refactor mp stack

am/arch/x86-qemu/src/mpe.c

@@ -4,22 +4,15 @@ int ncpu = 0;
 static void (* volatile user_entry)();
 static intptr_t apboot_done = 0;
 
-static void mpuser_entry();
+static void mp_entry();
+
+static uint8_t cpu_stk[MAX_CPU][4096];
+static void call_switch_stk(void (*entry)());
 
 int _mpe_init(void (*entry)()) {
   user_entry = entry;
 
-  for (int cpu = 1; cpu < ncpu; cpu ++) {
-    *(uint16_t*)(0x7c00 + 510) = 0x55aa;
-    *(uint32_t*)(0x7000) = 0x007c00ea;  // code for ljmp
-    *(uint32_t*)(0x7004) = 0x00000000;
-    *(void**)(0x7010) = (void*)mpuser_entry;
-    *(uint32_t*)(0x7020) += 1024; // 1KB bootstrap stack
-    lapic_bootap(cpu, 0x7000);
-    while (_atomic_xchg(&apboot_done, 0) != 1);
-  }
-
-  mpuser_entry();
+  call_switch_stk(mp_entry);
   return 0; // never reaches here
 }
 
@@ -38,13 +31,36 @@ intptr_t _atomic_xchg(volatile intptr_t *addr, intptr_t newval) {
   return result;
 }
 
-static void mpuser_entry() {
-  if (_cpu() != 0) {
-    cpu_initgdt();
-    lapic_init();
-    ioapic_enable(IRQ_KBD, _cpu());
-    cpu_initpte();
-  }
+void ap_init() {
+  cpu_initgdt();
+  lapic_init();
+  ioapic_enable(IRQ_KBD, _cpu());
+  cpu_initpte();
   _atomic_xchg(&apboot_done, 1);
   user_entry();
 }
+
+#include <klib.h>
+
+static void mp_entry() {
+  if (_cpu() != 0) {
+    call_switch_stk(ap_init);
+  } else {
+    for (int cpu = 1; cpu < ncpu; cpu ++) {
+      *(uint16_t*)(0x7c00 + 510) = 0x55aa;
+      *(uint32_t*)(0x7000) = 0x007c00ea;  // code for ljmp
+      *(uint32_t*)(0x7004) = 0x00000000;
+      *(void**)(0x7010) = (void*)mp_entry;
+      *(uint32_t*)(0x7020) = 0x4000; // 1KB bootstrap stack
+      lapic_bootap(cpu, 0x7000);
+      while (_atomic_xchg(&apboot_done, 0) != 1);
+    }
+    user_entry();
+  }
+}
+
+static void call_switch_stk(void (*entry)()) {
+  asm volatile (
+    "movl %0, %%esp;"
+    "call *%1" : : "r"(&cpu_stk[_cpu() + 1][0]), "r"(entry));
+}