[Xen-changelog] [xen master] x86/PV: split out dealing with DRn from privileged instruction handling

[patchbot@xxxxxxx]

commit 39b682388bb37688bd969e27240e2696246205cd
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Fri Sep 30 09:55:08 2016 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Sep 30 09:55:08 2016 +0200

    x86/PV: split out dealing with DRn from privileged instruction handling
    
    This is in preparation for using the generic emulator here.
    
    Some care is needed temporarily to not unduly alter guest register
    state: The local variable "res" can only go away once this code got
    fully switched over to using x86_emulate().
    
    Also switch to IS_ERR_VALUE() instead of (incorrectly) open coding it.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/arch/x86/traps.c | 28 +++++++++++++++++++++++-----
 1 file changed, 23 insertions(+), 5 deletions(-)

diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index 7618575..f79d86a 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -2355,6 +2355,26 @@ static int priv_op_write_cr(unsigned int reg, unsigned 
long val,
     return X86EMUL_UNHANDLEABLE;
 }
 
+static int priv_op_read_dr(unsigned int reg, unsigned long *val,
+                           struct x86_emulate_ctxt *ctxt)
+{
+    unsigned long res = do_get_debugreg(reg);
+
+    if ( IS_ERR_VALUE(res) )
+        return X86EMUL_UNHANDLEABLE;
+
+    *val = res;
+
+    return X86EMUL_OKAY;
+}
+
+static int priv_op_write_dr(unsigned int reg, unsigned long val,
+                            struct x86_emulate_ctxt *ctxt)
+{
+    return do_set_debugreg(reg, val) == 0
+           ? X86EMUL_OKAY : X86EMUL_UNHANDLEABLE;
+}
+
 static inline uint64_t guest_misc_enable(uint64_t val)
 {
     val &= ~(MSR_IA32_MISC_ENABLE_PERF_AVAIL |
@@ -2773,16 +2793,14 @@ static int emulate_privileged_op(struct cpu_user_regs 
*regs)
         break;
 
     case 0x21: /* MOV DR?,<reg> */ {
-        unsigned long res;
         opcode = insn_fetch(u8, code_base, eip, code_limit);
         if ( opcode < 0xc0 )
             goto fail;
         modrm_reg += ((opcode >> 3) & 7) + (lock << 3);
         modrm_rm  |= (opcode >> 0) & 7;
-        reg = decode_register(modrm_rm, regs, 0);
-        if ( (res = do_get_debugreg(modrm_reg)) > (unsigned long)-256 )
+        if ( priv_op_read_dr(modrm_reg, decode_register(modrm_rm, regs, 0),
+                             NULL) != X86EMUL_OKAY )
             goto fail;
-        *reg = res;
         break;
     }
 
@@ -2811,7 +2829,7 @@ static int emulate_privileged_op(struct cpu_user_regs 
*regs)
         modrm_reg += ((opcode >> 3) & 7) + (lock << 3);
         modrm_rm  |= (opcode >> 0) & 7;
         reg = decode_register(modrm_rm, regs, 0);
-        if ( do_set_debugreg(modrm_reg, *reg) != 0 )
+        if ( priv_op_write_dr(modrm_reg, *reg, NULL) != X86EMUL_OKAY )
             goto fail;
         break;
 
--
generated by git-patchbot for /home/xen/git/xen.git#master

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