Rewrite syscalls

src/platform/syscall.cpp

@@ -69,83 +69,68 @@ uint64_t Syscall::callByName(const char *name) {
 void __attribute((naked)) Syscall::wrapper() {
   asm volatile(
       // Save registers
-      "push %rax;"
-      "push %rcx;"
-      "push %rdx;"
       "push %rbx;"
-      "push %rbp;"
-      "push %rsi;"
-      "push %rdi;"
-      "push %r8;"
-      "push %r9;"
-      "push %r10;"
       "push %r11;"
       "push %r12;"
       "push %r13;"
       "push %r14;"
       "push %r15;"
 
-      // Save pagetable & stack
-      "mov %cr3, %rax; mov %rsp, %rbx; push %rax; push %rbx;"
+      // Save pagetable
+      "mov %cr3, %rbx;"
 
       // Set stack to absolute address
-      "sub $16, %rbx; ror $48, %rbx;"
-      "mov $4, %rcx;"
-      "1:"
-      "rol $9, %rbx;"
-      "mov %rbx, %rdx;"
-      "and $0x1FF, %rdx;"
-      "mov (%rax,%rdx,8), %rax;"
-      "and $~0xFFF, %rax; btr $63, %rax;"
-      "loop 1b;"
-      "rol $12, %rbx; and $0xFFF, %rbx; add %rax, %rbx; mov %rbx, %rsp;"
+      "mov %rsp, %r12; shr $39, %r12; and $0x1FF, %r12;" // r12 = ptx
+      "mov (%rbx,%r12,8), %r13; and $~0xFFF, %r13; btr $63, %r13;" // rbx = pt, r12 = pte
+
+      "mov %rsp, %r12; shr $30, %r12; and $0x1FF, %r12;" // r12 = pdx
+      "mov (%r13,%r12,8), %r13; and $~0xFFF, %r13; btr $63, %r13;" // r13 = pde
+
+      "mov %rsp, %r12; shr $21, %r12; and $0x1FF, %r12;" // r12 = pdpx
+      "mov (%r13,%r12,8), %r13; and $~0xFFF, %r13; btr $63, %r13;" // r13 = pdpe
+
+      "mov %rsp, %r12; shr $12, %r12; and $0x1FF, %r12;" // r12 = pml4x
+      "mov (%r13,%r12,8), %r13; and $~0xFFF, %r13; btr $63, %r13;" // r13 = pml4e
+
+      // Save stack
+      "mov %rsp, %r12;"
+      "mov %rsp, %r14; and $0xFFF, %r14; add %r14, %r13; mov %r13, %rsp;"
 
       // Set kernel pagetable
-      "_wrapper_mov_cr3: movabsq $0, %rax; mov %rax, %cr3;"
+      "_wrapper_mov_cr3: movabsq $0, %r13; mov %r13, %cr3;"
 
       // Find syscall handler
-      "mov 128(%rsp), %rdx;"
-      "lea _ZL11syscall_map(%rip), %rax;"
+      "lea _ZL11syscall_map(%rip), %r13;"
       "1:"
-      "cmp %rdx, (%rax);"
+      "cmp %rax, (%r13);"
       "je 1f;"
-      "cmpq $0, (%rax);"
+      "cmpq $0, (%r13);"
       "je 2f;"
-      "add $16, %rax;"
+      "add $16, %r13;"
       "jmp 1b;"
-      "1: mov 8(%rax), %rax; callq *%rax; jmp 3f;"
-      "2: ud2;"
-      "3:"
+
+      "1:"
+      "mov %rcx, %r14; callq *8(%r13); mov %r14, %rcx;"
 
       // Restore process stack & pagetable
-      "pop %rcx; pop %rax; mov %rcx, %rsp; mov %rax, %cr3;"
+      "mov %r12, %rsp; mov %rbx, %cr3;"
 
       // Restore registers
       "pop %r15;"
       "pop %r14;"
       "pop %r13;"
       "pop %r12;"
       "pop %r11;"
-      "pop %r10;"
-      "pop %r9;"
-      "pop %r8;"
-      "pop %rdi;"
-      "pop %rsi;"
-      "pop %rbp;"
       "pop %rbx;"
-      "pop %rdx;"
-      "pop %rcx;"
-      "pop %rax;"
 
