Fix the same bug when getting a slab's name in ksalloc

Previously, we always used the name of CPU 0's kmem for a slab (owing to the same type of pointer decay problem fixed by the last commit). This is why all mtrace labels are called things like "0kstack" instead of having the right CPU number.

Fix the same bug when getting a slab's name in ksalloc
23af7cf9 · Austin Clements · bc0ff894 · 23af7cf9
--- a/kernel/kalloc.cc
+++ b/kernel/kalloc.cc
@@ -228,7 +228,7 @@ kalloc(const char *name)
 void *
 ksalloc(int slab)
 {
-  return kalloc_pool(slabmem[slab], slabmem[slab]->name);
+  return kalloc_pool(slabmem[slab], slabmem[slab][mycpuid()].name);
 }
 void