[llvm] 1a83756 - [DebugInfo] Refine the condition to detect CIEs.

[Igor Kudrin via llvm-commits]

Author: Igor Kudrin
Date: 2020-03-05T17:37:09+07:00
New Revision: 1a837569db3b611c6bd0b891b79f1585be20c323

URL: https://github.com/llvm/llvm-project/commit/1a837569db3b611c6bd0b891b79f1585be20c323
DIFF: https://github.com/llvm/llvm-project/commit/1a837569db3b611c6bd0b891b79f1585be20c323.diff

LOG: [DebugInfo] Refine the condition to detect CIEs.

The condition was not accurate enough and could interpret some FDEs in
.eh_frame or 64-bit DWARF .debug_frame sections as CIEs. Even though
such FDEs are unlikely in a normal situation, the wrong interpretation
could hide an issue in a buggy generator.

Differential Revision: https://reviews.llvm.org/D73886

Added: 
    llvm/test/DebugInfo/X86/debug-frame-cie-id-dwarf64.s
    llvm/test/DebugInfo/X86/eh-frame-cie-id.s

Modified: 
    llvm/lib/DebugInfo/DWARF/DWARFDebugFrame.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/DebugInfo/DWARF/DWARFDebugFrame.cpp b/llvm/lib/DebugInfo/DWARF/DWARFDebugFrame.cpp
index c3057f245d7d..fec1bc11713b 100644
--- a/llvm/lib/DebugInfo/DWARF/DWARFDebugFrame.cpp
+++ b/llvm/lib/DebugInfo/DWARF/DWARFDebugFrame.cpp
@@ -285,6 +285,18 @@ void CFIProgram::dump(raw_ostream &OS, const MCRegisterInfo *MRI, bool IsEH,
   }
 }
 
+// Returns the CIE identifier to be used by the requested format.
+// CIE ids for .debug_frame sections are defined in Section 7.24 of DWARFv5.
+// For CIE ID in .eh_frame sections see
+// https://refspecs.linuxfoundation.org/LSB_5.0.0/LSB-Core-generic/LSB-Core-generic/ehframechpt.html
+constexpr uint64_t getCIEId(bool IsDWARF64, bool IsEH) {
+  if (IsEH)
+    return 0;
+  if (IsDWARF64)
+    return DW64_CIE_ID;
+  return DW_CIE_ID;
+}
+
 void CIE::dump(raw_ostream &OS, const MCRegisterInfo *MRI, bool IsEH) const {
   OS << format("%08x %08x %08x CIE", (uint32_t)Offset, (uint32_t)Length,
                IsEH ? 0 : DW_CIE_ID)
@@ -379,10 +391,7 @@ void DWARFDebugFrame::parse(DWARFDataExtractor Data) {
     // The Id field's size depends on the DWARF format
     bool IsDWARF64 = Format == DWARF64;
     Id = Data.getRelocatedValue((IsDWARF64 && !IsEH) ? 8 : 4, &Offset);
-    bool IsCIE =
-        ((IsDWARF64 && Id == DW64_CIE_ID) || Id == DW_CIE_ID || (IsEH && !Id));
-
-    if (IsCIE) {
+    if (Id == getCIEId(IsDWARF64, IsEH)) {
       uint8_t Version = Data.getU8(&Offset);
       const char *Augmentation = Data.getCStr(&Offset);
       StringRef AugmentationString(Augmentation ? Augmentation : "");

diff  --git a/llvm/test/DebugInfo/X86/debug-frame-cie-id-dwarf64.s b/llvm/test/DebugInfo/X86/debug-frame-cie-id-dwarf64.s
new file mode 100644
index 000000000000..b66be5af6a4c
--- /dev/null
+++ b/llvm/test/DebugInfo/X86/debug-frame-cie-id-dwarf64.s
@@ -0,0 +1,16 @@
+# RUN: llvm-mc -triple x86_64-unknown-linux %s -filetype=obj -o - | \
+# RUN:   llvm-dwarfdump -debug-frame - | \
+# RUN:   FileCheck %s
+
+# CHECK: 00000000 {{.*}} FDE
+
+        .section .debug_frame,"", at progbits
+## This FDE was formerly wrongly interpreted as a CIE because its CIE pointer
+## is similar to DWARF32 CIE id.
+        .long 0xffffffff        # DWARF64 mark
+        .quad .Lend - .LCIEptr  # Length
+.LCIEptr:
+        .quad 0xffffffff        # CIE pointer
+        .quad 0x1111abcd        # Initial location
+        .quad 0x00010000        # Address range
+.Lend:

diff  --git a/llvm/test/DebugInfo/X86/eh-frame-cie-id.s b/llvm/test/DebugInfo/X86/eh-frame-cie-id.s
new file mode 100644
index 000000000000..51098e67c08f
--- /dev/null
+++ b/llvm/test/DebugInfo/X86/eh-frame-cie-id.s
@@ -0,0 +1,15 @@
+# RUN: llvm-mc -triple x86_64-unknown-linux %s -filetype=obj -o - | \
+# RUN:   not --crash llvm-dwarfdump -debug-frame - 2>&1 | \
+# RUN:   FileCheck %s
+
+# CHECK: Parsing FDE data at 0 failed due to missing CIE
+
+        .section .eh_frame,"a", at unwind
+## This FDE was formerly wrongly interpreted as a CIE because its CIE pointer
+## is similar to CIE id of a .debug_frame FDE.
+        .long .Lend - .LCIEptr  # Length
+.LCIEptr:
+        .long 0xffffffff        # CIE pointer
+        .quad 0x1111abcd        # Initial location
+        .quad 0x00010000        # Address range
+.Lend: