[xen staging-4.15] x86/PV: make '0' debug key dump Dom0's stacks again

[patchbot@xxxxxxx]

commit b033a41572333936b9b859280875fc73e72c3e47
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Fri Nov 19 09:29:12 2021 +0100
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Fri Nov 19 09:29:12 2021 +0100

    x86/PV: make '0' debug key dump Dom0's stacks again
    
    The conversion to __get_guest() failed to account for the fact that for
    remote vCPU-s dumping gets done through a pointer obtained from
    map_domain_page(): __get_guest() arranges for (apparent) accesses to
    hypervisor space to cause #GP(0).
    
    Fixes: 6a1d72d3739e ('x86: split __{get,put}_user() into "guest" and 
"unsafe" variants')
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    master commit: 4843546fef5e024d5754f722fd01a8dfb482ac7d
    master date: 2021-10-19 10:07:00 +0200
---
 xen/arch/x86/traps.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index 939c91a0ca..948e422397 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -274,7 +274,9 @@ static void compat_show_guest_stack(struct vcpu *v,
     {
         if ( (((long)stack - 1) ^ ((long)(stack + 1) - 1)) & mask )
             break;
-        if ( __get_guest(addr, stack) )
+        if ( stack_page )
+            addr = *stack;
+        else if ( __get_guest(addr, stack) )
         {
             if ( i != 0 )
                 printk("\n    ");
@@ -343,7 +345,9 @@ static void show_guest_stack(struct vcpu *v, const struct 
cpu_user_regs *regs)
     {
         if ( (((long)stack - 1) ^ ((long)(stack + 1) - 1)) & mask )
             break;
-        if ( __get_guest(addr, stack) )
+        if ( stack_page )
+            addr = *stack;
+        else if ( __get_guest(addr, stack) )
         {
             if ( i != 0 )
                 printk("\n    ");
--
generated by git-patchbot for /home/xen/git/xen.git#staging-4.15