Simplify reading of Linux notes to correctly handle endianess.

[hhellyer]

Summary

This patch changes and simplifies the way notes are read from Linux Elf cores.
The current implementation copies the bytes from the notes directly over the lldb structure for 64 bit cores and reads field by field for 32 bit cores. Reading the bytes directly only works if the endianess of the core dump and the platform that lldb are running on matches. The case statements for s390x and x86_64 would would only work on big endian systems and little endian systems respectively. That meant that x86_64 generally worked but s390x didn't unless you were on s390x or another big endian platform.
This patch just reads field by field on all platform and updates the field by field version to allow for those fields which are word size instead of fixed size. It should also slightly simplify adding support for a new Linux platform.

This patch also re-enables the s390x test case in TestLinuxCore.py on all non-s390x platforms as it now passes.

[hhellyer]

I spotted this when looking at why https://reviews.llvm.org/D26676 didn't quite fix reading the z/Linux core dump. Do I need to raise a bug to track this as well or is this sufficient?

[uweigand]

As far as I can see, this should work fine everywhere. Looks good to me.

[clayborg]

The main question is why is the s390 core file test failing on any architectures? That seems like a bug.

packages/Python/lldbsuite/test/functionalities/postmortem/elf-core/TestLinuxCore.py

41

Why is this test skipped for any architectures? If we have a core file we should be good to go? How can this test pass on some architectures but not others?

[hhellyer]

packages/Python/lldbsuite/test/functionalities/postmortem/elf-core/TestLinuxCore.py

41

I've just reset the skip annotations to match the annotations on test_i386 and test_x86_64.
It looks like the annotations for Windows and mips were added globally under https://reviews.llvm.org/rL283380 and https://reviews.llvm.org/rL283739 respectively so if they are still required I think they should probably be included on this test.

[clayborg]

Ok, lets get this in for now, but all core files should work on all systems as long as the Process plug-in they use are compiled into the binary.

packages/Python/lldbsuite/test/functionalities/postmortem/elf-core/TestLinuxCore.py

def test_i386(self):
         self.do_test("linux-i386", self._i386_pid, self._i386_regions)
 
     @skipIf(oslist=['windows'])
     @skipIf(triple='^mips')
     def test_x86_64(self):
         """Test that lldb can read the process information from an x86_64 linux core file."""
         self.do_test("linux-x86_64", self._x86_64_pid, self._x86_64_regions)
 
-    # This seems to hang on non-s390x platforms for some reason.  Disabling
-    # for now.
-    @skipIf(archs=no_match(['s390x']))
+    @skipIf(oslist=['windows'])
     @skipIf(triple='^mips')
     def test_s390x(self):
         """Test that lldb can read the process information from an s390x linux core file."""
         self.do_test("linux-s390x", self._s390x_pid, self._s390x_regions)
 
     @skipIf(oslist=['windows'])
     @skipIf(triple='^mips')
     def test_same_pid_running(self):

source/Plugins/Process/elf-core/ThreadElfCore.cpp

 // Parse PRSTATUS from NOTE entry
 //----------------------------------------------------------------
 ELFLinuxPrStatus::ELFLinuxPrStatus() {
   memset(this, 0, sizeof(ELFLinuxPrStatus));
 }
 
 Error ELFLinuxPrStatus::Parse(DataExtractor &data, ArchSpec &arch) {
   Error error;
-  ByteOrder byteorder = data.GetByteOrder();
   if (GetSize(arch) > data.GetByteSize()) {
     error.SetErrorStringWithFormat(
         "NT_PRSTATUS size should be %zu, but the remaining bytes are: %" PRIu64,
         GetSize(arch), data.GetByteSize());
     return error;
   }
 
-  switch (arch.GetCore()) {
-  case ArchSpec::eCore_s390x_generic:
-  case ArchSpec::eCore_x86_64_x86_64:
-    data.ExtractBytes(0, sizeof(ELFLinuxPrStatus), byteorder, this);
-    break;
-  case ArchSpec::eCore_x86_32_i386:
-  case ArchSpec::eCore_x86_32_i486: {
-    // Parsing from a 32 bit ELF core file, and populating/reusing the structure
-    // properly, because the struct is for the 64 bit version
-    offset_t offset = 0;
-    si_signo = data.GetU32(&offset);
-    si_code = data.GetU32(&offset);
-    si_errno = data.GetU32(&offset);
+  // Read field by field to correctly account for endianess
+  // of both the core dump and the platform running lldb.
 
