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    Subject[PATCH] [12/22] x86_64: wakeup.S misc cleanups
    Date

    From: Vivek Goyal <vgoyal@in.ibm.com>


    o Various cleanups. One of the main purpose of cleanups is that make
    wakeup.S as close as possible to trampoline.S.

    o Following are the changes
    - Indentations for comments.
    - Changed the gdt table to compact form and to resemble the
    one in trampoline.S
    - Take the jump to 32bit from real mode using ljmpl. Makes code
    more readable.
    - After enabling long mode, directly take a long jump for 64bit
    mode. No need to take an extra jump to "reach_comaptibility_mode"
    - Stack is not used after real mode. So don't load stack in
    32 bit mode.
    - No need to enable PGE here.
    - No need to do extra EFER read, anyway we trash the read contents.
    - No need to enable system call (EFER_SCE). Anyway it will be
    enabled when original EFER is restored.
    - No need to set MP, ET, NE, WP, AM bits in cr0. Very soon we will
    reload the original cr0 while restroing the processor state.

    Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
    Signed-off-by: Vivek Goyal <vgoyal@in.ibm.com>
    Signed-off-by: Andi Kleen <ak@suse.de>

    ---

    arch/x86_64/kernel/acpi/wakeup.S | 112 +++++++++++++--------------------------
    1 file changed, 40 insertions(+), 72 deletions(-)

    Index: linux/arch/x86_64/kernel/acpi/wakeup.S
    ===================================================================
    --- linux.orig/arch/x86_64/kernel/acpi/wakeup.S
    +++ linux/arch/x86_64/kernel/acpi/wakeup.S
    @@ -30,11 +30,12 @@ wakeup_code:
    cld
    # setup data segment
    movw %cs, %ax
    - movw %ax, %ds # Make ds:0 point to wakeup_start
    + movw %ax, %ds # Make ds:0 point to wakeup_start
    movw %ax, %ss
    - mov $(wakeup_stack - wakeup_code), %sp # Private stack is needed for ASUS board
    + # Private stack is needed for ASUS board
    + mov $(wakeup_stack - wakeup_code), %sp

    - pushl $0 # Kill any dangerous flags
    + pushl $0 # Kill any dangerous flags
    popfl

    movl real_magic - wakeup_code, %eax
    @@ -45,7 +46,7 @@ wakeup_code:
    jz 1f
    lcall $0xc000,$3
    movw %cs, %ax
    - movw %ax, %ds # Bios might have played with that
    + movw %ax, %ds # Bios might have played with that
    movw %ax, %ss
    1:

    @@ -75,9 +76,12 @@ wakeup_code:
    jmp 1f
    1:

    - .byte 0x66, 0xea # prefix + jmpi-opcode
    - .long wakeup_32 - __START_KERNEL_map
    - .word __KERNEL_CS
    + ljmpl *(wakeup_32_vector - wakeup_code)
    +
    + .balign 4
    +wakeup_32_vector:
    + .long wakeup_32 - __START_KERNEL_map
    + .word __KERNEL32_CS, 0

    .code32
    wakeup_32:
    @@ -96,65 +100,50 @@ wakeup_32:
    jnc bogus_cpu
    movl %edx,%edi

    - movw $__KERNEL_DS, %ax
    - movw %ax, %ds
    - movw %ax, %es
    - movw %ax, %fs
    - movw %ax, %gs
    + movl $__KERNEL_DS, %eax
    + movl %eax, %ds

    - movw $__KERNEL_DS, %ax
    - movw %ax, %ss
    -
    - mov $(wakeup_stack - __START_KERNEL_map), %esp
    movl saved_magic - __START_KERNEL_map, %eax
    cmpl $0x9abcdef0, %eax
    jne bogus_32_magic

    + movw $0x0e00 + 'i', %ds:(0xb8012)
    + movb $0xa8, %al ; outb %al, $0x80;
    +
    /*
    * Prepare for entering 64bits mode
    */

    - /* Enable PAE mode and PGE */
    + /* Enable PAE */
    xorl %eax, %eax
    btsl $5, %eax
    - btsl $7, %eax
    movl %eax, %cr4

    /* Setup early boot stage 4 level pagetables */
    movl $(wakeup_level4_pgt - __START_KERNEL_map), %eax
    movl %eax, %cr3

    - /* Setup EFER (Extended Feature Enable Register) */
    - movl $MSR_EFER, %ecx
    - rdmsr
    - /* Fool rdmsr and reset %eax to avoid dependences */
    - xorl %eax, %eax
    /* Enable Long Mode */
    + xorl %eax, %eax
    btsl $_EFER_LME, %eax
    - /* Enable System Call */
    - btsl $_EFER_SCE, %eax

    - /* No Execute supported? */
    + /* No Execute supported? */
    btl $20,%edi
    jnc 1f
    btsl $_EFER_NX, %eax
    -1:

