[PATCH] D92641: [llvm-readelf/obj] - Handle out-of-order PT_LOADs better.

[George Rimar via Phabricator via llvm-commits]

grimar created this revision.
grimar added reviewers: jhenderson, MaskRay.
Herald added subscribers: rupprecht, hiraditya, emaste.
Herald added a reviewer: espindola.
grimar requested review of this revision.
Herald added a project: LLVM.

This is https://bugs.llvm.org/show_bug.cgi?id=45698.

Specification says that
"Loadable segment entries in the program header table appear
in ascending order, sorted on the p_vaddr member."

Out `toMappedAddr()` relies on this condition. This patch
adds a warning when the sorting order of loadable segments is wrong.


https://reviews.llvm.org/D92641

Files:
  llvm/lib/Object/ELF.cpp
  llvm/test/tools/llvm-readobj/ELF/dynamic-malformed.test


Index: llvm/test/tools/llvm-readobj/ELF/dynamic-malformed.test
===================================================================
--- llvm/test/tools/llvm-readobj/ELF/dynamic-malformed.test
+++ llvm/test/tools/llvm-readobj/ELF/dynamic-malformed.test
@@ -414,3 +414,57 @@
 # PAST-THE-EOF-NEXT: {{[(]?}}RPATH{{[)]?}}     Library rpath: [<?>]
 # PAST-THE-EOF-NEXT: {{[(]?}}RUNPATH{{[)]?}}   Library runpath: [<?>]
 # PAST-THE-EOF-NEXT: {{[(]?}}NULL{{[)]?}}      0x0
+
+## Check that we report a warning when we try to map an address, but loadable
+## segments appear unsorted on the p_vaddr member.
+
+# RUN: yaml2obj %s --docnum=7 -o %t10
+# RUN: llvm-readobj --dynamic-table %t10 2>&1 | \
+# RUN:   FileCheck %s -DFILE=%t10 --implicit-check-not=warning: --check-prefixes=OUT-OF-ORDER,OUT-OF-ORDER-LLVM
+# RUN: llvm-readelf --dynamic-table %t10 2>&1 | \
+# RUN:   FileCheck %s -DFILE=%t10 --implicit-check-not=warning: --check-prefixes=OUT-OF-ORDER,OUT-OF-ORDER-GNU
+
+# OUT-OF-ORDER:           warning: '[[FILE]]': unable to parse DT_STRTAB: unable to map address 0x1000 to a segment: loadable segments must be in ascending address order
+
+# OUT-OF-ORDER-LLVM:      DynamicSection [ (2 entries)
+# OUT-OF-ORDER-LLVM-NEXT:   Tag                Type   Name/Value
+# OUT-OF-ORDER-LLVM-NEXT:   0x0000000000000005 STRTAB 0x1000
+# OUT-OF-ORDER-LLVM-NEXT:   0x0000000000000000 NULL   0x0
+# OUT-OF-ORDER-LLVM-NEXT: ]
+
+# OUT-OF-ORDER-GNU:       Dynamic section at offset 0xe9 contains 2 entries:
+# OUT-OF-ORDER-GNU-NEXT:   Tag                Type     Name/Value
+# OUT-OF-ORDER-GNU-NEXT:   0x0000000000000005 (STRTAB) 0x1000
+# OUT-OF-ORDER-GNU-NEXT:   0x0000000000000000 (NULL)   0x0
+
+--- !ELF
+FileHeader:
+  Class: ELFCLASS64
+  Data:  ELFDATA2LSB
+  Type:  ET_EXEC
+Sections:
+  - Name:    .dynstr
+    Type:    SHT_STRTAB
+    Address: 0x1000
+  - Name:    .dynamic
+    Type:    SHT_DYNAMIC
+    Address: 0x1010
+    Entries:
+      - Tag:   DT_STRTAB
+        Value: 0x1000
+      - Tag:   DT_NULL
+        Value: 0
+Symbols: []
+ProgramHeaders:
+  - Type:     PT_LOAD
+    VAddr:    0x1010
+    FirstSec: .dynamic
+    LastSec:  .dynamic
+  - Type:     PT_LOAD
+    VAddr:    0x1000
+    FirstSec: .dynstr
+    LastSec:  .dynstr
+  - Type:     PT_DYNAMIC
+    VAddr:    0x1010
+    FirstSec: .dynamic
+    LastSec:  .dynamic
Index: llvm/lib/Object/ELF.cpp
===================================================================
--- llvm/lib/Object/ELF.cpp
+++ llvm/lib/Object/ELF.cpp
@@ -577,6 +577,14 @@
     if (Phdr.p_type == ELF::PT_LOAD)
       LoadSegments.push_back(const_cast<Elf_Phdr *>(&Phdr));
 
+  if (!llvm::is_sorted(LoadSegments, [](const Elf_Phdr_Impl<ELFT> *A,
+                                        const Elf_Phdr_Impl<ELFT> *B) {
+        return A->p_vaddr < B->p_vaddr;
+      }))
+    return createError(
+        "unable to map address 0x" + Twine::utohexstr(VAddr) +
+        " to a segment: loadable segments must be in ascending address order");
+
   const Elf_Phdr *const *I =
       std::upper_bound(LoadSegments.begin(), LoadSegments.end(), VAddr,
                        [](uint64_t VAddr, const Elf_Phdr_Impl<ELFT> *Phdr) {


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