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Re: [PATCH v5 01/11] mac_oldworld: Allow loading binary ROM image


From: BALATON Zoltan
Subject: Re: [PATCH v5 01/11] mac_oldworld: Allow loading binary ROM image
Date: Fri, 26 Jun 2020 23:57:16 +0200 (CEST)
User-agent: Alpine 2.22 (BSF 395 2020-01-19)

On Fri, 26 Jun 2020, Mark Cave-Ayland wrote:
On 16/06/2020 14:47, BALATON Zoltan wrote:
The beige G3 Power Macintosh has a 4MB firmware ROM. Fix the size of
the rom region and fall back to loading a binary image with -bios if
loading ELF image failed. This allows testing emulation with a ROM
image from real hardware as well as using an ELF OpenBIOS image.

Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
---
v4: use load address from ELF to check if ROM is too big

 hw/ppc/mac_oldworld.c | 29 ++++++++++++++++++++---------
 1 file changed, 20 insertions(+), 9 deletions(-)

diff --git a/hw/ppc/mac_oldworld.c b/hw/ppc/mac_oldworld.c
index f8c204ead7..baf3da6f90 100644
--- a/hw/ppc/mac_oldworld.c
+++ b/hw/ppc/mac_oldworld.c
@@ -59,6 +59,8 @@
 #define NDRV_VGA_FILENAME "qemu_vga.ndrv"

 #define GRACKLE_BASE 0xfec00000
+#define PROM_BASE 0xffc00000
+#define PROM_SIZE (4 * MiB)

 static void fw_cfg_boot_set(void *opaque, const char *boot_device,
                             Error **errp)
@@ -99,6 +101,7 @@ static void ppc_heathrow_init(MachineState *machine)
     SysBusDevice *s;
     DeviceState *dev, *pic_dev;
     BusState *adb_bus;
+    uint64_t bios_addr;
     int bios_size;
     unsigned int smp_cpus = machine->smp.cpus;
     uint16_t ppc_boot_device;
@@ -127,24 +130,32 @@ static void ppc_heathrow_init(MachineState *machine)

     memory_region_add_subregion(sysmem, 0, machine->ram);

-    /* allocate and load BIOS */
-    memory_region_init_rom(bios, NULL, "ppc_heathrow.bios", BIOS_SIZE,
+    /* allocate and load firmware ROM */
+    memory_region_init_rom(bios, NULL, "ppc_heathrow.bios", PROM_SIZE,
                            &error_fatal);
+    memory_region_add_subregion(sysmem, PROM_BASE, bios);

-    if (bios_name == NULL)
+    if (!bios_name) {
         bios_name = PROM_FILENAME;
+    }
     filename = qemu_find_file(QEMU_FILE_TYPE_BIOS, bios_name);
-    memory_region_add_subregion(sysmem, PROM_ADDR, bios);
-
-    /* Load OpenBIOS (ELF) */
     if (filename) {
-        bios_size = load_elf(filename, NULL, 0, NULL, NULL, NULL, NULL, NULL,
-                             1, PPC_ELF_MACHINE, 0, 0);
+        /* Load OpenBIOS (ELF) */
+        bios_size = load_elf(filename, NULL, NULL, NULL, NULL, &bios_addr,
+                             NULL, NULL, 1, PPC_ELF_MACHINE, 0, 0);
+        if (bios_size <= 0) {
+            /* or load binary ROM image */
+            bios_size = load_image_targphys(filename, PROM_BASE, PROM_SIZE);
+            bios_addr = PROM_BASE;
+        } else {
+            /* load_elf sets high 32 bits for some reason, strip those */
+            bios_addr &= 0xffffffffULL;

This is certainly the approach I suggested, but this seems wrong - otherwise
load_elf() would be broken for quite a few use cases.

+        }
         g_free(filename);
     } else {
         bios_size = -1;
     }
-    if (bios_size < 0 || bios_size > BIOS_SIZE) {
+    if (bios_size < 0 || bios_addr - PROM_BASE + bios_size > PROM_SIZE) {
         error_report("could not load PowerPC bios '%s'", bios_name);
         exit(1);
     }

(goes and looks)

This is similar to how the SPARC32 loader works and it seems fine there:
https://git.qemu.org/?p=qemu.git;a=blob;f=hw/sparc/sun4m.c;h=ee52b5cbbcd22284384225c80ad50cdbd1415743;hb=HEAD#l721.
Looks like you might have the wrong addr parameter here?

I don't get this. Can you explain more please what is wrong and what's the proposed solution?

Regards,
BALATON Zoltan



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