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 c74f2f5..4281988 100644 (file)
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -859,18 +859,16 @@ void math_state_restore(void)
                local_irq_disable();
        }
 
+       /* Avoid __kernel_fpu_begin() right after __thread_fpu_begin() */
+       kernel_fpu_disable();
        __thread_fpu_begin(tsk);
-
-       /*
-        * Paranoid restore. send a SIGSEGV if we fail to restore the state.
-        */
        if (unlikely(restore_fpu_checking(tsk))) {
                drop_init_fpu(tsk);
                force_sig_info(SIGSEGV, SEND_SIG_PRIV, tsk);
-               return;
+       } else {
+               tsk->thread.fpu_counter++;
        }
-
-       tsk->thread.fpu_counter++;
+       kernel_fpu_enable();
 }
 EXPORT_SYMBOL_GPL(math_state_restore);
 
@@ -927,9 +925,17 @@ 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);
 #ifdef CONFIG_X86_32
        set_intr_gate(X86_TRAP_PF, page_fault);
 #endif
@@ -1007,6 +1013,15 @@ 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();
 
 #ifdef CONFIG_X86_64