COFF: Set section permissions

[labath]

Summary

This enables us to reason about whether a given address can be
executable, for instance during unwinding.

[labath]

source/Plugins/ObjectFile/PECOFF/ObjectFilePECOFF.cpp

800 ↗

(On Diff #225403)

Are these the right permissions for the header?

[labath]

source/Plugins/ObjectFile/PECOFF/ObjectFilePECOFF.cpp

800 ↗

(On Diff #225403)

I've dug around in some minidumps I have around and this does appear to be correct. It looks like the entire block of memory for the object is first allocated with PAGE_EXECUTE_WRITE_COPY, and the permissions for the header region are later changed to PAGE_READ_ONLY.

[mstorsjo]

source/Plugins/ObjectFile/PECOFF/ObjectFilePECOFF.cpp

800 ↗

(On Diff #225403)

I haven't checked, but I certainly would expect it to be readonly.

[mstorsjo]

source/Plugins/ObjectFile/PECOFF/ObjectFilePECOFF.cpp

800 ↗

(On Diff #225403)

I wrote the last comment before seeing the preceding update, which is why it seems odd here.

lldb/source/Plugins/ObjectFile/PECOFF/ObjectFilePECOFF.cpp

if (module_sp) {
 
     SectionSP header_sp = std::make_shared<Section>(
         module_sp, this, ~user_id_t(0), ConstString("PECOFF header"),
         eSectionTypeOther, m_coff_header_opt.image_base,
         m_coff_header_opt.header_size,
         /*file_offset*/ 0, m_coff_header_opt.header_size,
         m_coff_header_opt.sect_alignment,
         /*flags*/ 0);
+    header_sp->SetPermissions(ePermissionsReadable);
     m_sections_up->AddSection(header_sp);
     unified_section_list.AddSection(header_sp);
 
     const uint32_t nsects = m_sect_headers.size();
     ModuleSP module_sp(GetModule());
     for (uint32_t idx = 0; idx < nsects; ++idx) {
       ConstString const_sect_name(GetSectionName(m_sect_headers[idx]));
       static ConstString g_code_sect_name(".code");
for (uint32_t idx = 0; idx < nsects; ++idx) {
           m_sect_headers[idx].vmsize,     // VM size in bytes of this section
           m_sect_headers[idx]
               .offset, // Offset to the data for this section in the file
           m_sect_headers[idx]
               .size, // Size in bytes of this section as found in the file
           m_coff_header_opt.sect_alignment, // Section alignment
           m_sect_headers[idx].flags));      // Flags for this section
 
+      uint32_t permissions = 0;
+      if (m_sect_headers[idx].flags & llvm::COFF::IMAGE_SCN_MEM_EXECUTE)
+        permissions |= ePermissionsExecutable;
+      if (m_sect_headers[idx].flags & llvm::COFF::IMAGE_SCN_MEM_READ)
+        permissions |= ePermissionsReadable;
+      if (m_sect_headers[idx].flags & llvm::COFF::IMAGE_SCN_MEM_WRITE)
+        permissions |= ePermissionsWritable;
+      section_sp->SetPermissions(permissions);
+
       m_sections_up->AddSection(section_sp);
       unified_section_list.AddSection(section_sp);
     }
   }
 }
 
 UUID ObjectFilePECOFF::GetUUID() {
   if (m_uuid.IsValid())

lldb/test/Shell/ObjectFile/PECOFF/sections.yaml

 # RUN: yaml2obj %s > %t
 # RUN: lldb-test object-file %t | FileCheck %s
 
 
 # CHECK:      Showing 3 sections
 # CHECK-NEXT:   Index: 0
 # CHECK-NEXT:   ID: 0xffffffffffffffff
 # CHECK-NEXT:   Name: PECOFF header
 # CHECK-NEXT:   Type: regular
-# CHECK-NEXT:   Permissions: ---
+# CHECK-NEXT:   Permissions: r--
 # CHECK-NEXT:   Thread specific: no
 # CHECK-NEXT:   VM address: 0x40000000
 # CHECK-NEXT:   VM size: 512
 # CHECK-NEXT:   File size: 512
 # CHECK-EMPTY: 
 # CHECK-NEXT:   Index: 1
 # CHECK-NEXT:   ID: 0x1
 # CHECK-NEXT:   Name: .text
 # CHECK-NEXT:   Type: code
-# CHECK-NEXT:   Permissions: ---
+# CHECK-NEXT:   Permissions: r-x
 # CHECK-NEXT:   Thread specific: no
 # CHECK-NEXT:   VM address: 0x40001000
 # CHECK-NEXT:   VM size: 64
 # CHECK-NEXT:   File size: 512
 # CHECK-EMPTY:
 # CHECK-NEXT:   Index: 2
 # CHECK-NEXT:   ID: 0x2
 # CHECK-NEXT:   Name: .data
 # CHECK-NEXT:   Type: data
-# CHECK-NEXT:   Permissions: ---
+# CHECK-NEXT:   Permissions: r--
 # CHECK-NEXT:   Thread specific: no
 # CHECK-NEXT:   VM address: 0x40002000
 # CHECK-NEXT:   VM size: 64
 # CHECK-NEXT:   File size: 512
 
 
 --- !COFF
 OptionalHeader: