On Thu, 26 Feb 2015 11:57:56 +0800 Wang Nan <wangn...@huawei.com> wrote:
> 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. Looks fine to me, except for some grammar issues in the comments. > > Signed-off-by: Wang Nan <wangn...@huawei.com> > --- > arch/x86/kernel/traps.c | 20 ++++++++++++++++++-- > 1 file changed, 18 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c > index 9d2073e..a9b8640 100644 > --- a/arch/x86/kernel/traps.c > +++ b/arch/x86/kernel/traps.c > @@ -925,9 +925,16 @@ 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 there should be impossible to hit a invalid "so it should be impossible", although I might prefer, "it is impossible to", but nothing is ever guaranteed. "an invalid" > + * stack. Use original stack is enough. DEBUG_STACK will be "Using the original stack works well enough at this early stage." > + * 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 +1012,15 @@ void __init trap_init(void) > */ > cpu_init(); > > + /* > + * X86_TRAP_DB and X86_TRAP_BP have been setup > + * in early_trap_init(). However, DEBUG_STACK works only after > + * cpu_init() load TSS. See comments in early_trap_init(). "cpu_init() loads TSS" -- Steve > + */ > + 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 majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/