1.1 --- a/xen/arch/x86/x86_64/entry.S	Thu Feb 10 18:11:07 2005 +0000
     1.2 +++ b/xen/arch/x86/x86_64/entry.S	Thu Feb 10 18:49:57 2005 +0000
     1.3 @@ -24,14 +24,21 @@ restore_all_guest:
     1.4          jc    failsafe_callback
     1.5          RESTORE_ALL
     1.6          testw $TRAP_syscall,4(%rsp)
     1.7 -        jz    1f
     1.8 -        addq  $8,%rsp
     1.9 -        popq  %rcx
    1.10 +        jz    iret_exit_to_guest
    1.11 +
    1.12          addq  $8,%rsp
    1.13 -        popq  %r11
    1.14 -        popq  %rsp
    1.15 +        popq  %rcx                    # RIP
    1.16 +        popq  %r11                    # CS
    1.17 +        cmpw  $__GUEST_CS32,%r11
    1.18 +        popq  %r11                    # RFLAGS
    1.19 +        popq  %rsp                    # RSP
    1.20 +        je    1f
    1.21          sysretq
    1.22 -1:      addq  $8,%rsp
    1.23 +1:      sysretl
    1.24 +
    1.25 +        ALIGN
    1.26 +iret_exit_to_guest:
    1.27 +        addq  $8,%rsp
    1.28  FLT1:   iretq
    1.29  .section .fixup,"ax"
    1.30  FIX1:   popq  -15*8-8(%rsp)            # error_code/entry_vector
    1.31 @@ -89,16 +96,24 @@ restore_all_xen:
    1.32          iretq
    1.33  
    1.34  /*
    1.35 - * %rax                            = hypercall vector
    1.36 - * %rdi, %rsi, %rdx, %r10, %r8, %9 = hypercall arguments
    1.37 - * %r11, %rcx                      = SYSCALL-saved %rflags and %rip
    1.38 - * NB. We must move %r10 to %rcx for C function-calling ABI.
    1.39 + * When entering SYSCALL from kernel mode:
    1.40 + *  %rax                            = hypercall vector
    1.41 + *  %rdi, %rsi, %rdx, %r10, %r8, %9 = hypercall arguments
    1.42 + *  %r11, %rcx                      = SYSCALL-saved %rflags and %rip
    1.43 + *  NB. We must move %r10 to %rcx for C function-calling ABI.
    1.44 + *
    1.45 + * When entering SYSCALL from user mode:
    1.46 + *  Vector directly to the registered arch.syscall_addr.
    1.47 + *
    1.48 + * Initial work is done by per-CPU stack trampolines. At this point %rsp
    1.49 + * has been initialised to point at the correct Xen stack, and %rsp, %rflags
    1.50 + * and %cs have been saved. All other registers are still to be saved onto
    1.51 + * the stack, starting with %rip, and an appropriate %ss must be saved into
    1.52 + * the space left by the trampoline.
    1.53   */
    1.54          ALIGN
    1.55  ENTRY(syscall_enter)
    1.56 -        movl  $__GUEST_SS,8(%rsp)
    1.57 -        pushq %r11
    1.58 -        pushq $__GUEST_CS
    1.59 +        movl  $__GUEST_SS,24(%rsp)
    1.60          pushq %rcx
    1.61          pushq $0
    1.62          movl  $TRAP_syscall,4(%rsp)

     2.1 --- a/xen/arch/x86/x86_64/traps.c	Thu Feb 10 18:11:07 2005 +0000
     2.2 +++ b/xen/arch/x86/x86_64/traps.c	Thu Feb 10 18:49:57 2005 +0000
     2.3 @@ -196,16 +196,24 @@ void __init percpu_traps_init(void)
     2.4      stack[9] = 0x25;
     2.5      *(u32 *)&stack[10] = (stack_bottom - &stack[14]) - 16;
     2.6  
     2.7 +    /* pushq %r11 */
     2.8 +    stack[14] = 0x41;
     2.9 +    stack[15] = 0x53;
    2.10 +
    2.11 +    /* pushq $__GUEST_CS64 */
    2.12 +    stack[16] = 0x68;
    2.13 +    *(u32 *)&stack[17] = __GUEST_CS64;
    2.14 +
    2.15      /* jmp syscall_enter */
    2.16 -    stack[14] = 0xe9;
    2.17 -    *(u32 *)&stack[15] = (char *)syscall_enter - &stack[19];
    2.18 +    stack[21] = 0xe9;
    2.19 +    *(u32 *)&stack[22] = (char *)syscall_enter - &stack[26];
    2.20  
    2.21      /*
    2.22       * Trampoline for SYSCALL entry from compatibility mode.
    2.23       */
    2.24  
    2.25      /* Skip the long-mode entry trampoline. */
    2.26 -    stack = &stack[19];
    2.27 +    stack = &stack[26];
    2.28      wrmsr(MSR_CSTAR, (unsigned long)stack, ((unsigned long)stack>>32)); 
    2.29  
    2.30      /* movq %rsp, saversp(%rip) */
    2.31 @@ -220,9 +228,17 @@ void __init percpu_traps_init(void)
    2.32      stack[9] = 0x25;
    2.33      *(u32 *)&stack[10] = (stack_bottom - &stack[14]) - 16;
    2.34  
    2.35 +    /* pushq %r11 */
    2.36 +    stack[14] = 0x41;
    2.37 +    stack[15] = 0x53;
    2.38 +
    2.39 +    /* pushq $__GUEST_CS32 */
    2.40 +    stack[16] = 0x68;
    2.41 +    *(u32 *)&stack[17] = __GUEST_CS32;
    2.42 +
    2.43      /* jmp syscall_enter */
    2.44 -    stack[14] = 0xe9;
    2.45 -    *(u32 *)&stack[15] = (char *)syscall_enter - &stack[19];
    2.46 +    stack[21] = 0xe9;
    2.47 +    *(u32 *)&stack[22] = (char *)syscall_enter - &stack[26];
    2.48  
    2.49      /*
    2.50       * Common SYSCALL parameters.

     3.1 --- a/xen/include/asm-x86/config.h	Thu Feb 10 18:11:07 2005 +0000
     3.2 +++ b/xen/include/asm-x86/config.h	Thu Feb 10 18:49:57 2005 +0000
     3.3 @@ -202,7 +202,9 @@ extern void __out_of_line_bug(int line) 
     3.4  #define __HYPERVISOR_DS32 0x0818
     3.5  #define __HYPERVISOR_DS   __HYPERVISOR_DS64
     3.6  
     3.7 -#define __GUEST_CS        0x0833
     3.8 +#define __GUEST_CS64      0x0833
     3.9 +#define __GUEST_CS32      0x0823
    3.10 +#define __GUEST_CS        __GUEST_CS64
    3.11  #define __GUEST_DS        0x0000
    3.12  #define __GUEST_SS        0x082b
    3.13