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Re: [Qemu-devel] [PATCH] Add multi-boot kernel loading support
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From: |
Anthony Liguori |
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Subject: |
Re: [Qemu-devel] [PATCH] Add multi-boot kernel loading support |
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Date: |
Mon, 02 Feb 2009 16:42:52 -0600 |
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User-agent: |
Thunderbird 2.0.0.19 (X11/20090105) |
Rene Rebe wrote:
Hi all,
Alexander Graf implemented multi-boot kernel loading during
his work to run Darwin inside Qemu/KVM. As the boot loader
expects to load the kernel in an EFI environment a custom
booter is used to load the kernel using a legacy BIOS.
This is a port of the patch to the new extload / INT 19
machinery (including minor cleanups).
Signed-off-by: René Rebe <address@hidden>
Index: elf_ops.h
===================================================================
--- elf_ops.h (revision 6501)
+++ elf_ops.h (working copy)
@@ -195,6 +195,10 @@
}
if (ELF_MACHINE != ehdr.e_machine)
+#if (ELF_MACHINE == EM_X86_64) && !defined(CONFIG_USER_ONLY)
+ /* x86_64 systems can run i386 code as well */
+ if(ehdr.e_machine != EM_386)
+#endif
goto fail;
if (pentry)
Seems like an unrelated fix.
Index: hw/pc.c
===================================================================
--- hw/pc.c (revision 6501)
+++ hw/pc.c (working copy)
@@ -533,6 +533,438 @@
return size;
}
+/* Generate an initial boot sector which sets state and jump to
+ a specified vector */
+static void generate_bootsect_multiboot(uint8_t *option_rom,
+ uint32_t mh_entry_addr,
uint32_t bootinfo)
+{
+ uint8_t rom[512], *p, *reloc, *pgdt, *pmmaploop;
+ uint8_t sum;
+ uint32_t ip;
+ int i;
+ int mmaploop;
+
+ memset(rom, 0, sizeof(rom));
+
+ p = rom;
+ /* Make sure we have an option rom signature */
+ *p++ = 0x55;
+ *p++ = 0xaa;
+
+ /* ROM size in sectors*/
+ *p++ = 1;
+
+ /* Hook int19 */
+
+ *p++ = 0x50; /* push ax */
+ *p++ = 0x1e; /* push ds */
+ *p++ = 0x31; *p++ = 0xc0; /* xor ax, ax */
+ *p++ = 0x8e; *p++ = 0xd8; /* mov ax, ds */
+
+ *p++ = 0xc7; *p++ = 0x06; /* movvw _start,0x64 */
+ *p++ = 0x64; *p++ = 0x00;
+ reloc = p;
+ *p++ = 0x00; *p++ = 0x00;
+
+ *p++ = 0x8c; *p++ = 0x0e; /* mov cs,0x66 */
+ *p++ = 0x66; *p++ = 0x00;
+
+ *p++ = 0x1f; /* pop ds */
+ *p++ = 0x58; /* pop ax */
+ *p++ = 0xcb; /* lret */
+ /* Actual code */
+ *reloc = (p - rom);
The above could be refactored to common code.
+ *p++ = 0xfa; /* CLI */
+ *p++ = 0xfc; /* CLD */
+
+ /* 660f011528000000 lgdt [0x28] */
+ *p++ = 0x66; /* 32-bit operand size */
+ *p++ = 0x67; /* 32-bit addr size */
+ *p++ = 0x0f; /* LGDT [0x128] */
+ *p++ = 0x01;
+ *p++ = 0x15;
+ pgdt=p; /* we calculate the gdt position later */
+ p+=4;
+
