Kernel: Add exception_code to RegisterDump.

Added the exception_code field to RegisterDump, removing the need
for RegisterDumpWithExceptionCode. To accomplish this, I had to
push a dummy exception code during some interrupt entries to properly
pad out the RegisterDump. Note that we also needed to change some code
in sys$sigreturn to deal with the new RegisterDump layout.

Kernel/Arch/i386/CPU.cpp

@@ -46,6 +46,7 @@ extern "C" void asm_irq_entry();
 asm(
     ".globl asm_irq_entry\n"
     "asm_irq_entry: \n"
+    "    pushl $0x0\n"
     "    pusha\n"
     "    pushw %ds\n"
     "    pushw %es\n"
@@ -57,10 +58,11 @@ asm(
     "    popw %es\n"
     "    popw %ds\n"
     "    popa\n"
+    "    add $0x4, %esp\n"
     "    iret\n");
 
 #define EH_ENTRY(ec)                                                          \
-    extern "C" void exception_##ec##_handler(RegisterDumpWithExceptionCode&); \
+    extern "C" void exception_##ec##_handler(RegisterDump&); \
     extern "C" void exception_##ec##_entry();                                 \
     asm(                                                                      \
         ".globl exception_" #ec "_entry\n"                                    \
@@ -96,6 +98,7 @@ asm(
     asm(                                                     \
         ".globl exception_" #ec "_entry\n"                   \
         "exception_" #ec "_entry: \n"                        \
+        "    pushl $0x0\n"                                   \
         "    pusha\n"                                        \
         "    pushw %ds\n"                                    \
         "    pushw %es\n"                                    \
@@ -118,10 +121,10 @@ asm(
         "    popw %es\n"                                     \
         "    popw %ds\n"                                     \
         "    popa\n"                                         \
+        "    add $0x4, %esp\n"                               \
         "    iret\n");
 
-template<typename DumpType>
-static void dump(const DumpType& regs)
+static void dump(const RegisterDump& regs)
 {
     u16 ss;
     u32 esp;
@@ -133,9 +136,7 @@ static void dump(const DumpType& regs)
         esp = regs.esp_if_crossRing;
     }
 
-    if constexpr (IsSame<DumpType, RegisterDumpWithExceptionCode>::value) {
     kprintf("exception code: %04x\n", regs.exception_code);
-    }
     kprintf("  pc=%04x:%08x ds=%04x es=%04x fs=%04x gs=%04x\n", regs.cs, regs.eip, regs.ds, regs.es, regs.fs, regs.gs);
     kprintf(" stk=%04x:%08x\n", ss, esp);
     if (current)
@@ -157,8 +158,7 @@ static void dump(const DumpType& regs)
     }
 }
 
-template<typename RegisterDumpType>
-static void handle_crash(RegisterDumpType& regs, const char* description, int signal)
+static void handle_crash(RegisterDump& regs, const char* description, int signal)
 {
     if (!current) {
         kprintf("%s with !current\n", description);
@@ -195,7 +195,7 @@ void exception_0_handler(RegisterDump& regs)
 }
 
 EH_ENTRY(13);
-void exception_13_handler(RegisterDumpWithExceptionCode& regs)
+void exception_13_handler(RegisterDump& regs)
 {
     handle_crash(regs, "General protection fault", SIGSEGV);
 }
@@ -232,7 +232,7 @@ void exception_7_handler(RegisterDump& regs)
 
 // 14: Page Fault
 EH_ENTRY(14);
-void exception_14_handler(RegisterDumpWithExceptionCode& regs)
+void exception_14_handler(RegisterDump& regs)
 {
     ASSERT(current);
 

Kernel/Arch/i386/CPU.h

@@ -333,29 +333,6 @@ private:
 };
 
 struct [[gnu::packed]] RegisterDump
-{
-    u16 ss;
-    u16 gs;
-    u16 fs;
-    u16 es;
-    u16 ds;
-    u32 edi;
-    u32 esi;
-    u32 ebp;
-    u32 esp;
-    u32 ebx;
-    u32 edx;
-    u32 ecx;
-    u32 eax;
-    u32 eip;
-    u16 cs;
-    u16 __csPadding;
-    u32 eflags;
-    u32 esp_if_crossRing;
-    u16 ss_if_crossRing;
-};
-
-struct [[gnu::packed]] RegisterDumpWithExceptionCode
 {
     u16 ss;
     u16 gs;
@@ -380,6 +357,7 @@ struct [[gnu::packed]] RegisterDumpWithExceptionCode
     u16 ss_if_crossRing;
 };
 
+
 struct [[gnu::aligned(16)]] FPUState
 {
     u8 buffer[512];

Kernel/Arch/i386/PIT.cpp

@@ -12,6 +12,7 @@ extern "C" void timer_interrupt_handler(RegisterDump&);
 asm(
     ".globl timer_interrupt_entry \n"
     "timer_interrupt_entry: \n"
+    "    pushl $0x0\n"
     "    pusha\n"
     "    pushw %ds\n"
     "    pushw %es\n"
@@ -34,6 +35,7 @@ asm(
     "    popw %es\n"
     "    popw %ds\n"
     "    popa\n"
+    "    add $0x4, %esp\n"
     "    iret\n");
 
 static u32 s_ticks_this_second;

Kernel/Process.cpp

@@ -864,9 +864,12 @@ int Process::sys$sigreturn(RegisterDump& registers)
     current->m_signal_mask = *stack_ptr;
     stack_ptr++;
 
-    //pop edi, esi, ebp, esp, ebx, edx, ecx, eax and eip
-    memcpy(&registers.edi, stack_ptr, 9 * sizeof(u32));
-    stack_ptr += 9;
+    //pop edi, esi, ebp, esp, ebx, edx, ecx and eax
+    memcpy(&registers.edi, stack_ptr, 8 * sizeof(u32));
+    stack_ptr += 8;
+
+    registers.eip = *stack_ptr;
+    stack_ptr++;
 
     registers.eflags = *stack_ptr;
     stack_ptr++;

Kernel/Scheduler.cpp

@@ -561,8 +561,8 @@ void Scheduler::timer_tick(RegisterDump& regs)
     outgoing_tss.eflags = regs.eflags;
 
     // Compute process stack pointer.
-    // Add 12 for CS, EIP, EFLAGS (interrupt mechanic)
-    outgoing_tss.esp = regs.esp + 12;
+    // Add 16 for CS, EIP, EFLAGS, exception code (interrupt mechanic)
+    outgoing_tss.esp = regs.esp + 16;
     outgoing_tss.ss = regs.ss;
 
     if ((outgoing_tss.cs & 3) != 0) {

Kernel/Syscall.cpp

@@ -13,6 +13,7 @@ extern volatile RegisterDump* syscallRegDump;
 asm(
     ".globl syscall_trap_handler \n"
     "syscall_trap_handler:\n"
+    "    pushl $0x0\n"
     "    pusha\n"
     "    pushw %ds\n"
     "    pushw %es\n"
@@ -35,6 +36,7 @@ asm(
     "    popw %es\n"
     "    popw %ds\n"
     "    popa\n"
+    "    add $0x4, %esp\n"
     "    iret\n");
 
 namespace Syscall {