Introduce Basic Junction Patching

This commit introduces basic junction patching or patching code to jump to a junction then execute intermediate functions and jump back.

.idea/codeStyles/Project.xml

@@ -15,10 +15,13 @@
       <option name="FUNCTION_TOP_AFTER_RETURN_TYPE_WRAP" value="0" />
       <option name="FUNCTION_PARAMETERS_WRAP" value="5" />
       <option name="FUNCTION_CALL_ARGUMENTS_WRAP" value="5" />
+      <option name="SHIFT_OPERATION_WRAP" value="0" />
       <option name="TEMPLATE_DECLARATION_STRUCT_WRAP" value="1" />
       <option name="TEMPLATE_DECLARATION_FUNCTION_WRAP" value="1" />
       <option name="TEMPLATE_CALL_ARGUMENTS_WRAP" value="5" />
       <option name="TEMPLATE_CALL_ARGUMENTS_ALIGN_MULTILINE" value="true" />
+      <option name="CLASS_CONSTRUCTOR_INIT_LIST_WRAP" value="0" />
+      <option name="SUPERCLASS_LIST_WRAP" value="0" />
       <option name="ALIGN_INIT_LIST_IN_COLUMNS" value="false" />
       <option name="HEADER_GUARD_STYLE_PATTERN" value="${PROJECT_NAME}_${PROJECT_REL_PATH}_${FILE_NAME}_${EXT}" />
       <option name="MACROS_NAMING_CONVENTION">

.idea/misc.xml

@@ -43,7 +43,7 @@
       </value>
     </option>
   </component>
-  <component name="ProjectRootManager" version="2" languageLevel="JDK_1_8" project-jdk-name="1.8" project-jdk-type="JavaSDK">
+  <component name="ProjectRootManager" version="2" languageLevel="JDK_1_8" project-jdk-name="JDK" project-jdk-type="JavaSDK">
     <output url="file://$PROJECT_DIR$/build/classes" />
   </component>
   <component name="ProjectType">

app/CMakeLists.txt

@@ -7,6 +7,7 @@ set(CMAKE_CXX_STANDARD 17)
 set(CMAKE_CXX_STANDARD_REQUIRED TRUE)
 set(source_DIR ${CMAKE_SOURCE_DIR}/src/main/cpp)
 set(CMAKE_CXX_FLAGS_RELEASE "-Ofast -flto=full -Wno-unused-command-line-argument")
+enable_language(ASM)
 if (uppercase_CMAKE_BUILD_TYPE STREQUAL "RELEASE")
     add_compile_definitions(NDEBUG)
 endif()
@@ -21,6 +22,7 @@ include_directories(${source_DIR}/skyline)
 add_library(skyline SHARED
         ${source_DIR}/main.cpp
         ${source_DIR}/skyline/common.cpp
+        ${source_DIR}/skyline/guest.S
         ${source_DIR}/skyline/nce.cpp
         ${source_DIR}/skyline/jvm.cpp
         ${source_DIR}/skyline/gpu.cpp

app/src/main/cpp/skyline/common.h

@@ -47,7 +47,7 @@ namespace skyline {
         // Loader
         constexpr u32 NroMagic = 0x304F524E; //!< "NRO0" in reverse, this is written at the start of every NRO file
         // NCE
-        constexpr u8 NumRegs = 31; //!< The amount of registers that ARMv8 has
+        constexpr u8 NumRegs = 30; //!< The amount of registers that ARMv8 has
         constexpr u16 SvcLast = 0x7F; //!< The index of the last SVC
         constexpr u16 BrkRdy = 0xFF; //!< This is reserved for our kernel's to know when a process/thread is ready
         constexpr u32 TpidrroEl0 = 0x5E83; //!< ID of TPIDRRO_EL0 in MRS
@@ -105,86 +105,6 @@ namespace skyline {
         NSP, //!< The NSP format from "nspwn" exploit: https://switchbrew.org/wiki/Switch_System_Flaws
     };
 
