_GPRELHIGH:
value = (long)(value - gp + 0x8000) >> 16;
if ((short) value != value)
goto reloc_overflow;
*(u16 *)location = value;
break;
case R_ALPHA_GPRELLOW:
value -= gp;
*(u16 *)location = value;
break;
case R_ALPHA_GPREL16:
value -= gp;
if ((short) value != value)
goto reloc_overflow;
*(u16 *)location = value;
break;
default:
printk(KERN_ERR "module %s: Unknown relocation: %lu\n",
me->name, r_type);
return -ENOEXEC;
reloc_overflow:
if (ELF64_ST_TYPE (sym->st_info) == STT_SECTION)
printk(KERN_ERR
"module %s: Relocation overflow vs section %d\n",
me->name, sym->st_shndx);
else
printk(KERN_ERR
"module %s: Relocation overflow vs %s\n",
me->name, strtab + sym->st_name);
return -ENOEXEC;
}
}
return 0;
}
int
module_finalize(const Elf_Ehdr *hdr, const Elf_Shdr *sechdrs,
struct module *me)
{
return 0;
}
void
module_arch_cleanup(struct module *mod)
{
}
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