Before printing a back-trace make sure that page containing the
address stored in the stack pointer is mapped. Fixes a corner case.
git-svn-id: svn://svn.valgrind.org/valgrind/trunk@12749 a5019735-40e9-0310-863c-91ae7b9d1cf9
diff --git a/coregrind/m_signals.c b/coregrind/m_signals.c
index 9ef6b85..44774be 100644
--- a/coregrind/m_signals.c
+++ b/coregrind/m_signals.c
@@ -1638,6 +1638,26 @@
obviously stupid place (not mapped readable) that would
likely cause a segfault. */
if (VG_(is_valid_tid)(tid)) {
+
+#if defined(VGO_linux)
+ /* Make sure that the address stored in the stack pointer is
+ located in a mapped page. That is not necessarily so. E.g.
+ consider the scenario where the stack pointer was decreased
+ and now has a value that is just below the end of a page that has
+ not been mapped yet. In that case VG_(am_is_valid_for_client)
+ will consider the address of the stack pointer invalid and that
+ would cause a back-trace of depth 1 to be printed, instead of a
+ full back-trace. */
+ if (tid == 1) { // main thread
+ Addr esp = VG_(get_SP)(tid);
+ Addr base = VG_PGROUNDDN(esp - VG_STACK_REDZONE_SZB);
+ if (VG_(extend_stack)(base, VG_(threads)[tid].client_stack_szB)) {
+ if (VG_(clo_trace_signals))
+ VG_(dmsg)(" -> extended stack base to %#lx\n",
+ VG_PGROUNDDN(esp));
+ }
+ }
+#endif
ExeContext* ec = VG_(am_is_valid_for_client)
(VG_(get_SP)(tid), sizeof(Addr), VKI_PROT_READ)
? VG_(record_ExeContext)( tid, 0/*first_ip_delta*/ )
