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-rw-r--r--kernel/arch/x86/xen/xen-asm_64.S159
1 files changed, 159 insertions, 0 deletions
diff --git a/kernel/arch/x86/xen/xen-asm_64.S b/kernel/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 <asm/errno.h>
+#include <asm/percpu.h>
+#include <asm/processor-flags.h>
+#include <asm/segment.h>
+
+#include <xen/interface/xen.h>
+
+#include "xen-asm.h"
+
+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 $0
+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, PER_CPU_VAR(rsp_scratch)
+ movq PER_CPU_VAR(kernel_stack), %rsp
+
+ pushq $__USER_DS
+ pushq PER_CPU_VAR(rsp_scratch)
+ 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, PER_CPU_VAR(rsp_scratch)
+ movq PER_CPU_VAR(kernel_stack), %rsp
+
+ pushq $__USER32_DS
+ pushq PER_CPU_VAR(rsp_scratch)
+ pushq %r11
+ pushq $__USER32_CS
+ pushq %rcx
+
+ pushq $0
+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 $0
+ jmp hypercall_iret
+ENDPROC(xen_syscall32_target)
+ENDPROC(xen_sysenter_target)
+
+#endif /* CONFIG_IA32_EMULATION */