-    namespace instr {
-        /**
-         * @brief A bit-field struct that encapsulates a BRK instruction. See https://developer.arm.com/docs/ddi0596/latest/base-instructions-alphabetic-order/brk-breakpoint-instruction.
-         */
-        struct Brk {
-            /**
-             * @brief Creates a BRK instruction with a specific immediate value, used for generating BRK opcodes
-             * @param val The immediate value of the instruction
-             */
-            Brk(u16 val) {
-                start = 0x0; // First 5 bits of a BRK instruction are 0
-                value = val;
-                end = 0x6A1; // Last 11 bits of a BRK instruction stored as u16
-            }
-
-            /**
-             * @brief Returns if the opcode is valid or not
-             * @return If the opcode represents a valid BRK instruction
-             */
-            bool Verify() {
-                return (start == 0x0 && end == 0x6A1);
-            }
-
-            u8 start : 5;
-            u32 value : 16;
-            u16 end : 11;
-        };
-
-        static_assert(sizeof(Brk) == sizeof(u32));
-
-        /**
-         * @brief A bit-field struct that encapsulates a SVC instruction. See https://developer.arm.com/docs/ddi0596/latest/base-instructions-alphabetic-order/svc-supervisor-call.
-         */
-        struct Svc {
-            /**
-             * @brief Returns if the opcode is valid or not
-             * @return If the opcode represents a valid SVC instruction
-             */
-            bool Verify() {
-                return (start == 0x1 && end == 0x6A0);
-            }
-
-            u8 start : 5;
-            u32 value : 16;
-            u16 end : 11;
-        };
-
-        static_assert(sizeof(Svc) == sizeof(u32));
-
-        /**
-         * @brief A bit-field struct that encapsulates a MRS instruction. See https://developer.arm.com/docs/ddi0596/latest/base-instructions-alphabetic-order/mrs-move-system-register.
-         */
-        struct Mrs {
-            /**
-             * @brief Creates a MRS instruction, used for generating BRK opcodes
-             * @param srcReg The source system register
-             * @param dstReg The destination Xn register
-             */
-            Mrs(u32 srcReg, u8 dstReg) {
-                this->srcReg = srcReg;
-                this->dstReg = dstReg;
-                end = 0xD53; // Last 12 bits of a MRS instruction stored as u16
-            }
-
-            /**
-             * @brief Returns if the opcode is valid or not
-             * @return If the opcode represents a valid MRS instruction
-             */
-            bool Verify() {
-                return (end == 0xD53);
-            }
-
-            u8 dstReg : 5;
-            u32 srcReg : 15;
-            u16 end : 12;
-        };
-
-        static_assert(sizeof(Mrs) == sizeof(u32));
-    };
-
     /**
      * Read about ARMv8 registers here: https://developer.arm.com/docs/100878/latest/registers
      */

app/src/main/cpp/skyline/guest.S

@@ -0,0 +1,46 @@
+.text
+.global saveCtx
+saveCtx:
+    STR LR, [SP, #-16]!
+    MRS LR, TPIDR_EL0
+    #LDR LR, [LR]
+    STP X0, X1, [LR, #0]
+    STP X2, X3, [LR, #16]
+    STP X4, X5, [LR, #32]
+    STP X6, X7, [LR, #48]
+    STP X8, X9, [LR, #64]
+    STP X10, X11, [LR, #80]
+    STP X12, X13, [LR, #96]
+    STP X14, X15, [LR, #112]
+    STP X16, X17, [LR, #128]
+    STP X18, X19, [LR, #144]
+    STP X20, X21, [LR, #160]
+    STP X22, X23, [LR, #176]
+    STP X24, X25, [LR, #192]
+    STP X26, X27, [LR, #208]
+    STP X28, X29, [LR, #224]
+    LDR LR, [SP], #16
+    RET
+
+.global loadCtx
+loadCtx:
+    STR LR, [SP, #-16]!
+    MRS LR, TPIDR_EL0
+    #LDR LR, [LR]
+    LDP X0, X1, [LR, #0]
+    LDP X2, X3, [LR, #16]
+    LDP X4, X5, [LR, #32]
+    LDP X6, X7, [LR, #48]
+    LDP X8, X9, [LR, #64]
+    LDP X10, X11, [LR, #80]
+    LDP X12, X13, [LR, #96]
+    LDP X14, X15, [LR, #112]
+    LDP X16, X17, [LR, #128]
+    LDP X18, X19, [LR, #144]
+    LDP X20, X21, [LR, #160]
+    LDP X22, X23, [LR, #176]
+    LDP X24, X25, [LR, #192]
+    LDP X26, X27, [LR, #208]
+    LDP X28, X29, [LR, #224]
+    LDR LR, [SP], #16
+    RET

