1 files changed, 19 insertions, 2 deletions

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 9d2073e2ecc9..42819886be0c 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -925,9 +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
@@ -1005,6 +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