[PATCH 15/16] hw/core/loader-fit: Fix missing ERRP_GUARD() for error_prepend()

[Zhao Liu <zhao1.liu@linux.intel.com>]

From: Zhao Liu <zhao1.liu@intel.com>

As the comment in qapi/error, passing @errp to error_prepend() requires
ERRP_GUARD():

* = Why, when and how to use ERRP_GUARD() =
*
* Without ERRP_GUARD(), use of the @errp parameter is restricted:
...
* - It should not be passed to error_prepend(), error_vprepend() or
*   error_append_hint(), because that doesn't work with &error_fatal.
* ERRP_GUARD() lifts these restrictions.
*
* To use ERRP_GUARD(), add it right at the beginning of the function.
* @errp can then be used without worrying about the argument being
* NULL or &error_fatal.

ERRP_GUARD() could avoid the case when @errp is the pointer of
error_fatal, the user can't see this additional information, because
exit() happens in error_setg earlier than information is added [1].

In hw/core/loader-fit.c, there're 2 functions passing @errp to
error_prepend() without ERRP_GUARD():
 - fit_load_kernel()
 - fit_load_fdt()

Their @errp parameters are both the pointers of the local @err virable
in load_fit().

Though they don't cause the issue like [1] said, to follow the
requirement of @errp, add missing ERRP_GUARD() at their beginning.

[1]: Issue description in the commit message of commit ae7c80a7bd73
     ("error: New macro ERRP_GUARD()").

Cc: Paul Burton <paulburton@kernel.org>
Cc: Aleksandar Rikalo <aleksandar.rikalo@syrmia.com>
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
---
 hw/core/loader-fit.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/hw/core/loader-fit.c b/hw/core/loader-fit.c
index b7c7b3ba94d4..9f20007dbb51 100644
--- a/hw/core/loader-fit.c
+++ b/hw/core/loader-fit.c
@@ -120,6 +120,7 @@ static int fit_load_kernel(const struct fit_loader *ldr, const void *itb,
                            int cfg, void *opaque, hwaddr *pend,
                            Error **errp)
 {
+    ERRP_GUARD();
     const char *name;
     const void *data;
     const void *load_data;
@@ -178,6 +179,7 @@ static int fit_load_fdt(const struct fit_loader *ldr, const void *itb,
                         int cfg, void *opaque, const void *match_data,
                         hwaddr kernel_end, Error **errp)
 {
+    ERRP_GUARD();
     Error *err = NULL;
     const char *name;
     const void *data;
-- 
2.34.1