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-rw-r--r--arch/x86/xen/xen-asm_64.S271
1 files changed, 271 insertions, 0 deletions
diff --git a/arch/x86/xen/xen-asm_64.S b/arch/x86/xen/xen-asm_64.S
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+/*
+ Asm versions of Xen pv-ops, suitable for either direct use or inlining.
+ The inline versions are the same as the direct-use versions, with the
+ pre- and post-amble chopped off.
+
+ This code is encoded for size rather than absolute efficiency,
+ with a view to being able to inline as much as possible.
+
+ We only bother with direct forms (ie, vcpu in pda) of the operations
+ here; the indirect forms are better handled in C, since they're
+ generally too large to inline anyway.
+ */
+
+#include <linux/linkage.h>
+
+#include <asm/asm-offsets.h>
+#include <asm/processor-flags.h>
+#include <asm/errno.h>
+#include <asm/segment.h>
+
+#include <xen/interface/xen.h>
+
+#define RELOC(x, v) .globl x##_reloc; x##_reloc=v
+#define ENDPATCH(x) .globl x##_end; x##_end=.
+
+/* Pseudo-flag used for virtual NMI, which we don't implement yet */
+#define XEN_EFLAGS_NMI 0x80000000
+
+#if 0
+#include <asm/percpu.h>
+
+/*
+ Enable events. This clears the event mask and tests the pending
+ event status with one and operation. If there are pending
+ events, then enter the hypervisor to get them handled.
+ */
+ENTRY(xen_irq_enable_direct)
+ /* Unmask events */
+ movb $0, PER_CPU_VAR(xen_vcpu_info, XEN_vcpu_info_mask)
+
+ /* Preempt here doesn't matter because that will deal with
+ any pending interrupts. The pending check may end up being
+ run on the wrong CPU, but that doesn't hurt. */
+
+ /* Test for pending */
+ testb $0xff, PER_CPU_VAR(xen_vcpu_info, XEN_vcpu_info_pending)
+ jz 1f
+
+2: call check_events
+1:
+ENDPATCH(xen_irq_enable_direct)
+ ret
+ ENDPROC(xen_irq_enable_direct)
+ RELOC(xen_irq_enable_direct, 2b+1)
+
+/*
+ Disabling events is simply a matter of making the event mask
+ non-zero.
+ */
+ENTRY(xen_irq_disable_direct)
+ movb $1, PER_CPU_VAR(xen_vcpu_info, XEN_vcpu_info_mask)
+ENDPATCH(xen_irq_disable_direct)
+ ret
+ ENDPROC(xen_irq_disable_direct)
+ RELOC(xen_irq_disable_direct, 0)
+
+/*
+ (xen_)save_fl is used to get the current interrupt enable status.
+ Callers expect the status to be in X86_EFLAGS_IF, and other bits
+ may be set in the return value. We take advantage of this by
+ making sure that X86_EFLAGS_IF has the right value (and other bits
+ in that byte are 0), but other bits in the return value are
+ undefined. We need to toggle the state of the bit, because
+ Xen and x86 use opposite senses (mask vs enable).
+ */
+ENTRY(xen_save_fl_direct)
+ testb $0xff, PER_CPU_VAR(xen_vcpu_info, XEN_vcpu_info_mask)
+ setz %ah
+ addb %ah,%ah
+ENDPATCH(xen_save_fl_direct)
+ ret
+ ENDPROC(xen_save_fl_direct)
+ RELOC(xen_save_fl_direct, 0)
+
+/*
+ In principle the caller should be passing us a value return
+ from xen_save_fl_direct, but for robustness sake we test only
+ the X86_EFLAGS_IF flag rather than the whole byte. After
+ setting the interrupt mask state, it checks for unmasked
+ pending events and enters the hypervisor to get them delivered
+ if so.
+ */
+ENTRY(xen_restore_fl_direct)
+ testb $X86_EFLAGS_IF>>8, %ah
+ setz PER_CPU_VAR(xen_vcpu_info, XEN_vcpu_info_mask)
+ /* Preempt here doesn't matter because that will deal with
+ any pending interrupts. The pending check may end up being
+ run on the wrong CPU, but that doesn't hurt. */
+
+ /* check for unmasked and pending */
+ cmpw $0x0001, PER_CPU_VAR(xen_vcpu_info, XEN_vcpu_info_pending)
+ jz 1f
+2: call check_events
+1:
+ENDPATCH(xen_restore_fl_direct)
+ ret
+ ENDPROC(xen_restore_fl_direct)
+ RELOC(xen_restore_fl_direct, 2b+1)
+
+
+/*
+ Force an event check by making a hypercall,
+ but preserve regs before making the call.
