[Pcre-svn] [1174] code/trunk: Better description for jit-sea…

Revision: 1174

          http://www.exim.org/viewvc/pcre2?view=rev&revision=1174
Author:   zherczeg
Date:     2019-10-01 14:46:41 +0100 (Tue, 01 Oct 2019)
Log Message:
-----------
Better description for jit-sealloc option and early check for executable memory.

Modified Paths:
--------------
    code/trunk/CMakeLists.txt
    code/trunk/README
    code/trunk/configure.ac
    code/trunk/src/pcre2_jit_compile.c

Modified: code/trunk/CMakeLists.txt
===================================================================
--- code/trunk/CMakeLists.txt    2019-09-26 16:10:30 UTC (rev 1173)
+++ code/trunk/CMakeLists.txt    2019-10-01 13:46:41 UTC (rev 1174)
@@ -178,7 +178,7 @@
     "Enable support for Just-in-time compiling.")

 SET(PCRE2_SUPPORT_JIT_SEALLOC OFF CACHE BOOL
-    "Enable SELinux compatible execmem allocator in JIT.")
+    "Enable SELinux compatible execmem allocator in JIT (experimental).")

 SET(PCRE2GREP_SUPPORT_JIT ON CACHE BOOL
     "Enable use of Just-in-time compiling in pcre2grep.")

Modified: code/trunk/README
===================================================================
--- code/trunk/README    2019-09-26 16:10:30 UTC (rev 1173)
+++ code/trunk/README    2019-10-01 13:46:41 UTC (rev 1174)
@@ -164,9 +164,11 @@
   will be a compile time error. If in doubt, use --enable-jit=auto, which
   enables JIT only if the current hardware is supported.

-. If you are enabling JIT under SELinux you may also want to add
- --enable-jit-sealloc, which enables the use of an execmem allocator in JIT
- that is compatible with SELinux. This has no effect if JIT is not enabled.
+. If you are enabling JIT under SELinux environment you may also want to add
+ --enable-jit-sealloc, which enables the use of an executable memory allocator
+ that is compatible with SELinux. Warning: this allocator is experimental!
+ It does not support fork() operation and may crash when no disk space is
+ available. This option has no effect if JIT is disabled.

. If you do not want to make use of the default support for UTF-8 Unicode
character strings in the 8-bit library, UTF-16 Unicode character strings in

Modified: code/trunk/configure.ac
===================================================================
--- code/trunk/configure.ac    2019-09-26 16:10:30 UTC (rev 1173)
+++ code/trunk/configure.ac    2019-10-01 13:46:41 UTC (rev 1174)
@@ -161,7 +161,7 @@
 # Handle --enable-jit-sealloc (disabled by default)
 AC_ARG_ENABLE(jit-sealloc,
               AS_HELP_STRING([--enable-jit-sealloc],
-                             [enable SELinux compatible execmem allocator in JIT]),
+                             [enable SELinux compatible execmem allocator in JIT (experimental)]),
               , enable_jit_sealloc=no)

# Handle --disable-pcre2grep-jit (enabled by default)

Modified: code/trunk/src/pcre2_jit_compile.c
===================================================================
--- code/trunk/src/pcre2_jit_compile.c    2019-09-26 16:10:30 UTC (rev 1173)
+++ code/trunk/src/pcre2_jit_compile.c    2019-10-01 13:46:41 UTC (rev 1174)
@@ -13740,6 +13740,8 @@
 PCRE2_EXP_DEFN int PCRE2_CALL_CONVENTION
 pcre2_jit_compile(pcre2_code *code, uint32_t options)
 {
+static int executable_allocator_is_working = 0;
+
 pcre2_real_code *re = (pcre2_real_code *)code;

#ifdef SUPPORT_JIT
@@ -13746,6 +13748,25 @@
executable_functions *functions = (executable_functions *)re->executable_jit;
#endif

+if (executable_allocator_is_working == 0)
+  {
+  /* Checks whether the executable allocator is working. This check
+     might run multiple times in multi-threaded environments, but the result
+     should not be affected by it. */
+  void *ptr = SLJIT_MALLOC_EXEC(32);
+
+  executable_allocator_is_working = -1;
+
+  if (ptr != NULL)
+    {
+    SLJIT_FREE_EXEC(((sljit_u8*)(ptr)) + SLJIT_EXEC_OFFSET(ptr));
+    executable_allocator_is_working = 1;
+    }
+  }
+
+if (executable_allocator_is_working < 0)
+  return PCRE2_ERROR_NOMEMORY;
+
 if (code == NULL)
   return PCRE2_ERROR_NULL;