       // Return to ring3
       "sysretq;"
+      "2: ud2;"
   );
 }
 
 void Syscall::setup() {
-  asm volatile(
-      "mov %%cr3, %%rax; mov %%rax, 2 + _wrapper_mov_cr3(%%rip)":::"%rax"
-      );
+  asm volatile("mov %%cr3, %%rax; mov %%rax, 2 + _wrapper_mov_cr3(%%rip)":::"%rax");
   wrmsr(MSR_STAR, uint64_t(0x10) << 48 | uint64_t(0x8) << 32);
   wrmsr(MSR_LSTAR, uintptr_t(wrapper));
   wrmsr(MSR_SFMASK, MSR_SFMASK_IE);

src/process/include/process.hpp

@@ -28,7 +28,8 @@ class Process {
   List<ProcessSymbol> symbols;
   uintptr_t entry;
   Pagetable::Entry* addPage(uintptr_t vaddr, void* paddr, uint8_t flags);
-  uintptr_t _aslrCode, _aslrStack;
+  uintptr_t _aslrCode, _aslrStack, _syscallPage;
+  size_t _syscallNum;
   void *iomap[2];
 
  public:

src/process/process.cpp

@@ -8,13 +8,15 @@
 
 using PTE = Pagetable::Entry;
 
-Process::Process() {
-  id = size_t(-1);
-  pagetable = nullptr;
-  entry = 0;
-  _aslrCode = RAND::get<uintptr_t>(0x80000000llu, 0x100000000llu) << 12;
-  _aslrStack = RAND::get<uintptr_t>(0x40000000llu, 0x80000000llu) << 12;
+Process::Process() :
+    id(uint64_t(-1)), entry(0),
+    _aslrCode(RAND::get<uintptr_t>(0x80000000llu, 0x100000000llu) << 12),
+    _aslrStack(RAND::get<uintptr_t>(0x40000000llu, 0x80000000llu) << 12),
+    _syscallPage(0), _syscallNum(0),
+    pagetable(nullptr) {
+  iomap[0] = iomap[1] = nullptr;
 }
+
 Process::~Process() {
   void *rsp; asm volatile("mov %%rsp, %q0; and $~0xFFF, %q0":"=r"(rsp));
   if (pagetable != nullptr) {
@@ -143,30 +145,32 @@ uintptr_t Process::getSymbolByName(const char* name) {
   }
   return 0;
 }
+struct SyscallEntry {
+  const uint8_t _pre[2] = {
+    // movabsq ..., %rax
+    0x48, 0xb8,
+  };
+  const uint64_t syscall_id;
+  const uint8_t _post[3] = {
+    // syscallq; ret
+    0x0f, 0x05, 0xc3,
+  };
+
+  explicit SyscallEntry(uint64_t idx) : syscall_id(idx) {}
+} PACKED;
 uintptr_t Process::linkLibrary(const char* funcname) {
   uintptr_t ptr = getSymbolByName(funcname);
   if (ptr != 0) return ptr;
 
   uint64_t syscall_id;
   if ((syscall_id = Syscall::callByName(funcname)) != 0) {
-    struct {
-      uint8_t sbp[4];
-      uint8_t pushac11[4];
-      uint8_t movabs[2];
-      uint64_t syscall_id;
-      uint8_t syscall[2];
-      uint8_t popac11b[5];
-      uint8_t ret;
-    } PACKED call = {
-      { 0x55, 0x48, 0x89, 0xe5 },
-      { 0x50, 0x51, 0x41, 0x53 },
-      { 0x48, 0xb8 },
-      syscall_id,
-      { 0x0f, 0x05 },
-      { 0x41, 0x5b, 0x59, 0x58, 0x5d },
-      0xc3
-    };
-    ptr = addSection(SectionTypeCode, sizeof(call));
+    static const constexpr size_t countInPage = 0x1000 / sizeof(SyscallEntry);
+    if (_syscallPage == 0 || _syscallNum == countInPage) {
+      _syscallPage = addSection(SectionTypeCode, sizeof(SyscallEntry) * countInPage);
+      _syscallNum = 0;
+    }
+    struct SyscallEntry call(syscall_id);
+    ptr = _syscallPage + (_syscallNum++) * sizeof(SyscallEntry);
     writeData(ptr, &call, sizeof(call));
     addSymbol(funcname, ptr);
   }