From 869c3df00e8bb468df5e08734d9d82b7bf236bfd Mon Sep 17 00:00:00 2001
From: Sotiris Apostolakis <apostolakis@google.com>
Date: Mon, 5 Apr 2021 23:11:34 +0000
Subject: [PATCH 1/2] i#4425: handle unspecified-by-the-app sigaction restorer
for AArch64
Prevents a seg fault in the burst_aarch64_sys test that was caused by reading an unspecified
sigaction restorer in sig_has_restorer() in unix/signal.c. Does so by returning false early
in sig_has_restorer() for AArch64 when the SA_RESTORER flag is not set.
By preventing the seg fault, it also prevents the nested signal handling and consequently
the stack overflow in burst_aarch64_sys.
Issue: #4425
---
clients/drcachesim/tests/burst_aarch64_sys.cpp | 4 +---
core/unix/signal.c | 11 +++++++++++
2 files changed, 12 insertions(+), 3 deletions(-)
diff --git a/clients/drcachesim/tests/burst_aarch64_sys.cpp b/clients/drcachesim/tests/burst_aarch64_sys.cpp
index 1b274ea20..71c12f5e4 100644
--- a/clients/drcachesim/tests/burst_aarch64_sys.cpp
+++ b/clients/drcachesim/tests/burst_aarch64_sys.cpp
@@ -177,9 +177,7 @@ static std::string
gather_trace()
{
if (!my_setenv("DYNAMORIO_OPTIONS",
- // XXX i#4425: Fix debug-build stack overflow issue and
- // remove custom signal_stack_size below.
- "-stderr_mask 0xc -signal_stack_size 64K "
+ "-stderr_mask 0xc "
"-client_lib ';;-offline'"))
std::cerr << "failed to set env var!\n";
diff --git a/core/unix/signal.c b/core/unix/signal.c
index 882523fe1..4dd105ab2 100644
--- a/core/unix/signal.c
+++ b/core/unix/signal.c
@@ -2879,6 +2879,17 @@ sig_has_restorer(thread_sig_info_t *info, int sig)
return false;
if (TEST(SA_RESTORER, info->app_sigaction[sig]->flags))
return true;
+# ifdef AARCH64
+ /* In AArch64 either the app or the kernel defines a restorer, not glibc, contrary
+ * to x86/ARM where glibc defines a restorer if the app did not define one. Thus,
+ * reading info->app_sigaction[sig]->restorer when SA_RESTORER is not specified by
+ * the app was never an issue for x86/ARM, but for AArch64 if the SA_RESTORER is
+ * not specified DR will read garbage leading to a seg fault later when
+ * safe_reading the restorer. To avoid this issue return false early for AArch64 if
+ * SA_RESTORER is not specified.
+ */
+ return false;
+# endif
if (info->app_sigaction[sig]->restorer == NULL)
return false;
/* we cache the result due to the safe_read cost */
--
GitLab
From 104936162a1286398c065277a376fd5e267c1a6f Mon Sep 17 00:00:00 2001
From: Sotiris Apostolakis <apostolakis@google.com>
Date: Wed, 7 Apr 2021 14:50:06 +0000
Subject: [PATCH 2/2] formatting
---
clients/drcachesim/tests/burst_aarch64_sys.cpp | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/clients/drcachesim/tests/burst_aarch64_sys.cpp b/clients/drcachesim/tests/burst_aarch64_sys.cpp
index 71c12f5e4..f8807d6a1 100644
--- a/clients/drcachesim/tests/burst_aarch64_sys.cpp
+++ b/clients/drcachesim/tests/burst_aarch64_sys.cpp
@@ -176,9 +176,7 @@ post_process()
static std::string
gather_trace()
{
- if (!my_setenv("DYNAMORIO_OPTIONS",
- "-stderr_mask 0xc "
- "-client_lib ';;-offline'"))
+ if (!my_setenv("DYNAMORIO_OPTIONS", "-stderr_mask 0xc -client_lib ';;-offline'"))
std::cerr << "failed to set env var!\n";
std::cerr << "pre-DR init\n";
--
GitLab