Merge branch 'stable-3.2' into pandora-3.2

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

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index edbd30a..f755bff 100644 (file)
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -314,7 +314,6 @@ gp_in_kernel:
        die("general protection fault", regs, error_code);
 }
 
-/* May run on IST stack. */
 dotraplinkage void __kprobes do_int3(struct pt_regs *regs, long error_code)
 {
 #ifdef CONFIG_KGDB_LOW_LEVEL_TRAP
@@ -718,9 +717,17 @@ 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 +788,12 @@ void __init trap_init(void)
         */
        cpu_init();
 
+       /*
+        * X86_TRAP_DB was installed 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);
+
        x86_init.irqs.trap_init();
 }