[Qemu-devel] [PATCH] MIPS Malta-bootloader replacement

[Qemu-devel] [PATCH] MIPS Malta-bootloader replacement

[Alexander Voropay]

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Hi!

 This patch replaces hardcoded MIPS Malta bootloader with "soft" version.
This preserves ROM area clean. Also it initializes MIPS $sp register as
YAMON does.



 The GPR values before execution:

=== less /tmp/qemu.log ===
------------------------------------------------
pc=0x80294040 HI=0x00000000 LO=0x00000000 ds 0002 00000000 0
GPR00: r0 00000000 at 00000000 v0 00000000 v1 00000000
GPR04: a0 00000002 a1 80002000 a2 80002008 a3 08000000
...
GPR28: gp 00000000 sp 80003ff8 s8 00000000 ra 00000000
CP0 Status  0x00400004 Cause   0x00000400 EPC    0x00000000
    Config0 0x80000082 Config1 0x9e190c8b LLAddr 0x00000000


--
-=AV=-

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[-- Attachment #2: malta-bootloader.patch --]
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--- ../qemu-CVS/qemu/hw/mips_malta.c	2007-02-02 23:57:24.000000000 +0300
+++ hw/mips_malta.c	2007-02-11 19:48:25.000000000 +0300
@@ -383,29 +383,21 @@
      a3 - RAM size in bytes
 */
 
-static void write_bootloader (CPUState *env, unsigned long bios_offset, int64_t kernel_addr)
+static void emulate_bootloader (CPUState *env, int64_t kernel_addr)
 {
     uint32_t *p;
 
-    /* Small bootloader */
-    p = (uint32_t *) (phys_ram_base + bios_offset);
-    stl_raw(p++, 0x0bf00010);                                      /* j 0x1fc00040 */
-    stl_raw(p++, 0x00000000);                                      /* nop */
-
-    /* Second part of the bootloader */
-    p = (uint32_t *) (phys_ram_base + bios_offset + 0x040);
-    stl_raw(p++, 0x3c040000);                                      /* lui a0, 0 */
-    stl_raw(p++, 0x34840002);                                      /* ori a0, a0, 2 */
-    stl_raw(p++, 0x3c050000 | ((ENVP_ADDR >> 16) & 0xffff));       /* lui a1, high(ENVP_ADDR) */
-    stl_raw(p++, 0x34a50000 | (ENVP_ADDR & 0xffff));               /* ori a1, a0, low(ENVP_ADDR) */
-    stl_raw(p++, 0x3c060000 | (((ENVP_ADDR + 8) >> 16) & 0xffff)); /* lui a2, high(ENVP_ADDR + 8) */
-    stl_raw(p++, 0x34c60000 | ((ENVP_ADDR + 8) & 0xffff));         /* ori a2, a2, low(ENVP_ADDR + 8) */
-    stl_raw(p++, 0x3c070000 | (env->ram_size >> 16));              /* lui a3, high(env->ram_size) */
-    stl_raw(p++, 0x34e70000 | (env->ram_size & 0xffff));           /* ori a3, a3, low(env->ram_size) */
-    stl_raw(p++, 0x3c1f0000 | ((kernel_addr >> 16) & 0xffff));     /* lui ra, high(kernel_addr) */;
-    stl_raw(p++, 0x37ff0000 | (kernel_addr & 0xffff));             /* ori ra, ra, low(kernel_addr) */
-    stl_raw(p++, 0x03e00008);                                      /* jr ra */
-    stl_raw(p++, 0x00000000);                                      /* nop */
+    env->gpr[4] = 2;			/* a0 */
+    env->gpr[5] = ENVP_ADDR;		/* a1 */
+    env->gpr[6] = (ENVP_ADDR + 8);	/* a2 */
+    env->gpr[7] = env->ram_size;	/* a3 */
+    env->PC = kernel_addr;
+
+    /* Stack frame (at 64-bit boudary) */
+    env->gpr[29] = (int32_t)(0x80004000-8);	/* SP */
+    p = (uint32_t *)(phys_ram_base +0x4000-8);
+    stl_raw(p++, 0);
+    stl_raw(p++, 0);
 }
 
 static void prom_set(int index, const char *string, ...)
@@ -481,13 +473,13 @@
 static void main_cpu_reset(void *opaque)
 {
     CPUState *env = opaque;
+    int64_t kernel_addr;
     cpu_reset(env);
 
-    /* The bootload does not need to be rewritten as it is located in a
-       read only location. The kernel location and the arguments table
-       location does not change. */
-    if (env->kernel_filename)
-        load_kernel (env);
+    if (env->kernel_filename) {
+        kernel_addr = load_kernel (env);
+        emulate_bootloader(env, kernel_addr);
+    }
 }
 
 void mips_malta_init (int ram_size, int vga_ram_size, int boot_device,
@@ -528,7 +520,7 @@
         env->kernel_cmdline = kernel_cmdline;
         env->initrd_filename = initrd_filename;
         kernel_addr = load_kernel(env);
-        write_bootloader(env, bios_offset, kernel_addr);
+        emulate_bootloader(env, kernel_addr);
     } else {
         snprintf(buf, sizeof(buf), "%s/%s", bios_dir, BIOS_FILENAME);
         ret = load_image(buf, phys_ram_base + bios_offset);

[Qemu-devel] Re: [PATCH] MIPS Malta-bootloader replacement

[Aurelien Jarno]

Alexander Voropay a écrit :
> Hi!
>  
>  This patch replaces hardcoded MIPS Malta bootloader with "soft" version.
> This preserves ROM area clean. Also it initializes MIPS $sp register as
> YAMON does.
>  

Well this patch looks basically ok, except that
- It's not possible anymore for an OS to jmp at 0x1f000000 to reboot (is
it really necessary to simulate that).
- It's not possible anymore to add some code to initialize the GT64120
BARs the way YAMON does (and from our discussion on IRC, it looks like
this is necessary). It is also possible to modify the GT64120 code
directly, but that can mess a possible bootloader (when one is available).

So I suggest to hold this patch, at least until we have solved the
GT64120 BARs problem.


-- 
  .''`.  Aurelien Jarno	            | GPG: 1024D/F1BCDB73
 : :' :  Debian developer           | Electrical Engineer
 `. `'   aurel32@debian.org         | aurelien@aurel32.net
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