x86/traps: Enable DEBUG_STACK after cpu_init() for TRAP_DB/BP
Before this patch early_trap_init() installs DEBUG_STACK for
X86_TRAP_BP and X86_TRAP_DB. However, DEBUG_STACK doesn't work
correctly until cpu_init() <-- trap_init().
This patch passes 0 to set_intr_gate_ist() and
set_system_intr_gate_ist() instead of DEBUG_STACK to let it use
same stack as kernel, and installs DEBUG_STACK for them in
trap_init().
As core runs at ring 0 between early_trap_init() and
trap_init(), there is no chance to get a bad stack before
trap_init().
As NMI is also enabled in trap_init(), we don't need to care
about is_debug_stack() and related things used in
arch/x86/kernel/nmi.c.
Signed-off-by: Wang Nan <wangnan0@huawei.com>
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: <dave.hansen@linux.intel.com>
Cc: <lizefan@huawei.com>
Cc: <luto@amacapital.net>
Cc: <oleg@redhat.com>
Link: http://lkml.kernel.org/r/1424929779-13174-1-git-send-email-wangnan0@huawei.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 9d2073e..4281988 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -925,9 +925,17 @@
/* 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 @@
*/
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