* [PATCH 2/2] lib: add optional linked list debugging
2024-01-03 10:19 [PATCH 1/2] list: rename debugging hooks Ahmad Fatoum
@ 2024-01-03 10:19 ` Ahmad Fatoum
2024-01-04 9:12 ` [PATCH 1/2] list: rename debugging hooks Sascha Hauer
1 sibling, 0 replies; 3+ messages in thread
From: Ahmad Fatoum @ 2024-01-03 10:19 UTC (permalink / raw)
To: barebox; +Cc: Ahmad Fatoum
When enabled, this outputs messages like:
list_del corruption, 000000005fe4a9d0->next is LIST_POISON1 (0000000000000100)
which can be useful when debugging.
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
common/Kconfig | 8 +++++
include/linux/bug.h | 17 +++++++++++
lib/Kconfig.hardening | 10 +++++++
lib/Makefile | 1 +
lib/list_debug.c | 68 +++++++++++++++++++++++++++++++++++++++++++
5 files changed, 104 insertions(+)
create mode 100644 lib/list_debug.c
diff --git a/common/Kconfig b/common/Kconfig
index c8c23a8e03a2..18ad01713293 100644
--- a/common/Kconfig
+++ b/common/Kconfig
@@ -1704,6 +1704,14 @@ config DMA_API_DEBUG
If unsure, say N.
+config DEBUG_LIST
+ bool "Debug linked list manipulation"
+ help
+ Enable this to turn on extended checks in the linked-list
+ walking routines.
+
+ If unsure, say N.
+
config PBL_BREAK
bool "Execute software break on pbl start"
depends on ARM && (!CPU_32v4T && !ARCH_TEGRA)
diff --git a/include/linux/bug.h b/include/linux/bug.h
index d8fc328a0706..8ea5f8d1b260 100644
--- a/include/linux/bug.h
+++ b/include/linux/bug.h
@@ -6,4 +6,21 @@
#include <asm-generic/bug.h>
#include <linux/build_bug.h>
+/*
+ * Since detected data corruption should stop operation on the affected
+ * structures. Return value must be checked and sanely acted on by caller.
+ */
+static inline __must_check bool check_data_corruption(bool v) { return v; }
+#define CHECK_DATA_CORRUPTION(condition, fmt, ...) \
+ check_data_corruption(({ \
+ bool corruption = unlikely(condition); \
+ if (corruption) { \
+ if (IS_ENABLED(CONFIG_BUG_ON_DATA_CORRUPTION)) { \
+ panic(fmt, ##__VA_ARGS__); \
+ } else \
+ WARN(1, fmt, ##__VA_ARGS__); \
+ } \
+ corruption; \
+ }))
+
#endif /* _LINUX_BUG_H */
diff --git a/lib/Kconfig.hardening b/lib/Kconfig.hardening
index 7f74d0d98a9c..28be42a27465 100644
--- a/lib/Kconfig.hardening
+++ b/lib/Kconfig.hardening
@@ -1,5 +1,15 @@
menu "Hardening options"
+config BUG_ON_DATA_CORRUPTION
+ bool "Trigger a BUG when data corruption is detected"
+ select DEBUG_LIST
+ help
+ Select this option if barebox should BUG when it encounters
+ data corruption in its memory structures when they get checked
+ for validity.
+
+ If unsure, say N.
+
config STACK_GUARD_PAGE
bool "Place guard page to catch stack overflows"
depends on ARM && MMU
diff --git a/lib/Makefile b/lib/Makefile
index 38204c8273e5..853d8870fe14 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -71,6 +71,7 @@ obj-$(CONFIG_FONTS) += fonts/
obj-$(CONFIG_BAREBOX_LOGO) += logo/
obj-y += reed_solomon/
obj-$(CONFIG_RATP) += ratp.o
+obj-$(CONFIG_DEBUG_LIST) += list_debug.o
obj-y += list_sort.o
obj-y += refcount.o
obj-y += int_sqrt.o
diff --git a/lib/list_debug.c b/lib/list_debug.c
new file mode 100644
index 000000000000..7de4c709a391
--- /dev/null
+++ b/lib/list_debug.c
@@ -0,0 +1,68 @@
+/*
+ * Copyright 2006, Red Hat, Inc., Dave Jones
+ * Released under the General Public License (GPL).
+ *
+ * This file contains the linked list validation for DEBUG_LIST.
+ */
+
+#include <linux/export.h>
+#include <linux/list.h>
+#include <linux/bug.h>
+#include <linux/kernel.h>
+
+/*
+ * Check that the data structures for the list manipulations are reasonably
+ * valid. Failures here indicate memory corruption (and possibly an exploit
+ * attempt).