app/src/main/cpp/skyline/guest.h

@@ -0,0 +1,8 @@
+#pragma once
+
+namespace skyline::guest {
+    constexpr size_t saveCtxSize = 20 * sizeof(u32);
+    constexpr size_t loadCtxSize = 20 * sizeof(u32);
+    extern "C" void saveCtx(void);
+    extern "C" void loadCtx(void);
+}

app/src/main/cpp/skyline/loader/loader.h

@@ -21,32 +21,6 @@ namespace skyline::loader {
             pread64(romFd, output, size, offset);
         }
 
-        /**
-         * @brief This patches specific parts of the code
-         * @param code A vector with the code to be patched
-         */
-        inline void PatchCode(std::vector<u8> &code) {
-            u32 *address = reinterpret_cast<u32 *>(code.data());
-            u32 *end = address + (code.size() / sizeof(u32));
-            while (address < end) {
-                auto instrSvc = reinterpret_cast<instr::Svc *>(address);
-                auto instrMrs = reinterpret_cast<instr::Mrs *>(address);
-                if (instrSvc->Verify()) {
-                    instr::Brk brk(static_cast<u16>(instrSvc->value));
-                    *address = *reinterpret_cast<u32 *>(&brk);
-                } else if (instrMrs->Verify()) {
-                    if (instrMrs->srcReg == constant::TpidrroEl0) {
-                        instr::Brk brk(static_cast<u16>(constant::SvcLast + 1 + instrMrs->dstReg));
-                        *address = *reinterpret_cast<u32 *>(&brk);
-                    } else if (instrMrs->srcReg == constant::CntpctEl0) {
-                        instr::Mrs mrs(constant::CntvctEl0, instrMrs->dstReg);
-                        *address = *reinterpret_cast<u32 *>(&mrs);
-                    }
-                }
-                address++;
-            }
-        }
-
       public:
         /**
          * @param filePath The path to the ROM file

app/src/main/cpp/skyline/loader/nro.cpp

@@ -17,11 +17,12 @@ namespace skyline::loader {
         ReadOffset(rodata.data(), header.ro.offset, header.ro.size);
         ReadOffset(data.data(), header.data.offset, header.data.size);
 
-        PatchCode(text);
+        std::vector<u32> patch = state.nce->PatchCode(text, header.text.size + header.ro.size + header.data.size + header.bssSize);
 
         u64 textSize = text.size();
         u64 rodataSize = rodata.size();
         u64 dataSize = data.size();
+        u64 patchSize = patch.size() * sizeof(u32);
 
         process->MapPrivateRegion(constant::BaseAddr, textSize, {true, true, true}, memory::Type::CodeStatic, memory::Region::Text); // R-X
         state.logger->Debug("Successfully mapped region .text @ 0x{0:X}, Size = 0x{1:X}", constant::BaseAddr, textSize);
@@ -35,8 +36,12 @@ namespace skyline::loader {
         process->MapPrivateRegion(constant::BaseAddr + textSize + rodataSize + dataSize, header.bssSize, {true, true, true}, memory::Type::CodeMutable, memory::Region::Bss); // RWX
         state.logger->Debug("Successfully mapped region .bss @ 0x{0:X}, Size = 0x{1:X}", constant::BaseAddr + textSize + rodataSize + dataSize, header.bssSize);
 
