Commit-ID: b4d8327024637cb2a1f7910dcb5d0ad7a096f473 Gitweb: http://git.kernel.org/tip/b4d8327024637cb2a1f7910dcb5d0ad7a096f473 Author: Wang Nan <[email protected]> AuthorDate: Thu, 26 Feb 2015 13:49:39 +0800 Committer: Ingo Molnar <[email protected]> CommitDate: Thu, 26 Feb 2015 12:29:20 +0100
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 <[email protected]> Reviewed-by: Masami Hiramatsu <[email protected]> Acked-by: Steven Rostedt <[email protected]> Cc: <[email protected]> Cc: <[email protected]> Cc: <[email protected]> Cc: <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> --- arch/x86/kernel/traps.c | 21 +++++++++++++++++++-- 1 file changed, 19 insertions(+), 2 deletions(-) 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 @@ 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
