[PATCH v4 52/57] x86/dumpstack: warn on stack recursion

From: Josh Poimboeuf
Date: Thu Aug 18 2016 - 09:10:18 EST


Print a warning if stack recursion is detected.

Use printk_deferred_once() because the unwinder can be called with the
console lock by lockdep via save_stack_trace().

Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
---
arch/x86/kernel/dumpstack_32.c | 5 ++++-
arch/x86/kernel/dumpstack_64.c | 5 ++++-
2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/dumpstack_32.c b/arch/x86/kernel/dumpstack_32.c
index fa7a85c..d78bd4b 100644
--- a/arch/x86/kernel/dumpstack_32.c
+++ b/arch/x86/kernel/dumpstack_32.c
@@ -101,8 +101,11 @@ recursion_check:
* just break out and report an unknown stack type.
*/
if (visit_mask) {
- if (*visit_mask & (1UL << info->type))
+ if (*visit_mask & (1UL << info->type)) {
+ printk_deferred_once(KERN_WARNING "WARNING: stack recursion on stack type %d\n",
+ info->type);
goto unknown;
+ }
*visit_mask |= 1UL << info->type;
}

diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c
index 33f3142..fa2ba2f 100644
--- a/arch/x86/kernel/dumpstack_64.c
+++ b/arch/x86/kernel/dumpstack_64.c
@@ -125,8 +125,11 @@ recursion_check:
* just break out and report an unknown stack type.
*/
if (visit_mask) {
- if (*visit_mask & (1UL << info->type))
+ if (*visit_mask & (1UL << info->type)) {
+ printk_deferred_once(KERN_WARNING "WARNING: stack recursion on stack type %d\n",
+ info->type);
goto unknown;
+ }
*visit_mask |= 1UL << info->type;
}

--
2.7.4