[Lldb-commits] [PATCH] D130534: loading a binary at a slide multiple times leaves old entries in the SectionLoadList

[Jason Molenda via Phabricator via lldb-commits]

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If you add a binary to lldb and do `target modules load -s slide -f name` multiple times, the old entries are not cleared from the SectionLoadList's addr->section map, leading to confusing lldb behavior.

SectionLoadList has a section-to-address map (m_sect_to_addr) and an address to section map (m_addr_to_sect) that are registered with the Target.  SectionLoadList::SetSectionLoadAddress updates the entry in the m_sect_to_addr map if it exists, or adds it.  And it adds a new entry to m_addr_to_sect as long as there isn't a section at that address already.  But it never removes the old entry from m_addr_to_sect.

This results in each section having multiple entries, with each the load addresses that had been set previously, so load address -> file address translation behaves very oddly.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D130534

Files:
  lldb/source/Target/SectionLoadList.cpp
  lldb/test/API/functionalities/multiple-slides/Makefile
  lldb/test/API/functionalities/multiple-slides/TestMultipleSlides.py
  lldb/test/API/functionalities/multiple-slides/main.c


Index: lldb/test/API/functionalities/multiple-slides/main.c
===================================================================
--- /dev/null
+++ lldb/test/API/functionalities/multiple-slides/main.c
@@ -0,0 +1,5 @@
+int first[2048] = { 5 };
+int second[2048] = { 6 };
+int main()  {
+  return first[0] + second[0];
+}
Index: lldb/test/API/functionalities/multiple-slides/TestMultipleSlides.py
===================================================================
--- /dev/null
+++ lldb/test/API/functionalities/multiple-slides/TestMultipleSlides.py
@@ -0,0 +1,44 @@
+"""
+Test that a binary can be slid to different load addresses correctly
+"""
+
+
+
+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+
+class MultipleSlidesTestCase(TestBase):
+
+    NO_DEBUG_INFO_TESTCASE = True
+    def test_mulitple_slides(self):
+        """Test that a binary can be slid multiple times correctly."""
+        self.build()
+        exe = self.getBuildArtifact("a.out")
+        err = lldb.SBError()
+        load_dependent_modules = False
+        target = self.dbg.CreateTarget(exe, '', '', load_dependent_modules, err)
+        self.assertTrue(target.IsValid())
+        module = target.GetModuleAtIndex(0)
+        self.assertTrue(module.IsValid())
+
+        # View the first element of `first` and `second` while
+        # they have no load address set.
+        self.expect("p/d ((int*)&first)[0]", substrs=['= 5'])
+        self.expect("p/d ((int*)&second)[0]", substrs=['= 6'])
+
+        target.SetModuleLoadAddress(module, 1990)
+
+        # View the first element of `first` and `second` with
+        # a load address .
+        self.expect("p/d ((int*)&first)[0]", substrs=['= 5'])
+        self.expect("p/d ((int*)&second)[0]", substrs=['= 6'])
+
+        target.SetModuleLoadAddress(module, 4)
+
+        # View the first element of `first` and `second` with
+        # a new load address.
+        self.expect("p/d ((int*)&first)[0]", substrs=['= 5'])
+        self.expect("p/d ((int*)&second)[0]", substrs=['= 6'])
Index: lldb/test/API/functionalities/multiple-slides/Makefile
===================================================================
--- /dev/null
+++ lldb/test/API/functionalities/multiple-slides/Makefile
@@ -0,0 +1,12 @@
+C_SOURCES := main.c
+MAKE_DSYM := NO
+
+include Makefile.rules
+
+# lldb has a separate bug where this test case
+# does not work if we have debug info - after
+# sliding the binary, the address of `first` and
+# `second` are not slid for some reason on Darwin.
+main.o: main.c
+	$(CC) $(CFLAGS_NO_DEBUG) -c $< -o $@
+
Index: lldb/source/Target/SectionLoadList.cpp
===================================================================
--- lldb/source/Target/SectionLoadList.cpp
+++ lldb/source/Target/SectionLoadList.cpp
@@ -116,8 +116,18 @@
         }
       }
       ats_pos->second = section;
-    } else
+    } else {
+      // Remove the old address->section entry, if
+      // there is one.
+      for (const auto &it : m_addr_to_sect) {
+        if (it.second == section) {
+          const auto &it_pos = m_addr_to_sect.find(it.first);
+          m_addr_to_sect.erase(it_pos);
+          break;
+        }
+      }
       m_addr_to_sect[load_addr] = section;
+    }
     return true; // Changed
 
   } else {


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