x86/traps: Enable DEBUG_STACK after cpu_init() for TRAP_DB/BP

[pandora-kernel.git] / arch / x86 / kernel / traps.c

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index edbd30a..55e5f64 100644 (file)
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -718,9 +718,17 @@ dotraplinkage void do_iret_error(struct pt_regs *regs, long error_code)
 /* Set of traps needed for early debugging. */
 void __init early_trap_init(void)
 {
-       set_intr_gate_ist(X86_TRAP_DB, &debug, DEBUG_STACK);
+       /*
+        * Don't set ist to DEBUG_STACK as it doesn't work until TSS is
+        * ready in cpu_init() <-- trap_init(). Before trap_init(), CPU
+        * runs at ring 0 so it is impossible to hit an invalid stack.
+        * Using the original stack works well enough at this early
+        * stage. DEBUG_STACK will be equipped after cpu_init() in
+        * trap_init().
+        */
+       set_intr_gate_ist(X86_TRAP_DB, &debug, 0);
        /* int3 can be called from all */
-       set_system_intr_gate_ist(X86_TRAP_BP, &int3, DEBUG_STACK);
+       set_system_intr_gate_ist(X86_TRAP_BP, &int3, 0);
        set_intr_gate(X86_TRAP_PF, &page_fault);
        load_idt(&idt_descr);
 }
@@ -781,5 +789,14 @@ void __init trap_init(void)
         */
        cpu_init();
 
+       /*
+        * X86_TRAP_DB and X86_TRAP_BP have been set
+        * in early_trap_init(). However, DEBUG_STACK works only after
+        * cpu_init() loads TSS. See comments in early_trap_init().
+        */
+       set_intr_gate_ist(X86_TRAP_DB, &debug, DEBUG_STACK);
+       /* int3 can be called from all */
+       set_system_intr_gate_ist(X86_TRAP_BP, &int3, DEBUG_STACK);
+
        x86_init.irqs.trap_init();
 }