x86/dumpstack: Add support for unwinding empty IRQ stacks

When an interrupt happens in entry code while running on a software IRQ
stack, and the IRQ stack was empty, regs->sp will contain the stack end
address (e.g., irq_stack_ptr).  If the regs are passed to dump_trace(),
get_stack_info() will report STACK_TYPE_UNKNOWN, causing dump_trace() to
return prematurely without trying to go to the next stack.

Update the bounds checking for software interrupt stacks so that the
ending address is now considered part of the stack.

This means that it's now possible for the 'walk_stack' callbacks --
print_context_stack() and print_context_stack_bp() -- to be called with
an empty stack.  But that's fine; they're already prepared to deal with
that due to their on_stack() checks.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nilay Vaish <nilayvaish@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/5a5e5de92dcf11e8dc6b6e8e50ad7639d067830b.1473905218.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/kernel/dumpstack_32.c b/arch/x86/kernel/dumpstack_32.c
index c92da5a4d6635a5be2d63246c9457b7204c93c8c..50076d4366c4eaab96a2861e08e3bb3472f5505d 100644 (file)
--- a/arch/x86/kernel/dumpstack_32.c
+++ b/arch/x86/kernel/dumpstack_32.c
@@ -35,7 +35,11 @@ static bool in_hardirq_stack(unsigned long *stack, struct stack_info *info)
        unsigned long *begin = (unsigned long *)this_cpu_read(hardirq_stack);
        unsigned long *end   = begin + (THREAD_SIZE / sizeof(long));
 
-       if (stack < begin || stack >= end)
+       /*
+        * This is a software stack, so 'end' can be a valid stack pointer.
+        * It just means the stack is empty.
+        */
+       if (stack < begin || stack > end)
                return false;
 
        info->type      = STACK_TYPE_IRQ;
@@ -56,7 +60,11 @@ static bool in_softirq_stack(unsigned long *stack, struct stack_info *info)
        unsigned long *begin = (unsigned long *)this_cpu_read(softirq_stack);
        unsigned long *end   = begin + (THREAD_SIZE / sizeof(long));
 
-       if (stack < begin || stack >= end)
+       /*
+        * This is a software stack, so 'end' can be a valid stack pointer.
+        * It just means the stack is empty.
+        */
+       if (stack < begin || stack > end)
                return false;
 
        info->type      = STACK_TYPE_SOFTIRQ;

diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c
index 41813abc7380fe63dddeb4fb46e9eda4305f8719..2e708afe146d5644f163d3bfe2511f4806961823 100644 (file)
--- a/arch/x86/kernel/dumpstack_64.c
+++ b/arch/x86/kernel/dumpstack_64.c
@@ -90,7 +90,11 @@ static bool in_irq_stack(unsigned long *stack, struct stack_info *info)
        unsigned long *end   = (unsigned long *)this_cpu_read(irq_stack_ptr);
        unsigned long *begin = end - (IRQ_STACK_SIZE / sizeof(long));
 
-       if (stack < begin || stack >= end)
+       /*
+        * This is a software stack, so 'end' can be a valid stack pointer.
+        * It just means the stack is empty.
+        */
+       if (stack < begin || stack > end)
                return false;
 
        info->type      = STACK_TYPE_IRQ;