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Atmosphere/libraries/libmesosphere/source/init/kern_init_elf.cpp

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/*
* Copyright (c) Atmosphère-NX
*
* This program is free software; you can redistribute it and/or modify it
* under the terms and conditions of the GNU General Public License,
* version 2, as published by the Free Software Foundation.
*
* This program is distributed in the hope 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, see <http://www.gnu.org/licenses/>.
*/
#include <mesosphere.hpp>
namespace ams::kern::init::Elf {
/* API to apply relocations or call init array. */
void ApplyRelocations(uintptr_t base_address, const Dyn *dynamic) {
uintptr_t dyn_rel = 0;
uintptr_t dyn_rela = 0;
uintptr_t dyn_relr = 0;
uintptr_t rel_count = 0;
uintptr_t rela_count = 0;
uintptr_t relr_sz = 0;
uintptr_t rel_ent = 0;
uintptr_t rela_ent = 0;
uintptr_t relr_ent = 0;
/* Iterate over all tags, identifying important extents. */
for (const Dyn *cur_entry = dynamic; cur_entry->GetTag() != DT_NULL; cur_entry++) {
switch (cur_entry->GetTag()) {
case DT_REL:
dyn_rel = base_address + cur_entry->GetPtr();
break;
case DT_RELA:
dyn_rela = base_address + cur_entry->GetPtr();
break;
case DT_RELR:
dyn_relr = base_address + cur_entry->GetPtr();
break;
case DT_RELENT:
rel_ent = cur_entry->GetValue();
break;
case DT_RELAENT:
rela_ent = cur_entry->GetValue();
break;
case DT_RELRENT:
relr_ent = cur_entry->GetValue();
break;
case DT_RELCOUNT:
rel_count = cur_entry->GetValue();
break;
case DT_RELACOUNT:
rela_count = cur_entry->GetValue();
break;
case DT_RELRSZ:
relr_sz = cur_entry->GetValue();
break;
}
}
/* Apply all Rel relocations */
if (rel_count > 0) {
/* Check that the rel relocations are applyable. */
MESOSPHERE_INIT_ABORT_UNLESS(dyn_rel != 0);
MESOSPHERE_INIT_ABORT_UNLESS(rel_ent == sizeof(Elf::Rel));
for (size_t i = 0; i < rel_count; ++i) {
const auto &rel = reinterpret_cast<const Elf::Rel *>(dyn_rel)[i];
/* Only allow architecture-specific relocations. */
while (rel.GetType() != R_ARCHITECTURE_RELATIVE) { /* ... */ }
/* Apply the relocation. */
Elf::Addr *target_address = reinterpret_cast<Elf::Addr *>(base_address + rel.GetOffset());
*target_address += base_address;
}
}
/* Apply all Rela relocations. */
if (rela_count > 0) {
/* Check that the rela relocations are applyable. */
MESOSPHERE_INIT_ABORT_UNLESS(dyn_rela != 0);
MESOSPHERE_INIT_ABORT_UNLESS(rela_ent == sizeof(Elf::Rela));
for (size_t i = 0; i < rela_count; ++i) {
const auto &rela = reinterpret_cast<const Elf::Rela *>(dyn_rela)[i];
/* Only allow architecture-specific relocations. */
while (rela.GetType() != R_ARCHITECTURE_RELATIVE) { /* ... */ }
/* Apply the relocation. */
Elf::Addr *target_address = reinterpret_cast<Elf::Addr *>(base_address + rela.GetOffset());
*target_address = base_address + rela.GetAddend();
}
}
/* Apply all Relr relocations. */
if (relr_sz >= sizeof(Elf::Relr)) {
/* Check that the relr relocations are applyable. */
MESOSPHERE_INIT_ABORT_UNLESS(dyn_relr != 0);
MESOSPHERE_INIT_ABORT_UNLESS(relr_ent == sizeof(Elf::Relr));
const size_t relr_count = relr_sz / sizeof(Elf::Relr);
Elf::Addr *where = nullptr;
for (size_t i = 0; i < relr_count; ++i) {
const auto &relr = reinterpret_cast<const Elf::Relr *>(dyn_relr)[i];
if (relr.IsLocation()) {
/* Update location. */
where = reinterpret_cast<Elf::Addr *>(base_address + relr.GetLocation());
/* Apply the relocation. */
*(where++) += base_address;
} else {
/* Get the bitmap. */
u64 bitmap = relr.GetBitmap();
/* Apply all relocations. */
while (bitmap != 0) {
const u64 next = util::CountTrailingZeros(bitmap);
bitmap &= ~(static_cast<u64>(1) << next);
where[next] += base_address;
}
/* Advance. */
where += BITSIZEOF(bitmap) - 1;
}
}
}
}
void CallInitArrayFuncs(uintptr_t init_array_start, uintptr_t init_array_end) {
for (uintptr_t cur_entry = init_array_start; cur_entry < init_array_end; cur_entry += sizeof(void *)) {
(*(void (**)())(cur_entry))();
}
}
}