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kern: patch svc tables via asm, instead of relying on compiler to be nice

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This commit is contained in:
Michael Scire 2020-07-13 19:16:05 -07:00 committed by SciresM
parent d9e9fbe3c2
commit ef1763334b
2 changed files with 37 additions and 9 deletions
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19
libraries/libmesosphere/source/arch/arm64/svc/kern_svc_tables.cpp
View file

@ -92,6 +92,8 @@ namespace ams::kern::svc {
constinit const std::array<SvcTableEntry, NumSupervisorCalls> SvcTable64From32 = SvcTable64From32Impl;
void PatchSvcTableEntry(const SvcTableEntry *table, u32 id, SvcTableEntry entry);
namespace {
/* NOTE: Although the SVC tables are constants, our global constructor will run before .rodata is protected R--. */
@ -101,34 +103,33 @@ namespace ams::kern::svc {
private:
static SvcTablePatcher s_instance;
private:
ALWAYS_INLINE volatile SvcTableEntry *GetEditableTable(const SvcTable *table) {
ALWAYS_INLINE const SvcTableEntry *GetTableData(const SvcTable *table) {
if (table != nullptr) {
return const_cast<volatile SvcTableEntry *>(table->data());
return table->data();
} else {
return nullptr;
}
}
/* TODO: This should perhaps be implemented in assembly. */
NOINLINE void PatchTables(volatile SvcTableEntry *table_64, volatile SvcTableEntry *table_64_from_32) {
NOINLINE void PatchTables(const SvcTableEntry *table_64, const SvcTableEntry *table_64_from_32) {
/* Get the target firmware. */
const auto target_fw = kern::GetTargetFirmware();
/* 10.0.0 broke the ABI for QueryIoMapping. */
if (target_fw < TargetFirmware_10_0_0) {
if (table_64) { table_64[ svc::SvcId_QueryIoMapping] = LegacyQueryIoMapping::Call64; }
if (table_64_from_32) { table_64_from_32[svc::SvcId_QueryIoMapping] = LegacyQueryIoMapping::Call64From32; }
if (table_64) { ::ams::kern::svc::PatchSvcTableEntry(table_64, svc::SvcId_QueryIoMapping, LegacyQueryIoMapping::Call64); }
if (table_64_from_32) { ::ams::kern::svc::PatchSvcTableEntry(table_64_from_32, svc::SvcId_QueryIoMapping, LegacyQueryIoMapping::Call64From32); }
}
/* 3.0.0 broke the ABI for ContinueDebugEvent. */
if (target_fw < TargetFirmware_3_0_0) {
if (table_64) { table_64[ svc::SvcId_ContinueDebugEvent] = LegacyContinueDebugEvent::Call64; }
if (table_64_from_32) { table_64_from_32[svc::SvcId_ContinueDebugEvent] = LegacyContinueDebugEvent::Call64From32; }
if (table_64) { ::ams::kern::svc::PatchSvcTableEntry(table_64, svc::SvcId_ContinueDebugEvent, LegacyContinueDebugEvent::Call64); }
if (table_64_from_32) { ::ams::kern::svc::PatchSvcTableEntry(table_64_from_32, svc::SvcId_ContinueDebugEvent, LegacyContinueDebugEvent::Call64From32); }
}
}
public:
SvcTablePatcher(const SvcTable *table_64, const SvcTable *table_64_from_32) {
PatchTables(GetEditableTable(table_64), GetEditableTable(table_64_from_32));
PatchTables(GetTableData(table_64), GetTableData(table_64_from_32));
}
};

27
mesosphere/kernel/source/arch/arm64/svc/kern_svc_tables_asm.s Normal file
View file

@ -0,0 +1,27 @@
/*
* Copyright (c) 2018-2020 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/>.
*/
/* ams::kern::svc::PatchSvcTableEntry(void (* const*)(), unsigned int, void (*)()) */
.section .text._ZN3ams4kern3svc18PatchSvcTableEntryEPKPFvvEjS3_, "ax", %progbits
.global _ZN3ams4kern3svc18PatchSvcTableEntryEPKPFvvEjS3_
.type _ZN3ams4kern3svc18PatchSvcTableEntryEPKPFvvEjS3_, %function
_ZN3ams4kern3svc18PatchSvcTableEntryEPKPFvvEjS3_:
/* This function violates const correctness by design, to patch the svc tables. */
/* The svc tables live in .rodata (.rel.ro), but must be patched by initial constructors */
/* to support firmware-specific table entries. */
mov w1, w1
str x2, [x0, x1, lsl #3]
ret