Introduce functions that provide safe pointer to panic data

panic_get_data() function should always return pointer to panic_data
structure that can be safely interpreted. When structure layout
left by previous EC is different than ours then panic_get_data()
should return NULL. Difference in layout can occur when we are jumping
from old RO, this happens in eve.

Introduce two new functions:

get_panic_data_start() - It can be used to obtain beginning of panic
data, eg. when copying raw data or when determining where jump data is.

get_panic_data_write() - It can be used to obtain pointer to panic_data
structure that can be safely written. This function moves jump data and
jump tags if necessary.

Signed-off-by: Patryk Duda <pdk@semihalf.com>
Change-Id: If5f73c86e2176a0169b0be4b890e399c2c259740
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2379845
Reviewed-by: Jett Rink <jettrink@chromium.org>

1 files changed, 24 insertions, 2 deletions

diff --git a/include/panic.h b/include/panic.h
index 6daa4c408f..b6e1c0d8cd 100644
--- a/include/panic.h
+++ b/include/panic.h
@@ -198,14 +198,36 @@ void panic_get_reason(uint32_t *reason, uint32_t *info, uint8_t *exception);
 void ignore_bus_fault(int ignored);
 
 /**
- * Return a pointer to the saved data from a previous panic.
+ * Return a pointer to the saved data from a previous panic that can be
+ * safely interpreted
  *
- * @param pointer to the panic data, or NULL if none available (for example,
+ * @param pointer to the valid panic data, or NULL if none available (for example,
  * the last reboot was not caused by a panic).
  */
 struct panic_data *panic_get_data(void);
 
 /**
+ * Return a pointer to the beginning of panic data. This function can be
+ * used to obtain pointer which can be used to calculate place of other
+ * structures (eg. jump_data). This function should not be used to get access
+ * to panic_data structure as it might not be valid
+ *
+ * @param pointer to the beginning of panic_data, or NULL if there is no
+ * panic_data
+ */
+uintptr_t get_panic_data_start(void);
+
+/*
+ * Return a pointer to panic_data structure that can be safely written.
+ * Please note that this function can move jump data and jump tags.
+ * It can also delete panic data from previous boot, so this function
+ * should be used when we are sure that we don't need it.
+ *
+ * @param pointer to panic_data structure that can be safely written
+ */
+struct panic_data *get_panic_data_write(void);
+
+/**
  * Chip-specific implementation for backing up panic data to persistent
  * storage. This function is used to ensure that the panic data can survive loss
  * of VCC power rail.