/*
* Copyright (C) 2015 Imagination Technologies
* Author: Alex Smith <alex.smith@imgtec.com>
*
* 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.
*/
static inline bool FUNC(patch_vdso)(const char *path, void *vdso)
{
const ELF(Ehdr) *ehdr = vdso;
void *shdrs;
ELF(Shdr) *shdr;
char *shstrtab, *name;
uint16_t sh_count, sh_entsize, i;
unsigned int local_gotno, symtabno, gotsym;
ELF(Dyn) *dyn = NULL;
shdrs = vdso + FUNC(swap_uint)(ehdr->e_shoff);
sh_count = swap_uint16(ehdr->e_shnum);
sh_entsize = swap_uint16(ehdr->e_shentsize);
shdr = shdrs + (sh_entsize * swap_uint16(ehdr->e_shstrndx));
shstrtab = vdso + FUNC(swap_uint)(shdr->sh_offset);
for (i = 0; i < sh_count; i++) {
shdr = shdrs + (i * sh_entsize);
name = shstrtab + swap_uint32(shdr->sh_name);
/*
* Ensure there are no relocation sections - ld.so does not
* relocate the VDSO so if there are relocations things will
* break.
*/
switch (swap_uint32(shdr->sh_type)) {
case SHT_REL:
case SHT_RELA:
fprintf(stderr,
"%s: '%s' contains relocation sections\n",
program_name, path);
return false;
case SHT_DYNAMIC:
dyn = vdso + FUNC(swap_uint)(shdr->sh_offset);
break;
}
/* Check for existing sections. */
if (strcmp(name, ".MIPS.abiflags") == 0) {
fprintf(stderr,
"%s: '%s' already contains a '.MIPS.abiflags' section\n",
program_name, path);
return false;
}
if (strcmp(name, ".mips_abiflags") == 0) {
strcpy(name, ".MIPS.abiflags");
shdr->sh_type = swap_uint32(SHT_MIPS_ABIFLAGS);
shdr->sh_entsize = shdr->sh_size;
}
}
/*
* Ensure the GOT has no entries other than the standard 2, for the same
* reason we check that there's no relocation sections above.
* The standard two entries are:
* - Lazy resolver
* - Module pointer
*/
if (dyn) {
local_gotno = symtabno = gotsym = 0;
while (FUNC(swap_uint)(dyn->d_tag) != DT_NULL) {
switch (FUNC(swap_uint)(dyn->d_tag)) {
/*
* This member holds the number of local GOT entries.
*/
case DT_MIPS_LOCAL_GOTNO:
local_gotno = FUNC(swap_uint)(dyn->d_un.d_val);
break;
/*
* This member holds the number of entries in the
* .dynsym section.
*/
case DT_MIPS_SYMTABNO:
symtabno = FUNC(swap_uint)(dyn->d_un.d_val);
break;
/*
* This member holds the index of the first dynamic
* symbol table entry that corresponds to an entry in
* the GOT.
*/
case DT_MIPS_GOTSYM:
gotsym = FUNC(swap_uint)(dyn->d_un.d_val);
break;
}
dyn++;
}
if (local_gotno > 2 || symtabno - gotsym) {
fprintf(stderr,
"%s: '%s' contains unexpected GOT entries\n",
program_name, path);
return false;
}
}
return true;
}
static inline bool FUNC(get_symbols)(const char *path, void *vdso)
{
const ELF(Ehdr) *ehdr = vdso;
void *shdrs, *symtab;
ELF(Shdr) *shdr;
const ELF(Sym) *sym;
char *strtab, *name;
uint16_t sh_count, sh_entsize, st_count, st_entsize, i, j;
uint64_t offset;
uint32_t flags;
shdrs = vdso + FUNC(swap_uint)(ehdr->e_shoff);
sh_count = swap_uint16(ehdr->e_shnum);
sh_entsize = swap_uint16(ehdr->e_shentsize);
for (i = 0; i < sh_count; i++) {
shdr = shdrs + (i * sh_entsize);
if (swap_uint32(shdr->sh_type) == SHT_SYMTAB)
break;
}
if (i == sh_count) {
fprintf(stderr, "%s: '%s' has no symbol table\n", program_name,
path);
return false;
}
/* Get flags */
flags = swap_uint32(ehdr->e_flags);
if (elf_class == ELFCLASS64)
elf_abi = ABI_N64;
else if (flags & EF_MIPS_ABI2)
elf_abi = ABI_N32;
else
elf_abi = ABI_O32;
/* Get symbol table. */
symtab = vdso + FUNC(swap_uint)(shdr->sh_offset);
st_entsize = FUNC(swap_uint)(shdr->sh_entsize);
st_count = FUNC(swap_uint)(shdr->sh_size) / st_entsize;
/* Get string table. */
shdr = shdrs + (swap_uint32(shdr->sh_link) * sh_entsize);
strtab = vdso + FUNC(swap_uint)(shdr->sh_offset);
/* Write offsets for symbols needed by the kernel. */
for (i = 0; vdso_symbols[i].name; i++) {
if (!(vdso_symbols[i].abis & elf_abi))
continue;
for (j = 0; j < st_count; j++) {
sym = symtab + (j * st_entsize);
name = strtab + swap_uint32(sym->st_name);
if (!strcmp(name, vdso_symbols[i].name)) {
offset = FUNC(swap_uint)(sym->st_value);
fprintf(out_file,
"\t.%s = 0x%" PRIx64 ",\n",
vdso_symbols[i].offset_name, offset);
break;
}
}
if (j == st_count) {
fprintf(stderr,
"%s: '%s' is missing required symbol '%s'\n",
program_name, path, vdso_symbols[i].name);
return false;
}
}
return true;
}
