[RFC Patch 2/2] x86/traps: Change show_stack_overflow() to use frame pointers if available

[Andrew Cooper <andrew.cooper3@citrix.com>]

Pass a full set of cpu_user_regs, and defer the hand-coded stack printing to
__show_trace(), which will correctly use frame pointers if available.

One issue in the case with frame pointer; subtracting two words from the stack
pointer and using it as a boundary condition might now result in a triple
fault.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
 xen/arch/x86/traps.c            |   19 +++++--------------
 xen/arch/x86/x86_64/traps.c     |    2 +-
 xen/include/asm-x86/processor.h |    2 +-
 3 files changed, 7 insertions(+), 16 deletions(-)

diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index 324b0f1..05e5b74 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -219,8 +219,8 @@ static void __show_trace(unsigned long sp, unsigned long bp)
     unsigned long *frame, next, addr, low, high;
 
     /* Bounds for range of valid frame pointer. */
-    low  = sp - 2*sizeof(unsigned long);
-    high = (low & ~(STACK_SIZE - 1)) + 
+    low = sp;
+    high = (low & ~(STACK_SIZE - 1)) +
         (STACK_SIZE - sizeof(struct cpu_info) - 2*sizeof(unsigned long));
 
     /* The initial frame pointer. */
@@ -316,11 +316,11 @@ void show_stack(struct cpu_user_regs *regs)
     show_trace(regs);
 }
 
-void show_stack_overflow(unsigned int cpu, unsigned long esp)
+void show_stack_overflow(unsigned int cpu, const struct cpu_user_regs *regs)
 {
 #ifdef MEMORY_GUARD
+    unsigned long esp = regs->rsp;
     unsigned long esp_top, esp_bottom;
-    unsigned long *stack, addr;
 
     esp_bottom = (esp | (STACK_SIZE - 1)) + 1;
     esp_top    = esp_bottom - PRIMARY_STACK_SIZE;
@@ -343,16 +343,7 @@ void show_stack_overflow(unsigned int cpu, unsigned long esp)
     printk("Xen stack overflow (dumping trace %p-%p):\n   ",
            (void *)esp, (void *)esp_bottom);
 
-    stack = (unsigned long *)esp;
-    while ( ((long)stack & (STACK_SIZE-BYTES_PER_LONG)) != 0 )
-    {
-        addr = *stack++;
-        if ( is_active_kernel_text(addr) )
-        {
-            printk("%p: [<%p>]", stack, _p(addr));
-            print_symbol(" %s\n   ", addr);
-        }
-    }
+    __show_trace(esp, regs->rbp);
 
     printk("\n");
 #endif
diff --git a/xen/arch/x86/x86_64/traps.c b/xen/arch/x86/x86_64/traps.c
index bcd7609..385b366 100644
--- a/xen/arch/x86/x86_64/traps.c
+++ b/xen/arch/x86/x86_64/traps.c
@@ -247,7 +247,7 @@ void do_double_fault(struct cpu_user_regs *regs)
 
     printk("CPU:    %d\n", cpu);
     _show_registers(regs, crs, CTXT_hypervisor, NULL);
-    show_stack_overflow(cpu, regs->rsp);
+    show_stack_overflow(cpu, regs);
 
     panic("DOUBLE FAULT -- system shutdown\n");
 }
diff --git a/xen/include/asm-x86/processor.h b/xen/include/asm-x86/processor.h
index 5cdacc7..d050bac 100644
--- a/xen/include/asm-x86/processor.h
+++ b/xen/include/asm-x86/processor.h
@@ -507,7 +507,7 @@ extern always_inline void prefetchw(const void *x)
 #endif
 
 void show_stack(struct cpu_user_regs *regs);
-void show_stack_overflow(unsigned int cpu, unsigned long esp);
+void show_stack_overflow(unsigned int cpu, const struct cpu_user_regs *regs);
 void show_registers(struct cpu_user_regs *regs);
 void show_execution_state(struct cpu_user_regs *regs);
 #define dump_execution_state() run_in_exception_handler(show_execution_state)
-- 
1.7.10.4