[gem5-dev] Change in gem5/gem5[master]: base: Set up a guard page for fiber stacks.

[Gabe Black (Gerrit)]

Gabe Black has uploaded this change for review. (  
https://gem5-review.googlesource.com/c/public/gem5/+/14395

Change subject: base: Set up a guard page for fiber stacks.
......................................................................

base: Set up a guard page for fiber stacks.

This will help detect stack overflow for fibers.

Change-Id: Iff2b102120ec351709e495291d6bead597f8d10c
---
M src/base/fiber.cc
M src/base/fiber.hh
2 files changed, 33 insertions(+), 14 deletions(-)



diff --git a/src/base/fiber.cc b/src/base/fiber.cc
index eac1d93..d81cab1 100644
--- a/src/base/fiber.cc
+++ b/src/base/fiber.cc
@@ -33,7 +33,11 @@
 #include <valgrind/valgrind.h>
 #endif

+#include <sys/mman.h>
+#include <unistd.h>
+
 #include <cerrno>
+#include <cstdio>
 #include <cstring>

 #include "base/logging.hh"
@@ -71,20 +75,32 @@
     startingFiber->start();
 }

-Fiber::Fiber(size_t stack_size) :
-    link(primaryFiber()),
-    stack(stack_size ? new uint8_t[stack_size] : nullptr),
-    stackSize(stack_size), started(false), _finished(false)
-{
-#if HAVE_VALGRIND
-    valgrindStackId = VALGRIND_STACK_REGISTER(stack, stack + stack_size);
-#endif
-}
+Fiber::Fiber(size_t stack_size) : Fiber(primaryFiber(), stack_size)
+{}

 Fiber::Fiber(Fiber *link, size_t stack_size) :
-    link(link), stack(stack_size ? new uint8_t[stack_size] : nullptr),
-    stackSize(stack_size), started(false), _finished(false)
-{}
+    link(link), stack(nullptr), stackSize(stack_size), guardPage(nullptr),
+    guardPageSize(sysconf(_SC_PAGE_SIZE)), started(false), _finished(false)
+{
+    if (stack_size) {
+        guardPage = mmap(nullptr, guardPageSize + stack_size,
+                         PROT_READ | PROT_WRITE,
+                         MAP_ANON | MAP_PRIVATE, -1, 0);
+        if (guardPage == (void *)MAP_FAILED) {
+            perror("mmap");
+            fatal("Could not mmap %d byte fiber stack.\n", stack_size);
+        }
+        stack = (void *)((uint8_t *)guardPage + guardPageSize);
+        if (mprotect(stack, guardPageSize, PROT_NONE)) {
+            perror("mprotect");
+            fatal("Could not forbid access to fiber stack guard page.");
+        }
+    }
+#if HAVE_VALGRIND
+    valgrindStackId = VALGRIND_STACK_REGISTER(
+            stack, (uint8_t *)stack + stack_size);
+#endif
+}

 Fiber::~Fiber()
 {
@@ -92,7 +108,8 @@
 #if HAVE_VALGRIND
     VALGRIND_STACK_DEREGISTER(valgrindStackId);
 #endif
-    delete [] stack;
+    if (guardPage)
+        munmap(guardPage, guardPageSize + stackSize);
 }

 void
diff --git a/src/base/fiber.hh b/src/base/fiber.hh
index 3d82075..4d95e03 100644
--- a/src/base/fiber.hh
+++ b/src/base/fiber.hh
@@ -106,8 +106,10 @@
     Fiber *link;

     // The stack for this context, or a nullptr if allocated elsewhere.
-    uint8_t *stack;
+    void *stack;
     size_t stackSize;
+    void *guardPage;
+    size_t guardPageSize;
 #if HAVE_VALGRIND
     unsigned valgrindStackId;
 #endif

--
To view, visit https://gem5-review.googlesource.com/c/public/gem5/+/14395
To unsubscribe, or for help writing mail filters, visit  
https://gem5-review.googlesource.com/settings

Gerrit-Project: public/gem5
Gerrit-Branch: master
Gerrit-Change-Id: Iff2b102120ec351709e495291d6bead597f8d10c
Gerrit-Change-Number: 14395
Gerrit-PatchSet: 1
Gerrit-Owner: Gabe Black <gabebl...@google.com>
Gerrit-MessageType: newchange
_______________________________________________
gem5-dev mailing list
gem5-dev@gem5.org
http://m5sim.org/mailman/listinfo/gem5-dev