[Qemu-devel] [PATCH V1 1/3] leon3: add a little bootloader

[KONRAD Frederic <frederic.konrad@adacore.com>]

This adds a little bootloader to the leon3_machine when a ram image is
given through the kernel parameter and no bios are provided:
  * The UART transmiter is enabled.
  * The TIMER is initialized.

Signed-off-by: KONRAD Frederic <frederic.konrad@adacore.com>
---
 hw/sparc/leon3.c | 80 +++++++++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 70 insertions(+), 10 deletions(-)

diff --git a/hw/sparc/leon3.c b/hw/sparc/leon3.c
index 774639a..2c6f486 100644
--- a/hw/sparc/leon3.c
+++ b/hw/sparc/leon3.c
@@ -1,7 +1,7 @@
 /*
  * QEMU Leon3 System Emulator
  *
- * Copyright (c) 2010-2011 AdaCore
+ * Copyright (c) 2010-2019 AdaCore
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -44,6 +44,8 @@
 #define CPU_CLK (40 * 1000 * 1000)
 
 #define PROM_FILENAME        "u-boot.bin"
+#define LEON3_PROM_OFFSET    (0x00000000)
+#define LEON3_RAM_OFFSET     (0x40000000)
 
 #define MAX_PILS 16
 
@@ -53,6 +55,55 @@ typedef struct ResetData {
     target_ulong sp;            /* initial stack pointer */
 } ResetData;
 
+static uint32_t *gen_write_to_addr(uint32_t *code, hwaddr addr, uint32_t val)
+{
+    stl_p(code++, 0x82100000); /* mov %g0, %g1                */
+    stl_p(code++, 0x84100000); /* mov %g0, %g2                */
+    stl_p(code++, 0x03000000 +
+      extract32(addr, 10, 22));
+                               /* sethi %hi(addr), %g1        */
+    stl_p(code++, 0x82106000 +
+      extract32(addr, 0, 10));
+                               /* or %g1, addr, %g1           */
+    stl_p(code++, 0x05000000 +
+      extract32(val, 10, 22));
+                               /* sethi %hi(val), %g2         */
+    stl_p(code++, 0x8410a000 +
+      extract32(val, 0, 10));
+                               /* or %g2, val, %g2            */
+    stl_p(code++, 0xc4204000); /* st %g2, [ %g1 ]             */
+
+    return code;
+}
+
+/*
+ * When loading a kernel in RAM the machine is expected to be in a different
+ * state (eg: initialized by the bootloader). This little code reproduces
+ * this behavior.
+ */
+static void write_bootloader(CPUSPARCState *env, uint8_t *base,
+                             hwaddr kernel_addr)
+{
+    uint32_t *p = (uint32_t *) base;
+
+    /* Initialize the UARTs                                */
+    p = gen_write_to_addr(p, 0x80000108, 3);
+
+    /* Initialize the TIMER 0                              */
+    p = gen_write_to_addr(p, 0x80000304, 39);
+    p = gen_write_to_addr(p, 0x80000314, 0xFFFFFFFE);
+    p = gen_write_to_addr(p, 0x80000318, 3);
+
+    /* JUMP to the entry point                             */
+    stl_p(p++, 0x82100000); /* mov %g0, %g1                */
+    stl_p(p++, 0x03000000 + extract32(kernel_addr, 10, 22));
+                            /* sethi %hi(kernel_addr), %g1 */
+    stl_p(p++, 0x82106000 + extract32(kernel_addr, 0, 10));
+                            /* or kernel_addr, %g1 */
+    stl_p(p++, 0x81c04000); /* jmp  %g1 */
+    stl_p(p++, 0x01000000); /* nop */
+}
+
 static void main_cpu_reset(void *opaque)
 {
     ResetData *s   = (ResetData *)opaque;
@@ -131,11 +182,12 @@ static void leon3_generic_hw_init(MachineState *machine)
     /* Reset data */
     reset_info        = g_malloc0(sizeof(ResetData));
     reset_info->cpu   = cpu;
-    reset_info->sp    = 0x40000000 + ram_size;
+    reset_info->sp    = LEON3_RAM_OFFSET + ram_size;
     qemu_register_reset(main_cpu_reset, reset_info);
 
     /* Allocate IRQ manager */
-    grlib_irqmp_create(0x80000200, env, &cpu_irqs, MAX_PILS, &leon3_set_pil_in);
+    grlib_irqmp_create(0x80000200, env, &cpu_irqs, MAX_PILS,
+                       &leon3_set_pil_in);
 
     env->qemu_irq_ack = leon3_irq_manager;
 
@@ -148,13 +200,13 @@ static void leon3_generic_hw_init(MachineState *machine)
     }
 
     memory_region_allocate_system_memory(ram, NULL, "leon3.ram", ram_size);
-    memory_region_add_subregion(address_space_mem, 0x40000000, ram);
+    memory_region_add_subregion(address_space_mem, LEON3_RAM_OFFSET, ram);
 
     /* Allocate BIOS */
     prom_size = 8 * MiB;
     memory_region_init_ram(prom, NULL, "Leon3.bios", prom_size, &error_fatal);
     memory_region_set_readonly(prom, true);
-    memory_region_add_subregion(address_space_mem, 0x00000000, prom);
+    memory_region_add_subregion(address_space_mem, LEON3_PROM_OFFSET, prom);
 
     /* Load boot prom */
     if (bios_name == NULL) {
@@ -174,7 +226,7 @@ static void leon3_generic_hw_init(MachineState *machine)
     }
 
     if (bios_size > 0) {
-        ret = load_image_targphys(filename, 0x00000000, bios_size);
+        ret = load_image_targphys(filename, LEON3_PROM_OFFSET, bios_size);
         if (ret < 0 || ret > prom_size) {
             error_report("could not load prom '%s'", filename);
             exit(1);
@@ -198,10 +250,18 @@ static void leon3_generic_hw_init(MachineState *machine)
             exit(1);
         }
         if (bios_size <= 0) {
-            /* If there is no bios/monitor, start the application.  */
-            env->pc = entry;
-            env->npc = entry + 4;
-            reset_info->entry = entry;
+            /*
+             * If there is no bios/monitor just start the application but put
+             * the machine in an initialized state through a little
+             * bootloader.
+             */
+            uint8_t *bootloader_entry;
+
+            bootloader_entry = memory_region_get_ram_ptr(prom);
+            write_bootloader(env, bootloader_entry, entry);
+            env->pc = LEON3_PROM_OFFSET;
+            env->npc = LEON3_PROM_OFFSET + 4;
+            reset_info->entry = LEON3_PROM_OFFSET;
         }
     }
 
-- 
1.8.3.1