tashaboot: devicetree relocate and grow, real chosen properties

Firmware edits the devicetree it hands the kernel: new
properties cannot go into a packed fdt in place, the blob moves
to scratch first and the blocks grow there. The insert moves the
strings block up by the prop size, opens the prop slot before
/chosen's end token, the new name lands at the strings end, and
all four header fields track the geometry, totalsize, off_dt_
strings, size_dt_strings and size_dt_struct. The last one bounds
the token walk in libfdt and a stale value there reads as
BADSTRUCTURE, the kernel parsed no memory node and panicked on
page table allocation before the first print.

The strings block length comes from the size_dt_strings header
field, not totalsize minus off_dt_strings, qemu's tree carries
a hole after the strings block and the subtraction drags it
along as tree.

The initrd start and end land in /chosen as real properties now,
the initrd= bootargs shortcut is gone.

receipt: smp brought up 1 node 4 cpus, run /init, userspace,
busybox shell, the initrd mounted from the chosen cells.

1 files changed, 60 insertions, 9 deletions

diff --git a/common/main.c b/common/main.c
index cd234bb..a8fdf58 100644
--- a/common/main.c
+++ b/common/main.c
@@ -43,10 +43,6 @@
 extern int tb_console_init(void);
 
 /*
- * fixed load address, the osdev way. past the bootloader at the
- * bottom of RAM, the image header decides its final resting place.
- */
-/*
  * the payload goes 16MB clear of wherever this bootloader is
  * actually running, ADR knows the runtime base and qemu is free
  * to place us anywhere. hardcoding 0x40200000 smashed our own
@@ -59,6 +55,11 @@ extern char __image_copy_end[];
 #define TB_BOOTFILE	"Image"
 
 extern void __NO_RETURN tb_boot_linux(uintptr_t ep, uintptr_t fw_arg);
+extern uintptr_t tb_dtb_relocate(uintptr_t dtb, void *scratch,
+				 size_t scratch_size, size_t grow);
+extern int tb_dtb_add_chosen_prop(uintptr_t dtb, const char *name,
+				  const void *val, size_t len);
+static size_t initrd_size;
 
 void tashaboot_main(uintptr_t fw_arg)
 {
@@ -141,22 +142,72 @@ void tashaboot_main(uintptr_t fw_arg)
 	}
 
 	/*
+	 * firmware owns the devicetree it hands the kernel. ours
+	 * relocates into scratch with grow room, then the chosen
+	 * properties are added there and the kernel gets the new
+	 * address, the same flow libfdt firmware uses.
+	 */
+	{
+		/*
+		 * the scratch lives at a fixed free address, clear of
+		 * our image, the payload, and the kernel relocation
+		 * zone. a bss array would sit inside 0x40080000+ and
+		 * the kernel overwrites it while copying itself.
+		 */
+		uint8_t *dtb_scratch = (uint8_t *)0x45000000ULL;
+		uintptr_t newdtb;
+
+		newdtb = tb_dtb_relocate(fw_arg, dtb_scratch,
+					 0x10000, 0x200);
+		if (!newdtb) {
+			dprintf(ALWAYS, "dtb: relocate failed\n");
+			platform_halt();
+		}
+
+		fw_arg = newdtb;
+	}
+
+	/*
 	 * the initrd rides after the kernel, the dtb /chosen carries
 	 * linux,initrd-start and -end, both already patched in place
 	 * with this layout.
 	 */
 	{
-		extern int tb_load_raw(const char *fname,
-				       uintptr_t load_addr);
-		int r = tb_load_raw(TB_INITRD_FILE, TB_INITRD_ADDR);
+		int r = tb_load_raw(TB_INITRD_FILE, TB_INITRD_ADDR,
+				    &initrd_size);
 
 		if (r == 0)
-			dprintf(ALWAYS, "initrd at %lx\n",
-				(unsigned long)TB_INITRD_ADDR);
+			dprintf(ALWAYS, "initrd at %lx, %lx bytes\n",
+				(unsigned long)TB_INITRD_ADDR,
+				(unsigned long)initrd_size);
 		else
 			dprintf(ALWAYS, "no initrd (%d)\n", r);
 	}
 
+	/*
+	 * the chosen properties, written now that the initrd size
+	 * is known. the cells are big endian, the fdt is a big
+	 * endian format end to end.
+	 */
+	{
+		uint8_t start_cells[8], end_cells[8];
+		uint64_t start = TB_INITRD_ADDR;
+		uint64_t end = TB_INITRD_ADDR + initrd_size;
+		int a, b;
+
+		for (int i = 0; i < 8; i++) {
+			start_cells[i] = (uint8_t)(start >> (56 - 8 * i));
+			end_cells[i] = (uint8_t)(end >> (56 - 8 * i));
+		}
+		a = tb_dtb_add_chosen_prop(fw_arg, "linux,initrd-start",
+					   start_cells, 8);
+		b = tb_dtb_add_chosen_prop(fw_arg, "linux,initrd-end",
+					   end_cells, 8);
+		dprintf(ALWAYS, "dtb: initrd props %d %d\n", a, b);
+	}
+
+
+
 	dprintf(ALWAYS, "loaded %llu bytes at %lx, entry %lx\n",
 		(unsigned long long)img.size, img.load, img.ep);
 	dprintf(ALWAYS, "jumping\n");