+ /* Initialize multiboot mmap structs using the 0x15(e820) */
+ *p++ = 0x31; /* XOR BX,BX */
+ *p++ = 0xdb;
+
+ *p++ = 0x66; /* 32-bit operand size */
+ *p++ = 0x67; /* 32-bit addr size */
+ *p++ = 0xbf; /* MOV EDI,0x9004 */
+ *p++ = 0x04;
+ *p++ = 0x90;
+ *p++ = 0x00;
+ *p++ = 0x00;
+
+ pmmaploop = p;
+ *p++ = 0x66; /* 32-bit operand size */
+ *p++ = 0x67; /* 32-bit addr size */
+ *p++ = 0xb8; /* MOV EAX,0x20 */
+ *p++ = 0x20;
+ *p++ = 0x00;
+ *p++ = 0x00;
+ *p++ = 0x00;
+
+ *p++ = 0x66; /* 32-bit operand size */
+ *p++ = 0x67; /* 32-bit addr size */
+ *p++ = 0x89; /* MOV -4(EDI),EAX */
+ *p++ = 0x47;
+ *p++ = 0xfc;
+
+ *p++ = 0x66; /* 32-bit operand size */
+ *p++ = 0x67; /* 32-bit addr size */
+ *p++ = 0xb8; /* MOV EAX,0x0000e820 */
+ *p++ = 0x20;
+ *p++ = 0xe8;
+ *p++ = 0x00;
+ *p++ = 0x00;
+
+ *p++ = 0x66; /* 32-bit operand size */
+ *p++ = 0x67; /* 32-bit addr size */
+ *p++ = 0xba; /* MOV EDX,0x534d4150 */
+ *p++ = 0x50;
+ *p++ = 0x41;
+ *p++ = 0x4d;
+ *p++ = 0x53;
+
+ *p++ = 0x66; /* 32-bit operand size */
+ *p++ = 0x67; /* 32-bit addr size */
+ *p++ = 0xb9; /* MOV ECX,0x20 */
+ *p++ = 0x20;
+ *p++ = 0x00;
+ *p++ = 0x00;
+ *p++ = 0x00;
+
+ *p++ = 0xcd; /* INT 0x15 */
+ *p++ = 0x15;
+
+ *p++ = 0x66; /* 32-bit operand size */
+ *p++ = 0x67; /* 32-bit addr size */
+ *p++ = 0xb8; /* MOV EAX, 0x24 */
+ *p++ = 0x24;
+ *p++ = 0x00;
+ *p++ = 0x00;
+ *p++ = 0x00;
+
+ *p++ = 0xf7; /* MUL AX, BX */
+ *p++ = 0xe3;
+
+ *p++ = 0x66; /* 32-bit operand size */
+ *p++ = 0x67; /* 32-bit addr size */
+ *p++ = 0x21; /* AND EBX, EBX */
+ *p++ = 0xdb;
+
+ /* don't store if bx = 0 */
+ *p++ = 0x66; /* 32-bit operand size */
+ *p++ = 0x67; /* 32-bit addr size */
+ *p++ = 0x0f; /* JZ next instruction */
+ *p++ = 0x84;
+ *p++ = 0x07;
+ *p++ = 0x00;
+ *p++ = 0x00;
+ *p++ = 0x00;
+
+ /* store the amount of blocks in the bootinfo struct */
+ *p++ = 0x66; /* 32-bit operand size */
+ *p++ = 0x67; /* 32-bit addr size */
+ *p++ = 0xa3; /* MOV [bootinfo+0x2c], EAX */
+ *p++ = (bootinfo+0x2c);
+ *p++ = (bootinfo+0x2c) >> 8;
+ *p++ = (bootinfo+0x2c) >> 16;
+ *p++ = (bootinfo+0x2c) >> 24;
+
+ *p++ = 0x66; /* 32-bit operand size */
+ *p++ = 0x67; /* 32-bit addr size */
+ *p++ = 0x05; /* ADD EAX, 0x9004 */
+ *p++ = 0x04;
+ *p++ = 0x90;
+ *p++ = 0x00;
+ *p++ = 0x00;
+
+ *p++ = 0x89; /* MOV DI, AX */
+ *p++ = 0xc7;
+
+ *p++ = 0x66; /* 32-bit operand size */
+ *p++ = 0x67; /* 32-bit addr size */
+ *p++ = 0x21; /* AND EBX, EBX */
+ *p++ = 0xdb;
+
+ /* process next entry */
+ *p++ = 0x66; /* 32-bit operand size */
+ *p++ = 0x67; /* 32-bit addr size */
+ *p++ = 0x0f; /* JNZ mmaploop */
+ *p++ = 0x85;
+ mmaploop = (int)((long)pmmaploop) - ((long)p) - 4;
+ *p++ = mmaploop;
+ *p++ = mmaploop >> 8;
+ *p++ = mmaploop >> 16;
+ *p++ = mmaploop >> 24;
+
+ /* get us to protected mode now */
+
+ *p++ = 0x66;
+ *p++ = 0xb8; /* MOV EAX,0x01 */
