dev-ruby/ffi patch

ffi.patch (text/plain), 2.22 KB, created by Hans de Graaff on 2016-09-11 09:01:45 UTC

diff --git a/ext/ffi_c/ClosurePool.c b/ext/ffi_c/ClosurePool.c
index 5499b40..66d31d9 100644
--- a/ext/ffi_c/ClosurePool.c
+++ b/ext/ffi_c/ClosurePool.c
@@ -57,6 +57,7 @@
 #include <ffi.h>
 #include "rbffi.h"
 #include "compat.h"
+#include "emutramp.h"
 
 #include "Function.h"
 #include "Types.h"
@@ -271,7 +272,10 @@ protectPage(void* page)
     DWORD oldProtect;
     return VirtualProtect(page, pageSize, PAGE_EXECUTE_READ, &oldProtect);
 #else
-    return mprotect(page, pageSize, PROT_READ | PROT_EXEC) == 0;
+    int prot = PROT_READ | PROT_EXEC;
+    if (is_emutramp_enabled ())
+      prot &= ~PROT_EXEC;
+    return mprotect(page, pageSize, prot) == 0;
 #endif
 }
 
diff --git a/ext/ffi_c/emutramp.h b/ext/ffi_c/emutramp.h
new file mode 100644
index 0000000..a38efee
--- /dev/null
+++ b/ext/ffi_c/emutramp.h
@@ -0,0 +1,46 @@
+/* On PaX enable kernels that have MPROTECT enable we can't use PROT_EXEC.
+
+   This is, apparently, an undocumented change to ffi_prep_closure():
+   depending on the Linux kernel we're running on, we must give it a
+   mmap that is either PROT_READ|PROT_WRITE|PROT_EXEC or only
+   PROT_READ|PROT_WRITE.  In the latter case, just trying to obtain a
+   mmap with PROT_READ|PROT_WRITE|PROT_EXEC would kill our process(!),
+   but in that situation libffi is fine with only PROT_READ|PROT_WRITE.
+   There is nothing in the libffi API to know that, though, so we have
+   to guess by parsing /proc/self/status.  "Meh."
+ */
+#ifdef __linux__
+#include <stdlib.h>
+
+static int emutramp_enabled = -1;
+
+static int
+emutramp_enabled_check (void)
+{
+    char *buf = NULL;
+    size_t len = 0;
+    FILE *f;
+    int ret;
+    f = fopen ("/proc/self/status", "r");
+    if (f == NULL)
+        return 0;
+    ret = 0;
+
+    while (getline (&buf, &len, f) != -1)
+        if (!strncmp (buf, "PaX:", 4))
+            {
+                char emutramp;
+                if (sscanf (buf, "%*s %*c%c", &emutramp) == 1)
+                    ret = (emutramp == 'E');
+                break;
+            }
+    free (buf);
+    fclose (f);
+    return ret;
+}
+
+#define is_emutramp_enabled() (emutramp_enabled >= 0 ? emutramp_enabled \
+        : (emutramp_enabled = emutramp_enabled_check ()))
+#else
+#define is_emutramp_enabled() 0
+#endif