I attach a patch that leaves the boot time %cs and %ds at their old values
(0x10 and 0x18), and shifts to the new GDT layout after the switch to
protected mode has been accomplished.
For those who don't have this GDT boot problem, it reduces the size of the
boot code by about 64 bytes.
James
You can import this changeset into BK by piping this whole message to:
'| bk receive [path to repository]' or apply the patch as usual.
===================================================================
ChangeSet@1.486, 2002-08-16 18:23:02-05:00, jejb@mulgrave.(none)
Separate boot GDT from runtime GDT. Allow small compact GDT at boot
for those PCs which have problems with big ones during the protected
mode transition.
arch/i386/boot/compressed/head.S | 8 ++++----
arch/i386/boot/compressed/misc.c | 2 +-
arch/i386/boot/setup.S | 15 +++++++--------
arch/i386/kernel/head.S | 15 +++++++++++++--
arch/i386/kernel/trampoline.S | 6 +++---
include/asm-i386/segment.h | 8 ++++++++
6 files changed, 36 insertions(+), 18 deletions(-)
diff -Nru a/arch/i386/boot/compressed/head.S b/arch/i386/boot/compressed/head.S
--- a/arch/i386/boot/compressed/head.S Fri Aug 16 19:29:20 2002
+++ b/arch/i386/boot/compressed/head.S Fri Aug 16 19:29:20 2002
@@ -31,7 +31,7 @@
startup_32:
cld
cli
- movl $(__KERNEL_DS),%eax
+ movl $(__BOOT_DS),%eax
movl %eax,%ds
movl %eax,%es
movl %eax,%fs
@@ -74,7 +74,7 @@
popl %esi # discard address
popl %esi # real mode pointer
xorl %ebx,%ebx
- ljmp $(__KERNEL_CS), $0x100000
+ ljmp $(__BOOT_CS), $0x100000
/*
* We come here, if we were loaded high.
@@ -101,7 +101,7 @@
popl %eax # hcount
movl $0x100000,%edi
cli # make sure we don't get interrupted
- ljmp $(__KERNEL_CS), $0x1000 # and jump to the move routine
+ ljmp $(__BOOT_CS), $0x1000 # and jump to the move routine
/*
* Routine (template) for moving the decompressed kernel in place,
@@ -124,5 +124,5 @@
movsl
movl %ebx,%esi # Restore setup pointer
xorl %ebx,%ebx
- ljmp $(__KERNEL_CS), $0x100000
+ ljmp $(__BOOT_CS), $0x100000
move_routine_end:
diff -Nru a/arch/i386/boot/compressed/misc.c b/arch/i386/boot/compressed/misc.c
--- a/arch/i386/boot/compressed/misc.c Fri Aug 16 19:29:20 2002
+++ b/arch/i386/boot/compressed/misc.c Fri Aug 16 19:29:20 2002
@@ -299,7 +299,7 @@
struct {
long * a;
short b;
- } stack_start = { & user_stack [STACK_SIZE] , __KERNEL_DS };
+ } stack_start = { & user_stack [STACK_SIZE] , __BOOT_DS };
static void setup_normal_output_buffer(void)
