When reading Aux file in chunks, read consecutive byte ranges

qemu has a very small maximum packet size (4096) and it actually
only uses half of that buffer for some implementation reason,
so when lldb asks for the register target definitions, the x86_64
definition is larger than 4096/2 and we need to fetch it in two parts.

This patch and test is fixing a bug in
GDBRemoteCommunicationClient::ReadExtFeature when reading a target
file in multiple parts.  lldb was assuming that it would always
get back the maximum packet size response (4096) instead of
using the actual size received and asking for the next group of
bytes.

We now have two tests in gdb_remote_client for unique features
of qemu - TestNestedRegDefinitions.py would test the ability
of lldb to follow multiple levels of xml includes; I opted to
create a separate TestRegDefinitionInParts.py test to test this
wrinkle in qemu's gdb remote serial protocol stub implementation.
Instead of combining both tests into a single test file.

<rdar://problem/49537922>

diff --git a/lldb/packages/Python/lldbsuite/test/functionalities/gdb_remote_client/TestRegDefinitionInParts.py b/lldb/packages/Python/lldbsuite/test/functionalities/gdb_remote_client/TestRegDefinitionInParts.py
new file mode 100644 (file)
index 0000000..c4ba19c
--- /dev/null
+++ b/lldb/packages/Python/lldbsuite/test/functionalities/gdb_remote_client/TestRegDefinitionInParts.py
@@ -0,0 +1,160 @@
+from __future__ import print_function
+import lldb
+import time
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test.decorators import *
+from gdbclientutils import *
+
+class TestRegDefinitionInParts(GDBRemoteTestBase):
+
+    @skipIfXmlSupportMissing
+    @skipIfRemote
+    def test(self):
+        """
+        Test that lldb correctly fetches the target definition file
+        in multiple chunks if the remote server only provides the 
+        content in small parts, and the small parts it provides is
+        smaller than the maximum packet size that it declared at
+        the start of the debug session.  qemu does this.
+        """
+        class MyResponder(MockGDBServerResponder):
+
+            def qXferRead(self, obj, annex, offset, length):
+                if annex == "target.xml":
+                    return """<?xml version="1.0"?>
+                              <!DOCTYPE feature SYSTEM "gdb-target.dtd">
+                              <target version="1.0">
+                              <architecture>i386:x86-64</architecture>
+                              <xi:include href="i386-64bit-core.xml"/>
+                              </target>""", False
+
+                if annex == "i386-64bit-core.xml" and offset == 0:
+                    return """<?xml version="1.0"?>
+<!-- Copyright (C) 2010-2015 Free Software Foundation, Inc.
+
+     Copying and distribution of this file, with or without modification,
+     are permitted in any medium without royalty provided the copyright
+     notice and this notice are preserved.  -->
+
+<!DOCTYPE feature SYSTEM "gdb-target.dtd">
+<feature name="org.gnu.gdb.i386.core">
+  <flags id="i386_eflags" size="4">
+    <field name="CF" start="0" end="0"/>
+    <field name="" start="1" end="1"/>
+    <field name="PF" start="2" end="2"/>
+    <field name="AF" start="4" end="4"/>
+    <field name="ZF" start="6" end="6"/>
+    <field name="SF" start="7" end="7"/>
+    <field name="TF" start="8" end="8"/>
+    <field name="IF" start="9" end="9"/>
+    <field name="DF" start="10" end="10"/>
+    <field name="OF" start="11" end="11"/>
+    <field name="NT" start="14" end="14"/>
+    <field name="RF" start="16" end="16"/>
+    <field name="VM" start="17" end="17"/>
+    <field name="AC" start="18" end="18"/>
+    <field name="VIF" start="19" end="19"/>
+    <field name="VIP" start="20" end="20"/>
+    <field name="ID" start="21" end="21"/>
+  </flags>
+
+  <reg name="rax" bitsize="64" type="int64"/>
+  <reg name="rbx" bitsize="64" type="int64"/>
+  <reg name="rcx" bitsize="64" type="int64"/>
+  <reg name="rdx" bitsize="64" type="int64"/>
+  <reg name="rsi" bitsize="64" type="int64"/>
+  <reg name="rdi" bitsize="64" type="int64"/>
+  <reg name="rbp" bitsize="64" type="data_ptr"/>
+  <reg name="rsp" bitsize="64" type="data_ptr"/>
