[Lldb-commits] [lldb] e9fe788 - Target::ReadMemory read from read-only binary file Section, not memory

Jason Molenda via lldb-commits lldb-commits at lists.llvm.org
Fri Apr 16 16:13:15 PDT 2021


Author: Jason Molenda
Date: 2021-04-16T16:13:07-07:00
New Revision: e9fe788d326090cb6155c0dec90b44c932273dd3

URL: https://github.com/llvm/llvm-project/commit/e9fe788d326090cb6155c0dec90b44c932273dd3
DIFF: https://github.com/llvm/llvm-project/commit/e9fe788d326090cb6155c0dec90b44c932273dd3.diff

LOG: Target::ReadMemory read from read-only binary file Section, not memory

Commiting this patch for Augusto Noronha who is getting set
up still.

This patch changes Target::ReadMemory so the default behavior
when a read is in a Section that is read-only is to fetch the
data from the local binary image, instead of reading it from
memory.  Update all callers to use their old preferences
(the old prefer_file_cache bool) using the new API; we should
revisit these calls and see if they really intend to read
live memory, or if reading from a read-only Section would be
equivalent and important for performance-sensitive cases.

rdar://30634422

Differential revision: https://reviews.llvm.org/D100338

Added: 
    

Modified: 
    lldb/include/lldb/Core/Disassembler.h
    lldb/include/lldb/Symbol/Function.h
    lldb/include/lldb/Target/Target.h
    lldb/source/API/SBFunction.cpp
    lldb/source/API/SBSymbol.cpp
    lldb/source/API/SBTarget.cpp
    lldb/source/Commands/CommandObjectMemory.cpp
    lldb/source/Core/Address.cpp
    lldb/source/Core/Disassembler.cpp
    lldb/source/Core/IOHandlerCursesGUI.cpp
    lldb/source/Core/Value.cpp
    lldb/source/Core/ValueObject.cpp
    lldb/source/Expression/IRMemoryMap.cpp
    lldb/source/Plugins/Architecture/Mips/ArchitectureMips.cpp
    lldb/source/Plugins/DynamicLoader/Darwin-Kernel/DynamicLoaderDarwinKernel.cpp
    lldb/source/Plugins/DynamicLoader/MacOSX-DYLD/DynamicLoaderDarwin.cpp
    lldb/source/Plugins/DynamicLoader/Windows-DYLD/DynamicLoaderWindowsDYLD.cpp
    lldb/source/Plugins/Instruction/MIPS/EmulateInstructionMIPS.cpp
    lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp
    lldb/source/Plugins/UnwindAssembly/InstEmulation/UnwindAssemblyInstEmulation.cpp
    lldb/source/Plugins/UnwindAssembly/x86/UnwindAssembly-x86.cpp
    lldb/source/Symbol/Function.cpp
    lldb/source/Symbol/Symbol.cpp
    lldb/source/Target/Process.cpp
    lldb/source/Target/StackFrame.cpp
    lldb/source/Target/Target.cpp
    lldb/source/Target/ThreadPlanStepRange.cpp
    lldb/source/Target/Trace.cpp

Removed: 
    


################################################################################
diff  --git a/lldb/include/lldb/Core/Disassembler.h b/lldb/include/lldb/Core/Disassembler.h
index 9a694de0f60a0..0a76f0a12b9d2 100644
--- a/lldb/include/lldb/Core/Disassembler.h
+++ b/lldb/include/lldb/Core/Disassembler.h
@@ -394,10 +394,12 @@ class Disassembler : public std::enable_shared_from_this<Disassembler>,
     lldb::addr_t value;
   };
 
-  static lldb::DisassemblerSP
-  DisassembleRange(const ArchSpec &arch, const char *plugin_name,
-                   const char *flavor, Target &target,
-                   const AddressRange &disasm_range, bool prefer_file_cache);
+  static lldb::DisassemblerSP DisassembleRange(const ArchSpec &arch,
+                                               const char *plugin_name,
+                                               const char *flavor,
+                                               Target &target,
+                                               const AddressRange &disasm_range,
+                                               bool force_live_memory = false);
 
   static lldb::DisassemblerSP
   DisassembleBytes(const ArchSpec &arch, const char *plugin_name,
@@ -426,7 +428,8 @@ class Disassembler : public std::enable_shared_from_this<Disassembler>,
                          Stream &strm);
 
   size_t ParseInstructions(Target &target, Address address, Limit limit,
-                           Stream *error_strm_ptr, bool prefer_file_cache);
+                           Stream *error_strm_ptr,
+                           bool force_live_memory = false);
 
   virtual size_t DecodeInstructions(const Address &base_addr,
                                     const DataExtractor &data,

diff  --git a/lldb/include/lldb/Symbol/Function.h b/lldb/include/lldb/Symbol/Function.h
index 300d829219d4d..aae5b4a496c2c 100644
--- a/lldb/include/lldb/Symbol/Function.h
+++ b/lldb/include/lldb/Symbol/Function.h
@@ -631,10 +631,10 @@ class Function : public UserID, public SymbolContextScope {
 
   lldb::DisassemblerSP GetInstructions(const ExecutionContext &exe_ctx,
                                        const char *flavor,
-                                       bool prefer_file_cache);
+                                       bool force_live_memory = false);
 
   bool GetDisassembly(const ExecutionContext &exe_ctx, const char *flavor,
-                      bool prefer_file_cache, Stream &strm);
+                      Stream &strm, bool force_live_memory = false);
 
