From d83414e1fd1941ca8228b5cf6a06697bd1ff7f83 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marc-Andr=C3=A9=20Lureau?= <marcandre.lureau@redhat.com>
Date: Tue, 16 Jan 2018 16:11:52 +0100
Subject: ucontext: annotate coroutine stack for ASAN
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It helps ASAN to detect more leaks on coroutine stacks, and to get rid
of some extra warnings.

Before:

tests/test-coroutine -p
/basic/lifecycle
/basic/lifecycle: ==20781==WARNING: ASan doesn't fully support
makecontext/swapcontext functions and may produce false positives in
some cases!
==20781==WARNING: ASan is ignoring requested __asan_handle_no_return:
stack top: 0x7ffcb184d000; bottom 0x7ff6c4cfd000; size: 0x0005ecb50000
(25446121472)
False positive error reports may follow
For details see https://github.com/google/sanitizers/issues/189
OK

After:

tests/test-coroutine -p /basic/lifecycle
/basic/lifecycle: ==21110==WARNING: ASan doesn't fully support
makecontext/swapcontext functions and may produce false positives in
some cases!
OK

A similar work would need to be done for sigaltstack & windows fibers
to have similar coverage. Since ucontext is preferred, I didn't bother
checking the other coroutine implementations for now.

Update travis to fix the build with ASAN annotations.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20180116151152.4040-4-marcandre.lureau@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 util/coroutine-ucontext.c | 48 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

(limited to 'util/coroutine-ucontext.c')

diff --git a/util/coroutine-ucontext.c b/util/coroutine-ucontext.c
index 6621f3f692..926d3402e3 100644
--- a/util/coroutine-ucontext.c
+++ b/util/coroutine-ucontext.c
@@ -31,6 +31,13 @@
 #include <valgrind/valgrind.h>
 #endif
 
+#if defined(__SANITIZE_ADDRESS__) || __has_feature(address_sanitizer)
+#ifdef CONFIG_ASAN_IFACE_FIBER
+#define CONFIG_ASAN 1
+#include <sanitizer/asan_interface.h>
+#endif
+#endif
+
 typedef struct {
     Coroutine base;
     void *stack;
@@ -59,11 +66,37 @@ union cc_arg {
     int i[2];
 };
 
+static void finish_switch_fiber(void *fake_stack_save)
+{
+#ifdef CONFIG_ASAN
+    const void *bottom_old;
+    size_t size_old;
+
+    __sanitizer_finish_switch_fiber(fake_stack_save, &bottom_old, &size_old);
+
+    if (!leader.stack) {
+        leader.stack = (void *)bottom_old;
+        leader.stack_size = size_old;
+    }
+#endif
+}
+
+static void start_switch_fiber(void **fake_stack_save,
+                               const void *bottom, size_t size)
+{
+#ifdef CONFIG_ASAN
+    __sanitizer_start_switch_fiber(fake_stack_save, bottom, size);
+#endif
+}
+
 static void coroutine_trampoline(int i0, int i1)
 {
     union cc_arg arg;
     CoroutineUContext *self;
     Coroutine *co;
+    void *fake_stack_save = NULL;
+
+    finish_switch_fiber(NULL);
 
     arg.i[0] = i0;
     arg.i[1] = i1;
@@ -72,9 +105,13 @@ static void coroutine_trampoline(int i0, int i1)
 
     /* Initialize longjmp environment and switch back the caller */
     if (!sigsetjmp(self->env, 0)) {
+        start_switch_fiber(&fake_stack_save,
+                           leader.stack, leader.stack_size);
         siglongjmp(*(sigjmp_buf *)co->entry_arg, 1);
     }
 
+    finish_switch_fiber(fake_stack_save);
+
     while (true) {
         co->entry(co->entry_arg);
         qemu_coroutine_switch(co, co->caller, COROUTINE_TERMINATE);
@@ -87,6 +124,7 @@ Coroutine *qemu_coroutine_new(void)
     ucontext_t old_uc, uc;
     sigjmp_buf old_env;
     union cc_arg arg = {0};
+    void *fake_stack_save = NULL;
 
     /* The ucontext functions preserve signal masks which incurs a
      * system call overhead.  sigsetjmp(buf, 0)/siglongjmp() does not
@@ -122,8 +160,12 @@ Coroutine *qemu_coroutine_new(void)
 
     /* swapcontext() in, siglongjmp() back out */
     if (!sigsetjmp(old_env, 0)) {
+        start_switch_fiber(&fake_stack_save, co->stack, co->stack_size);
         swapcontext(&old_uc, &uc);
     }
+
+    finish_switch_fiber(fake_stack_save);
+
     return &co->base;
 }
 
@@ -169,13 +211,19 @@ qemu_coroutine_switch(Coroutine *from_, Coroutine *to_,
     CoroutineUContext *from = DO_UPCAST(CoroutineUContext, base, from_);
     CoroutineUContext *to = DO_UPCAST(CoroutineUContext, base, to_);
     int ret;
+    void *fake_stack_save = NULL;
 
     current = to_;
 
     ret = sigsetjmp(from->env, 0);
     if (ret == 0) {
+        start_switch_fiber(action == COROUTINE_TERMINATE ?
+                           NULL : &fake_stack_save, to->stack, to->stack_size);
         siglongjmp(to->env, action);
     }
+
+    finish_switch_fiber(fake_stack_save);
+
     return ret;
 }
 
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