+ */
+
+bool __list_add_valid_or_report(struct list_head *new, struct list_head *prev,
+ struct list_head *next)
+{
+ if (CHECK_DATA_CORRUPTION(prev == NULL,
+ "list_add corruption. prev is NULL.\n") ||
+ CHECK_DATA_CORRUPTION(next == NULL,
+ "list_add corruption. next is NULL.\n") ||
+ CHECK_DATA_CORRUPTION(next->prev != prev,
+ "list_add corruption. next->prev should be prev (%px), but was %px. (next=%px).\n",
+ prev, next->prev, next) ||
+ CHECK_DATA_CORRUPTION(prev->next != next,
+ "list_add corruption. prev->next should be next (%px), but was %px. (prev=%px).\n",
+ next, prev->next, prev) ||
+ CHECK_DATA_CORRUPTION(new == prev || new == next,
+ "list_add double add: new=%px, prev=%px, next=%px.\n",
+ new, prev, next))
+ return false;
+
+ return true;
+}
+EXPORT_SYMBOL(__list_add_valid_or_report);
+
+bool __list_del_entry_valid_or_report(struct list_head *entry)
+{
+ struct list_head *prev, *next;
+
+ prev = entry->prev;
+ next = entry->next;
+
+ if (CHECK_DATA_CORRUPTION(next == NULL,
+ "list_del corruption, %px->next is NULL\n", entry) ||
+ CHECK_DATA_CORRUPTION(prev == NULL,
+ "list_del corruption, %px->prev is NULL\n", entry) ||
+ CHECK_DATA_CORRUPTION(next == LIST_POISON1,
+ "list_del corruption, %px->next is LIST_POISON1 (%px)\n",
+ entry, LIST_POISON1) ||
+ CHECK_DATA_CORRUPTION(prev == LIST_POISON2,
+ "list_del corruption, %px->prev is LIST_POISON2 (%px)\n",
+ entry, LIST_POISON2) ||
+ CHECK_DATA_CORRUPTION(prev->next != entry,
+ "list_del corruption. prev->next should be %px, but was %px. (prev=%px)\n",
+ entry, prev->next, prev) ||
+ CHECK_DATA_CORRUPTION(next->prev != entry,
+ "list_del corruption. next->prev should be %px, but was %px. (next=%px)\n",
+ entry, next->prev, next))
+ return false;
+
+ return true;
+}
+EXPORT_SYMBOL(__list_del_entry_valid_or_report);
--
2.39.2
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH 1/2] list: rename debugging hooks
2024-01-03 10:19 [PATCH 1/2] list: rename debugging hooks Ahmad Fatoum
2024-01-03 10:19 ` [PATCH 2/2] lib: add optional linked list debugging Ahmad Fatoum
@ 2024-01-04 9:12 ` Sascha Hauer
1 sibling, 0 replies; 3+ messages in thread
From: Sascha Hauer @ 2024-01-04 9:12 UTC (permalink / raw)
To: Ahmad Fatoum; +Cc: barebox
On Wed, Jan 03, 2024 at 11:19:47AM +0100, Ahmad Fatoum wrote:
> Linux recently renamed the name of these helpers, so have barebox follow
> suit before implementing them out of line when optional list debugging
> is enabled.
>
> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
> ---
> include/linux/list.h | 20 ++++++++++----------
> 1 file changed, 10 insertions(+), 10 deletions(-)
Applied, thanks
Sascha
>
> diff --git a/include/linux/list.h b/include/linux/list.h
> index 1341806b59da..60b0111f467c 100644
> --- a/include/linux/list.h
> +++ b/include/linux/list.h
> @@ -37,18 +37,18 @@ static inline void INIT_LIST_HEAD(struct list_head *list)
> }
>
> #ifdef CONFIG_DEBUG_LIST
> -extern bool __list_add_valid(struct list_head *new,
> - struct list_head *prev,
> - struct list_head *next);
> -extern bool __list_del_entry_valid(struct list_head *entry);
> +extern bool __list_add_valid_or_report(struct list_head *new,
> + struct list_head *prev,
> + struct list_head *next);
> +extern bool __list_del_entry_valid_or_report(struct list_head *entry);
> #else
> -static inline bool __list_add_valid(struct list_head *new,
> - struct list_head *prev,
> - struct list_head *next)
> +static inline bool __list_add_valid_or_report(struct list_head *new,
> + struct list_head *prev,
> + struct list_head *next)
> {
> return true;
> }
> -static inline bool __list_del_entry_valid(struct list_head *entry)
> +static inline bool __list_del_entry_valid_or_report(struct list_head *entry)
> {
> return true;
> }
> @@ -64,7 +64,7 @@ static inline void __list_add(struct list_head *new,
> struct list_head *prev,
> struct list_head *next)
> {
> - if (!__list_add_valid(new, prev, next))
> + if (!__list_add_valid_or_report(new, prev, next))
> return;
>
> next->prev = new;
> @@ -129,7 +129,7 @@ static inline void __list_del_clearprev(struct list_head *entry)
>
> static inline void __list_del_entry(struct list_head *entry)
> {
> - if (!__list_del_entry_valid(entry))
> + if (!__list_del_entry_valid_or_report(entry))
> return;
>
> __list_del(entry->prev, entry->next);
> --
> 2.39.2
>
>
>
--
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