lib: sbi: call platform load/store emulators

sbi_load/store_access_handler now tries to call platform emulators
if defined. Otherwise, redirects the fault. If the platform code
returns failure, this means the H/S/U has accessed the emulated
devices in an unexpected manner, which is very likely caused by
buggy code in H/S/U. We redirect the fault, so lower privileged
level can get notified, and act accordingly. (E.g., oops in Linux)

We let the handler truly fail if the trap was originated from M mode.
In this case, something must be very wrong and we should just fail.

Signed-off-by: Bo Gan <ganboing@gmail.com>
Reviewed-by: Anup Patel <anup@brainfault.org>

1 files changed, 45 insertions, 0 deletions

diff --git a/include/sbi/sbi_platform.h b/include/sbi/sbi_platform.h
index f962aa46..581935ab 100644
--- a/include/sbi/sbi_platform.h
+++ b/include/sbi/sbi_platform.h
@@ -48,6 +48,7 @@
 #include <sbi/sbi_error.h>
 #include <sbi/sbi_scratch.h>
 #include <sbi/sbi_version.h>
+#include <sbi/sbi_trap_ldst.h>
 
 struct sbi_domain_memregion;
 struct sbi_ecall_return;
@@ -683,6 +684,50 @@ static inline int sbi_platform_vendor_ext_provider(
 	return SBI_ENOTSUPP;
 }
 
+/**
+ * Ask platform to emulate the trapped load
+ *
+ * @param plat pointer to struct sbi_platform
+ * @param rlen length of the load: 1/2/4/8...
+ * @param addr virtual address of the load. Platform needs to page-walk and
+ *        find the physical address if necessary
+ * @param out_val value loaded
+ *
+ * @return 0 on success and negative error code on failure
+ */
+static inline int sbi_platform_emulate_load(const struct sbi_platform *plat,
+					    int rlen, unsigned long addr,
+					    union sbi_ldst_data *out_val)
+{
+	if (plat && sbi_platform_ops(plat)->emulate_load) {
+		return sbi_platform_ops(plat)->emulate_load(rlen, addr,
+							    out_val);
+	}
+	return SBI_ENOTSUPP;
+}
+
+/**
+ * Ask platform to emulate the trapped store
+ *
+ * @param plat pointer to struct sbi_platform
+ * @param wlen length of the store: 1/2/4/8...
+ * @param addr virtual address of the store. Platform needs to page-walk and
+ *        find the physical address if necessary
+ * @param in_val value to store
+ *
+ * @return 0 on success and negative error code on failure
+ */
+static inline int sbi_platform_emulate_store(const struct sbi_platform *plat,
+					     int wlen, unsigned long addr,
+					     union sbi_ldst_data in_val)
+{
+	if (plat && sbi_platform_ops(plat)->emulate_store) {
+		return sbi_platform_ops(plat)->emulate_store(wlen, addr,
+							     in_val);
+	}
+	return SBI_ENOTSUPP;
+}
+
 #endif
 
 #endif