3 files changed, 65 insertions, 0 deletions

diff --git a/machine/fdt.c b/machine/fdt.c
index 061b19e..27f5462 100644
--- a/machine/fdt.c
+++ b/machine/fdt.c
@@ -548,6 +548,63 @@ void filter_compat(uintptr_t fdt, const char *compat)
   fdt_scan(fdt, &cb);
 }
 
+//////////////////////////////////////////// CHOSEN SCAN ////////////////////////////////////////
+
+struct chosen_scan {
+  const struct fdt_scan_node *chosen;
+  void* kernel_start;
+  void* kernel_end;
+};
+
+static void chosen_open(const struct fdt_scan_node *node, void *extra)
+{
+  struct chosen_scan *scan = (struct chosen_scan *)extra;
+  if (!strcmp(node->name, "chosen")) {
+    scan->chosen = node;
+  }
+}
+
+static int chosen_close(const struct fdt_scan_node *node, void *extra)
+{
+  struct chosen_scan *scan = (struct chosen_scan *)extra;
+  if (scan->chosen && scan->chosen == node) {
+    scan->chosen = NULL;
+  }
+  return 0;
+}
+
+static void chosen_prop(const struct fdt_scan_prop *prop, void *extra)
+{
+  struct chosen_scan *scan = (struct chosen_scan *)extra;
+  uint64_t val;
+  if (!scan->chosen) return;
+  if (!strcmp(prop->name, "riscv,kernel-start")) {
+    fdt_get_address(prop->node->parent, prop->value, &val);
+    scan->kernel_start = (void*)val;
+  } else if (!strcmp(prop->name, "riscv,kernel-end")) {
+    fdt_get_address(prop->node->parent, prop->value, &val);
+    scan->kernel_end = (void*)val;
+  }
+}
+
+void query_chosen(uintptr_t fdt)
+{
+  struct fdt_cb cb;
+  struct chosen_scan chosen;
+
+  memset(&cb, 0, sizeof(cb));
+  cb.open = chosen_open;
+  cb.close = chosen_close;
+  cb.prop = chosen_prop;
+
+  memset(&chosen, 0, sizeof(chosen));
+  cb.extra = &chosen;
+
+  fdt_scan(fdt, &cb);
+  kernel_start = chosen.kernel_start;
+  kernel_end = chosen.kernel_end;
+}
+
 //////////////////////////////////////////// HART FILTER ////////////////////////////////////////
 
 struct hart_filter {
diff --git a/machine/fdt.h b/machine/fdt.h
index d436778..6c8a6fe 100644
--- a/machine/fdt.h
+++ b/machine/fdt.h
@@ -59,6 +59,7 @@ void query_mem(uintptr_t fdt);
 void query_harts(uintptr_t fdt);
 void query_plic(uintptr_t fdt);
 void query_clint(uintptr_t fdt);
+void query_chosen(uintptr_t fdt);
 
 // Remove information from FDT
 void filter_harts(uintptr_t fdt, long *disabled_hart_mask);
@@ -68,6 +69,10 @@ void filter_compat(uintptr_t fdt, const char *compat);
 // The hartids of available harts
 extern uint64_t hart_mask;
 
+// Optional FDT preloaded external payload
+extern void* kernel_start;
+extern void* kernel_end;
+
 #ifdef PK_PRINT_DEVICE_TREE
 // Prints the device tree to the console as a DTS
 void fdt_print(uintptr_t fdt);
diff --git a/machine/minit.c b/machine/minit.c
index 32c6fd7..ceae6b7 100644
--- a/machine/minit.c
+++ b/machine/minit.c
@@ -16,6 +16,8 @@ uintptr_t mem_size;
 volatile uint64_t* mtime;
 volatile uint32_t* plic_priorities;
 size_t plic_ndevs;
+void* kernel_start;
+void* kernel_end;
 
 static void mstatus_init()
 {
@@ -162,6 +164,7 @@ void init_first_hart(uintptr_t hartid, uintptr_t dtb)
   query_harts(dtb);
   query_clint(dtb);
   query_plic(dtb);
+  query_chosen(dtb);
 
   wake_harts();