Add a feature to mark mmap-allocated pages on Linux too

We can't tag mmap anonymous segments, like Mach/Darwin can, but we can
use a memfd (which can take a name) and then its name will show in
/proc/PID/maps. For example, pmap shows for tst_qjsengine at an
arbitrary point I stopped execution at:

 Address           Kbytes     RSS     PSS   Dirty    Swap Mode  Mapping
 00007f9cc2db7000    2040       4       4       4       0 rw-p- /memfd:JSVMStack:/home/tjmaciei/obj/qt/qt5/qtbase/lib/libQt5Qml.t.so.5 (deleted)
 00007f9cc2fb7000    4344       4       4       4       0 rw-p- /memfd:JSVMStack:/home/tjmaciei/obj/qt/qt5/qtbase/lib/libQt5Qml.t.so.5 (deleted)
 00007f9cc33f6000      40       0       0       0       0 ---p- /memfd:JSGCHeap:/home/tjmaciei/obj/qt/qt5/qtbase/lib/libQt5Qml.t.so.5 (deleted)
 00007f9cc3400000     128      64      64      64       0 rw-p- /memfd:JSGCHeap:/home/tjmaciei/obj/qt/qt5/qtbase/lib/libQt5Qml.t.so.5 (deleted)
 00007f9cc3420000    3928       0       0       0       0 ---p- /memfd:JSGCHeap:/home/tjmaciei/obj/qt/qt5/qtbase/lib/libQt5Qml.t.so.5 (deleted)
 00007f9cd099e000       4       4       4       4       0 rw-p- /memfd:unknown-usage:/home/tjmaciei/obj/qt/qt5/qtbase/lib/libQt5Qml.t.so.5 (deleted)
 00007f9cd099f000       4       4       4       4       0 r-xp- /memfd:JITCode:/home/tjmaciei/obj/qt/qt5/qtbase/lib/libQt5Qml.t.so.5 (deleted)

I suppose that before upstreaming this patch, we'd change the "QtQml"
name prefix or remove it.

Change-Id: I84e45059a888497fb55ffffd14d3ba60f9707051
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

3 files changed, 91 insertions, 2 deletions

diff --git a/src/3rdparty/masm/masm.pri b/src/3rdparty/masm/masm.pri
index 6c301fea38..aeb9babb05 100644
--- a/src/3rdparty/masm/masm.pri
+++ b/src/3rdparty/masm/masm.pri
@@ -127,3 +127,8 @@ QMAKE_EXTRA_COMPILERS += retgen
         }
     }
 }
+
+linux {
+    requires(qtConfig(dlopen))
+    QMAKE_USE_PRIVATE += libdl
+}
diff --git a/src/3rdparty/masm/wtf/OSAllocatorPosix.cpp b/src/3rdparty/masm/wtf/OSAllocatorPosix.cpp
index 0c902c7172..17a5150de5 100644
--- a/src/3rdparty/masm/wtf/OSAllocatorPosix.cpp
+++ b/src/3rdparty/masm/wtf/OSAllocatorPosix.cpp
@@ -31,13 +31,75 @@
 #include <cstdlib>
 
 #include "PageAllocation.h"
+#include <dlfcn.h>
 #include <errno.h>
 #include <sys/mman.h>
 #include <wtf/Assertions.h>
 #include <wtf/UnusedParam.h>
 
+#if OS(LINUX)
+#include <sys/syscall.h>
+#ifndef MFD_CLOEXEC
+#define MFD_CLOEXEC         0x0001U
+#endif
+#endif
+
 namespace WTF {
 
