[Xen-devel] [PATCH 8/9] x86/hvm: Add hvm_copy_{to, from}_guest_virt() helpers

[Euan Harris <euan.harris@xxxxxxxxxx>]

hvm_copy_{to,from}_guest_virt() copy data to and from a guest, performing
segmentatino and paging checks on the provided seg:offset virtual address.

Signed-off-by: Euan Harris <euan.harris@xxxxxxxxxx>
---
 xen/arch/x86/hvm/hvm.c            | 57 +++++++++++++++++++++++++++++++++++++++
 xen/include/asm-x86/hvm/support.h | 12 +++++++++
 2 files changed, 69 insertions(+)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 205b4cb685..5d2bdd6b2b 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -3312,6 +3312,63 @@ unsigned long copy_from_user_hvm(void *to, const void 
*from, unsigned len)
     return rc ? len : 0; /* fake a copy_from_user() return code */
 }
 
+static int _hvm_copy_guest_virt(
+    enum x86_segment seg, unsigned long offset, void *buf, unsigned int bytes,
+    uint32_t pfec, unsigned int flags)
+{
+    struct vcpu *curr = current;
+    struct segment_register sreg, cs;
+    enum hvm_translation_result res;
+    pagefault_info_t pfinfo;
+    unsigned long linear;
+
+    ASSERT(is_x86_user_segment(seg));
+
+    hvm_get_segment_register(curr, seg, &sreg);
+    hvm_get_segment_register(curr, x86_seg_cs, &cs);
+
+    if ( !hvm_virtual_to_linear_addr(
+             seg, &sreg, offset, bytes,
+             flags & HVMCOPY_to_guest ? hvm_access_write : hvm_access_read,
+             &cs, &linear) )
+    {
+        hvm_inject_hw_exception(
+            (seg == x86_seg_ss) ? TRAP_stack_error : TRAP_gp_fault, 0);
+        return X86EMUL_EXCEPTION;
+    }
+
+    if ( flags & HVMCOPY_to_guest )
+        res = hvm_copy_to_guest_linear(linear, buf, bytes, pfec, &pfinfo);
+    else
+        res = hvm_copy_from_guest_linear(buf, linear, bytes, pfec, &pfinfo);
+
+    if ( res == HVMTRANS_bad_linear_to_gfn )
+    {
+        hvm_inject_page_fault(pfinfo.ec, pfinfo.linear);
+        return X86EMUL_EXCEPTION;
+    }
+    else if ( res )
+        return X86EMUL_RETRY;
+
+    return X86EMUL_OKAY;
+}
+
+int hvm_copy_to_guest_virt(
+    enum x86_segment seg, unsigned long offset, void *buf, unsigned int bytes,
+    uint32_t pfec)
+{
+    return _hvm_copy_guest_virt(seg, offset, buf, bytes, pfec,
+                                HVMCOPY_to_guest);
+}
+
+int hvm_copy_from_guest_virt(
+    void *buf, enum x86_segment seg, unsigned long offset, unsigned int bytes,
+    uint32_t pfec)
+{
+    return _hvm_copy_guest_virt(seg, offset, buf, bytes, pfec,
+                                HVMCOPY_from_guest);
+}
+
 bool hvm_check_cpuid_faulting(struct vcpu *v)
 {
     const struct msr_vcpu_policy *vp = v->arch.msr;
diff --git a/xen/include/asm-x86/hvm/support.h 
b/xen/include/asm-x86/hvm/support.h
index d784fc1856..9af2ae77b7 100644
--- a/xen/include/asm-x86/hvm/support.h
+++ b/xen/include/asm-x86/hvm/support.h
@@ -115,6 +115,18 @@ enum hvm_translation_result hvm_translate_get_page(
     pagefault_info_t *pfinfo, struct page_info **page_p,
     gfn_t *gfn_p, p2m_type_t *p2mt_p);
 
+/*
+ * Copy data to and from a guest, performing segmentation and paging checks
+ * on the provided seg:offset virtual address.
+ * Returns X86EMUL_* and raises exceptions with the current vcpu.
+ */
+int hvm_copy_to_guest_virt(
+    enum x86_segment seg, unsigned long offset, void *buf, unsigned int bytes,
+    uint32_t pfec);
+int hvm_copy_from_guest_virt(
+    void *buf, enum x86_segment seg, unsigned long offset, unsigned int bytes,
+    uint32_t pfec);
+
 #define HVM_HCALL_completed  0 /* hypercall completed - no further action */
 #define HVM_HCALL_preempted  1 /* hypercall preempted - re-execute VMCALL */
 int hvm_hypercall(struct cpu_user_regs *regs);
-- 
2.13.6


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