Check the return value from SBI ecalls

Signed-off-by: Miquel Sabaté Solà <mikisabate@gmail.com>

3 files changed, 29 insertions, 12 deletions

diff --git a/include/fbos/compiler.h b/include/fbos/compiler.h
index 5e61ebd..35091c0 100644
--- a/include/fbos/compiler.h
+++ b/include/fbos/compiler.h
@@ -24,6 +24,13 @@ typedef unsigned long size_t;
 typedef unsigned long uint64_t;
 typedef unsigned long uintptr_t;
 
+/*
+ * NULL
+ */
+
+#define NULL (void *)0
+#define nullptr NULL
+
 // Helpful macro when prototyping.
 #define __unused(x) (void)x
 
diff --git a/include/fbos/sbi.h b/include/fbos/sbi.h
index a6b893d..2575415 100644
--- a/include/fbos/sbi.h
+++ b/include/fbos/sbi.h
@@ -1,31 +1,38 @@
 #ifndef __FBOS_SBI_H_
 #define __FBOS_SBI_H_
 
-// TODO
-/* SBI_SUCCESS 0 Completed successfully */
-/* SBI_ERR_FAILED -1 Failed */
-/* SBI_ERR_NOT_SUPPORTED -2 Not supported */
-/* SBI_ERR_INVALID_PARAM -3 Invalid parameter(s) */
-/* SBI_ERR_DENIED -4 Denied or not allowed */
-/* SBI_ERR_INVALID_ADDRESS -5 Invalid address(s) */
-/* SBI_ERR_ALREADY_AVAILABLE -6 Already available */
-/* SBI_ERR_ALREADY_STARTED -7 Already started */
-/* SBI_ERR_ALREADY_STOPPED -8 Already stopped */
-/* SBI_ERR_NO_SHMEM -9 Shared memory not available */
+// Possible values for `sbi_ret.error` as defined in the SBI Specification 2.0.
+enum sbi_ret_error {
+	SBI_SUCCESS = 0, // Completed successfully
+	SBI_ERR_FAILED = -1, // Failed
+	SBI_ERR_NOT_SUPPORTED = -2, // Not supported
+	SBI_ERR_INVALID_PARAM = -3, // Invalid parameter(s)
+	SBI_ERR_DENIED = -4, // Denied or not allowed
+	SBI_ERR_INVALID_ADDRESS = -5, // Invalid address(s)
+	SBI_ERR_ALREADY_AVAILABLE = -6, // Already available
+	SBI_ERR_ALREADY_STARTED = -7, // Already started
+	SBI_ERR_ALREADY_STOPPED = -8, // Already stopped
+	SBI_ERR_NO_SHMEM = -9, // Shared memory not available
+};
 
+// SBI extensions supported by this kernel.
 enum sbi_ext {
 	DBCN_EXT = 0x4442434E,
 };
 
+// Function IDs for the Debug Console Extension "DBCN".
 enum dbcn_actions {
 	DBCN_WRITE = 0x00,
 };
 
+// Return value for any SBI ecall.
 struct sbi_ret {
 	long error;
 	long value;
 };
 
+// Perform an SBI ecall. Never call this directly, use any of the macros as
+// defined below.
 extern struct sbi_ret __sbi_ecall(unsigned long arg0, unsigned long arg1, unsigned long arg2,
 								  unsigned long arg3, unsigned long arg4, unsigned long arg5,
 								  int fid, int ext);
diff --git a/kernel/printk.c b/kernel/printk.c
index c0eedd9..51c1a7a 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -19,5 +19,8 @@ void __kernel printk(const char *const message)
 		return;
 	}
 
-	sbi_ecall2(DBCN_EXT, DBCN_WRITE, len, (unsigned long)message);
+	struct sbi_ret ret = sbi_ecall2(DBCN_EXT, DBCN_WRITE, len, (unsigned long)message);
+	if (ret.error != SBI_SUCCESS) {
+		die(nullptr);
+	}
 }