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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/196397">196397</a></dd>
<dt>Author</dt> <dd>mark.lam@apple.com</dd>
<dt>Date</dt> <dd>2016-02-10 15:02:24 -0800 (Wed, 10 Feb 2016)</dd>
</dl>
<h3>Log Message</h3>
<pre>Changed WTFCrash to not trash the crash site register state.
https://bugs.webkit.org/show_bug.cgi?id=153996
Reviewed by Geoffrey Garen.
When doing post-mortem crash site analysis using data from crash reports, it is
immensely valuable to be able to infer the crashing program's state from the
register values at crash time. However, for RELEASE_ASSERT failures, we crash
using WTFCrash(), and WTFCrash() is currently implemented as a function call
that, in turn, calls a lot of other functions to do crash handling before
actually crashing. As a result, the register values captured in the crash
reports are not likely to still contain the values used by the caller function
that failed the RELEASE_ASSERT.
This patch aims to remedy this issue for non-debug builds on OS(DARWIN) ports.
It does so by changing WTFCrash() into an inlined function that has an inlined
asm statement to issues the CPU specific breakpoint trap instruction. As a
result, for non-debug OS(DARWIN) builds, crashes due to failed RELEASE_ASSERTs
will now show up in crash reports as crashing due to EXC_BREAKPOINT (SIGTRAP)
instead of a EXC_BAD_ACCESS (SIGSEGV) on address 0xbbadbeef.
For debug and non-DARWIN builds, WTFCrash() behavior currently remains unchanged.
* wtf/Assertions.cpp:
* wtf/Assertions.h:</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceWTFChangeLog">trunk/Source/WTF/ChangeLog</a></li>
<li><a href="#trunkSourceWTFwtfAssertionscpp">trunk/Source/WTF/wtf/Assertions.cpp</a></li>
<li><a href="#trunkSourceWTFwtfAssertionsh">trunk/Source/WTF/wtf/Assertions.h</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceWTFChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/WTF/ChangeLog (196396 => 196397)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WTF/ChangeLog 2016-02-10 22:50:12 UTC (rev 196396)
+++ trunk/Source/WTF/ChangeLog 2016-02-10 23:02:24 UTC (rev 196397)
</span><span class="lines">@@ -1,3 +1,31 @@
</span><ins>+2016-02-09 Mark Lam <mark.lam@apple.com>
+
+ Changed WTFCrash to not trash the crash site register state.
+ https://bugs.webkit.org/show_bug.cgi?id=153996
+
+ Reviewed by Geoffrey Garen.
+
+ When doing post-mortem crash site analysis using data from crash reports, it is
+ immensely valuable to be able to infer the crashing program's state from the
+ register values at crash time. However, for RELEASE_ASSERT failures, we crash
+ using WTFCrash(), and WTFCrash() is currently implemented as a function call
+ that, in turn, calls a lot of other functions to do crash handling before
+ actually crashing. As a result, the register values captured in the crash
+ reports are not likely to still contain the values used by the caller function
+ that failed the RELEASE_ASSERT.
+
+ This patch aims to remedy this issue for non-debug builds on OS(DARWIN) ports.
+ It does so by changing WTFCrash() into an inlined function that has an inlined
+ asm statement to issues the CPU specific breakpoint trap instruction. As a
+ result, for non-debug OS(DARWIN) builds, crashes due to failed RELEASE_ASSERTs
+ will now show up in crash reports as crashing due to EXC_BREAKPOINT (SIGTRAP)
+ instead of a EXC_BAD_ACCESS (SIGSEGV) on address 0xbbadbeef.
+
+ For debug and non-DARWIN builds, WTFCrash() behavior currently remains unchanged.
+
+ * wtf/Assertions.cpp:
+ * wtf/Assertions.h:
+
</ins><span class="cx"> 2016-02-09 Csaba Osztrogonác <ossy@webkit.org>
</span><span class="cx">
</span><span class="cx"> [GTK][EFL] Fix several build configuration related to SamplingProfiler after r196245
</span></span></pre></div>
<a id="trunkSourceWTFwtfAssertionscpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/WTF/wtf/Assertions.cpp (196396 => 196397)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WTF/wtf/Assertions.cpp 2016-02-10 22:50:12 UTC (rev 196396)
+++ trunk/Source/WTF/wtf/Assertions.cpp 2016-02-10 23:02:24 UTC (rev 196397)
</span><span class="lines">@@ -312,6 +312,7 @@
</span><span class="cx"> globalHook = function;
</span><span class="cx"> }
</span><span class="cx">
</span><ins>+#if !defined(NDEBUG) || !OS(DARWIN)
</ins><span class="cx"> void WTFCrash()
</span><span class="cx"> {
</span><span class="cx"> if (globalHook)
</span><span class="lines">@@ -326,6 +327,7 @@
</span><span class="cx"> ((void(*)())0)();
</span><span class="cx"> #endif
</span><span class="cx"> }
</span><ins>+#endif // !defined(NDEBUG) || !OS(DARWIN)
</ins><span class="cx">
</span><span class="cx"> void WTFCrashWithSecurityImplication()
</span><span class="cx"> {
</span></span></pre></div>
<a id="trunkSourceWTFwtfAssertionsh"></a>
<div class="modfile"><h4>Modified: trunk/Source/WTF/wtf/Assertions.h (196396 => 196397)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WTF/wtf/Assertions.h 2016-02-10 22:50:12 UTC (rev 196396)
+++ trunk/Source/WTF/wtf/Assertions.h 2016-02-10 23:02:24 UTC (rev 196397)
</span><span class="lines">@@ -162,7 +162,27 @@
</span><span class="cx"> #ifdef __cplusplus
</span><span class="cx"> extern "C" {
</span><span class="cx"> #endif
</span><del>- WTF_EXPORT_PRIVATE NO_RETURN_DUE_TO_CRASH void WTFCrash();
</del><ins>+#if defined(NDEBUG) && OS(DARWIN)
+ALWAYS_INLINE NO_RETURN_DUE_TO_CRASH void WTFCrash()
+{
+ // Crash with a SIGTRAP i.e EXC_BREAKPOINT.
+ // We are not using __builtin_trap because it is only guaranteed to abort, but not necessarily
+ // trigger a SIGTRAP. Instead, we use inline asm to ensure that we trigger the SIGTRAP.
+#if CPU(X86_64) || CPU(X86)
+ asm volatile ("int3");
+#elif CPU(ARM_THUMB2)
+ asm volatile ("bkpt #0");
+#elif CPU(ARM64)
+ asm volatile ("brk #0");
+#else
+#error "Unsupported CPU".
+#endif
+ __builtin_unreachable();
+}
+#else
+WTF_EXPORT_PRIVATE NO_RETURN_DUE_TO_CRASH void WTFCrash();
+#endif
+
</ins><span class="cx"> #ifdef __cplusplus
</span><span class="cx"> }
</span><span class="cx"> #endif
</span></span></pre>
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