 protected:
   enum {

diff  --git a/lldb/include/lldb/Target/Target.h b/lldb/include/lldb/Target/Target.h
index 0c2131a60b4bb..219213312f644 100644
--- a/lldb/include/lldb/Target/Target.h
+++ b/lldb/include/lldb/Target/Target.h
@@ -1005,11 +1005,12 @@ class Target : public std::enable_shared_from_this<Target>,
   // read from const sections in object files, read from the target. This
   // version of ReadMemory will try and read memory from the process if the
   // process is alive. The order is:
-  // 1 - if (prefer_file_cache == true) then read from object file cache
-  // 2 - if there is a valid process, try and read from its memory
-  // 3 - if (prefer_file_cache == false) then read from object file cache
-  size_t ReadMemory(const Address &addr, bool prefer_file_cache, void *dst,
-                    size_t dst_len, Status &error,
+  // 1 - if (force_live_memory == false) and the address falls in a read-only
+  // section, then read from the file cache
+  // 2 - if there is a process, then read from memory
+  // 3 - if there is no process, then read from the file cache
+  size_t ReadMemory(const Address &addr, void *dst, size_t dst_len,
+                    Status &error, bool force_live_memory = false,
                     lldb::addr_t *load_addr_ptr = nullptr);
 
   size_t ReadCStringFromMemory(const Address &addr, std::string &out_str,
@@ -1018,18 +1019,19 @@ class Target : public std::enable_shared_from_this<Target>,
   size_t ReadCStringFromMemory(const Address &addr, char *dst,
                                size_t dst_max_len, Status &result_error);
 
-  size_t ReadScalarIntegerFromMemory(const Address &addr,
-                                     bool prefer_file_cache, uint32_t byte_size,
+  size_t ReadScalarIntegerFromMemory(const Address &addr, uint32_t byte_size,
                                      bool is_signed, Scalar &scalar,
-                                     Status &error);
+                                     Status &error,
+                                     bool force_live_memory = false);
 
   uint64_t ReadUnsignedIntegerFromMemory(const Address &addr,
-                                         bool prefer_file_cache,
                                          size_t integer_byte_size,
-                                         uint64_t fail_value, Status &error);
+                                         uint64_t fail_value, Status &error,
+                                         bool force_live_memory = false);
 
-  bool ReadPointerFromMemory(const Address &addr, bool prefer_file_cache,
-                             Status &error, Address &pointer_addr);
+  bool ReadPointerFromMemory(const Address &addr, Status &error,
+                             Address &pointer_addr,
+                             bool force_live_memory = false);
 
   SectionLoadList &GetSectionLoadList() {
     return m_section_load_history.GetCurrentSectionLoadList();

diff  --git a/lldb/source/API/SBFunction.cpp b/lldb/source/API/SBFunction.cpp
index 9f3cf817fc8c3..7d81716347525 100644
--- a/lldb/source/API/SBFunction.cpp
+++ b/lldb/source/API/SBFunction.cpp
@@ -132,10 +132,10 @@ SBInstructionList SBFunction::GetInstructions(SBTarget target,
         m_opaque_ptr->GetAddressRange().GetBaseAddress().GetModule());
     if (target_sp && module_sp) {
       lock = std::unique_lock<std::recursive_mutex>(target_sp->GetAPIMutex());
-      const bool prefer_file_cache = false;
+      const bool force_live_memory = true;
       sb_instructions.SetDisassembler(Disassembler::DisassembleRange(
           module_sp->GetArchitecture(), nullptr, flavor, *target_sp,
-          m_opaque_ptr->GetAddressRange(), prefer_file_cache));
+          m_opaque_ptr->GetAddressRange(), force_live_memory));
     }
   }
   return LLDB_RECORD_RESULT(sb_instructions);

diff  --git a/lldb/source/API/SBSymbol.cpp b/lldb/source/API/SBSymbol.cpp
index eafc3e630bcd5..7b9c90032e1a8 100644
--- a/lldb/source/API/SBSymbol.cpp
+++ b/lldb/source/API/SBSymbol.cpp
@@ -132,10 +132,10 @@ SBInstructionList SBSymbol::GetInstructions(SBTarget target,
       ModuleSP module_sp = symbol_addr.GetModule();
       if (module_sp) {
         AddressRange symbol_range(symbol_addr, m_opaque_ptr->GetByteSize());
-        const bool prefer_file_cache = false;
+        const bool force_live_memory = true;
         sb_instructions.SetDisassembler(Disassembler::DisassembleRange(
             module_sp->GetArchitecture(), nullptr, flavor_string, *target_sp,
-            symbol_range, prefer_file_cache));
+            symbol_range, force_live_memory));
       }
     }
   }

diff  --git a/lldb/source/API/SBTarget.cpp b/lldb/source/API/SBTarget.cpp
index ad1ef6910701f..b0b12dc73d88e 100644
--- a/lldb/source/API/SBTarget.cpp
+++ b/lldb/source/API/SBTarget.cpp
@@ -705,7 +705,7 @@ size_t SBTarget::ReadMemory(const SBAddress addr, void *buf, size_t size,
   if (target_sp) {
     std::lock_guard<std::recursive_mutex> guard(target_sp->GetAPIMutex());
     bytes_read =
-        target_sp->ReadMemory(addr.ref(), false, buf, size, sb_error.ref());
+        target_sp->ReadMemory(addr.ref(), buf, size, sb_error.ref(), true);
   } else {
     sb_error.SetErrorString("invalid target");
   }
@@ -2085,12 +2085,12 @@ lldb::SBInstructionList SBTarget::ReadInstructions(lldb::SBAddress base_addr,
     if (addr_ptr) {
       DataBufferHeap data(
           target_sp->GetArchitecture().GetMaximumOpcodeByteSize() * count, 0);
-      bool prefer_file_cache = false;
+      bool force_live_memory = true;
       lldb_private::Status error;
       lldb::addr_t load_addr = LLDB_INVALID_ADDRESS;
       const size_t bytes_read =
-          target_sp->ReadMemory(*addr_ptr, prefer_file_cache, data.GetBytes(),
-                                data.GetByteSize(), error, &load_addr);
+          target_sp->ReadMemory(*addr_ptr, data.GetBytes(), data.GetByteSize(),
+                                error, force_live_memory, &load_addr);
       const bool data_from_file = load_addr == LLDB_INVALID_ADDRESS;
       sb_instructions.SetDisassembler(Disassembler::DisassembleBytes(
           target_sp->GetArchitecture(), nullptr, flavor_string, *addr_ptr,

diff  --git a/lldb/source/Commands/CommandObjectMemory.cpp b/lldb/source/Commands/CommandObjectMemory.cpp
index a2201c4d8bd95..19c13c089503d 100644
--- a/lldb/source/Commands/CommandObjectMemory.cpp
+++ b/lldb/source/Commands/CommandObjectMemory.cpp
@@ -669,8 +669,8 @@ class CommandObjectMemoryRead : public CommandObjectParsed {
       }
 
