Kernel: Simplify scanning BIOS/EBDA and MP parser initialization

Add a MappedROM::find_chunk_starting_with() helper since that's a very
common usage pattern in clients of this code.

Also convert MultiProcessorParser from a persistent singleton object
to a temporary object constructed via a failable factory function.

1 files changed, 9 insertions, 0 deletions

diff --git a/Kernel/VM/MappedROM.h b/Kernel/VM/MappedROM.h
index 5eb37f57ce..9be57c2f45 100644
--- a/Kernel/VM/MappedROM.h
+++ b/Kernel/VM/MappedROM.h
@@ -39,6 +39,15 @@ struct MappedROM {
     size_t offset { 0 };
     PhysicalAddress paddr;
 
+    Optional<PhysicalAddress> find_chunk_starting_with(StringView prefix, size_t chunk_size) const
+    {
+        for (auto* candidate = base(); candidate < end(); candidate += chunk_size) {
+            if (!__builtin_memcmp(prefix.characters_without_null_termination(), candidate, prefix.length()))
+                return paddr_of(candidate);
+        }
+        return {};
+    }
+
     PhysicalAddress paddr_of(const u8* ptr) const { return paddr.offset(ptr - this->base()); }
 };