Merge pull request #107 from michaeljclark/fdt-firmware-only

RISC-V: Support separate firmware and kernel payload

bbl/bbl.ac

@@ -4,8 +4,13 @@ AS_IF([test "x$enable_logo" == "xyes"], [
 ])
 
 AC_ARG_WITH([payload], AS_HELP_STRING([--with-payload], [Set ELF payload for bbl]),
-  [AC_SUBST([BBL_PAYLOAD], $with_payload, [Kernel payload for bbl])],
-  [AC_SUBST([BBL_PAYLOAD], [dummy_payload], [Kernel payload for bbl])])
+  [
+   AC_SUBST([BBL_PAYLOAD], $with_payload, [Kernel payload for bbl])
+   AC_DEFINE(RELAXED_ALIGNMENT,[0],[Use relaxed payload alignment])
+  ], [
+   AC_SUBST([BBL_PAYLOAD], [dummy_payload], [Kernel payload for bbl])
+   AC_DEFINE(RELAXED_ALIGNMENT,[1],[Use relaxed payload alignment])
+  ])
 
 AC_ARG_WITH([logo], AS_HELP_STRING([--with-logo], [Specify a better logo]),
   [AC_SUBST([BBL_LOGO_FILE], $with_logo, [Logo for bbl])],

bbl/bbl.c

@@ -7,13 +7,21 @@
 #include "fdt.h"
 #include <string.h>
 
+extern char _payload_start, _payload_end; /* internal payload */
 static const void* entry_point;
 long disabled_hart_mask;
 
 static uintptr_t dtb_output()
 {
-  extern char _payload_end;
-  uintptr_t end = (uintptr_t) &_payload_end;
+  /*
+   * Place DTB after the payload, either the internal payload or a
+   * preloaded external payload specified in device-tree, if present.
+   *
+   * Note: linux kernel calls __va(dtb) to get the device-tree virtual
+   * address. The kernel's virtual mapping begins at its load address,
+   * thus mandating device-tree is in physical memory after the kernel.
+   */
+  uintptr_t end = kernel_end ? (uintptr_t)kernel_end : (uintptr_t)&_payload_end;
   return (end + MEGAPAGE_SIZE - 1) / MEGAPAGE_SIZE * MEGAPAGE_SIZE;
 }
 
@@ -53,7 +61,6 @@ void boot_other_hart(uintptr_t unused __attribute__((unused)))
 
 void boot_loader(uintptr_t dtb)
 {
-  extern char _payload_start;
   filter_dtb(dtb);
 #ifdef PK_ENABLE_LOGO
   print_logo();
@@ -62,6 +69,7 @@ void boot_loader(uintptr_t dtb)
   fdt_print(dtb_output());
 #endif
   mb();
-  entry_point = &_payload_start;
+  /* Use optional FDT preloaded external payload if present */
+  entry_point = kernel_start ? kernel_start : &_payload_start;
   boot_other_hart(0);
 }

bbl/payload.S

@@ -1,7 +1,15 @@
+#include "config.h"
 #include "encoding.h"
 
   .section ".payload","a",@progbits
+
+#if RELAXED_ALIGNMENT
+  /* align payload minimally */
+  .align 3
+#else
+  /* align payload to megapage */
   .align RISCV_PGSHIFT + RISCV_PGLEVEL_BITS
+#endif
 
   .globl _payload_start, _payload_end
 _payload_start:

config.h.in

@@ -42,6 +42,9 @@
 /* Define if the DTS is to be displayed */
 #undef PK_PRINT_DEVICE_TREE
 
+/* Use relaxed payload alignment */
+#undef RELAXED_ALIGNMENT
+
 /* Define if subproject MCPPBS_SPROJ_NORM is enabled */
 #undef SOFTFLOAT_ENABLED
 

configure

@@ -4092,7 +4092,6 @@ case "${BUILD_32BIT}" in
 	CFLAGS="$default_CFLAGS"
 	LDFLAGS=
 	install_subdir=$host_alias
-
 	;;
 esac
 
@@ -4251,10 +4250,20 @@ fi
 
 # Check whether --with-payload was given.
 if test "${with_payload+set}" = set; then :
-  withval=$with_payload; BBL_PAYLOAD=$with_payload
+  withval=$with_payload;
+   BBL_PAYLOAD=$with_payload
+
+
+$as_echo "#define RELAXED_ALIGNMENT 0" >>confdefs.h
+
 
 else
-  BBL_PAYLOAD=dummy_payload
+
+   BBL_PAYLOAD=dummy_payload
+
+
+$as_echo "#define RELAXED_ALIGNMENT 1" >>confdefs.h
+
 
 fi
 

dummy_payload/dummy_entry.S

@@ -18,5 +18,11 @@ _start:
 
   .data
 str:
-  .asciz "This is bbl's dummy_payload.  To boot a real kernel, reconfigure\n\
-bbl with the flag --with-payload=PATH, then rebuild bbl.\n"
+  .asciz "This is bbl's dummy_payload.  To boot a real kernel, reconfigure bbl
+with the flag --with-payload=PATH, then rebuild bbl. Alternatively,
+bbl can be used in firmware-only mode by adding device-tree nodes
+for an external payload and use QEMU's -bios and -kernel options.\n
+    chosen {
+        riscv,kernel-start = <payload_start>;
+        riscv,kernel-end = <payload_end>;
+    };\n\n"

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 {

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);

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();