    /* Make changes effective */
    +1: movl $MSR_EFER, %ecx
    + xorl %edx, %edx
    wrmsr
    - wbinvd

    xorl %eax, %eax
    btsl $31, %eax /* Enable paging and in turn activate Long Mode */
    btsl $0, %eax /* Enable protected mode */
    - btsl $1, %eax /* Enable MP */
    - btsl $4, %eax /* Enable ET */
    - btsl $5, %eax /* Enable NE */
    - btsl $16, %eax /* Enable WP */
    - btsl $18, %eax /* Enable AM */

    /* Make changes effective */
    movl %eax, %cr0
    +
    /* At this point:
    CR4.PAE must be 1
    CS.L must be 0
    @@ -162,11 +151,6 @@ wakeup_32:
    Next instruction must be a branch
    This must be on identity-mapped page
    */
    - jmp reach_compatibility_mode
    -reach_compatibility_mode:
    - movw $0x0e00 + 'i', %ds:(0xb8012)
    - movb $0xa8, %al ; outb %al, $0x80;
    -
    /*
    * At this point we're in long mode but in 32bit compatibility mode
    * with EFER.LME = 1, CS.L = 0, CS.D = 1 (and in turn
    @@ -174,24 +158,19 @@ reach_compatibility_mode:
    * the new gdt/idt that has __KERNEL_CS with CS.L = 1.
    */

    - movw $0x0e00 + 'n', %ds:(0xb8014)
    - movb $0xa9, %al ; outb %al, $0x80
    -
    - /* Load new GDT with the 64bit segment using 32bit descriptor */
    - movl $(pGDT32 - __START_KERNEL_map), %eax
    - lgdt (%eax)
    -
    - movl $(wakeup_jumpvector - __START_KERNEL_map), %eax
    /* Finally jump in 64bit mode */
    - ljmp *(%eax)
    + ljmp *(wakeup_long64_vector - __START_KERNEL_map)

    -wakeup_jumpvector:
    - .long wakeup_long64 - __START_KERNEL_map
    - .word __KERNEL_CS
    + .balign 4
    +wakeup_long64_vector:
    + .long wakeup_long64 - __START_KERNEL_map
    + .word __KERNEL_CS, 0

    .code64

    - /* Hooray, we are in Long 64-bit mode (but still running in low memory) */
    + /* Hooray, we are in Long 64-bit mode (but still running in
    + * low memory)
    + */
    wakeup_long64:
    /*
    * We must switch to a new descriptor in kernel space for the GDT
    @@ -201,6 +180,9 @@ wakeup_long64:
    */
    lgdt cpu_gdt_descr - __START_KERNEL_map

    + movw $0x0e00 + 'n', %ds:(0xb8014)
    + movb $0xa9, %al ; outb %al, $0x80
    +
    movw $0x0e00 + 'u', %ds:(0xb8016)

    nop
    @@ -227,33 +209,19 @@ wakeup_long64:

    .align 64
    gdta:
    + /* Its good to keep gdt in sync with one in trampoline.S */
    .word 0, 0, 0, 0 # dummy
    -
    - .word 0, 0, 0, 0 # unused
    -
    - .word 0xFFFF # 4Gb - (0x100000*0x1000 = 4Gb)
    - .word 0 # base address = 0
    - .word 0x9B00 # code read/exec. ??? Why I need 0x9B00 (as opposed to 0x9A00 in order for this to work?)
    - .word 0x00CF # granularity = 4096, 386
    - # (+5th nibble of limit)
    -
    - .word 0xFFFF # 4Gb - (0x100000*0x1000 = 4Gb)
    - .word 0 # base address = 0
    - .word 0x9200 # data read/write
    - .word 0x00CF # granularity = 4096, 386
    - # (+5th nibble of limit)
    -# this is 64bit descriptor for code
    - .word 0xFFFF
    - .word 0
    - .word 0x9A00 # code read/exec
    - .word 0x00AF # as above, but it is long mode and with D=0
    + /* ??? Why I need the accessed bit set in order for this to work? */
    + .quad 0x00cf9b000000ffff # __KERNEL32_CS
    + .quad 0x00af9b000000ffff # __KERNEL_CS
    + .quad 0x00cf93000000ffff # __KERNEL_DS

    idt_48a:
    .word 0 # idt limit = 0
    .word 0, 0 # idt base = 0L

    gdt_48a:
    - .word 0x8000 # gdt limit=2048,
    + .word 0x800 # gdt limit=2048,
    # 256 GDT entries
    .word 0, 0 # gdt base (filled in later)

    @@ -263,7 +231,7 @@ video_mode: .quad 0
    video_flags: .quad 0

    bogus_real_magic:
    - movb $0xba,%al ; outb %al,$0x80
    + movb $0xba,%al ; outb %al,$0x80
    jmp bogus_real_magic

    bogus_32_magic:
    -
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