       Address address(addr, nullptr);
-      bytes_read = target->ReadMemory(address, false, data_sp->GetBytes(),
-                                      data_sp->GetByteSize(), error);
+      bytes_read = target->ReadMemory(address, data_sp->GetBytes(),
+                                      data_sp->GetByteSize(), error, true);
       if (bytes_read == 0) {
         const char *error_cstr = error.AsCString();
         if (error_cstr && error_cstr[0]) {

diff  --git a/lldb/source/Core/Address.cpp b/lldb/source/Core/Address.cpp
index 9d52f1db89186..24bb8417b69b4 100644
--- a/lldb/source/Core/Address.cpp
+++ b/lldb/source/Core/Address.cpp
@@ -65,9 +65,9 @@ static size_t ReadBytes(ExecutionContextScope *exe_scope,
   TargetSP target_sp(exe_scope->CalculateTarget());
   if (target_sp) {
     Status error;
-    bool prefer_file_cache = false;
-    return target_sp->ReadMemory(address, prefer_file_cache, dst, dst_len,
-                                 error);
+    bool force_live_memory = true;
+    return target_sp->ReadMemory(address, dst, dst_len, error,
+                                 force_live_memory);
   }
   return 0;
 }

diff  --git a/lldb/source/Core/Disassembler.cpp b/lldb/source/Core/Disassembler.cpp
index 3a975d9296f47..60c41e1d00ed9 100644
--- a/lldb/source/Core/Disassembler.cpp
+++ b/lldb/source/Core/Disassembler.cpp
@@ -122,7 +122,7 @@ static Address ResolveAddress(Target &target, const Address &addr) {
 
 lldb::DisassemblerSP Disassembler::DisassembleRange(
     const ArchSpec &arch, const char *plugin_name, const char *flavor,
-    Target &target, const AddressRange &range, bool prefer_file_cache) {
+    Target &target, const AddressRange &range, bool force_live_memory) {
   if (range.GetByteSize() <= 0)
     return {};
 
@@ -137,7 +137,7 @@ lldb::DisassemblerSP Disassembler::DisassembleRange(
 
   const size_t bytes_disassembled = disasm_sp->ParseInstructions(
       target, range.GetBaseAddress(), {Limit::Bytes, range.GetByteSize()},
-      nullptr, prefer_file_cache);
+      nullptr, force_live_memory);
   if (bytes_disassembled == 0)
     return {};
 
@@ -181,9 +181,9 @@ bool Disassembler::Disassemble(Debugger &debugger, const ArchSpec &arch,
   if (!disasm_sp)
     return false;
 
-  const bool prefer_file_cache = false;
+  const bool force_live_memory = true;
   size_t bytes_disassembled = disasm_sp->ParseInstructions(
-      exe_ctx.GetTargetRef(), address, limit, &strm, prefer_file_cache);
+      exe_ctx.GetTargetRef(), address, limit, &strm, force_live_memory);
   if (bytes_disassembled == 0)
     return false;
 
@@ -1036,7 +1036,7 @@ InstructionList::GetIndexOfInstructionAtLoadAddress(lldb::addr_t load_addr,
 
 size_t Disassembler::ParseInstructions(Target &target, Address start,
                                        Limit limit, Stream *error_strm_ptr,
-                                       bool prefer_file_cache) {
+                                       bool force_live_memory) {
   m_instruction_list.Clear();
 
   if (!start.IsValid())
@@ -1052,8 +1052,8 @@ size_t Disassembler::ParseInstructions(Target &target, Address start,
   Status error;
   lldb::addr_t load_addr = LLDB_INVALID_ADDRESS;
   const size_t bytes_read =
-      target.ReadMemory(start, prefer_file_cache, data_sp->GetBytes(),
-                        data_sp->GetByteSize(), error, &load_addr);
+      target.ReadMemory(start, data_sp->GetBytes(), data_sp->GetByteSize(),
+                        error, force_live_memory, &load_addr);
   const bool data_from_file = load_addr == LLDB_INVALID_ADDRESS;
 
   if (bytes_read == 0) {

diff  --git a/lldb/source/Core/IOHandlerCursesGUI.cpp b/lldb/source/Core/IOHandlerCursesGUI.cpp
index a1c9daa79be78..1de83d896bf3b 100644
--- a/lldb/source/Core/IOHandlerCursesGUI.cpp
+++ b/lldb/source/Core/IOHandlerCursesGUI.cpp
@@ -3550,7 +3550,7 @@ class SourceFileWindowDelegate : public WindowDelegate {
             if (m_disassembly_scope != m_sc.function) {
               m_disassembly_scope = m_sc.function;
               m_disassembly_sp = m_sc.function->GetInstructions(
-                  exe_ctx, nullptr, prefer_file_cache);
+                  exe_ctx, nullptr, !prefer_file_cache);
               if (m_disassembly_sp) {
                 set_selected_line_to_pc = true;
                 m_disassembly_range = m_sc.function->GetAddressRange();

diff  --git a/lldb/source/Core/Value.cpp b/lldb/source/Core/Value.cpp
index 7b52ff9e4207c..b5af03c0d001c 100644
--- a/lldb/source/Core/Value.cpp
+++ b/lldb/source/Core/Value.cpp
@@ -525,15 +525,10 @@ Status Value::GetValueAsData(ExecutionContext *exe_ctx, DataExtractor &data,
     } else if ((address_type == eAddressTypeLoad) ||
                (address_type == eAddressTypeFile)) {
       if (file_so_addr.IsValid()) {
-        // We have a file address that we were able to translate into a section
-        // offset address so we might be able to read this from the object
-        // files if we don't have a live process. Lets always try and read from
-        // the process if we have one though since we want to read the actual
-        // value by setting "prefer_file_cache" to false.
-        const bool prefer_file_cache = false;
-        if (exe_ctx->GetTargetRef().ReadMemory(file_so_addr, prefer_file_cache,
-                                               dst, byte_size,
-                                               error) != byte_size) {
+        const bool force_live_memory = true;
+        if (exe_ctx->GetTargetRef().ReadMemory(file_so_addr, dst, byte_size,
+                                               error, force_live_memory) !=
+            byte_size) {
           error.SetErrorStringWithFormat(
               "read memory from 0x%" PRIx64 " failed", (uint64_t)address);
         }

diff  --git a/lldb/source/Core/ValueObject.cpp b/lldb/source/Core/ValueObject.cpp
index 1988155a16acc..55fc5ff641729 100644
--- a/lldb/source/Core/ValueObject.cpp
+++ b/lldb/source/Core/ValueObject.cpp
@@ -721,7 +721,7 @@ size_t ValueObject::GetPointeeData(DataExtractor &data, uint32_t item_idx,
         if (target) {
           heap_buf_ptr->SetByteSize(bytes);
           size_t bytes_read = target->ReadMemory(
-              so_addr, false, heap_buf_ptr->GetBytes(), bytes, error);
+              so_addr, heap_buf_ptr->GetBytes(), bytes, error, true);
           if (error.Success()) {
             data.SetData(data_sp);
             return bytes_read;

diff  --git a/lldb/source/Expression/IRMemoryMap.cpp b/lldb/source/Expression/IRMemoryMap.cpp
index 6b1e4c313a391..4ae2724d4dd8c 100644
--- a/lldb/source/Expression/IRMemoryMap.cpp
+++ b/lldb/source/Expression/IRMemoryMap.cpp
@@ -639,7 +639,7 @@ void IRMemoryMap::ReadMemory(uint8_t *bytes, lldb::addr_t process_address,
 
     if (target_sp) {
       Address absolute_address(process_address);
-      target_sp->ReadMemory(absolute_address, false, bytes, size, error);
+      target_sp->ReadMemory(absolute_address, bytes, size, error, true);
       return;
     }
 

diff  --git a/lldb/source/Plugins/Architecture/Mips/ArchitectureMips.cpp b/lldb/source/Plugins/Architecture/Mips/ArchitectureMips.cpp
index 22508969ceed1..757c915700094 100644
--- a/lldb/source/Plugins/Architecture/Mips/ArchitectureMips.cpp
+++ b/lldb/source/Plugins/Architecture/Mips/ArchitectureMips.cpp
@@ -160,7 +160,6 @@ Instruction *ArchitectureMips::GetInstructionAtAddress(
 
   InstructionList instruction_list;
   InstructionSP prev_insn;
-  bool prefer_file_cache = true; // Read from file
   uint32_t inst_to_choose = 0;
 
   Address addr = resolved_addr;
@@ -171,8 +170,7 @@ Instruction *ArchitectureMips::GetInstructionAtAddress(
     uint32_t insn_size = 0;
 
     disasm_sp->ParseInstructions(target, addr,
-                                 {Disassembler::Limit::Bytes, i * 2}, nullptr,
-                                 prefer_file_cache);
+                                 {Disassembler::Limit::Bytes, i * 2}, nullptr);
 
     uint32_t num_insns = disasm_sp->GetInstructionList().GetSize();
     if (num_insns) {

diff  --git a/lldb/source/Plugins/DynamicLoader/Darwin-Kernel/DynamicLoaderDarwinKernel.cpp b/lldb/source/Plugins/DynamicLoader/Darwin-Kernel/DynamicLoaderDarwinKernel.cpp
index fd1916d296d5c..575a882697e07 100644
--- a/lldb/source/Plugins/DynamicLoader/Darwin-Kernel/DynamicLoaderDarwinKernel.cpp
+++ b/lldb/source/Plugins/DynamicLoader/Darwin-Kernel/DynamicLoaderDarwinKernel.cpp
@@ -1093,16 +1093,16 @@ bool DynamicLoaderDarwinKernel::ReadKextSummaryHeader() {
     uint8_t buf[24];
     DataExtractor data(buf, sizeof(buf), byte_order, addr_size);
     const size_t count = 4 * sizeof(uint32_t) + addr_size;
-    const bool prefer_file_cache = false;
+    const bool force_live_memory = true;
     if (m_process->GetTarget().ReadPointerFromMemory(
-            m_kext_summary_header_ptr_addr, prefer_file_cache, error,
-            m_kext_summary_header_addr)) {
+            m_kext_summary_header_ptr_addr, error,
+            m_kext_summary_header_addr, force_live_memory)) {
       // We got a valid address for our kext summary header and make sure it
       // isn't NULL
       if (m_kext_summary_header_addr.IsValid() &&
           m_kext_summary_header_addr.GetFileAddress() != 0) {
         const size_t bytes_read = m_process->GetTarget().ReadMemory(
-            m_kext_summary_header_addr, prefer_file_cache, buf, count, error);
+            m_kext_summary_header_addr, buf, count, error, force_live_memory);
         if (bytes_read == count) {
           lldb::offset_t offset = 0;
           m_kext_summary_header.version = data.GetU32(&offset);
@@ -1373,10 +1373,9 @@ uint32_t DynamicLoaderDarwinKernel::ReadKextSummaries(
   DataBufferHeap data(count, 0);
   Status error;
 
-  const bool prefer_file_cache = false;
+  const bool force_live_memory = true;
   const size_t bytes_read = m_process->GetTarget().ReadMemory(
-      kext_summary_addr, prefer_file_cache, data.GetBytes(), data.GetByteSize(),
-      error);
+      kext_summary_addr, data.GetBytes(), data.GetByteSize(), error, force_live_memory);
   if (bytes_read == count) {
 
     DataExtractor extractor(data.GetBytes(), data.GetByteSize(), endian,

diff  --git a/lldb/source/Plugins/DynamicLoader/MacOSX-DYLD/DynamicLoaderDarwin.cpp b/lldb/source/Plugins/DynamicLoader/MacOSX-DYLD/DynamicLoaderDarwin.cpp
index ddf6f1212a3e3..ac43112606002 100644
--- a/lldb/source/Plugins/DynamicLoader/MacOSX-DYLD/DynamicLoaderDarwin.cpp
+++ b/lldb/source/Plugins/DynamicLoader/MacOSX-DYLD/DynamicLoaderDarwin.cpp
@@ -1086,7 +1086,7 @@ DynamicLoaderDarwin::GetThreadLocalData(const lldb::ModuleSP module_sp,
     Status error;
     const size_t tsl_data_size = addr_size * 3;
     Target &target = m_process->GetTarget();
-    if (target.ReadMemory(tls_addr, false, buf, tsl_data_size, error) ==
+    if (target.ReadMemory(tls_addr, buf, tsl_data_size, error, true) ==
         tsl_data_size) {
       const ByteOrder byte_order = m_process->GetByteOrder();
       DataExtractor data(buf, sizeof(buf), byte_order, addr_size);

diff  --git a/lldb/source/Plugins/DynamicLoader/Windows-DYLD/DynamicLoaderWindowsDYLD.cpp b/lldb/source/Plugins/DynamicLoader/Windows-DYLD/DynamicLoaderWindowsDYLD.cpp
index 7f9504b9b3a92..f0a01ed4ba6e6 100644
--- a/lldb/source/Plugins/DynamicLoader/Windows-DYLD/DynamicLoaderWindowsDYLD.cpp
+++ b/lldb/source/Plugins/DynamicLoader/Windows-DYLD/DynamicLoaderWindowsDYLD.cpp
@@ -193,7 +193,7 @@ DynamicLoaderWindowsDYLD::GetStepThroughTrampolinePlan(Thread &thread,
   AddressRange range(pc, 2 * 15);
 
   DisassemblerSP disassembler_sp = Disassembler::DisassembleRange(
-      arch, nullptr, nullptr, m_process->GetTarget(), range, true);
+      arch, nullptr, nullptr, m_process->GetTarget(), range);
   if (!disassembler_sp) {
     return ThreadPlanSP();
   }

diff  --git a/lldb/source/Plugins/Instruction/MIPS/EmulateInstructionMIPS.cpp b/lldb/source/Plugins/Instruction/MIPS/EmulateInstructionMIPS.cpp
index d4cb726fc7e53..c0ec431584542 100644
--- a/lldb/source/Plugins/Instruction/MIPS/EmulateInstructionMIPS.cpp
+++ b/lldb/source/Plugins/Instruction/MIPS/EmulateInstructionMIPS.cpp
@@ -1018,8 +1018,9 @@ bool EmulateInstructionMIPS::SetInstruction(const Opcode &insn_opcode,
 
       const size_t bytes_read =
           target->ReadMemory(next_addr, /* Address of next instruction */
-                             true,      /* prefer_file_cache */
-                             buf, sizeof(uint32_t), error, &load_addr);
+                             buf, sizeof(uint32_t), error, 
+                             false,  /* force_live_memory */
+                             &load_addr);
 
       if (bytes_read == 0)
         return true;

diff  --git a/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp b/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp
index ae432ac89eaac..f30ed427f8535 100644
--- a/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp
+++ b/lldb/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp
@@ -859,8 +859,7 @@ Address ObjectFileELF::GetImageInfoAddress(Target *target) {
       if (symbol.d_tag == DT_MIPS_RLD_MAP) {
         // DT_MIPS_RLD_MAP tag stores an absolute address of the debug pointer.
         Address addr;
-        if (target->ReadPointerFromMemory(dyn_base + offset, false, error,
-                                          addr))
+        if (target->ReadPointerFromMemory(dyn_base + offset, error, addr, true))
           return addr;
       }
       if (symbol.d_tag == DT_MIPS_RLD_MAP_REL) {
@@ -868,7 +867,7 @@ Address ObjectFileELF::GetImageInfoAddress(Target *target) {
         // relative to the address of the tag.
         uint64_t rel_offset;
         rel_offset = target->ReadUnsignedIntegerFromMemory(
-            dyn_base + offset, false, GetAddressByteSize(), UINT64_MAX, error);
+            dyn_base + offset, GetAddressByteSize(), UINT64_MAX, error, true);
         if (error.Success() && rel_offset != UINT64_MAX) {
           Address addr;
           addr_t debug_ptr_address =

diff  --git a/lldb/source/Plugins/UnwindAssembly/InstEmulation/UnwindAssemblyInstEmulation.cpp b/lldb/source/Plugins/UnwindAssembly/InstEmulation/UnwindAssemblyInstEmulation.cpp
index 1bc071c2b161c..65947c5f833ba 100644
--- a/lldb/source/Plugins/UnwindAssembly/InstEmulation/UnwindAssemblyInstEmulation.cpp
+++ b/lldb/source/Plugins/UnwindAssembly/InstEmulation/UnwindAssemblyInstEmulation.cpp
@@ -38,10 +38,10 @@ bool UnwindAssemblyInstEmulation::GetNonCallSiteUnwindPlanFromAssembly(
   ProcessSP process_sp(thread.GetProcess());
   if (process_sp) {
     Status error;
-    const bool prefer_file_cache = true;
+    const bool force_live_memory = true;
     if (process_sp->GetTarget().ReadMemory(
-            range.GetBaseAddress(), prefer_file_cache, function_text.data(),
-            range.GetByteSize(), error) != range.GetByteSize()) {
+            range.GetBaseAddress(), function_text.data(), range.GetByteSize(),
+            error, force_live_memory) != range.GetByteSize()) {
       return false;
     }
   }

diff  --git a/lldb/source/Plugins/UnwindAssembly/x86/UnwindAssembly-x86.cpp b/lldb/source/Plugins/UnwindAssembly/x86/UnwindAssembly-x86.cpp
index fe1275d5b0cf6..402a70cd025fa 100644
--- a/lldb/source/Plugins/UnwindAssembly/x86/UnwindAssembly-x86.cpp
+++ b/lldb/source/Plugins/UnwindAssembly/x86/UnwindAssembly-x86.cpp
@@ -51,12 +51,11 @@ bool UnwindAssembly_x86::GetNonCallSiteUnwindPlanFromAssembly(
   ProcessSP process_sp(thread.GetProcess());
   if (process_sp.get() == nullptr)
     return false;
-  const bool prefer_file_cache = true;
   std::vector<uint8_t> function_text(func.GetByteSize());
   Status error;
   if (process_sp->GetTarget().ReadMemory(
-          func.GetBaseAddress(), prefer_file_cache, function_text.data(),
-          func.GetByteSize(), error) == func.GetByteSize()) {
+          func.GetBaseAddress(), function_text.data(), func.GetByteSize(),
+          error) == func.GetByteSize()) {
     RegisterContextSP reg_ctx(thread.GetRegisterContext());
     m_assembly_inspection_engine->Initialize(reg_ctx);
     return m_assembly_inspection_engine->GetNonCallSiteUnwindPlanFromAssembly(
@@ -153,12 +152,11 @@ bool UnwindAssembly_x86::AugmentUnwindPlanFromCallSite(
       return false;
     if (m_assembly_inspection_engine == nullptr)
       return false;
-    const bool prefer_file_cache = true;
     std::vector<uint8_t> function_text(func.GetByteSize());
     Status error;
     if (process_sp->GetTarget().ReadMemory(
-            func.GetBaseAddress(), prefer_file_cache, function_text.data(),
-            func.GetByteSize(), error) == func.GetByteSize()) {
+            func.GetBaseAddress(), function_text.data(), func.GetByteSize(),
+            error) == func.GetByteSize()) {
       RegisterContextSP reg_ctx(thread.GetRegisterContext());
       m_assembly_inspection_engine->Initialize(reg_ctx);
       return m_assembly_inspection_engine->AugmentUnwindPlanFromCallSite(
@@ -185,10 +183,9 @@ bool UnwindAssembly_x86::GetFastUnwindPlan(AddressRange &func, Thread &thread,
   ProcessSP process_sp = thread.GetProcess();
   if (process_sp) {
     Target &target(process_sp->GetTarget());
-    const bool prefer_file_cache = true;
     Status error;
-    if (target.ReadMemory(func.GetBaseAddress(), prefer_file_cache,
-                          opcode_data.data(), 4, error) == 4) {
+    if (target.ReadMemory(func.GetBaseAddress(), opcode_data.data(), 4,
+                          error) == 4) {
       uint8_t i386_push_mov[] = {0x55, 0x89, 0xe5};
       uint8_t x86_64_push_mov[] = {0x55, 0x48, 0x89, 0xe5};
 
@@ -220,12 +217,10 @@ bool UnwindAssembly_x86::FirstNonPrologueInsn(
   if (m_assembly_inspection_engine == nullptr)
     return false;
 
-  const bool prefer_file_cache = true;
   std::vector<uint8_t> function_text(func.GetByteSize());
   Status error;
-  if (target->ReadMemory(func.GetBaseAddress(), prefer_file_cache,
-                         function_text.data(), func.GetByteSize(),
-                         error) == func.GetByteSize()) {
+  if (target->ReadMemory(func.GetBaseAddress(), function_text.data(),
+                         func.GetByteSize(), error) == func.GetByteSize()) {
     size_t offset;
     if (m_assembly_inspection_engine->FindFirstNonPrologueInstruction(
             function_text.data(), func.GetByteSize(), offset)) {

diff  --git a/lldb/source/Symbol/Function.cpp b/lldb/source/Symbol/Function.cpp
index 67013f6dd8b1d..0aeb7597cfcf9 100644
--- a/lldb/source/Symbol/Function.cpp
+++ b/lldb/source/Symbol/Function.cpp
@@ -426,17 +426,16 @@ lldb::DisassemblerSP Function::GetInstructions(const ExecutionContext &exe_ctx,
                                                bool prefer_file_cache) {
   ModuleSP module_sp(GetAddressRange().GetBaseAddress().GetModule());
   if (module_sp && exe_ctx.HasTargetScope()) {
-    const bool prefer_file_cache = false;
     return Disassembler::DisassembleRange(module_sp->GetArchitecture(), nullptr,
                                           flavor, exe_ctx.GetTargetRef(),
-                                          GetAddressRange(), prefer_file_cache);
+                                          GetAddressRange(), !prefer_file_cache);
   }
   return lldb::DisassemblerSP();
 }
 
 bool Function::GetDisassembly(const ExecutionContext &exe_ctx,
-                              const char *flavor, bool prefer_file_cache,
-                              Stream &strm) {
+                              const char *flavor, Stream &strm,
+                              bool prefer_file_cache) {
   lldb::DisassemblerSP disassembler_sp =
       GetInstructions(exe_ctx, flavor, prefer_file_cache);
   if (disassembler_sp) {

