[Lldb-commits] [PATCH] D147462: Use kernel's global variable indicating how many bits are used in addressing when loading Darwin xnu kernel

[Jason Molenda via Phabricator via lldb-commits]

jasonmolenda updated this revision to Diff 510586.
jasonmolenda added a comment.

Update patch to address some of Jonas' comments.  I was adding a check that the ptrsize of the architecture was 64-bit, but we don't work on 32-bit xnu kernels for a few years now; we can assume 64-bit safely.  I am still forcing the addressable bits value to 55 globally inside lldb while I read & set the correct value.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D147462/new/

https://reviews.llvm.org/D147462

Files:
  lldb/source/Plugins/DynamicLoader/Darwin-Kernel/DynamicLoaderDarwinKernel.cpp


Index: lldb/source/Plugins/DynamicLoader/Darwin-Kernel/DynamicLoaderDarwinKernel.cpp
===================================================================
--- lldb/source/Plugins/DynamicLoader/Darwin-Kernel/DynamicLoaderDarwinKernel.cpp
+++ lldb/source/Plugins/DynamicLoader/Darwin-Kernel/DynamicLoaderDarwinKernel.cpp
@@ -1068,6 +1068,7 @@
 
     if (m_kernel.IsLoaded() && m_kernel.GetModule()) {
       static ConstString kext_summary_symbol("gLoadedKextSummaries");
+      static ConstString arm64_T1Sz_value("gT1Sz");
       const Symbol *symbol =
           m_kernel.GetModule()->FindFirstSymbolWithNameAndType(
               kext_summary_symbol, eSymbolTypeData);
@@ -1076,6 +1077,36 @@
         // Update all image infos
         ReadAllKextSummaries();
       }
+      // If the kernel global with the T1Sz setting is available,
+      // update the target.process.virtual-addressable-bits to be correct.
+      symbol = m_kernel.GetModule()->FindFirstSymbolWithNameAndType(
+          arm64_T1Sz_value, eSymbolTypeData);
+      if (symbol) {
+        const uint32_t orig_bits_value = m_process->GetVirtualAddressableBits();
+        // Mark all bits as addressable so we don't strip any from our
+        // memory read below, with an incorrect default value.
+        // b55 is the sign extension bit with PAC, b56:63 are TBI,
+        // don't mark those as addressable.
+        m_process->SetVirtualAddressableBits(55);
+        Status error;
+        // gT1Sz is 8 bytes.  We may run on a stripped kernel binary
+        // where we can't get the size accurately.  Hardcode it.
+        const size_t sym_bytesize = 8; // size of gT1Sz value
+        uint64_t sym_value =
+            m_process->GetTarget().ReadUnsignedIntegerFromMemory(
+                symbol->GetAddress(), sym_bytesize, 0, error);
+        if (error.Success()) {
+          // 64 - T1Sz is the highest bit used for auth.
+          // The value we pass in to SetVirtualAddressableBits is
+          // the number of bits used for addressing, so if
+          // T1Sz is 25, then 64-25 == 39, bits 0..38 are used for
+          // addressing, bits 39..63 are used for PAC/TBI or whatever.
+          uint32_t virt_addr_bits = 64 - sym_value;
+          m_process->SetVirtualAddressableBits(virt_addr_bits);
+        } else {
+          m_process->SetVirtualAddressableBits(orig_bits_value);
+        }
+      }
     } else {
       m_kernel.Clear();
     }


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D147462.510586.patch
Type: text/x-patch
Size: 2441 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/lldb-commits/attachments/20230403/c7601947/attachment-0001.bin>