+        process->MapPrivateRegion(constant::BaseAddr + textSize + rodataSize + dataSize + header.bssSize, patchSize, {true, true, true}, memory::Type::CodeStatic, memory::Region::Text); // RWX
+        state.logger->Debug("Successfully mapped region .patch @ 0x{0:X}, Size = 0x{1:X}", constant::BaseAddr + textSize + rodataSize + dataSize + header.bssSize, patchSize);
+
         process->WriteMemory(text.data(), constant::BaseAddr, textSize);
         process->WriteMemory(rodata.data(), constant::BaseAddr + textSize, rodataSize);
         process->WriteMemory(data.data(), constant::BaseAddr + textSize + rodataSize, dataSize);
+        process->WriteMemory(patch.data(), constant::BaseAddr + textSize + rodataSize + dataSize + header.bssSize, patchSize);
     }
 }

app/src/main/cpp/skyline/nce.cpp

@@ -3,11 +3,182 @@
 #include <linux/elf.h>
 #include "os.h"
 #include "jvm.h"
+#include "guest.h"
 
 extern bool Halt;
 extern std::mutex jniMtx;
 
 namespace skyline {
+
+    namespace instr {
+        /**
+         * @brief A bit-field struct that encapsulates a BRK instruction. See https://developer.arm.com/docs/ddi0596/latest/base-instructions-alphabetic-order/brk-breakpoint-instruction.
+         */
+        struct Brk {
+            /**
+             * @brief Creates a BRK instruction with a specific immediate value, used for generating BRK opcodes
+             * @param value The immediate value of the instruction
+             */
+            explicit Brk(u16 value) {
+                start = 0x0; // First 5 bits of a BRK instruction are 0
+                this->value = value;
+                end = 0x6A1; // Last 11 bits of a BRK instruction stored as u16
+            }
+
+            /**
+             * @brief Returns if the opcode is valid or not
+             * @return If the opcode represents a valid BRK instruction
+             */
+            inline bool Verify() {
+                return (start == 0x0 && end == 0x6A1);
+            }
+
+            union {
+                struct {
+                    u8 start  : 5;
+                    u32 value : 16;
+                    u16 end   : 11;
+                };
+                u32 raw{};
+            };
+        };
+
+        static_assert(sizeof(Brk) == sizeof(u32));
+
+        /**
+         * @brief A bit-field struct that encapsulates a SVC instruction. See https://developer.arm.com/docs/ddi0596/latest/base-instructions-alphabetic-order/svc-supervisor-call.
+         */
+        struct Svc {
+            /**
+             * @brief Returns if the opcode is valid or not
+             * @return If the opcode represents a valid SVC instruction
+             */
+            inline bool Verify() {
+                return (start == 0x1 && end == 0x6A0);
+            }
+
+            union {
+                struct {
+                    u8 start  : 5;
+                    u32 value : 16;
+                    u16 end   : 11;
+                };
+                u32 raw{};
+            };
+        };
+
+        static_assert(sizeof(Svc) == sizeof(u32));
+
+        /**
+         * @brief A bit-field struct that encapsulates a MRS instruction. See https://developer.arm.com/docs/ddi0596/latest/base-instructions-alphabetic-order/mrs-move-system-register.
+         */
+        struct Mrs {
+            /**
+             * @brief Creates a MRS instruction, used for generating BRK opcodes
+             * @param srcReg The source system register
+             * @param dstReg The destination Xn register
+             */
+            Mrs(u32 srcReg, u8 dstReg) {
+                this->srcReg = srcReg;
+                this->dstReg = dstReg;
+                end = 0xD53; // Last 12 bits of a MRS instruction stored as u16
+            }
+
+            /**
+             * @brief Returns if the opcode is valid or not
+             * @return If the opcode represents a valid MRS instruction
+             */
+            inline bool Verify() {
+                return (end == 0xD53);
+            }
+
+            union {
+                struct {
+                    u8 dstReg  : 5;
+                    u32 srcReg : 15;
+                    u16 end    : 12;
+                };
+                u32 raw{};
