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xen64: add hypervisor callbacks for events, etc

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Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Stephen Tweedie <sct@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Jeremy Fitzhardinge 2008-07-08 15:06:49 -07:00 • committed by Ingo Molnar
commit 3d75e1b8ef
1 changed files with 98 additions and 0 deletions
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98
arch/x86/kernel/entry_64.S
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@ -1312,3 +1312,101 @@ KPROBE_ENTRY(ignore_sysret)
sysret
CFI_ENDPROC
ENDPROC(ignore_sysret)
#ifdef CONFIG_XEN
ENTRY(xen_hypervisor_callback)
zeroentry xen_do_hypervisor_callback
END(xen_hypervisor_callback)
/*
# A note on the "critical region" in our callback handler.
# We want to avoid stacking callback handlers due to events occurring
# during handling of the last event. To do this, we keep events disabled
# until we've done all processing. HOWEVER, we must enable events before
# popping the stack frame (can't be done atomically) and so it would still
# be possible to get enough handler activations to overflow the stack.
# Although unlikely, bugs of that kind are hard to track down, so we'd
# like to avoid the possibility.
# So, on entry to the handler we detect whether we interrupted an
# existing activation in its critical region -- if so, we pop the current
# activation and restart the handler using the previous one.
*/
ENTRY(xen_do_hypervisor_callback) # do_hypervisor_callback(struct *pt_regs)
CFI_STARTPROC
/* Since we don't modify %rdi, evtchn_do_upall(struct *pt_regs) will
see the correct pointer to the pt_regs */
movq %rdi, %rsp # we don't return, adjust the stack frame
CFI_ENDPROC
CFI_DEFAULT_STACK
11: incl %gs:pda_irqcount
movq %rsp,%rbp
CFI_DEF_CFA_REGISTER rbp
cmovzq %gs:pda_irqstackptr,%rsp
pushq %rbp # backlink for old unwinder
call xen_evtchn_do_upcall
popq %rsp
CFI_DEF_CFA_REGISTER rsp
decl %gs:pda_irqcount
jmp error_exit
CFI_ENDPROC
END(do_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 do not need to fix up as Xen has already reloaded all segment
# registers that could be reloaded and zeroed the others.
# Category 2 we fix up by killing the current process. 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 comparing each saved segment register
# with its current contents: any discrepancy means we in category 1.
*/
ENTRY(xen_failsafe_callback)
#if 1
ud2a
#else
_frame (RIP-0x30)
CFI_REL_OFFSET rcx, 0
CFI_REL_OFFSET r11, 8
movw %ds,%cx
cmpw %cx,0x10(%rsp)
CFI_REMEMBER_STATE
jne 1f
movw %es,%cx
cmpw %cx,0x18(%rsp)
jne 1f
movw %fs,%cx
cmpw %cx,0x20(%rsp)
jne 1f
movw %gs,%cx
cmpw %cx,0x28(%rsp)
jne 1f
/* All segments match their saved values => Category 2 (Bad IRET). */
movq (%rsp),%rcx
CFI_RESTORE rcx
movq 8(%rsp),%r11
CFI_RESTORE r11
addq $0x30,%rsp
CFI_ADJUST_CFA_OFFSET -0x30
movq $11,%rdi /* SIGSEGV */
jmp do_exit
CFI_RESTORE_STATE
1: /* Segment mismatch => Category 1 (Bad segment). Retry the IRET. */
movq (%rsp),%rcx
CFI_RESTORE rcx
movq 8(%rsp),%r11
CFI_RESTORE r11
addq $0x30,%rsp
CFI_ADJUST_CFA_OFFSET -0x30
pushq $0
CFI_ADJUST_CFA_OFFSET 8
SAVE_ALL
jmp error_exit
CFI_ENDPROC
#endif
END(xen_failsafe_callback)
#endif /* CONFIG_XEN */