diff  --git a/lldb/source/Symbol/Symbol.cpp b/lldb/source/Symbol/Symbol.cpp
index 8d099e0cc7e1f..e6695c5008ea8 100644
--- a/lldb/source/Symbol/Symbol.cpp
+++ b/lldb/source/Symbol/Symbol.cpp
@@ -542,10 +542,9 @@ lldb::DisassemblerSP Symbol::GetInstructions(const ExecutionContext &exe_ctx,
                                              bool prefer_file_cache) {
   ModuleSP module_sp(m_addr_range.GetBaseAddress().GetModule());
   if (module_sp && exe_ctx.HasTargetScope()) {
-    const bool prefer_file_cache = false;
     return Disassembler::DisassembleRange(module_sp->GetArchitecture(), nullptr,
                                           flavor, exe_ctx.GetTargetRef(),
-                                          m_addr_range, prefer_file_cache);
+                                          m_addr_range, !prefer_file_cache);
   }
   return lldb::DisassemblerSP();
 }

diff  --git a/lldb/source/Target/Process.cpp b/lldb/source/Target/Process.cpp
index 9f39e78e5d726..5af8567733e3d 100644
--- a/lldb/source/Target/Process.cpp
+++ b/lldb/source/Target/Process.cpp
@@ -5810,10 +5810,8 @@ Process::AdvanceAddressToNextBranchInstruction(Address default_stop_addr,
 
   const char *plugin_name = nullptr;
   const char *flavor = nullptr;
-  const bool prefer_file_cache = true;
   disassembler_sp = Disassembler::DisassembleRange(
-      target.GetArchitecture(), plugin_name, flavor, GetTarget(), range_bounds,
-      prefer_file_cache);
+      target.GetArchitecture(), plugin_name, flavor, GetTarget(), range_bounds);
   if (disassembler_sp)
     insn_list = &disassembler_sp->GetInstructionList();
 

diff  --git a/lldb/source/Target/StackFrame.cpp b/lldb/source/Target/StackFrame.cpp
index 5402ba2626b10..cba51d266c5ba 100644
--- a/lldb/source/Target/StackFrame.cpp
+++ b/lldb/source/Target/StackFrame.cpp
@@ -1294,11 +1294,11 @@ lldb::ValueObjectSP StackFrame::GuessValueForAddress(lldb::addr_t addr) {
 
   const char *plugin_name = nullptr;
   const char *flavor = nullptr;
-  const bool prefer_file_cache = false;
+  const bool force_live_memory = true;
 
   DisassemblerSP disassembler_sp =
       Disassembler::DisassembleRange(target_arch, plugin_name, flavor,
-                                     *target_sp, pc_range, prefer_file_cache);
+                                     *target_sp, pc_range, force_live_memory);
 
   if (!disassembler_sp || !disassembler_sp->GetInstructionList().GetSize()) {
     return ValueObjectSP();
@@ -1674,10 +1674,10 @@ lldb::ValueObjectSP StackFrame::GuessValueForRegisterAndOffset(ConstString reg,
 
   const char *plugin_name = nullptr;
   const char *flavor = nullptr;
-  const bool prefer_file_cache = false;
+  const bool force_live_memory = true;
   DisassemblerSP disassembler_sp =
       Disassembler::DisassembleRange(target_arch, plugin_name, flavor,
-                                     *target_sp, pc_range, prefer_file_cache);
+                                     *target_sp, pc_range, force_live_memory);
 
   if (!disassembler_sp || !disassembler_sp->GetInstructionList().GetSize()) {
     return ValueObjectSP();

diff  --git a/lldb/source/Target/Target.cpp b/lldb/source/Target/Target.cpp
index 3aa1d30cb7762..177efa8f8f287 100644
--- a/lldb/source/Target/Target.cpp
+++ b/lldb/source/Target/Target.cpp
@@ -1717,8 +1717,8 @@ size_t Target::ReadMemoryFromFileCache(const Address &addr, void *dst,
   return 0;
 }
 
-size_t Target::ReadMemory(const Address &addr, bool prefer_file_cache,
-                          void *dst, size_t dst_len, Status &error,
+size_t Target::ReadMemory(const Address &addr, void *dst, size_t dst_len,
+                          Status &error, bool force_live_memory,
                           lldb::addr_t *load_addr_ptr) {
   error.Clear();
 
@@ -1753,10 +1753,20 @@ size_t Target::ReadMemory(const Address &addr, bool prefer_file_cache,
   if (!resolved_addr.IsValid())
     resolved_addr = addr;
 
-  if (prefer_file_cache) {
-    bytes_read = ReadMemoryFromFileCache(resolved_addr, dst, dst_len, error);
-    if (bytes_read > 0)
-      return bytes_read;
+  bool is_readonly = false;
+  // Read from file cache if read-only section.
+  if (!force_live_memory && resolved_addr.IsSectionOffset()) {
+    SectionSP section_sp(addr.GetSection());
+    if (section_sp) {
+      auto permissions = Flags(section_sp->GetPermissions());
+      is_readonly = !permissions.Test(ePermissionsWritable) &&
+                    permissions.Test(ePermissionsReadable);
+    }
+    if (is_readonly) {
+      bytes_read = ReadMemoryFromFileCache(resolved_addr, dst, dst_len, error);
+      if (bytes_read > 0)
+        return bytes_read;
+    }
   }
 
   if (ProcessIsValid()) {
@@ -1791,17 +1801,10 @@ size_t Target::ReadMemory(const Address &addr, bool prefer_file_cache,
           *load_addr_ptr = load_addr;
         return bytes_read;
       }
-      // If the address is not section offset we have an address that doesn't
-      // resolve to any address in any currently loaded shared libraries and we
-      // failed to read memory so there isn't anything more we can do. If it is
-      // section offset, we might be able to read cached memory from the object
-      // file.
-      if (!resolved_addr.IsSectionOffset())
-        return 0;
     }
   }
 
