From b02fcf9ba1211097754b286043cd87a8b4907e75 Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Mon, 4 Dec 2017 15:07:09 +0100 Subject: x86/unwinder: Handle stack overflows more gracefully There are at least two unwinder bugs hindering the debugging of stack-overflow crashes: - It doesn't deal gracefully with the case where the stack overflows and the stack pointer itself isn't on a valid stack but the to-be-dereferenced data *is*. - The ORC oops dump code doesn't know how to print partial pt_regs, for the case where if we get an interrupt/exception in *early* entry code before the full pt_regs have been saved. Fix both issues. http://lkml.kernel.org/r/20171126024031.uxi4numpbjm5rlbr@treble Signed-off-by: Josh Poimboeuf Signed-off-by: Thomas Gleixner Reviewed-by: Borislav Petkov Cc: Andy Lutomirski Cc: Boris Ostrovsky Cc: Borislav Petkov Cc: Brian Gerst Cc: Dave Hansen Cc: Dave Hansen Cc: David Laight Cc: Denys Vlasenko Cc: Eduardo Valentin Cc: Greg KH Cc: H. Peter Anvin Cc: Juergen Gross Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Rik van Riel Cc: Will Deacon Cc: aliguori@amazon.com Cc: daniel.gruss@iaik.tugraz.at Cc: hughd@google.com Cc: keescook@google.com Link: https://lkml.kernel.org/r/20171204150605.071425003@linutronix.de Signed-off-by: Ingo Molnar --- arch/x86/kernel/dumpstack.c | 32 +++++++++++++++++++++++++++----- 1 file changed, 27 insertions(+), 5 deletions(-) (limited to 'arch/x86/kernel/dumpstack.c') diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c index f13b4c00a5de..0bc95be5c638 100644 --- a/arch/x86/kernel/dumpstack.c +++ b/arch/x86/kernel/dumpstack.c @@ -50,6 +50,28 @@ static void printk_stack_address(unsigned long address, int reliable, printk("%s %s%pB\n", log_lvl, reliable ? "" : "? ", (void *)address); } +void show_iret_regs(struct pt_regs *regs) +{ + printk(KERN_DEFAULT "RIP: %04x:%pS\n", (int)regs->cs, (void *)regs->ip); + printk(KERN_DEFAULT "RSP: %04x:%016lx EFLAGS: %08lx", (int)regs->ss, + regs->sp, regs->flags); +} + +static void show_regs_safe(struct stack_info *info, struct pt_regs *regs) +{ + if (on_stack(info, regs, sizeof(*regs))) + __show_regs(regs, 0); + else if (on_stack(info, (void *)regs + IRET_FRAME_OFFSET, + IRET_FRAME_SIZE)) { + /* + * When an interrupt or exception occurs in entry code, the + * full pt_regs might not have been saved yet. In that case + * just print the iret frame. + */ + show_iret_regs(regs); + } +} + void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs, unsigned long *stack, char *log_lvl) { @@ -94,8 +116,8 @@ void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs, if (stack_name) printk("%s <%s>\n", log_lvl, stack_name); - if (regs && on_stack(&stack_info, regs, sizeof(*regs))) - __show_regs(regs, 0); + if (regs) + show_regs_safe(&stack_info, regs); /* * Scan the stack, printing any text addresses we find. At the @@ -119,7 +141,7 @@ void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs, /* * Don't print regs->ip again if it was already printed - * by __show_regs() below. + * by show_regs_safe() below. */ if (regs && stack == ®s->ip) goto next; @@ -155,8 +177,8 @@ next: /* if the frame has entry regs, print them */ regs = unwind_get_entry_regs(&state); - if (regs && on_stack(&stack_info, regs, sizeof(*regs))) - __show_regs(regs, 0); + if (regs) + show_regs_safe(&stack_info, regs); } if (stack_name) -- cgit v1.2.3