From: Andy Lutomirski <[email protected]> We currently special-case stack overflow on the task stack. We're going to start putting special stacks in the fixmap with a custom layout, so they'll have guard pages, too. Teach the unwinder to be able to unwind an overflow of any of the stacks.
Signed-off-by: Andy Lutomirski <[email protected]> Signed-off-by: Ingo Molnar <[email protected]> Signed-off-by: Thomas Gleixner <[email protected]> Reviewed-by: Borislav Petkov <[email protected]> Cc: Rik van Riel <[email protected]> Cc: Denys Vlasenko <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Brian Gerst <[email protected]> Cc: Dave Hansen <[email protected]> Cc: Josh Poimboeuf <[email protected]> Cc: Linus Torvalds <[email protected]> Link: https://lkml.kernel.org/r/5454bb325cb30a70457a47b50f22317be65eba7d.1511497875.git.l...@kernel.org --- arch/x86/kernel/dumpstack.c | 24 ++++++++++++++---------- 1 file changed, 14 insertions(+), 10 deletions(-) --- a/arch/x86/kernel/dumpstack.c +++ b/arch/x86/kernel/dumpstack.c @@ -112,24 +112,28 @@ void show_trace_log_lvl(struct task_stru * - task stack * - interrupt stack * - HW exception stacks (double fault, nmi, debug, mce) + * - SYSENTER stack * - * x86-32 can have up to three stacks: + * x86-32 can have up to four stacks: * - task stack * - softirq stack * - hardirq stack + * - SYSENTER stack */ for (regs = NULL; stack; stack = PTR_ALIGN(stack_info.next_sp, sizeof(long))) { const char *stack_name; - /* - * If we overflowed the task stack into a guard page, jump back - * to the bottom of the usable stack. - */ - if (task_stack_page(task) - (void *)stack < PAGE_SIZE) - stack = task_stack_page(task); - - if (get_stack_info(stack, task, &stack_info, &visit_mask)) - break; + if (get_stack_info(stack, task, &stack_info, &visit_mask)) { + /* + * We weren't on a valid stack. It's possible that + * we overflowed a valid stack into a guard page. + * See if the next page up is valid so that we can + * generate some kind of backtrace if this happens. + */ + stack = (unsigned long *)PAGE_ALIGN((unsigned long)stack); + if (get_stack_info(stack, task, &stack_info, &visit_mask)) + break; + } stack_name = stack_type_name(stack_info.type); if (stack_name)