-  if (!prefer_file_cache && resolved_addr.IsSectionOffset()) {
+  if (!is_readonly && resolved_addr.IsSectionOffset()) {
     // If we didn't already try and read from the object file cache, then try
     // it after failing to read from the process.
     return ReadMemoryFromFileCache(resolved_addr, dst, dst_len, error);
@@ -1856,7 +1859,7 @@ size_t Target::ReadCStringFromMemory(const Address &addr, char *dst,
       addr_t bytes_to_read =
           std::min<addr_t>(bytes_left, cache_line_bytes_left);
       size_t bytes_read =
-          ReadMemory(address, false, curr_dst, bytes_to_read, error);
+          ReadMemory(address, curr_dst, bytes_to_read, error, true);
 
       if (bytes_read == 0) {
         result_error = error;
@@ -1884,15 +1887,15 @@ size_t Target::ReadCStringFromMemory(const Address &addr, char *dst,
   return total_cstr_len;
 }
 
-size_t Target::ReadScalarIntegerFromMemory(const Address &addr,
-                                           bool prefer_file_cache,
-                                           uint32_t byte_size, bool is_signed,
-                                           Scalar &scalar, Status &error) {
+size_t Target::ReadScalarIntegerFromMemory(const Address &addr, uint32_t byte_size,
+                                           bool is_signed, Scalar &scalar,
+                                           Status &error,
+                                           bool force_live_memory) {
   uint64_t uval;
 
   if (byte_size <= sizeof(uval)) {
     size_t bytes_read =
-        ReadMemory(addr, prefer_file_cache, &uval, byte_size, error);
+        ReadMemory(addr, &uval, byte_size, error, force_live_memory);
     if (bytes_read == byte_size) {
       DataExtractor data(&uval, sizeof(uval), m_arch.GetSpec().GetByteOrder(),
                          m_arch.GetSpec().GetAddressByteSize());
@@ -1914,23 +1917,22 @@ size_t Target::ReadScalarIntegerFromMemory(const Address &addr,
 }
 
 uint64_t Target::ReadUnsignedIntegerFromMemory(const Address &addr,
-                                               bool prefer_file_cache,
                                                size_t integer_byte_size,
-                                               uint64_t fail_value,
-                                               Status &error) {
+                                               uint64_t fail_value, Status &error,
+                                               bool force_live_memory) {
   Scalar scalar;
-  if (ReadScalarIntegerFromMemory(addr, prefer_file_cache, integer_byte_size,
-                                  false, scalar, error))
+  if (ReadScalarIntegerFromMemory(addr, integer_byte_size, false, scalar, error,
+                                  force_live_memory))
     return scalar.ULongLong(fail_value);
   return fail_value;
 }
 
-bool Target::ReadPointerFromMemory(const Address &addr, bool prefer_file_cache,
-                                   Status &error, Address &pointer_addr) {
+bool Target::ReadPointerFromMemory(const Address &addr, Status &error,
+                                   Address &pointer_addr,
+                                   bool force_live_memory) {
   Scalar scalar;
-  if (ReadScalarIntegerFromMemory(addr, prefer_file_cache,
-                                  m_arch.GetSpec().GetAddressByteSize(), false,
-                                  scalar, error)) {
+  if (ReadScalarIntegerFromMemory(addr, m_arch.GetSpec().GetAddressByteSize(),
+                                  false, scalar, error, force_live_memory)) {
     addr_t pointer_vm_addr = scalar.ULongLong(LLDB_INVALID_ADDRESS);
     if (pointer_vm_addr != LLDB_INVALID_ADDRESS) {
       SectionLoadList &section_load_list = GetSectionLoadList();

diff  --git a/lldb/source/Target/ThreadPlanStepRange.cpp b/lldb/source/Target/ThreadPlanStepRange.cpp
index 3c42cd750dad9..896e647bbb523 100644
--- a/lldb/source/Target/ThreadPlanStepRange.cpp
+++ b/lldb/source/Target/ThreadPlanStepRange.cpp
@@ -264,10 +264,9 @@ InstructionList *ThreadPlanStepRange::GetInstructionsForAddress(
         // Disassemble the address range given:
         const char *plugin_name = nullptr;
         const char *flavor = nullptr;
-        const bool prefer_file_cache = true;
         m_instruction_ranges[i] = Disassembler::DisassembleRange(
             GetTarget().GetArchitecture(), plugin_name, flavor, GetTarget(),
-            m_address_ranges[i], prefer_file_cache);
+            m_address_ranges[i]);
       }
       if (!m_instruction_ranges[i])
         return nullptr;

diff  --git a/lldb/source/Target/Trace.cpp b/lldb/source/Target/Trace.cpp
index c2de3dac48b28..7f58dbc700394 100644
--- a/lldb/source/Target/Trace.cpp
+++ b/lldb/source/Target/Trace.cpp
@@ -200,7 +200,7 @@ DumpInstructionInfo(Stream &s, const SymbolContext &sc,
   // Now we try using the current function's disassembler
   if (sc.function) {
     DisassemblerSP disassembler =
-        sc.function->GetInstructions(exe_ctx, nullptr, true);
+        sc.function->GetInstructions(exe_ctx, nullptr);
     if (TryDumpInstructionInfo(s, disassembler, exe_ctx, address))
       return disassembler;
   }
@@ -209,9 +209,9 @@ DumpInstructionInfo(Stream &s, const SymbolContext &sc,
   Target &target = exe_ctx.GetTargetRef();
   const ArchSpec &arch = target.GetArchitecture();
   AddressRange range(address, arch.GetMaximumOpcodeByteSize() * 1);
-  DisassemblerSP disassembler = Disassembler::DisassembleRange(
-      arch, /*plugin_name*/ nullptr,
-      /*flavor*/ nullptr, target, range, /*prefer_file_cache*/ true);
+  DisassemblerSP disassembler =
+      Disassembler::DisassembleRange(arch, /*plugin_name*/ nullptr,
+                                     /*flavor*/ nullptr, target, range);
   if (TryDumpInstructionInfo(s, disassembler, exe_ctx, address))
     return disassembler;
   return nullptr;


        


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