[PATCH] i386: Use %gs as the PDA base-segment in the kernel

[pandora-kernel.git] / arch / i386 / kernel / head.S

diff --git a/arch/i386/kernel/head.S b/arch/i386/kernel/head.S
index 4a83384..5b14e95 100644 (file)
--- a/arch/i386/kernel/head.S
+++ b/arch/i386/kernel/head.S
@@ -302,6 +302,7 @@ is386:      movl $2,%ecx            # set MP
        movl %eax,%cr0
 
        call check_x87
+       call setup_pda
        lgdt cpu_gdt_descr
        lidt idt_descr
        ljmp $(__KERNEL_CS),$1f
@@ -312,10 +313,13 @@ is386:    movl $2,%ecx            # set MP
        movl %eax,%ds
        movl %eax,%es
 
-       xorl %eax,%eax                  # Clear FS/GS and LDT
+       xorl %eax,%eax                  # Clear FS and LDT
        movl %eax,%fs
-       movl %eax,%gs
        lldt %ax
+
+       movl $(__KERNEL_PDA),%eax
+       mov  %eax,%gs
+
        cld                     # gcc2 wants the direction flag cleared at all times
        pushl $0                # fake return address for unwinder
 #ifdef CONFIG_SMP
@@ -345,6 +349,23 @@ check_x87:
        .byte 0xDB,0xE4         /* fsetpm for 287, ignored by 387 */
        ret
 
+/*
+ * Point the GDT at this CPU's PDA.  On boot this will be
+ * cpu_gdt_table and boot_pda; for secondary CPUs, these will be
+ * that CPU's GDT and PDA.
+ */
+setup_pda:
+       /* get the PDA pointer */
+       movl start_pda, %eax
+
+       /* slot the PDA address into the GDT */
+       mov cpu_gdt_descr+2, %ecx
+       mov %ax, (__KERNEL_PDA+0+2)(%ecx)               /* base & 0x0000ffff */
+       shr $16, %eax
+       mov %al, (__KERNEL_PDA+4+0)(%ecx)               /* base & 0x00ff0000 */
+       mov %ah, (__KERNEL_PDA+4+3)(%ecx)               /* base & 0xff000000 */
+       ret
+
 /*
  *  setup_idt
  *
@@ -484,6 +505,8 @@ ENTRY(empty_zero_page)
  * This starts the data section.
  */
 .data
+ENTRY(start_pda)
+       .long boot_pda
 
 ENTRY(stack_start)
        .long init_thread_union+THREAD_SIZE
@@ -525,7 +548,7 @@ idt_descr:
 
 # boot GDT descriptor (later on used by CPU#0):
        .word 0                         # 32 bit align gdt_desc.address
-cpu_gdt_descr:
+ENTRY(cpu_gdt_descr)
        .word GDT_ENTRIES*8-1
        .long cpu_gdt_table
 
@@ -585,7 +608,7 @@ ENTRY(cpu_gdt_table)
        .quad 0x004092000000ffff        /* 0xc8 APM DS    data */
 
        .quad 0x00c0920000000000        /* 0xd0 - ESPFIX SS */
-       .quad 0x0000000000000000        /* 0xd8 - PDA */
+       .quad 0x00cf92000000ffff        /* 0xd8 - PDA */
        .quad 0x0000000000000000        /* 0xe0 - unused */
        .quad 0x0000000000000000        /* 0xe8 - unused */
        .quad 0x0000000000000000        /* 0xf0 - unused */