From fb9627cc985912a57de8b4bedc98991e290e4075 Mon Sep 17 00:00:00 2001
From: Miquel Sabaté Solà <mikisabate@gmail.com>
Date: Wed, 20 Nov 2024 11:43:08 +0100
Subject: Fetch the initrd address from the DTB blob
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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>
---
 kernel/dt.c     |  6 ------
 kernel/main.c   |  5 +++--
 kernel/string.S | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 kernel/strlen.S | 22 ----------------------
 4 files changed, 49 insertions(+), 30 deletions(-)
 delete mode 100644 kernel/dt.c
 create mode 100644 kernel/string.S
 delete mode 100644 kernel/strlen.S

(limited to 'kernel')

diff --git a/kernel/dt.c b/kernel/dt.c
deleted file mode 100644
index 55fa970..0000000
--- a/kernel/dt.c
+++ /dev/null
@@ -1,6 +0,0 @@
-#include <fbos/dt.h>
-
-__kernel void parse_dtb(uint64_t *dtb)
-{
-	__unused(dtb);
-}
diff --git a/kernel/main.c b/kernel/main.c
index 07188b9..11f2721 100644
--- a/kernel/main.c
+++ b/kernel/main.c
@@ -13,13 +13,14 @@ struct task_struct init_task = { .stack = init_stack };
  * function can (and will) assume that everything has been reset and that we can
  * start the whole thing.
  */
-__noreturn __kernel void start_kernel(uintptr_t *dtb)
+__noreturn __kernel void start_kernel(void *dtb)
 {
 	// TODO: disable irqs, etc.
 
 	printk("Welcome to FizzBuzz OS!\n");
 
-	parse_dtb(dtb);
+	struct initrd_addr addr = find_dt_initrd_addr(dtb);
+	__unused(addr); // TODO
 
 	// TODO: reenable stuff
 
diff --git a/kernel/string.S b/kernel/string.S
new file mode 100644
index 0000000..d09bbac
--- /dev/null
+++ b/kernel/string.S
@@ -0,0 +1,46 @@
+/*
+ * Defined in include/fbos/string.h
+ *
+ *     size_t strlen(const char *str)
+ *
+ * Returns (a0): string length.
+ * Parameter (a0): string to measure.
+ * Clobbers: t0, t1.
+ */
+.globl strlen
+.type strlen, @function
+strlen:
+	mv t1, a0
+1:
+	lbu t0, 0(t1)
+	beqz t0, 2f
+	addi t1, t1, 1
+	j 1b
+2:
+	sub a0, t1, a0
+	ret
+
+/*
+ * Defined in include/fbos/string.h
+ *
+ *     int strcmp(const char *s1, const char *s2)
+ *
+ * Returns (a0): comparison result as in stdlib.
+ * Parameter (a0, a1): strings to compare.
+ * Clobbers: t0, t1.
+ */
+.globl strcmp
+.type strcmp, @function
+strcmp:
+1:
+	lbu t0, 0(a0)
+	lbu	t1, 0(a1)
+	bne	t0, t1, 2f
+	addi a0, a0, 1
+	addi a1, a1, 1
+	bnez t0, 1b
+	li a0, 0
+	ret
+2:
+	sub	a0, t0, t1
+	ret
diff --git a/kernel/strlen.S b/kernel/strlen.S
deleted file mode 100644
index 6185b94..0000000
--- a/kernel/strlen.S
+++ /dev/null
@@ -1,22 +0,0 @@
-.globl strlen
-.type strlen, @function
-
-/*
- * Defined in include/fbos/string.h
- *
- *     size_t strlen(const char *str)
- *
- * Returns (a0): string length.
- * Parameter (a0): string to measure.
- * Clobbers: t0, t1.
- */
-strlen:
-	mv t1, a0
-1:
-	lbu t0, 0(t1)
-	beqz t0, 2f
-	addi t1, t1, 1
-	j 1b
-2:
-	sub a0, t1, a0
-	ret
-- 
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