[Xen-changelog] [xen master] x86/boot: Explicitly clean pcpu stacks in debug builds

[patchbot@xxxxxxx]

commit 8a3c4acc9907cfec9aae9f1bc251fbf50af6828e
Author:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Tue Aug 27 11:28:26 2013 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Aug 27 11:28:26 2013 +0200

    x86/boot: Explicitly clean pcpu stacks in debug builds
    
    This reduces confusion when looking at a hexdump of the pcpu stacks and
    wondering were on earth some of the junk was coming from.  Also leave some
    grep fodder for finding where the BSP switches stack (because it took me
    far longer to find than I care to admit to).
    
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/arch/x86/boot/x86_64.S |    9 +++++++++
 xen/arch/x86/smpboot.c     |    4 ++++
 2 files changed, 13 insertions(+), 0 deletions(-)

diff --git a/xen/arch/x86/boot/x86_64.S b/xen/arch/x86/boot/x86_64.S
index ed3888d..399541d 100644
--- a/xen/arch/x86/boot/x86_64.S
+++ b/xen/arch/x86/boot/x86_64.S
@@ -13,6 +13,15 @@
         mov     mmu_cr4_features(%rip),%rcx
         mov     %rcx,%cr4
 
+#ifndef NDEBUG
+        /* Clean stack. */
+        mov     stack_start(%rip),%rdi
+        mov     $(STACK_SIZE / 8),%rcx
+        xor     %eax,%eax
+        rep stosq
+#endif
+
+        /* Switch to cpu0_stack. */
         mov     stack_start(%rip),%rsp
         or      $(STACK_SIZE-CPUINFO_sizeof),%rsp
 
diff --git a/xen/arch/x86/smpboot.c b/xen/arch/x86/smpboot.c
index 9f81c7b..8bfa151 100644
--- a/xen/arch/x86/smpboot.c
+++ b/xen/arch/x86/smpboot.c
@@ -659,6 +659,10 @@ static int cpu_smpboot_alloc(unsigned int cpu)
     stack_base[cpu] = alloc_xenheap_pages(STACK_ORDER, 0);
     if ( stack_base[cpu] == NULL )
         goto oom;
+#ifndef NDEBUG
+    for ( order = 0 ; order < (1<<STACK_ORDER); ++order )
+        clear_page(stack_base[cpu] + order * PAGE_SIZE);
+#endif
     memguard_guard_stack(stack_base[cpu]);
 
     order = get_order_from_pages(NR_RESERVED_GDT_PAGES);
--
generated by git-patchbot for /home/xen/git/xen.git#master

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