aboutsummaryrefslogtreecommitdiff
path: root/pc-bios/optionrom
diff options
context:
space:
mode:
authorAlexander Graf <agraf@suse.de>2009-11-12 21:53:12 +0100
committerAnthony Liguori <aliguori@us.ibm.com>2009-11-17 10:39:02 -0600
commit77873196f344a56dfcd460f2cf69ac793fad1b40 (patch)
treee151d5d7fb56b4a0e6bbac80868defed331c2d74 /pc-bios/optionrom
parent235f86ef01470391925e7edec71638b41ffa5537 (diff)
downloadqemu-arm-77873196f344a56dfcd460f2cf69ac793fad1b40.tar.gz
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>
Diffstat (limited to 'pc-bios/optionrom')
-rw-r--r--pc-bios/optionrom/multiboot.S77
1 files changed, 60 insertions, 17 deletions
diff --git a/pc-bios/optionrom/multiboot.S b/pc-bios/optionrom/multiboot.S
index e6cbefdc92..dafac7392e 100644
--- a/pc-bios/optionrom/multiboot.S
+++ b/pc-bios/optionrom/multiboot.S
@@ -26,6 +26,14 @@
#define MULTIBOOT_MAGIC 0x2badb002
+#define GS_PROT_JUMP 0
+#define GS_GDT_DESC 6
+
+/* Break the translation block flow so -d cpu shows us values */
+#define DEBUG_HERE \
+ jmp 1f; \
+ 1:
+
/* Read a variable from the fw_cfg device.
Clobbers: %edx
Out: %eax */
@@ -44,12 +52,31 @@
bswap %eax
.endm
+/*
+ * Read a blob from the fw_cfg device.
+ * Requires _ADDR, _SIZE and _DATA values for the parameter.
+ *
+ * Clobbers: %eax, %edx, %es, %ecx, %edi
+ */
+#define read_fw_blob(var) \
+ read_fw var ## _ADDR; \
+ mov %eax, %edi; \
+ read_fw var ## _SIZE; \
+ mov %eax, %ecx; \
+ mov $var ## _DATA, %ax; \
+ mov $BIOS_CFG_IOPORT_CFG, %edx; \
+ outw %ax, (%dx); \
+ mov $BIOS_CFG_IOPORT_DATA, %dx; \
+ cld; \
+ DEBUG_HERE \
+ rep insb (%dx), %es:(%edi);
+
.code16
.text
.global _start
_start:
.short 0xaa55
- .byte 1 /* (_end - _start) / 512 */
+ .byte (_end - _start) / 512
push %eax
push %ds
@@ -57,10 +84,6 @@ _start:
xor %ax, %ax
mov %ax, %ds
- /* save old int 19 */
- mov (0x19*4), %eax
- mov %eax, %cs:old_int19
-
/* install our int 19 handler */
movw $int19_handler, (0x19*4)
mov %cs, (0x19*4+2)
@@ -84,15 +107,34 @@ run_multiboot:
mov %cs, %eax
shl $0x4, %eax
- /* fix the gdt descriptor to be PC relative */
- mov (gdt_desc+2), %ebx
- add %eax, %ebx
- mov %ebx, (gdt_desc+2)
+ /* set up a long jump descriptor that is PC relative */
- /* fix the prot mode indirect jump to be PC relative */
+ /* move stack memory to %gs */
+ mov %ss, %ecx
+ shl $0x4, %ecx
+ mov %esp, %ebx
+ add %ebx, %ecx
+ sub $0x20, %ecx
+ sub $0x30, %esp
+ shr $0x4, %ecx
+ mov %cx, %gs
+
+ /* now push the indirect jump decriptor there */
mov (prot_jump), %ebx
add %eax, %ebx
- mov %ebx, (prot_jump)
+ movl %ebx, %gs:GS_PROT_JUMP
+ mov $8, %bx
+ movw %bx, %gs:GS_PROT_JUMP + 4
+
+ /* fix the gdt descriptor to be PC relative */
+ movw (gdt_desc), %bx
+ movw %bx, %gs:GS_GDT_DESC
+ movl (gdt_desc+2), %ebx
+ add %eax, %ebx
+ movl %ebx, %gs:GS_GDT_DESC + 2
+
+ /* Read the bootinfo struct into RAM */
+ read_fw_blob(FW_CFG_INITRD)
/* FS = bootinfo_struct */
read_fw FW_CFG_INITRD_ADDR
@@ -100,7 +142,7 @@ run_multiboot:
mov %ax, %fs
/* ES = mmap_addr */
- read_fw FW_CFG_INITRD_SIZE
+ mov %eax, %fs:0x48
shr $4, %eax
mov %ax, %es
@@ -144,7 +186,7 @@ mmap_done:
real_to_prot:
/* Load the GDT before going into protected mode */
lgdt:
- data32 lgdt %cs:gdt_desc
+ data32 lgdt %gs:GS_GDT_DESC
/* get us to protected mode now */
movl $1, %eax
@@ -152,7 +194,7 @@ lgdt:
/* the LJMP sets CS for us and gets us to 32-bit */
ljmp:
- data32 ljmp *%cs:prot_jump
+ data32 ljmp *%gs:GS_PROT_JUMP
prot_mode:
.code32
@@ -165,8 +207,11 @@ prot_mode:
movl %eax, %fs
movl %eax, %gs
+ /* Read the kernel and modules into RAM */
+ read_fw_blob(FW_CFG_KERNEL)
+
/* Jump off to the kernel */
- read_fw FW_CFG_KERNEL_ADDR
+ read_fw FW_CFG_KERNEL_ENTRY
mov %eax, %ecx
/* EBX contains a pointer to the bootinfo struct */
@@ -180,8 +225,6 @@ ljmp2:
/* Variables */
.align 4, 0
-old_int19: .long 0
-
prot_jump: .long prot_mode
.short 8