+ *p++ = 0x01;
+ *p++ = 0x00;
+ *p++ = 0x00;
+ *p++ = 0x00;
+
+ *p++ = 0x0f; /* MOV CR0,EAX */
+ *p++ = 0x22;
+ *p++ = 0xc0;
+
+ /* the JMP sets CS for us and gets us to 32-bit */
+ ip = 0x000d0000 + (p - rom) + 8; /* set i to the IP after the JMP */
+ *p++ = 0x66; /* 32-bit operand size */
+ *p++ = 0xea; /* JMP */
+ *p++ = ip; /* IP */
+ *p++ = ip >> 8;
+ *p++ = ip >> 16;
+ *p++ = ip >> 24;
+ *p++ = 0x08;
+ *p++ = 0x00;
+
+ /* initialize all other segments */
+ *p++ = 0xb8; /* MOV EAX,0x10 */
+ *p++ = 0x10;
+ *p++ = 0x00;
+ *p++ = 0x00;
+ *p++ = 0x00;
+ for (i = 0; i < 6; i++) {
+ if (i == 1) /* Skip CS */
+ continue;
+
+ *p++ = 0x8e; /* MOV <seg>,EAX */
+ *p++ = 0xc0 + (i << 3);
+ }
+
+ /* EBX contains a pointer to the bootinfo struct */
+ *p++ = 0xbb; /* MOV EBX,imm32 */
+ *p++ = bootinfo;
+ *p++ = bootinfo >> 8;
+ *p++ = bootinfo >> 16;
+ *p++ = bootinfo >> 24;
+
+ /* EAX has to contain the following magic */
+ *p++ = 0xb8; /* MOV EAX,0x2badb002 */
+ *p++ = 0x02;
+ *p++ = 0xb0;
+ *p++ = 0xad;
+ *p++ = 0x2b;
+
+ /* Jump off to the kernel */
+ *p++ = 0xea; /* JMP */
+ *p++ = mh_entry_addr; /* IP */
+ *p++ = mh_entry_addr >> 8;
+ *p++ = mh_entry_addr >> 16;
+ *p++ = mh_entry_addr >> 24;
+ *p++ = 0x08;
+ *p++ = 0x00;
+
+ { /* GDT loading */
+ uint32_t gdt_base = 0x000d0000 + (p - rom); /* 0x00007c00 is
the first IP */
+ uint32_t gdtr = gdt_base + 0x28;
+ uint8_t gdt[] = { /* GDT base: 0x00000100 */
+ /* 0x00 */
+ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+ /* 0x08: code segment (base=0, limit=0xfffff, type=32bit
code exec/read, DPL=0, 4k) */
+ 0xff, 0xff, 0x00, 0x00, 0x00, 0x9a, 0xcf, 0x00,
+ /* 0x10: data segment (base=0, limit=0xfffff, type=32bit
data read/write, DPL=0, 4k) */
+ 0xff, 0xff, 0x00, 0x00, 0x00, 0x92, 0xcf, 0x00,
+ /* 0x18: code segment (base=0, limit=0x0ffff, type=16bit
code exec/read/conf, DPL=0, 1b) */
+ 0xff, 0xff, 0x00, 0x00, 0x00, 0x9e, 0x00, 0x00,
+ /* 0x20: data segment (base=0, limit=0x0ffff, type=16bit
data read/write, DPL=0, 1b) */
+ 0xff, 0xff, 0x00, 0x00, 0x00, 0x92, 0x00, 0x00,
+ /* 0x28: gdtdesc */
+ 0x27, 0x00, gdt_base, gdt_base >> 8, gdt_base >> 16,
gdt_base >> 24
+ };
+
+ memcpy(p, gdt, sizeof(gdt));
+ p+=sizeof(gdt);
+ *pgdt++ = gdtr;
+ *pgdt++ = gdtr >> 8;
+ *pgdt++ = gdtr >> 16;
+ *pgdt++ = gdtr >> 24;
+ }
It was already pushing the limit to embed the linux loader. This is a
bit too much. Perhaps we should split it to a separate .S file? I
guess we could apply it as is but I'd like to see this code (along with
the Linux code) moved to another file at least.
+ fprintf(stderr, "qemu: multiboot loader code is %d bytes
long.\n", (int)(p-rom));
+
+ /* sign rom */
+ sum = 0;
+ for (i = 0; i < (sizeof(rom) - 1); i++)
+ sum += rom[i];
+ rom[sizeof(rom) - 1] = -sum;
+
+ memcpy(option_rom, rom, sizeof(rom));
This too could be common code.