{
diff -Nru a/arch/i386/boot/setup.S b/arch/i386/boot/setup.S
--- a/arch/i386/boot/setup.S Fri Aug 16 19:29:20 2002
+++ b/arch/i386/boot/setup.S Fri Aug 16 19:29:20 2002
@@ -801,7 +801,7 @@
subw $DELTA_INITSEG, %si
shll $4, %esi # Convert to 32-bit pointer
# NOTE: For high loaded big kernels we need a
-# jmpi 0x100000,__KERNEL_CS
+# jmpi 0x100000,__BOOT_CS
#
# but we yet haven't reloaded the CS register, so the default size
# of the target offset still is 16 bit.
@@ -812,7 +812,7 @@
.byte 0x66, 0xea # prefix + jmpi-opcode
code32: .long 0x1000 # will be set to 0x100000
# for big kernels
- .word __KERNEL_CS
+ .word __BOOT_CS
# Here's a bunch of information about your current kernel..
kernel_version: .ascii UTS_RELEASE
@@ -1007,12 +1007,12 @@
# Descriptor tables
#
# NOTE: if you think the GDT is large, you can make it smaller by just
-# defining the KERNEL_CS and KERNEL_DS entries and shifting the gdt
-# address down by GDT_ENTRY_KERNEL_CS*8. This puts bogus entries into
+# defining the BOOT_CS and BOOT_DS entries and shifting the gdt
+# address down by GDT_ENTRY_BOOT_CS*8. This puts bogus entries into
# the GDT, but those wont be used so it's not a problem.
#
gdt:
- .fill GDT_ENTRY_KERNEL_CS,8,0
+ .fill GDT_ENTRY_BOOT_CS,8,0
.word 0xFFFF # 4Gb - (0x100000*0x1000 = 4Gb)
.word 0 # base address = 0
@@ -1025,13 +1025,12 @@
.word 0x9200 # data read/write
.word 0x00CF # granularity = 4096, 386
# (+5th nibble of limit)
+gdt_end:
idt_48:
.word 0 # idt limit = 0
.word 0, 0 # idt base = 0L
gdt_48:
- .word 0x8000 # gdt limit=2048,
- # 256 GDT entries
-
+ .word gdt_end - gdt - 1 # gdt limit
.word 0, 0 # gdt base (filled in later)
# Include video setup & detection code
diff -Nru a/arch/i386/kernel/head.S b/arch/i386/kernel/head.S
--- a/arch/i386/kernel/head.S Fri Aug 16 19:29:20 2002
+++ b/arch/i386/kernel/head.S Fri Aug 16 19:29:20 2002
@@ -46,7 +46,7 @@
* Set segments to known values
*/
cld
- movl $(__KERNEL_DS),%eax
+ movl $(__BOOT_DS),%eax
movl %eax,%ds
movl %eax,%es
movl %eax,%fs
@@ -306,7 +306,7 @@
ENTRY(stack_start)
.long init_thread_union+8192
- .long __KERNEL_DS
+ .long __BOOT_DS
/* This is the default interrupt "handler" :-) */
int_msg:
@@ -409,6 +409,17 @@
/*
* The Global Descriptor Table contains 28 quadwords, per-CPU.
*/
+#ifdef CONFIG_SMP
+/*
+ * The boot_gdt_table must mirror the equivalent in setup.S and is
+ * used only by the trampoline for booting other CPUs
+ */
+ENTRY(boot_gdt_table)
+ .fill GDT_ENTRY_BOOT_CS,8,0
+ .quad 0x00cf9a000000ffff /* kernel 4GB code at 0x00000000 */
+ .quad 0x00cf92000000ffff /* kernel 4GB data at 0x00000000 */
+#endif
+
ENTRY(cpu_gdt_table)
.quad 0x0000000000000000 /* NULL descriptor */
.quad 0x0000000000000000 /* 0x0b reserved */
diff -Nru a/arch/i386/kernel/trampoline.S b/arch/i386/kernel/trampoline.S
--- a/arch/i386/kernel/trampoline.S Fri Aug 16 19:29:20 2002
+++ b/arch/i386/kernel/trampoline.S Fri Aug 16 19:29:20 2002
@@ -56,7 +56,7 @@
lmsw %ax # into protected mode
jmp flush_instr
flush_instr:
- ljmpl $__KERNEL_CS, $0x00100000
+ ljmpl $__BOOT_CS, $0x00100000
# jump to startup_32 in arch/i386/kernel/head.S
idt_48:
@@ -69,8 +69,8 @@
#
gdt_48:
- .word 0x0800 # gdt limit = 2048, 256 GDT entries
- .long cpu_gdt_table-__PAGE_OFFSET # gdt base = gdt (first SMP CPU)
+ .word __BOOT_DS + 7 # gdt limit
+ .long boot_gdt_table-__PAGE_OFFSET # gdt base = gdt (first SMP CPU)
.globl trampoline_end
trampoline_end:
diff -Nru a/include/asm-i386/segment.h b/include/asm-i386/segment.h
--- a/include/asm-i386/segment.h Fri Aug 16 19:29:20 2002
+++ b/include/asm-i386/segment.h Fri Aug 16 19:29:20 2002
@@ -69,6 +69,14 @@
#define GDT_SIZE (GDT_ENTRIES * 8)
+/* Simple and small GDT entries for booting only */
+
+#define GDT_ENTRY_BOOT_CS 2
+#define __BOOT_CS (GDT_ENTRY_BOOT_CS * 8)
+
+#define GDT_ENTRY_BOOT_DS (GDT_ENTRY_BOOT_CS + 1)
+#define __BOOT_DS (GDT_ENTRY_BOOT_DS * 8)
+
/*
* The interrupt descriptor table has room for 256 idt's,
* the global descriptor table is dependent on the number
===================================================================
This BitKeeper patch contains the following changesets:
+
## Wrapped with gzip_uu ##
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end
-
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