[PATCH] D36262: [ELF] - Do not forget to fill last bytes of PT_LOADs with trap instructions.

[George Rimar via Phabricator via llvm-commits]

grimar created this revision.
Herald added a subscriber: emaste.

https://reviews.llvm.org/D33630 implemented filling load segments with trap,
but it has bug - it forgets to set last 4 bytes.
Patch fixes the issue.


https://reviews.llvm.org/D36262

Files:
  ELF/LinkerScript.h
  ELF/OutputSections.cpp
  ELF/Writer.cpp
  test/ELF/build-id.s


Index: test/ELF/build-id.s
===================================================================
--- test/ELF/build-id.s
+++ test/ELF/build-id.s
@@ -48,15 +48,15 @@
 # DEFAULT:      Contents of section .note.test:
 # DEFAULT:      Contents of section .note.gnu.build-id:
 # DEFAULT-NEXT: 04000000 08000000 03000000 474e5500  ............GNU.
-# DEFAULT-NEXT: d618a375 bc6301ec
+# DEFAULT-NEXT: b0148597 ba5eb7e9
 
 # MD5:      Contents of section .note.gnu.build-id:
 # MD5-NEXT: 04000000 10000000 03000000 474e5500  ............GNU.
-# MD5-NEXT: 051084fe ce1f30ed e035b79e 11262808
+# MD5-NEXT: dce3bcaf 5219454c e89a1fc7 86ab17bd
 
 # SHA1:      Contents of section .note.gnu.build-id:
 # SHA1-NEXT: 04000000 14000000 03000000 474e5500  ............GNU.
-# SHA1-NEXT: c70b9aec 903fd291 8b677cd8 1e04f8b6
+# SHA1-NEXT: 2f716666 fe3668fe 370a02a1 579c3eb2
 
 # UUID:      Contents of section .note.gnu.build-id:
 # UUID-NEXT: 04000000 10000000 03000000 474e5500  ............GNU.
Index: ELF/Writer.cpp
===================================================================
--- ELF/Writer.cpp
+++ ELF/Writer.cpp
@@ -1830,12 +1830,12 @@
       Sec->writeTo<ELFT>(Buf + Sec->Offset);
 }
 
-static void fillTrapInstr(uint8_t *I, uint8_t *End) {
-  for (; I + 4 < End; I += 4)
-    memcpy(I, &Target->TrapInstr, 4);
+static void fillPage(uint8_t *Buf, uint64_t Offset, uint32_t Filler) {
+  uint64_t Begin = alignDown(Offset, Target->PageSize);
+  uint64_t End = alignTo(Offset, Target->PageSize);
+  fill(Buf + Begin, End - Begin, Filler);
 }
 
-
 // Fill the first and the last page of executable segments with trap
 // instructions instead of leaving them as zero. Even though it is not required
 // by any standard , it is in general a good thing to do for security reasons.
@@ -1851,10 +1851,8 @@
 
     // We only fill the first and the last page of the segment because the
     // middle part will be overwritten by output sections.
-    fillTrapInstr(Buf + alignDown(P->p_offset, Target->PageSize),
-                  Buf + alignTo(P->p_offset, Target->PageSize));
-    fillTrapInstr(Buf + alignDown(P->p_offset + P->p_filesz, Target->PageSize),
-                  Buf + alignTo(P->p_offset + P->p_filesz, Target->PageSize));
+    fillPage(Buf, P->p_offset, Target->TrapInstr);
+    fillPage(Buf, P->p_offset + P->p_filesz, Target->TrapInstr);
   }
 
   PhdrEntry *LastRX = nullptr;
Index: ELF/OutputSections.cpp
===================================================================
--- ELF/OutputSections.cpp
+++ ELF/OutputSections.cpp
@@ -307,7 +307,7 @@
 
 // Fill [Buf, Buf + Size) with Filler.
 // This is used for linker script "=fillexp" command.
-static void fill(uint8_t *Buf, size_t Size, uint32_t Filler) {
+void elf::fill(uint8_t *Buf, size_t Size, uint32_t Filler) {
   size_t I = 0;
   for (; I + 4 < Size; I += 4)
     memcpy(Buf + I, &Filler, 4);
Index: ELF/LinkerScript.h
===================================================================
--- ELF/LinkerScript.h
+++ ELF/LinkerScript.h
@@ -264,6 +264,8 @@
 
 extern LinkerScript *Script;
 
+void fill(uint8_t *Buf, size_t Size, uint32_t Filler);
+
 } // end namespace elf
 } // end namespace lld
 


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