[Xen-changelog] [xen stable-4.8] x86: also show FS/GS base addresses when dumping registers

[patchbot@xxxxxxx]

commit 14826e327b3dc4e7dfbda7671b6a052e29da374c
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Thu Nov 16 11:51:11 2017 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Nov 16 11:51:11 2017 +0100

    x86: also show FS/GS base addresses when dumping registers
    
    Their state may be important to figure the reason for a crash. To not
    further grow duplicate code, break out a helper function.
    
    I realize that (ab)using the control register array here may not be
    considered the nicest solution, but it seems easier (and less overall
    overhead) to do so compared to the alternative of introducing another
    helper structure.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    master commit: be7f60b5a39741eab0a8fea0324f7be0cb724cfb
    master date: 2017-10-24 18:13:13 +0200
---
 xen/arch/x86/x86_64/traps.c | 46 ++++++++++++++++++++++++++++-----------------
 1 file changed, 29 insertions(+), 17 deletions(-)

diff --git a/xen/arch/x86/x86_64/traps.c b/xen/arch/x86/x86_64/traps.c
index f83686f..02f4717 100644
--- a/xen/arch/x86/x86_64/traps.c
+++ b/xen/arch/x86/x86_64/traps.c
@@ -38,6 +38,22 @@ static void print_xen_info(void)
 
 enum context { CTXT_hypervisor, CTXT_pv_guest, CTXT_hvm_guest };
 
+/* (ab)use crs[5..7] for fs/gs bases. */
+static void read_registers(struct cpu_user_regs *regs, unsigned long crs[8])
+{
+    crs[0] = read_cr0();
+    crs[2] = read_cr2();
+    crs[3] = read_cr3();
+    crs[4] = read_cr4();
+    regs->ds = read_sreg(ds);
+    regs->es = read_sreg(es);
+    regs->fs = read_sreg(fs);
+    regs->gs = read_sreg(gs);
+    crs[5] = rdfsbase();
+    crs[6] = rdgsbase();
+    rdmsrl(MSR_SHADOW_GS_BASE, crs[7]);
+}
+
 static void _show_registers(
     const struct cpu_user_regs *regs, unsigned long crs[8],
     enum context context, const struct vcpu *v)
@@ -76,6 +92,8 @@ static void _show_registers(
     else
         printk("cr0: %016lx   cr4: %016lx\n", crs[0], crs[4]);
     printk("cr3: %016lx   cr2: %016lx\n", crs[3], crs[2]);
+    printk("fsb: %016lx   gsb: %016lx   gss: %016lx\n",
+           crs[5], crs[6], crs[7]);
     printk("ds: %04x   es: %04x   fs: %04x   gs: %04x   "
            "ss: %04x   cs: %04x\n",
            regs->ds, regs->es, regs->fs,
@@ -105,13 +123,18 @@ void show_registers(const struct cpu_user_regs *regs)
         fault_regs.es = sreg.sel;
         hvm_get_segment_register(v, x86_seg_fs, &sreg);
         fault_regs.fs = sreg.sel;
+        fault_crs[5] = sreg.base;
         hvm_get_segment_register(v, x86_seg_gs, &sreg);
         fault_regs.gs = sreg.sel;
+        fault_crs[6] = sreg.base;
         hvm_get_segment_register(v, x86_seg_ss, &sreg);
         fault_regs.ss = sreg.sel;
+        fault_crs[7] = hvm_get_shadow_gs_base(v);
     }
     else
     {
+        read_registers(&fault_regs, fault_crs);
+
         if ( guest_mode(regs) )
         {
             context = CTXT_pv_guest;
@@ -122,14 +145,6 @@ void show_registers(const struct cpu_user_regs *regs)
             context = CTXT_hypervisor;
             fault_crs[2] = read_cr2();
         }
-
-        fault_crs[0] = read_cr0();
-        fault_crs[3] = read_cr3();
-        fault_crs[4] = read_cr4();
-        fault_regs.ds = read_sreg(ds);
-        fault_regs.es = read_sreg(es);
-        fault_regs.fs = read_sreg(fs);
-        fault_regs.gs = read_sreg(gs);
     }
 
     print_xen_info();
@@ -148,6 +163,7 @@ void show_registers(const struct cpu_user_regs *regs)
 void vcpu_show_registers(const struct vcpu *v)
 {
     const struct cpu_user_regs *regs = &v->arch.user_regs;
+    bool kernel = guest_kernel_mode(v, regs);
     unsigned long crs[8];
 
     /* Only handle PV guests for now */
@@ -156,10 +172,13 @@ void vcpu_show_registers(const struct vcpu *v)
 
     crs[0] = v->arch.pv_vcpu.ctrlreg[0];
     crs[2] = arch_get_cr2(v);
-    crs[3] = pagetable_get_paddr(guest_kernel_mode(v, regs) ?
+    crs[3] = pagetable_get_paddr(kernel ?
                                  v->arch.guest_table :
                                  v->arch.guest_table_user);
     crs[4] = v->arch.pv_vcpu.ctrlreg[4];
+    crs[5] = v->arch.pv_vcpu.fs_base;
+    crs[6 + !kernel] = v->arch.pv_vcpu.gs_base_kernel;
+    crs[7 - !kernel] = v->arch.pv_vcpu.gs_base_user;
 
     _show_registers(regs, crs, CTXT_pv_guest, v);
 }
@@ -239,14 +258,7 @@ void do_double_fault(struct cpu_user_regs *regs)
     printk("*** DOUBLE FAULT ***\n");
     print_xen_info();
 
-    crs[0] = read_cr0();
-    crs[2] = read_cr2();
-    crs[3] = read_cr3();
-    crs[4] = read_cr4();
-    regs->ds = read_sreg(ds);
-    regs->es = read_sreg(es);
-    regs->fs = read_sreg(fs);
-    regs->gs = read_sreg(gs);
+    read_registers(regs, crs);
 
     printk("CPU:    %d\n", cpu);
     _show_registers(regs, crs, CTXT_hypervisor, NULL);
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.8

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