+  <reg name="r8" bitsize="64" type="int64"/>
+  <reg name="r9" bitsize="64" type="int64"/>
+  <reg name="r10" bitsize="64" type="int64"/>
+  <reg name="r11" bitsize="64" type="int64"/>
+  <reg name="r12" bitsize="64" type="int64"/>
+  <reg name="r13" bitsize="64" type="int64"/>
+  <reg name="r14" bitsize="64" type="int64"/>
+  <reg name="r15" bitsize="64" type="int64"/>
+
+  <reg name="rip" bitsize="64" type="code_ptr"/>
+  <reg name="eflags" bitsize="32" type="i386_eflags"/>
+  <reg name="cs" bitsize="32" type="int32"/>
+  <reg name="ss" bitsize="32" ty""", True
+
+                if annex == "i386-64bit-core.xml" and offset == 2045:
+                    return """pe="int32"/>
+  <reg name="ds" bitsize="32" type="int32"/>
+  <reg name="es" bitsize="32" type="int32"/>
+  <reg name="fs" bitsize="32" type="int32"/>
+  <reg name="gs" bitsize="32" type="int32"/>
+
+  <reg name="st0" bitsize="80" type="i387_ext"/>
+  <reg name="st1" bitsize="80" type="i387_ext"/>
+  <reg name="st2" bitsize="80" type="i387_ext"/>
+  <reg name="st3" bitsize="80" type="i387_ext"/>
+  <reg name="st4" bitsize="80" type="i387_ext"/>
+  <reg name="st5" bitsize="80" type="i387_ext"/>
+  <reg name="st6" bitsize="80" type="i387_ext"/>
+  <reg name="st7" bitsize="80" type="i387_ext"/>
+
+  <reg name="fctrl" bitsize="32" type="int" group="float"/>
+  <reg name="fstat" bitsize="32" type="int" group="float"/>
+  <reg name="ftag" bitsize="32" type="int" group="float"/>
+  <reg name="fiseg" bitsize="32" type="int" group="float"/>
+  <reg name="fioff" bitsize="32" type="int" group="float"/>
+  <reg name="foseg" bitsize="32" type="int" group="float"/>
+  <reg name="fooff" bitsize="32" type="int" group="float"/>
+  <reg name="fop" bitsize="32" type="int" group="float"/>
+</feature>""", False
+
+                return None, False
+
+            def readRegister(self, regnum):
+                return ""
+
+            def readRegisters(self):
+                return "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"
+
+            def haltReason(self):
+                return "T02thread:dead;threads:dead;"
+
+            def qfThreadInfo(self):
+                return "mdead"
+            
+            def qC(self):
+                return ""
+
+            def qSupported(self, client_supported):
+                return "PacketSize=1000;qXfer:features:read+"
+
+            def QThreadSuffixSupported(self):
+                return "OK"
+
+            def QListThreadsInStopReply(self):
+                return "OK"
+
+        self.server.responder = MyResponder()
+        if self.TraceOn():
+            self.runCmd("log enable gdb-remote packets")
+            time.sleep(10)
+            self.addTearDownHook(
+                    lambda: self.runCmd("log disable gdb-remote packets"))
+
+        target = self.dbg.CreateTargetWithFileAndArch(None, None)
+
+        process = self.connect(target)
+
+        if self.TraceOn():
+            interp = self.dbg.GetCommandInterpreter()
+            result = lldb.SBCommandReturnObject()
+            interp.HandleCommand("target list", result)
+            print(result.GetOutput())
+
+        rip_valobj = process.GetThreadAtIndex(0).GetFrameAtIndex(0).FindRegister("rip")
+        self.assertEqual(rip_valobj.GetValueAsUnsigned(), 0x00ffff800041120e)
+
+        ss_valobj = process.GetThreadAtIndex(0).GetFrameAtIndex(0).FindRegister("ss")
+        self.assertEqual(ss_valobj.GetValueAsUnsigned(), 0x22222222)
+
+        if self.TraceOn():
+            print("rip is 0x%x" % rip_valobj.GetValueAsUnsigned())
+            print("ss is 0x%x" % ss_valobj.GetValueAsUnsigned())

diff --git a/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationClient.cpp b/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationClient.cpp
index 19c3a5b..b2f1ee5 100644 (file)
--- a/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationClient.cpp
+++ b/lldb/source/Plugins/Process/gdb-remote/GDBRemoteCommunicationClient.cpp
@@ -3740,7 +3740,7 @@ bool GDBRemoteCommunicationClient::ReadExtFeature(
     case ('m'):
       if (str.length() > 1)
         output << &str[1];
-      offset += size;
+      offset += str.length() - 1;
       break;
 
     // unknown chunk