Convert multiboot to fw_cfg backed data storage

Right now we load the guest kernel to RAM, fire off the BIOS, hope it
doesn't clobber memory and run an option rom that jumps into the kernel.

That breaks with SeaBIOS, as that clears memory. So let's read all
kernel, module etc. data using the fw_cfg interface when in the int19
handler.

This patch implements said mechanism for multiboot.

Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

2 files changed, 34 insertions, 14 deletions

diff --git a/hw/fw_cfg.h b/hw/fw_cfg.h
index 359d45afe9..1e004b7070 100644
--- a/hw/fw_cfg.h
+++ b/hw/fw_cfg.h
@@ -17,7 +17,10 @@
 #define FW_CFG_NUMA             0x0d
 #define FW_CFG_BOOT_MENU        0x0e
 #define FW_CFG_MAX_CPUS         0x0f
-#define FW_CFG_MAX_ENTRY        0x10
+#define FW_CFG_KERNEL_ENTRY     0x10
+#define FW_CFG_KERNEL_DATA      0x11
+#define FW_CFG_INITRD_DATA      0x12
+#define FW_CFG_MAX_ENTRY        0x13
 
 #define FW_CFG_WRITE_CHANNEL    0x4000
 #define FW_CFG_ARCH_LOCAL       0x8000
diff --git a/hw/pc.c b/hw/pc.c
index bf4718e682..55bd1a48b2 100644
--- a/hw/pc.c
+++ b/hw/pc.c
@@ -603,6 +603,8 @@ static int load_multiboot(void *fw_cfg,
     uint32_t mb_mod_end;
     uint8_t bootinfo[0x500];
     uint32_t cmdline = 0x200;
+    uint8_t *mb_kernel_data;
+    uint8_t *mb_bootinfo_data;
 
     /* Ok, let's see if it is a multiboot image.
        The header is 12x32bit long, so the latest entry may be 8192 - 48. */
@@ -643,6 +645,12 @@ static int load_multiboot(void *fw_cfg,
         mh_load_addr = mh_entry_addr = elf_entry;
         mb_kernel_size = kernel_size;
 
+        mb_kernel_data = qemu_malloc(mb_kernel_size);
+        if (rom_copy(mb_kernel_data, elf_entry, kernel_size) != kernel_size) {
+            fprintf(stderr, "Error while fetching elf kernel from rom\n");
+            exit(1);
+        }
+
 #ifdef DEBUG_MULTIBOOT
         fprintf(stderr, "qemu: loading multiboot-elf kernel (%#x bytes) with entry %#zx\n",
                 mb_kernel_size, (size_t)mh_entry_addr);
@@ -656,7 +664,6 @@ static int load_multiboot(void *fw_cfg,
         uint32_t mh_bss_end_addr = ldl_p(header+i+24);
 #endif
         uint32_t mb_kernel_text_offset = i - (mh_header_addr - mh_load_addr);
-        uint8_t *kernel;
 
         mh_entry_addr = ldl_p(header+i+28);
         mb_kernel_size = get_file_size(f) - mb_kernel_text_offset;
@@ -676,12 +683,9 @@ static int load_multiboot(void *fw_cfg,
                 mb_kernel_size, mh_load_addr);
 #endif
 
-        kernel = qemu_malloc(mb_kernel_size);
+        mb_kernel_data = qemu_malloc(mb_kernel_size);
         fseek(f, mb_kernel_text_offset, SEEK_SET);
-        fread(kernel, 1, mb_kernel_size, f);
-        rom_add_blob_fixed(kernel_filename, kernel, mb_kernel_size,
-                           mh_load_addr);
-        qemu_free(kernel);
+        fread(mb_kernel_data, 1, mb_kernel_size, f);
         fclose(f);
     }
 
@@ -732,9 +736,14 @@ static int load_multiboot(void *fw_cfg,
                 exit(1);
             }
             mb_mod_end = mb_mod_start + mb_mod_length;
-            rom_add_file_fixed(initrd_filename, mb_mod_start);
-
             mb_mod_count++;
+
+            /* append module data at the end of last module */
+            mb_kernel_data = qemu_realloc(mb_kernel_data,
+                                          mh_load_addr - mb_mod_end);
+            load_image(initrd_filename,
+                       mb_kernel_data + mb_mod_start - mh_load_addr);
+
             stl_p(bootinfo + mb_mod_info + 0, mb_mod_start);
             stl_p(bootinfo + mb_mod_info + 4, mb_mod_start + mb_mod_length);
             stl_p(bootinfo + mb_mod_info + 12, 0x0); /* reserved */
@@ -774,13 +783,21 @@ static int load_multiboot(void *fw_cfg,
     fprintf(stderr, "multiboot: mh_entry_addr = %#x\n", mh_entry_addr);
 #endif
 
+    /* save bootinfo off the stack */
+    mb_bootinfo_data = qemu_malloc(sizeof(bootinfo));
+    memcpy(mb_bootinfo_data, bootinfo, sizeof(bootinfo));
+
     /* Pass variables to option rom */
-    fw_cfg_add_i32(fw_cfg, FW_CFG_KERNEL_ADDR, mh_entry_addr);
-    fw_cfg_add_i32(fw_cfg, FW_CFG_INITRD_ADDR, mb_bootinfo);
-    fw_cfg_add_i32(fw_cfg, FW_CFG_INITRD_SIZE, mmap_addr);
+    fw_cfg_add_i32(fw_cfg, FW_CFG_KERNEL_ENTRY, mh_entry_addr);
+    fw_cfg_add_i32(fw_cfg, FW_CFG_KERNEL_ADDR, mh_load_addr);
+    fw_cfg_add_i32(fw_cfg, FW_CFG_KERNEL_SIZE, mb_mod_end - mh_load_addr);
+    fw_cfg_add_bytes(fw_cfg, FW_CFG_KERNEL_DATA, mb_kernel_data,
+                     mb_mod_end - mh_load_addr);
 
-    rom_add_blob_fixed("multiboot-info", bootinfo, sizeof(bootinfo),
-                       mb_bootinfo);
+    fw_cfg_add_i32(fw_cfg, FW_CFG_INITRD_ADDR, mb_bootinfo);
+    fw_cfg_add_i32(fw_cfg, FW_CFG_INITRD_SIZE, sizeof(bootinfo));
+    fw_cfg_add_bytes(fw_cfg, FW_CFG_INITRD_DATA, mb_bootinfo_data,
+                     sizeof(bootinfo));
 
     option_rom[nb_option_roms] = "multiboot.bin";
     nb_option_roms++;