replace stgMallocBytesRWX() with our own allocator

See bug #738

Allocating executable memory is getting more difficult these days.  In
particular, the default SELinux policy on Fedora Core 5 disallows
making the heap (i.e. malloc()'d memory) executable, although it does
apparently allow mmap()'ing anonymous executable memory by default.

Previously, stgMallocBytesRWX() used malloc() underneath, and then
tried to make the page holding the memory executable.  This was rather
hacky and fails with Fedora Core 5.  

This patch adds a mini-allocator for executable memory, based on the
block allocator.  We grab page-sized blocks and make them executable,
then allocate small objects from the page.  There's a simple free
function, that will free whole pages back to the system when they are
empty.

1 files changed, 12 insertions, 11 deletions

diff --git a/rts/Adjustor.c b/rts/Adjustor.c
index fc4182e731..4b042a17b2 100644
--- a/rts/Adjustor.c
+++ b/rts/Adjustor.c
@@ -40,6 +40,7 @@ Haskell side.
 #include "Rts.h"
 #include "RtsExternal.h"
 #include "RtsUtils.h"
+#include "Storage.h"
 #include <stdlib.h>
 
 #if defined(_WIN32)
@@ -266,7 +267,7 @@ createAdjustor(int cconv, StgStablePtr hptr,
      <c>: 	ff e0             jmp    %eax        	   # and jump to it.
 		# the callee cleans up the stack
     */
-    adjustor = stgMallocBytesRWX(14);
+    adjustor = allocateExec(14);
     {
 	unsigned char *const adj_code = (unsigned char *)adjustor;
 	adj_code[0x00] = (unsigned char)0x58;  /* popl %eax  */
@@ -311,7 +312,7 @@ createAdjustor(int cconv, StgStablePtr hptr,
     That's (thankfully) the case here with the restricted set of 
     return types that we support.
   */
-    adjustor = stgMallocBytesRWX(17);
+    adjustor = allocateExec(17);
     {
 	unsigned char *const adj_code = (unsigned char *)adjustor;
 
@@ -340,7 +341,7 @@ createAdjustor(int cconv, StgStablePtr hptr,
           
           We offload most of the work to AdjustorAsm.S.
         */
-        AdjustorStub *adjustorStub = stgMallocBytesRWX(sizeof(AdjustorStub));
+        AdjustorStub *adjustorStub = allocateExec(sizeof(AdjustorStub));
         adjustor = adjustorStub;
 
         extern void adjustorCode(void);
@@ -443,7 +444,7 @@ createAdjustor(int cconv, StgStablePtr hptr,
 	}
 
 	if (i < 6) {
-	    adjustor = stgMallocBytesRWX(0x30);
+	    adjustor = allocateExec(0x30);
 
 	    *(StgInt32 *)adjustor        = 0x49c1894d;
 	    *(StgInt32 *)(adjustor+0x4)  = 0x8948c889;
@@ -457,7 +458,7 @@ createAdjustor(int cconv, StgStablePtr hptr,
 	}
 	else
 	{
-	    adjustor = stgMallocBytesRWX(0x40);
+	    adjustor = allocateExec(0x40);
 
 	    *(StgInt32 *)adjustor        = 0x35ff5141;
 	    *(StgInt32 *)(adjustor+0x4)  = 0x00000020;
@@ -504,7 +505,7 @@ createAdjustor(int cconv, StgStablePtr hptr,
      similarly, and local variables should be accessed via %fp, not %sp. In a
      nutshell: This should work! (Famous last words! :-)
   */
-    adjustor = stgMallocBytesRWX(4*(11+1));
+    adjustor = allocateExec(4*(11+1));
     {
         unsigned long *const adj_code = (unsigned long *)adjustor;
 
@@ -581,7 +582,7 @@ TODO: Depending on how much allocation overhead stgMallocBytes uses for
       4 bytes (getting rid of the nop), hence saving memory. [ccshan]
   */
     ASSERT(((StgWord64)wptr & 3) == 0);
-    adjustor = stgMallocBytesRWX(48);
+    adjustor = allocateExec(48);
     {
 	StgWord64 *const code = (StgWord64 *)adjustor;
 
@@ -686,7 +687,7 @@ TODO: Depending on how much allocation overhead stgMallocBytes uses for
             */
                     // allocate space for at most 4 insns per parameter
                     // plus 14 more instructions.
-        adjustor = stgMallocBytesRWX(4 * (4*n + 14));
+        adjustor = allocateExec(4 * (4*n + 14));
         code = (unsigned*)adjustor;
         
         *code++ = 0x48000008; // b *+8
@@ -845,7 +846,7 @@ TODO: Depending on how much allocation overhead stgMallocBytes uses for
 #ifdef FUNDESCS
         adjustorStub = stgMallocBytes(sizeof(AdjustorStub), "createAdjustor");
 #else
-        adjustorStub = stgMallocBytesRWX(sizeof(AdjustorStub));
+        adjustorStub = allocateExec(sizeof(AdjustorStub));
 #endif
         adjustor = adjustorStub;
             
@@ -1088,7 +1089,7 @@ if ( *(unsigned char*)ptr != 0xe8 ) {
 #endif
  *((unsigned char*)ptr) = '\0';
 
- stgFree(ptr);
+ freeExec(ptr);
 }
 
 
@@ -1101,7 +1102,7 @@ void
 initAdjustor(void)
 {
 #if defined(i386_HOST_ARCH) && defined(openbsd_HOST_OS)
-    obscure_ccall_ret_code_dyn = stgMallocBytesRWX(4);
+    obscure_ccall_ret_code_dyn = allocateExec(4);
     obscure_ccall_ret_code_dyn[0] = ((unsigned char *)obscure_ccall_ret_code)[0];
     obscure_ccall_ret_code_dyn[1] = ((unsigned char *)obscure_ccall_ret_code)[1];
     obscure_ccall_ret_code_dyn[2] = ((unsigned char *)obscure_ccall_ret_code)[2];