Improve error messages.

Author: christianhaeubl

substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/AddressRangeCommittedMemoryProvider.java

@@ -111,6 +111,8 @@ public class AddressRangeCommittedMemoryProvider extends ChunkBasedCommittedMemo
     protected static final int OUT_OF_ADDRESS_SPACE = 1;
     protected static final int COMMIT_FAILED = 2;
 
+    protected static final String UNCOMMIT_FAILED_ERROR_MSG = "Failed while uncommitting memory. " +
+                    "This error may occur if the operating system's memory mapping limit is too low (see vm.max_map_count on Linux). Please increase this limit and try again.";
     private static final OutOfMemoryError NODE_ALLOCATION_FAILED = new OutOfMemoryError("Could not allocate node for free list, OS may be out of memory.");
     private static final OutOfMemoryError OUT_OF_METASPACE = new OutOfMemoryError("Could not allocate a metaspace chunk because the metaspace is exhausted.");
     private static final OutOfMemoryError ALIGNED_OUT_OF_ADDRESS_SPACE = new OutOfMemoryError("Could not allocate an aligned heap chunk because the heap address space is exhausted. " +
@@ -776,7 +778,7 @@ private static RuntimeException reportUncommitFailed(Pointer mapBegin, UnsignedW
 
     private static RuntimeException reportUncommitFailedInterruptibly(Pointer mapBegin, UnsignedWord mappingSize) {
         Log.log().string("Uncommitting ").unsigned(mappingSize).string(" bytes of unused memory at ").hex(mapBegin).string(" failed.").newline();
-        throw VMError.shouldNotReachHere("Uncommitting memory failed.");
+        throw VMError.shouldNotReachHere(UNCOMMIT_FAILED_ERROR_MSG);
     }
 
     @Uninterruptible(reason = CALLED_FROM_UNINTERRUPTIBLE_CODE, mayBeInlined = true)

substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/code/RuntimeCodeInfoAccess.java

@@ -238,10 +238,9 @@ public static void makeCodeMemoryExecutableWritable(CodePointer start, UnsignedW
     private static void protectCodeMemory(CodePointer codeStart, UnsignedWord codeSize, int permissions) {
         int result = VirtualMemoryProvider.get().protect(codeStart, codeSize, permissions);
         if (result != 0) {
-            throw VMError.shouldNotReachHere("Failed to modify protection of code memory. This may be caused by " +
-                            "a. a too restrictive OS-limit of allowed memory mappings (see vm.max_map_count on Linux), " +
-                            "b. a too strict security policy if you are running on Security-Enhanced Linux (SELinux), or " +
-                            "c. a Native Image internal error.");
+            throw VMError.shouldNotReachHere("Failed to modify protection of code memory. " +
+                            "This error may occur if the operating system's memory mapping limit is too low (see vm.max_map_count on Linux). Please increase this limit and try again." +
+                            "If you are running on Security-Enhanced Linux (SELinux), you may also need to check the configured security policy.");
         }
     }