[PATCH] D49607: [ELF] Check eh_frame_hdr overflow with PC offsets instead of PC absolute addresses

[Fangrui Song via Phabricator via llvm-commits]

MaskRay created this revision.
MaskRay added reviewers: grimar, ruiu.
Herald added subscribers: llvm-commits, arichardson, emaste.
Herald added a reviewer: espindola.

Repository:
  rLLD LLVM Linker

https://reviews.llvm.org/D49607

Files:
  ELF/SyntheticSections.cpp
  ELF/SyntheticSections.h
  test/ELF/eh-frame-pcaddr-overflow.s


Index: test/ELF/eh-frame-pcaddr-overflow.s
===================================================================
--- test/ELF/eh-frame-pcaddr-overflow.s
+++ test/ELF/eh-frame-pcaddr-overflow.s
@@ -3,7 +3,7 @@
 # RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
 # RUN: not ld.lld --eh-frame-hdr --section-start .text=0x1000000000000000 \
 # RUN:   %t.o -o /dev/null 2>&1 | FileCheck %s
-# CHECK: error: {{.*}}.o:(.eh_frame): PC address is too large: 2387527121043355528
+# CHECK: error: {{.*}}.o:(.eh_frame): PC offset is too large: 0x1122334455666788
 
 .text
 .global foo
@@ -14,19 +14,19 @@
   .long 12   # Size
   .long 0x00 # ID
   .byte 0x01 # Version.
-  
+
   .byte 0x52 # Augmentation string: 'R','\0'
   .byte 0x00
-  
+
   .byte 0x01
-  
+
   .byte 0x01 # LEB128
   .byte 0x01 # LEB128
 
   .byte 0x00 # DW_EH_PE_absptr
 
   .byte 0xFF
- 
+
   .long 12  # Size
   .long 0x14 # ID
   .quad foo + 0x1122334455667788
Index: ELF/SyntheticSections.h
===================================================================
--- ELF/SyntheticSections.h
+++ ELF/SyntheticSections.h
@@ -79,7 +79,7 @@
   size_t NumFdes = 0;
 
   struct FdeData {
-    uint32_t Pc;
+    uint64_t Pc;
     uint32_t FdeVA;
   };
 
Index: ELF/SyntheticSections.cpp
===================================================================
--- ELF/SyntheticSections.cpp
+++ ELF/SyntheticSections.cpp
@@ -502,14 +502,16 @@
   uint8_t *Buf = getParent()->Loc + OutSecOff;
   std::vector<FdeData> Ret;
 
+  uint64_t VA = InX::EhFrameHdr->getVA();
   for (CieRecord *Rec : CieRecords) {
     uint8_t Enc = getFdeEncoding(Rec->Cie);
     for (EhSectionPiece *Fde : Rec->Fdes) {
       uint64_t Pc = getFdePc(Buf, Fde->OutputOff, Enc);
-      if (Pc > UINT32_MAX)
-        fatal(toString(Fde->Sec) + ": PC address is too large: " + Twine(Pc));
+      if (Pc - VA != (uint64_t)signExtend(Pc - VA, 32))
+        fatal(toString(Fde->Sec) + ": PC offset is too large: 0x" +
+              Twine::utohexstr(Pc - VA));
       uint32_t FdeVA = getParent()->Addr + Fde->OutputOff;
-      Ret.push_back({(uint32_t)Pc, FdeVA});
+      Ret.push_back({Pc, FdeVA});
     }
   }
   return Ret;


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