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[Xen-devel] [xen-devel] [Patch 2/4] x86/stack: Adjust boundary conditions for printed stacks.



Move the boundary into current.h along with the other stack manipulation code,
and apply the same bottom boundary to both the frame pointer and non-frame
pointer case.  This will prevent the non-frame pointer case from finding
certainly-spurious values on the stack in the guest_cpu_user_regs section.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CC: Keir Fraser <keir@xxxxxxx>
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Tim Deegan <tim@xxxxxxx>
---
 xen/arch/x86/traps.c          |    9 ++++-----
 xen/include/asm-x86/current.h |    9 +++++++++
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index b686177..2bcfc7b 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -199,8 +199,9 @@ static void show_guest_stack(struct vcpu *v, struct 
cpu_user_regs *regs)
 static void __show_trace(unsigned long sp, unsigned long __maybe_unused bp)
 {
     unsigned long *stack = (unsigned long *)sp, addr;
+    unsigned long *bottom = (unsigned long *)get_printable_stack_bottom(sp);
 
-    while ( ((long)stack & (STACK_SIZE-BYTES_PER_LONG)) != 0 )
+    while ( stack <= bottom )
     {
         addr = *stack++;
         if ( is_active_kernel_text(addr) )
@@ -216,12 +217,10 @@ static void __show_trace(unsigned long sp, unsigned long 
__maybe_unused bp)
 /* Stack trace from frames in the stack, using frame pointers */
 static void __show_trace(unsigned long sp, unsigned long bp)
 {
-    unsigned long *frame, next, addr, low, high;
+    unsigned long *frame, next, addr;
 
     /* Bounds for range of valid frame pointer. */
-    low  = sp - 2*sizeof(unsigned long);
-    high = (low & ~(STACK_SIZE - 1)) + 
-        (STACK_SIZE - sizeof(struct cpu_info) - 2*sizeof(unsigned long));
+    unsigned long low = sp, high = get_printable_stack_bottom(sp);
 
     /* The initial frame pointer. */
     next = bp;
diff --git a/xen/include/asm-x86/current.h b/xen/include/asm-x86/current.h
index bec4dbe..da2d1bf 100644
--- a/xen/include/asm-x86/current.h
+++ b/xen/include/asm-x86/current.h
@@ -50,6 +50,15 @@ static inline struct cpu_info *get_cpu_info(void)
 #define get_stack_bottom()                      \
     ((unsigned long)&get_cpu_info()->guest_cpu_user_regs.es)
 
+/*
+ * Get the bottom-of-stack, as useful for printing stack traces. This is an
+ * equivalent place on the stack as guest_cpu_user_regs(), but works on an
+ * arbitrary stack pointer rather than the current stack.
+ */
+#define get_printable_stack_bottom(sp)          \
+    ((sp & (~(STACK_SIZE-1))) +                 \
+     (STACK_SIZE - sizeof(struct cpu_info) - 2*sizeof(unsigned long)))
+
 #define reset_stack_and_jump(__fn)              \
     __asm__ __volatile__ (                      \
         "mov %0,%%"__OP"sp; jmp %c1"            \
-- 
1.7.10.4


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