Fetch the initrd address from the DTB blob

The kernel entry has a pointer to the DTB blob as a parameter. From this
pointer we can parse the the DTB blob to find the properties
"chosen->linux,initrd-start" and "chosen->linux,initrd-start". These
properties are guaranteed to have 64-bit addresses which point where the
initrd is in memory, which we need to fetch the binaries to be loaded.

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

5 files changed, 38 insertions, 3 deletions

diff --git a/include/fbos/compiler.h b/include/fbos/compiler.h
index 35091c0..b88bb0b 100644
--- a/include/fbos/compiler.h
+++ b/include/fbos/compiler.h
@@ -11,16 +11,24 @@
  * Compiler attributes specific to linker sections.
  */
 
+#ifdef __KERNEL__
 #define __section(s) __attribute__((__section__(s)))
 #define __kernel __section(".kernel.text")
+#else
+#define __kernel
+#endif /* __KERNEL__ */
 
 /*
- * Multiple aliases for 64-bit integers which have their definition on the
+ * Multiple aliases for 32/64-bit integers which have their definition on the
  * standard library.
  */
 
+typedef int int32_t;
 typedef long ssize_t;
+typedef long int64_t;
+
 typedef unsigned long size_t;
+typedef unsigned int uint32_t;
 typedef unsigned long uint64_t;
 typedef unsigned long uintptr_t;
 
@@ -28,8 +36,10 @@ typedef unsigned long uintptr_t;
  * NULL
  */
 
+#ifdef __KERNEL__
 #define NULL (void *)0
 #define nullptr NULL
+#endif /* __KERNEL__ */
 
 // Helpful macro when prototyping.
 #define __unused(x) (void)x
diff --git a/include/fbos/dt.h b/include/fbos/dt.h
index 39d8381..fd77c35 100644
--- a/include/fbos/dt.h
+++ b/include/fbos/dt.h
@@ -3,6 +3,13 @@
 
 #include <fbos/compiler.h>
 
-void parse_dtb(uint64_t *dtb);
+// Pair of addresses where the initrd is located in memory.
+struct initrd_addr {
+	uintptr_t start;
+	uintptr_t end;
+};
+
+// Returns the `initrd` addresses as parsed from the given DTB blob.
+struct initrd_addr find_dt_initrd_addr(uint32_t *dtb);
 
 #endif // __FBOS_DT_H_
diff --git a/include/fbos/init.h b/include/fbos/init.h
index a919405..eb72508 100644
--- a/include/fbos/init.h
+++ b/include/fbos/init.h
@@ -6,6 +6,6 @@
 extern struct task_struct init_task;
 
 // The entry point for the kernel.
-__noreturn __kernel void start_kernel(uintptr_t *dtb);
+__noreturn __kernel void start_kernel(void *dtb);
 
 #endif /* __FBOS_INIT_H */
diff --git a/include/fbos/printk.h b/include/fbos/printk.h
index 2c82eda..6b32555 100644
--- a/include/fbos/printk.h
+++ b/include/fbos/printk.h
@@ -1,7 +1,24 @@
 #ifndef __FBOS_PRINTK_H_
 #define __FBOS_PRINTK_H_
 
+/*
+ * This file might be pulled from user space tests. Hence, define alternatives
+ * for this functions from glibc.
+ */
+
+#ifdef __KERNEL__
 extern void die(const char *const message);
 extern void printk(const char *const message);
+#else
+#include <stdio.h>
+#include <stdlib.h>
+
+#define die(x)     \
+	do {           \
+		printf(x); \
+		exit(1);   \
+	} while (0)
+#define printk(x) printf(x)
+#endif /* __KERNEL */
 
 #endif // __FBOS_PRINTK_H_
diff --git a/include/fbos/string.h b/include/fbos/string.h
index c3da266..af7e2ef 100644
--- a/include/fbos/string.h
+++ b/include/fbos/string.h
@@ -4,5 +4,6 @@
 #include <fbos/compiler.h>
 
 extern size_t strlen(const char *);
+extern int strcmp(const char *, const char *);
 
 #endif // __FBOS_STRING_H_