+ */
+check_events:
+ push %rax
+ push %rcx
+ push %rdx
+ push %rsi
+ push %rdi
+ push %r8
+ push %r9
+ push %r10
+ push %r11
+ call force_evtchn_callback
+ pop %r11
+ pop %r10
+ pop %r9
+ pop %r8
+ pop %rdi
+ pop %rsi
+ pop %rdx
+ pop %rcx
+ pop %rax
+ ret
+#endif
+
+ENTRY(xen_adjust_exception_frame)
+ mov 8+0(%rsp),%rcx
+ mov 8+8(%rsp),%r11
+ ret $16
+
+hypercall_iret = hypercall_page + __HYPERVISOR_iret * 32
+/*
+ Xen64 iret frame:
+
+ ss
+ rsp
+ rflags
+ cs
+ rip <-- standard iret frame
+
+ flags
+
+ rcx }
+ r11 }<-- pushed by hypercall page
+rsp -> rax }
+ */
+ENTRY(xen_iret)
+ pushq $0
+1: jmp hypercall_iret
+ENDPATCH(xen_iret)
+RELOC(xen_iret, 1b+1)
+
+/*
+ sysexit is not used for 64-bit processes, so it's
+ only ever used to return to 32-bit compat userspace.
+ */
+ENTRY(xen_sysexit)
+ pushq $__USER32_DS
+ pushq %rcx
+ pushq $X86_EFLAGS_IF
+ pushq $__USER32_CS
+ pushq %rdx
+
+ pushq $VGCF_in_syscall
+1: jmp hypercall_iret
+ENDPATCH(xen_sysexit)
+RELOC(xen_sysexit, 1b+1)
+
+ENTRY(xen_sysret64)
+ /* We're already on the usermode stack at this point, but still
+ with the kernel gs, so we can easily switch back */
+ movq %rsp, %gs:pda_oldrsp
+ movq %gs:pda_kernelstack,%rsp
+
+ pushq $__USER_DS
+ pushq %gs:pda_oldrsp
+ pushq %r11
+ pushq $__USER_CS
+ pushq %rcx
+
+ pushq $VGCF_in_syscall
+1: jmp hypercall_iret
+ENDPATCH(xen_sysret64)
+RELOC(xen_sysret64, 1b+1)
+
+ENTRY(xen_sysret32)
+ /* We're already on the usermode stack at this point, but still
+ with the kernel gs, so we can easily switch back */
+ movq %rsp, %gs:pda_oldrsp
+ movq %gs:pda_kernelstack, %rsp
+
+ pushq $__USER32_DS
+ pushq %gs:pda_oldrsp
+ pushq %r11
+ pushq $__USER32_CS
+ pushq %rcx
+
+ pushq $VGCF_in_syscall
+1: jmp hypercall_iret
+ENDPATCH(xen_sysret32)
+RELOC(xen_sysret32, 1b+1)
+
+/*
+ Xen handles syscall callbacks much like ordinary exceptions,
+ which means we have:
+ - kernel gs
+ - kernel rsp
+ - an iret-like stack frame on the stack (including rcx and r11):
+ ss
+ rsp
+ rflags
+ cs
+ rip
+ r11
+ rsp-> rcx
+
+ In all the entrypoints, we undo all that to make it look
+ like a CPU-generated syscall/sysenter and jump to the normal
+ entrypoint.
+ */
+
+.macro undo_xen_syscall
+ mov 0*8(%rsp),%rcx
+ mov 1*8(%rsp),%r11
+ mov 5*8(%rsp),%rsp
+.endm
+
+/* Normal 64-bit system call target */
+ENTRY(xen_syscall_target)
+ undo_xen_syscall
+ jmp system_call_after_swapgs
+ENDPROC(xen_syscall_target)
+
+#ifdef CONFIG_IA32_EMULATION
+
+/* 32-bit compat syscall target */
+ENTRY(xen_syscall32_target)
+ undo_xen_syscall
+ jmp ia32_cstar_target
+ENDPROC(xen_syscall32_target)
+
+/* 32-bit compat sysenter target */
+ENTRY(xen_sysenter_target)
+ undo_xen_syscall
+ jmp ia32_sysenter_target
+ENDPROC(xen_sysenter_target)
+
+#else /* !CONFIG_IA32_EMULATION */
+
+ENTRY(xen_syscall32_target)
+ENTRY(xen_sysenter_target)
+ lea 16(%rsp), %rsp /* strip %rcx,%r11 */
+ mov $-ENOSYS, %rax
+ pushq $VGCF_in_syscall
+ jmp hypercall_iret
+ENDPROC(xen_syscall32_target)
+ENDPROC(xen_sysenter_target)
+
+#endif /* CONFIG_IA32_EMULATION */