hw/riscv: Extend the kernel loading support

Extend the RISC-V kernel loader to support Image and uImage files.
A Linux kernel can now be booted with:

    qemu-system-riscv64 -machine virt -bios fw_jump.bin -kernel Image

Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Bin Meng <bmeng.cn@gmail.com>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>

hw/riscv/boot.c

@@ -56,12 +56,22 @@ target_ulong riscv_load_kernel(const char *kernel_filename)
     uint64_t kernel_entry, kernel_high;
 
     if (load_elf(kernel_filename, NULL, NULL, NULL,
-                 &kernel_entry, NULL, &kernel_high, 0, EM_RISCV, 1, 0) < 0) {
-        error_report("could not load kernel '%s'", kernel_filename);
-        exit(1);
+                 &kernel_entry, NULL, &kernel_high, 0, EM_RISCV, 1, 0) > 0) {
+        return kernel_entry;
     }
 
-    return kernel_entry;
+    if (load_uimage_as(kernel_filename, &kernel_entry, NULL, NULL,
+                       NULL, NULL, NULL) > 0) {
+        return kernel_entry;
+    }
+
+    if (load_image_targphys_as(kernel_filename, KERNEL_BOOT_ADDRESS,
+                               ram_size, NULL) > 0) {
+        return KERNEL_BOOT_ADDRESS;
+    }
+
+    error_report("could not load kernel '%s'", kernel_filename);
+    exit(1);
 }
 
 hwaddr riscv_load_initrd(const char *filename, uint64_t mem_size,