+}
+
+static int load_multiboot(uint8_t *option_rom,
+ FILE *f,
+ const char *kernel_filename,
+ const char *initrd_filename,
+ const char *kernel_cmdline,
+ uint8_t *header)
+{
+ int i, is_multiboot = 0;
+ uint32_t flags = 0;
+ uint32_t mh_entry_addr;
+ uint32_t mh_load_addr;
+ uint32_t mb_kernel_size;
+ uint32_t mb_bootinfo = 0x90000;
+ uint32_t tmp_size;
+
+ /* Ok, let's see if it is a multiboot image */
+ for(i = 0; i < 8144; i += 4) { /* the header is 12x32bit long, so */
+ /* the latest entry may be 8192 -
48 */
+ if(ldl_p(header+i) == 0x1BADB002) {
+ uint32_t checksum = ldl_p(header+i+8);
+ flags = ldl_p(header+i+4);
+ checksum += flags;
+ checksum += (uint32_t)0x1BADB002;
+ if(!checksum) {
+ is_multiboot = 1;
+ break;
+ }
+ }
+ }
+
+ if(!is_multiboot) return 0; /* no multiboot */
+ fprintf(stderr, "qemu: I believe we found a multiboot image!\n");
+
+ if(flags & 0x00000004) { /* MULTIBOOT_HEADER_HAS_VBE */
+ fprintf(stderr, "qemu: multiboot knows VBE. we don't.\n");
+ }
+ if(!(flags & 0x00010000)) { /* MULTIBOOT_HEADER_HAS_ADDR */
+ uint64_t elf_entry;
+ int kernel_size;
+ fclose(f);
+ kernel_size = load_elf(kernel_filename, 0, &elf_entry, NULL,
NULL);
+ if(kernel_size < 0) {
+ fprintf(stderr, "Error while loading elf kernel\n");
+ exit(1);
+ }
+ mh_load_addr = mh_entry_addr = elf_entry;
+ mb_kernel_size = kernel_size;
+
+ fprintf(stderr, "qemu: loading multiboot-elf kernel (%#x
bytes) with entry %#zx\n",
+ mb_kernel_size, (size_t)mh_entry_addr);
+ } else {
+ /* Valid if mh_flags sets MULTIBOOT_HEADER_HAS_ADDR. */
+ uint32_t mh_header_addr = ldl_p(header+i+12);
+ mh_load_addr = ldl_p(header+i+16);
Mixing variable definitions and code.
+ uint32_t mh_load_end_addr = ldl_p(header+i+20);
+ uint32_t mh_bss_end_addr = ldl_p(header+i+24);
+ uint8_t *mb_kernel_addr = phys_ram_base + (mh_load_addr);
+ uint32_t mb_kernel_text_offset = i - (mh_header_addr -
mh_load_addr);
+
+ mh_entry_addr = ldl_p(header+i+28);
+ mb_kernel_size = get_file_size(f) - mb_kernel_text_offset;
+
+ /* Valid if mh_flags sets MULTIBOOT_HEADER_HAS_VBE.
+ uint32_t mh_mode_type = ldl_p(header+i+32);
+ uint32_t mh_width = ldl_p(header+i+36);
+ uint32_t mh_height = ldl_p(header+i+40);
+ uint32_t mh_depth = ldl_p(header+i+44); */
+
+ fprintf(stderr, "multiboot: mh_header_addr = %#x\n",
mh_header_addr);
+ fprintf(stderr, "multiboot: mh_load_addr = %#x\n",
mh_load_addr);
+ fprintf(stderr, "multiboot: mh_load_end_addr = %#x\n",
mh_load_end_addr);
+ fprintf(stderr, "multiboot: mh_bss_end_addr = %#x\n",
mh_bss_end_addr);
It's a bit chatty by default.
+ fseek(f, mb_kernel_text_offset, SEEK_SET);
+
+ fprintf(stderr, "qemu: loading multiboot kernel (%#x bytes)
at %#zx\n",
+ mb_kernel_size, mb_kernel_addr - phys_ram_base);
+
+ if ((tmp_size=fread(mb_kernel_addr, 1, mb_kernel_size, f)) !=
mb_kernel_size) {
+ fprintf(stderr, "qemu: read error on multiboot kernel
'%s' (%#x != %#x)\n", kernel_filename, tmp_size, mb_kernel_size);
+ exit(1);
+ }
+ fclose(f);
+ }
+
+
+ /* load modules */
+
+ stl_p(phys_ram_base + mb_bootinfo + 20, 0x0); /* mods_count */
+ if(initrd_filename) {
+ uint32_t mb_mod_info = mb_bootinfo + 0x100;
+ uint32_t mb_mod_cmdline = mb_bootinfo+ 0x300;
+ uint32_t mb_mod_start = mh_load_addr;
+ uint32_t mb_mod_length = mb_kernel_size;
+ char *next_initrd;
+ char *next_space;
+ int mb_mod_count = 0;
+
+ do {
+ next_initrd = strchr(initrd_filename, ',');
+ if(next_initrd)
+ *next_initrd = '\0';
+ /* if a space comes after the module filename, treat
everything after that as parameters */
+ strcpy(phys_ram_base + mb_mod_cmdline, initrd_filename);
+ stl_p(phys_ram_base + mb_mod_info + 8, mb_mod_cmdline);
/* string */
+ mb_mod_cmdline += strlen(initrd_filename) + 1;
+ if(next_space = strchr(initrd_filename, ' '))
+ *next_space = '\0';
+printf("multiboot loading module: %s\n", initrd_filename);
Weird indent.
What all uses multiboot at this point? I know Xen does.
Some additional documentation would be nice too.
Regards,
Anthony Liguori
Re: [Qemu-devel] [PATCH] Add multi-boot kernel loading support, Kevin Wolf, 2009/02/03