+            };
+        };
+
+        static_assert(sizeof(Mrs) == sizeof(u32));
+
+        /**
+         * @brief A bit-field struct that encapsulates a B instruction. See https://developer.arm.com/docs/ddi0596/latest/base-instructions-alphabetic-order/b-branch.
+         */
+        struct B {
+        public:
+            explicit B(i64 offset) {
+                this->offset = static_cast<i32>(offset / 4);
+                end = 0x5;
+            }
+
+            /**
+             * @brief Returns the offset of the instruction
+             * @return The offset encoded within the instruction
+             */
+            inline i32 Offset() {
+                return offset * 4;
+            }
+
+            /**
+             * @brief Returns if the opcode is valid or not
+             * @return If the opcode represents a valid Branch instruction
+             */
+            inline bool Verify() {
+                return (end == 0x5);
+            }
+
+            union {
+                struct {
+                    i32 offset : 26;
+                    u8 end     : 6;
+                };
+                u32 raw{};
+            };
+        };
+
+        static_assert(sizeof(B) == sizeof(u32));
+
+        /**
+         * @brief A bit-field struct that encapsulates a BL instruction. See https://developer.arm.com/docs/ddi0596/latest/base-instructions-alphabetic-order/b-branch.
+         */
+        struct BL {
+        public:
+            explicit BL(i64 offset) {
+                this->offset = static_cast<i32>(offset / 4);
+                end = 0x25;
+            }
+
+            /**
+             * @brief Returns the offset of the instruction
+             * @return The offset encoded within the instruction
+             */
+            inline i32 Offset() {
+                return offset * 4;
+            }
+
+            /**
+             * @brief Returns if the opcode is valid or not
+             * @return If the opcode represents a valid Branch instruction
+             */
+            inline bool Verify() {
+                return (end == 0x85);
+            }
+
+            union {
+                struct {
+                    i32 offset : 26;
+                    u8 end     : 6;
+                };
+                u32 raw{};
+            };
+        };
+
+        static_assert(sizeof(BL) == sizeof(u32));
+    }
+
     void NCE::ReadRegisters(user_pt_regs &registers, pid_t pid) const {
         iovec iov = {&registers, sizeof(registers)};
         long status = ptrace(PTRACE_GETREGSET, pid ? pid : currPid, NT_PRSTATUS, &iov);
@@ -56,9 +227,11 @@ namespace skyline {
                                     SetRegister(static_cast<Xreg>(instr.value - (constant::SvcLast + 1)), state.thisThread->tls);
                                 } else if (instr.value == constant::BrkRdy)
                                     continue;
-                                else
+                                else {
+                                    ProcessTrace();
                                     throw exception("Received unhandled BRK: 0x{:X}", static_cast<u64>(instr.value));
                                 }
+                            }
                             currRegs.pc += sizeof(u32);
                             WriteRegisters(currRegs);
                             ResumeProcess();
@@ -181,12 +354,11 @@ namespace skyline {
             raw += fmt::format("{:08X}", instr);
         }
         state.logger->Debug("Raw Instructions: 0x{}", raw);
-        state.logger->Debug("CPU Context:");
+        std::string regStr;
-        state.logger->Debug("SP: 0x{:X}", regs.sp);
+        for (u16 index = 0; index < constant::NumRegs - 1; index+=2) {
-        state.logger->Debug("PSTATE: 0x{:X}", regs.pstate);
+            regStr += fmt::format("\nX{}: 0x{:X}, X{}: 0x{:X}", index, regs.regs[index], index+1, regs.regs[index+1]);
-        for (u16 index = 0; index < constant::NumRegs - 2; index++) {
-            state.logger->Debug("X{}: 0x{:X}", index, regs.regs[index]);
         }
+        state.logger->Debug("CPU Context:\nSP: 0x{:X}\nLR: 0x{:X}\nPSTATE: 0x{:X}{}", regs.sp, regs.regs[30], regs.pstate, regStr);
     }
 