+#ifdef SYS_memfd_create
+static int memfdForUsage(size_t bytes, OSAllocator::Usage usage)
+{
+    const char *type = "unknown-usage:";
+    switch (usage) {
+    case OSAllocator::UnknownUsage:
+        break;
+    case OSAllocator::FastMallocPages:
+        type = "fastmalloc:";
+        break;
+    case OSAllocator::JSGCHeapPages:
+        type = "JSGCHeap:";
+        break;
+    case OSAllocator::JSVMStackPages:
+        type = "JSVMStack:";
+        break;
+    case OSAllocator::JSJITCodePages:
+        type = "JITCode:";
+        break;
+    }
+
+    // try to get our own library name by giving dladdr a pointer pointing to
+    // something we know to be in it (using a pointer to string data)
+    static const char *libname = [=]() {
+        Dl_info info;
+        if (dladdr(type, &info) == 0)
+            info.dli_fname = nullptr;
+        return info.dli_fname;
+    }();
+
+    char buf[PATH_MAX];
+    strcpy(buf, type);
+    if (libname)
+        strcat(buf, libname);
+    else
+        strcat(buf, "QtQml");
+
+    int fd = syscall(SYS_memfd_create, buf, MFD_CLOEXEC);
+    if (fd != -1) {
+        if (ftruncate(fd, bytes) == 0)
+            return fd;
+    }
+    close(fd);
+    return -1;
+}
+#elif OS(LINUX)
+static int memfdForUsage(size_t bytes, OSAllocator::Usage usage)
+{
+    UNUSED_PARAM(bytes);
+    UNUSED_PARAM(usage);
+    return -1;
+}
+#endif
+
 void* OSAllocator::reserveUncommitted(size_t bytes, Usage usage, bool writable, bool executable)
 {
 #if OS(QNX)
@@ -46,14 +108,18 @@ void* OSAllocator::reserveUncommitted(size_t bytes, Usage usage, bool writable,
     if (result == MAP_FAILED)
         CRASH();
 #elif OS(LINUX)
-    UNUSED_PARAM(usage);
     UNUSED_PARAM(writable);
     UNUSED_PARAM(executable);
+    int fd = memfdForUsage(bytes, usage);
 
-    void* result = mmap(0, bytes, PROT_NONE, MAP_NORESERVE | MAP_PRIVATE | MAP_ANON, -1, 0);
+    void* result = mmap(0, bytes, PROT_NONE, MAP_NORESERVE | MAP_PRIVATE |
+                        (fd == -1 ? MAP_ANON : 0), fd, 0);
     if (result == MAP_FAILED)
         CRASH();
     madvise(result, bytes, MADV_DONTNEED);
+
+    if (fd != -1)
+        close(fd);
 #else
     void* result = reserveAndCommit(bytes, usage, writable, executable);
 #if HAVE(MADV_FREE_REUSE)
@@ -83,6 +149,10 @@ void* OSAllocator::reserveAndCommit(size_t bytes, Usage usage, bool writable, bo
 
 #if OS(DARWIN)
     int fd = usage;
+#elif OS(LINUX) && defined(SYS_memfd_create)
+    int fd = memfdForUsage(bytes, usage);
+    if (fd != -1)
+        flags &= ~MAP_ANON;
 #else
     UNUSED_PARAM(usage);
     int fd = -1;
@@ -126,6 +196,12 @@ void* OSAllocator::reserveAndCommit(size_t bytes, Usage usage, bool writable, bo
         mmap(result, pageSize(), PROT_NONE, MAP_FIXED | MAP_PRIVATE | MAP_ANON, fd, 0);
         mmap(static_cast<char*>(result) + bytes - pageSize(), pageSize(), PROT_NONE, MAP_FIXED | MAP_PRIVATE | MAP_ANON, fd, 0);
     }
+
+#if OS(LINUX)
+    if (fd != -1)
+        close(fd);
+#endif
+
     return result;
 }
 
diff --git a/src/3rdparty/masm/wtf/VMTags.h b/src/3rdparty/masm/wtf/VMTags.h
index 117bc3721e..af5352e471 100644
--- a/src/3rdparty/masm/wtf/VMTags.h
+++ b/src/3rdparty/masm/wtf/VMTags.h
@@ -62,6 +62,14 @@
 #define VM_TAG_FOR_WEBCORE_PURGEABLE_MEMORY VM_MAKE_TAG(69)
 #endif // defined(VM_MEMORY_WEBCORE_PURGEABLE_BUFFERS)
 
+#elif OS(LINUX)
+
+#define VM_TAG_FOR_TCMALLOC_MEMORY 0
+#define VM_TAG_FOR_COLLECTOR_MEMORY 1
+#define VM_TAG_FOR_EXECUTABLEALLOCATOR_MEMORY 2
+#define VM_TAG_FOR_REGISTERFILE_MEMORY 3
+#define VM_TAG_FOR_WEBCORE_PURGEABLE_MEMORY 4
+
 #else // OS(DARWIN)
 
 #define VM_TAG_FOR_TCMALLOC_MEMORY -1