diff options
Diffstat (limited to 'arch/i386/kernel/entry.S')
| -rw-r--r-- | arch/i386/kernel/entry.S | 85 |
1 files changed, 85 insertions, 0 deletions
diff --git a/arch/i386/kernel/entry.S b/arch/i386/kernel/entry.S index 3c3c220..32980b8 100644 --- a/arch/i386/kernel/entry.S +++ b/arch/i386/kernel/entry.S @@ -1023,6 +1023,91 @@ ENTRY(kernel_thread_helper) CFI_ENDPROC ENDPROC(kernel_thread_helper) +#ifdef CONFIG_XEN +ENTRY(xen_hypervisor_callback) + CFI_STARTPROC + pushl $0 + CFI_ADJUST_CFA_OFFSET 4 + SAVE_ALL + TRACE_IRQS_OFF + + /* Check to see if we got the event in the critical + region in xen_iret_direct, after we've reenabled + events and checked for pending events. This simulates + iret instruction's behaviour where it delivers a + pending interrupt when enabling interrupts. */ + movl PT_EIP(%esp),%eax + cmpl $xen_iret_start_crit,%eax + jb 1f + cmpl $xen_iret_end_crit,%eax + jae 1f + + call xen_iret_crit_fixup + +1: mov %esp, %eax + call xen_evtchn_do_upcall + jmp ret_from_intr + CFI_ENDPROC +ENDPROC(xen_hypervisor_callback) + +# Hypervisor uses this for application faults while it executes. +# We get here for two reasons: +# 1. Fault while reloading DS, ES, FS or GS +# 2. Fault while executing IRET +# Category 1 we fix up by reattempting the load, and zeroing the segment +# register if the load fails. +# Category 2 we fix up by jumping to do_iret_error. We cannot use the +# normal Linux return path in this case because if we use the IRET hypercall +# to pop the stack frame we end up in an infinite loop of failsafe callbacks. +# We distinguish between categories by maintaining a status value in EAX. +ENTRY(xen_failsafe_callback) + CFI_STARTPROC + pushl %eax + CFI_ADJUST_CFA_OFFSET 4 + movl $1,%eax +1: mov 4(%esp),%ds +2: mov 8(%esp),%es +3: mov 12(%esp),%fs +4: mov 16(%esp),%gs + testl %eax,%eax + popl %eax + CFI_ADJUST_CFA_OFFSET -4 + lea 16(%esp),%esp + CFI_ADJUST_CFA_OFFSET -16 + jz 5f + addl $16,%esp + jmp iret_exc # EAX != 0 => Category 2 (Bad IRET) +5: pushl $0 # EAX == 0 => Category 1 (Bad segment) + CFI_ADJUST_CFA_OFFSET 4 + SAVE_ALL + jmp ret_from_exception + CFI_ENDPROC + +.section .fixup,"ax" +6: xorl %eax,%eax + movl %eax,4(%esp) + jmp 1b +7: xorl %eax,%eax + movl %eax,8(%esp) + jmp 2b +8: xorl %eax,%eax + movl %eax,12(%esp) + jmp 3b +9: xorl %eax,%eax + movl %eax,16(%esp) + jmp 4b +.previous +.section __ex_table,"a" + .align 4 + .long 1b,6b + .long 2b,7b + .long 3b,8b + .long 4b,9b +.previous +ENDPROC(xen_failsafe_callback) + +#endif /* CONFIG_XEN */ + .section .rodata,"a" #include "syscall_table.S" |