     u64 NCE::GetRegister(Xreg regId, pid_t pid) {
@@ -228,4 +400,68 @@ namespace skyline {
                 registerMap.at(pid).pstate = value;
         }
     }
+
+    std::vector<u32> NCE::PatchCode(std::vector<u8>& code, i64 offset) {
+        u32 *address = reinterpret_cast<u32 *>(code.data());
+        u32 *end = address + (code.size() / sizeof(u32));
+        i64 patchOffset = offset;
+
+        std::vector<u32> patch;
+        patch.resize((guest::saveCtxSize + guest::loadCtxSize) / sizeof(u32));
+        std::memcpy(patch.data(), reinterpret_cast<void*>(&guest::saveCtx), guest::saveCtxSize);
+        offset += guest::saveCtxSize;
+
+        std::memcpy(reinterpret_cast<u8*>(patch.data()) + guest::saveCtxSize,
+                    reinterpret_cast<void*>(&guest::loadCtx), guest::loadCtxSize);
+        offset += guest::loadCtxSize;
+
+        while (address < end) {
+            auto instrSvc = reinterpret_cast<instr::Svc *>(address);
+            auto instrMrs = reinterpret_cast<instr::Mrs *>(address);
+
+            if (instrSvc->Verify()) {
+                instr::B bjunc(offset);
+                constexpr u32 strLr = 0xF81F0FFE; // STR LR, [SP, #-16]!
+                offset += sizeof(strLr);
+                instr::Brk brk(static_cast<u16>(instrSvc->value));
+                offset += sizeof(brk);
+                instr::BL bSvCtx(patchOffset - offset);
+                offset += sizeof(bSvCtx);
+                instr::BL bLdCtx((patchOffset + guest::saveCtxSize) - offset);
+                offset += sizeof(bLdCtx);
+                constexpr u32 ldrLr = 0xF84107FE; // LDR LR, [SP], #16
+                offset += sizeof(ldrLr);
+                instr::B bret(-offset + sizeof(u32));
+                offset += sizeof(bret);
+
+                *address = bjunc.raw;
+                patch.push_back(strLr);
+                patch.push_back(brk.raw);
+                patch.push_back(bSvCtx.raw);
+                patch.push_back(bLdCtx.raw);
+                patch.push_back(ldrLr);
+                patch.push_back(bret.raw);
+            }  else if (instrMrs->Verify()) {
+                if (instrMrs->srcReg == constant::TpidrroEl0) {
+                    instr::B bjunc(offset);
+                    instr::Brk brk(static_cast<u16>(constant::SvcLast + 1 + instrMrs->dstReg));
+                    offset += sizeof(u32);
+                    instr::B bret(-offset + sizeof(u32));
+                    offset += sizeof(u32);
+
+                    *address = bjunc.raw;
+                    patch.push_back(brk.raw);
+                    patch.push_back(bret.raw);
+                } else if (instrMrs->srcReg == constant::CntpctEl0) {
+                    instr::Mrs mrs(constant::CntvctEl0, instrMrs->dstReg);
+                    *address = mrs.raw;
                 }
+            }
+            address++;
+            offset -= sizeof(u32);
+            patchOffset -= sizeof(u32);
+        }
+        return patch;
+    }
+}
+

app/src/main/cpp/skyline/nce.h

@@ -9,6 +9,9 @@
 #include "kernel/types/KSharedMemory.h"
 
 namespace skyline {
+    namespace instr {
+        struct Brk;
+    }
     /**
      * @brief The NCE (Native Code Execution) class is responsible for managing the state of catching instructions and directly controlling processes/threads
      */
@@ -140,5 +143,11 @@ namespace skyline {
          * @param pid The PID of the process (Defaults to currPid)
          */
         void SetRegister(Sreg regId, u32 value, pid_t pid = 0);
+
+        /**
+         * @brief This patches specific parts of the code
+         * @param code A vector with the code to be patched
+         */
+        std::vector<u32> PatchCode(std::vector<u8> &code, i64 offset);
     };
 }