Interrupts: Remove ensure_handler and use a more reliable way of detecting if we are in a handler

kernel/include/interrupts/Interrupts.h

@@ -7,6 +7,5 @@ namespace Interrupts
     void disable();
 
     bool is_in_handler();
-    void ensure_handler();
     void return_from_handler(Context* context);
 }

kernel/include/trace/StackTracer.h

@@ -11,3 +11,5 @@ struct StackTracer
   private:
     uintptr_t m_base_pointer;
 };
+
+bool stack_trace_contains(uintptr_t address);

kernel/src/interrupts/Entry.cpp

@@ -17,8 +17,6 @@ extern "C" void common_handler(Context* context)
     ASSERT(Interrupts::is_in_handler());
     if (context->number >= 0x20 && context->number < 0x30)
     {
-        Interrupts::ensure_handler(); // restore the "in-interrupt flag" if an interrupt happened in the middle of this
-                                      // one
         IRQ::interrupt_handler(context);
         return;
     }
@@ -35,7 +33,6 @@ extern "C" void common_handler(Context* context)
 
             StackTracer tracer(context->rbp);
             tracer.trace_with_ip(context->rip);
-            Interrupts::ensure_handler();
             Scheduler::task_misbehave(context);
         }
     }
@@ -53,27 +50,14 @@ extern "C" void common_handler(Context* context)
             StackTracer tracer(context->rbp);
             tracer.trace_with_ip(context->rip);
 
-            Interrupts::ensure_handler();
             Scheduler::task_misbehave(context);
         }
     }
     if (context->number == 8) { int_panic(context, "Double fault, halting"); }
-    if (context->number == 48)
-    {
-        Interrupts::ensure_handler();
-        Scheduler::task_yield(context);
-    }
-    if (context->number == 49)
-    {
-        Interrupts::ensure_handler();
-        Scheduler::task_exit(context);
-    }
+    if (context->number == 48) { Scheduler::task_yield(context); }
+    if (context->number == 49) { Scheduler::task_exit(context); }
     if (context->number == 50) { Serial::print((const char*)context->rdi); }
-    if (context->number == 51)
-    {
-        Interrupts::ensure_handler();
-        Scheduler::task_sleep(context);
-    }
+    if (context->number == 51) { Scheduler::task_sleep(context); }
     if (context->number == 256) { kwarnln("Unused interrupt"); }
     return;
 }

kernel/src/interrupts/InterruptEntry.asm

@@ -37,11 +37,6 @@ unused:
 
 extern common_handler
 
-section .bss
-global __is_in_interrupt_handler
-__is_in_interrupt_handler:
-    resb 1
-
 section .text
 global asm_common
 asm_common:
@@ -68,8 +63,6 @@ asm_common:
     mov r8, cr2
     push r8
 
-    mov BYTE [__is_in_interrupt_handler], 1
-
     mov rdi, rsp
 
     call common_handler
@@ -83,8 +76,6 @@ _asm_interrupt_exit:
     mov ds, ax
     mov es, ax
 
-    mov BYTE [__is_in_interrupt_handler], 0
-
     pop r15
     pop r14
     pop r13

kernel/src/interrupts/Interrupts.cpp

@@ -1,4 +1,5 @@
 #include "interrupts/Interrupts.h"
+#include "trace/StackTracer.h"
 
 void Interrupts::disable()
 {
@@ -10,15 +11,11 @@ void Interrupts::enable()
     asm volatile("sti");
 }
 
-extern char __is_in_interrupt_handler;
+extern int _asm_interrupt_exit;
+
 bool Interrupts::is_in_handler()
 {
-    return __is_in_interrupt_handler;
-}
-
-void Interrupts::ensure_handler()
-{
-    __is_in_interrupt_handler = true;
+    return stack_trace_contains((uintptr_t)&_asm_interrupt_exit);
 }
 
 void Interrupts::return_from_handler(Context* context)

kernel/src/trace/StackTracer.cpp

@@ -36,3 +36,16 @@ void StackTracer::trace_with_ip(uintptr_t ip)
     printf("%lx: %s\n", ip, symbol_name);
     trace();
 }
+
+bool stack_trace_contains(uintptr_t address)
+{
+    uintptr_t base_pointer;
+    asm volatile("mov %%rbp, %0" : "=r"(base_pointer));
+    stackframe* frame = (stackframe*)base_pointer;
+    while (frame && (uint64_t)frame > 0xfffffffff8000000)
+    {
+        if (frame->instruction == address) return true;
+        frame = frame->next;
+    }
+    return false;
+}