[Xen-devel] [PATCH RFC v2 02/12] x86: don't use hypervisor stack size for dumping guest stacks

[Juergen Gross <jgross@xxxxxxxx>]

show_guest_stack() and compat_show_guest_stack() stop dumping the
stack of the guest whenever its virtual address reaches the same
alignment which is used for the hypervisor stacks.

Remove this arbitrary limit and try to dump a fixed number of lines
instead.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 xen/arch/x86/traps.c | 26 +++++++++++---------------
 1 file changed, 11 insertions(+), 15 deletions(-)

diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index a3e8f0c9b9..1115b69050 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -191,7 +191,8 @@ static void compat_show_guest_stack(struct vcpu *v,
                                     const struct cpu_user_regs *regs,
                                     int debug_stack_lines)
 {
-    unsigned int i, *stack, addr, mask = STACK_SIZE;
+    unsigned int i, *stack, addr;
+    unsigned long last_addr = -1L;
 
     stack = (unsigned int *)(unsigned long)regs->esp;
     printk("Guest stack trace from esp=%08lx:\n ", (unsigned long)stack);
@@ -220,13 +221,13 @@ static void compat_show_guest_stack(struct vcpu *v,
                 printk("Inaccessible guest memory.\n");
                 return;
             }
-            mask = PAGE_SIZE;
+            last_addr = round_pgup((unsigned long)stack);
         }
     }
 
     for ( i = 0; i < debug_stack_lines * 8; i++ )
     {
-        if ( (((long)stack - 1) ^ ((long)(stack + 1) - 1)) & mask )
+        if ( (unsigned long)stack >= last_addr )
             break;
         if ( __get_user(addr, stack) )
         {
@@ -241,11 +242,9 @@ static void compat_show_guest_stack(struct vcpu *v,
         printk(" %08x", addr);
         stack++;
     }
-    if ( mask == PAGE_SIZE )
-    {
-        BUILD_BUG_ON(PAGE_SIZE == STACK_SIZE);
+    if ( last_addr != -1L )
         unmap_domain_page(stack);
-    }
+
     if ( i == 0 )
         printk("Stack empty.");
     printk("\n");
@@ -254,8 +253,7 @@ static void compat_show_guest_stack(struct vcpu *v,
 static void show_guest_stack(struct vcpu *v, const struct cpu_user_regs *regs)
 {
     int i;
-    unsigned long *stack, addr;
-    unsigned long mask = STACK_SIZE;
+    unsigned long *stack, addr, last_addr = -1L;
 
     /* Avoid HVM as we don't know what the stack looks like. */
     if ( is_hvm_vcpu(v) )
@@ -290,13 +288,13 @@ static void show_guest_stack(struct vcpu *v, const struct 
cpu_user_regs *regs)
                 printk("Inaccessible guest memory.\n");
                 return;
             }
-            mask = PAGE_SIZE;
+            last_addr = round_pgup((unsigned long)stack);
         }
     }
 
     for ( i = 0; i < (debug_stack_lines*stack_words_per_line); i++ )
     {
-        if ( (((long)stack - 1) ^ ((long)(stack + 1) - 1)) & mask )
+        if ( (unsigned long)stack >= last_addr )
             break;
         if ( __get_user(addr, stack) )
         {
@@ -311,11 +309,9 @@ static void show_guest_stack(struct vcpu *v, const struct 
cpu_user_regs *regs)
         printk(" %p", _p(addr));
         stack++;
     }
-    if ( mask == PAGE_SIZE )
-    {
-        BUILD_BUG_ON(PAGE_SIZE == STACK_SIZE);
+    if ( last_addr != -1L )
         unmap_domain_page(stack);
-    }
+
     if ( i == 0 )
         printk("Stack empty.");
     printk("\n");
-- 
2.13.6


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