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Commit b4d83270 authored by Wang Nan's avatar Wang Nan Committed by Ingo Molnar
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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: default avatarWang Nan <wangnan0@huawei.com>
Reviewed-by: default avatarMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Acked-by: default avatarSteven 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: default avatarIngo Molnar <mingo@kernel.org>
parent 72c6fb4f

arch/x86/kernel/traps.c

+19 −2
Original line number Diff line number Diff line
@@ -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