-    pr_cursig = data.GetU16(&offset);
-    offset += 2; // pad
 
-    pr_sigpend = data.GetU32(&offset);
-    pr_sighold = data.GetU32(&offset);
+  pr_sigpend = data.GetPointer(&offset);
+  pr_sighold = data.GetPointer(&offset);
 
-    pr_pid = data.GetU32(&offset);
-    pr_ppid = data.GetU32(&offset);
-    pr_pgrp = data.GetU32(&offset);
-    pr_sid = data.GetU32(&offset);
 
-    pr_utime.tv_sec = data.GetU32(&offset);
-    pr_utime.tv_usec = data.GetU32(&offset);
+  pr_utime.tv_sec = data.GetPointer(&offset);
+  pr_utime.tv_usec = data.GetPointer(&offset);
 
-    pr_stime.tv_sec = data.GetU32(&offset);
-    pr_stime.tv_usec = data.GetU32(&offset);
+  pr_stime.tv_sec = data.GetPointer(&offset);
+  pr_stime.tv_usec = data.GetPointer(&offset);
 
-    pr_cutime.tv_sec = data.GetU32(&offset);
-    pr_cutime.tv_usec = data.GetU32(&offset);
+  pr_cutime.tv_sec = data.GetPointer(&offset);
+  pr_cutime.tv_usec = data.GetPointer(&offset);
 
-    pr_cstime.tv_sec = data.GetU32(&offset);
-    pr_cstime.tv_usec = data.GetU32(&offset);
+  pr_cstime.tv_sec = data.GetPointer(&offset);
+  pr_cstime.tv_usec = data.GetPointer(&offset);
 
-    break;
-  }
-  default:
-    error.SetErrorStringWithFormat("ELFLinuxPrStatus::%s Unknown architecture",
-                                   __FUNCTION__);
-    break;
-  }
 
   return error;
 }
 
 //----------------------------------------------------------------
 // Parse PRPSINFO from NOTE entry
 //----------------------------------------------------------------
 ELFLinuxPrPsInfo::ELFLinuxPrPsInfo() {
   memset(this, 0, sizeof(ELFLinuxPrPsInfo));
 }
 
 Error ELFLinuxPrPsInfo::Parse(DataExtractor &data, ArchSpec &arch) {
   Error error;
   ByteOrder byteorder = data.GetByteOrder();
   if (GetSize(arch) > data.GetByteSize()) {
     error.SetErrorStringWithFormat(
         "NT_PRPSINFO size should be %zu, but the remaining bytes are: %" PRIu64,
         GetSize(arch), data.GetByteSize());
     return error;
   }
-
-  switch (arch.GetCore()) {
-  case ArchSpec::eCore_s390x_generic:
-  case ArchSpec::eCore_x86_64_x86_64:
-    data.ExtractBytes(0, sizeof(ELFLinuxPrPsInfo), byteorder, this);
-    break;
-  case ArchSpec::eCore_x86_32_i386:
-  case ArchSpec::eCore_x86_32_i486: {
-    // Parsing from a 32 bit ELF core file, and populating/reusing the structure
-    // properly, because the struct is for the 64 bit version
-    size_t size = 0;
-    offset_t offset = 0;
 
-    pr_state = data.GetU8(&offset);
-    pr_sname = data.GetU8(&offset);
-    pr_zomb = data.GetU8(&offset);
-    pr_nice = data.GetU8(&offset);
+  if (data.GetAddressByteSize() == 8) {
+    // Word align the next field on 64 bit.
+    offset += 4;
+  }
 
-    pr_flag = data.GetU32(&offset);
-    pr_uid = data.GetU16(&offset);
-    pr_gid = data.GetU16(&offset);
+  pr_flag = data.GetPointer(&offset);
+
+  // 16 bit on 32 bit platforms, 32 bit on 64 bit platforms
+  pr_uid = data.GetMaxU64(&offset, data.GetAddressByteSize() >> 1);
+  pr_gid = data.GetMaxU64(&offset, data.GetAddressByteSize() >> 1);
 
-    pr_pid = data.GetU32(&offset);
-    pr_ppid = data.GetU32(&offset);
-    pr_pgrp = data.GetU32(&offset);
-    pr_sid = data.GetU32(&offset);
 
-    size = 16;
-    data.ExtractBytes(offset, size, byteorder, pr_fname);
-    offset += size;
 
-    size = 80;
-    data.ExtractBytes(offset, size, byteorder, pr_psargs);
-    offset += size;
 
-    break;
-  }
-  default:
-    error.SetErrorStringWithFormat("ELFLinuxPrPsInfo::%s Unknown architecture",
-                                   __FUNCTION__);
-    break;
-  }
-
   return error;
 }
 
 //----------------------------------------------------------------
 // Parse SIGINFO from NOTE entry
 //----------------------------------------------------------------
 ELFLinuxSigInfo::ELFLinuxSigInfo() {
   memset(this, 0, sizeof(ELFLinuxSigInfo));
 }
 
 Error ELFLinuxSigInfo::Parse(DataExtractor &data, const ArchSpec &arch) {
   Error error;
-  ByteOrder byteorder = data.GetByteOrder();
   if (GetSize(arch) > data.GetByteSize()) {
     error.SetErrorStringWithFormat(
         "NT_SIGINFO size should be %zu, but the remaining bytes are: %" PRIu64,
         GetSize(arch), data.GetByteSize());
     return error;
   }
 
-  switch (arch.GetCore()) {
-  case ArchSpec::eCore_x86_64_x86_64:
-    data.ExtractBytes(0, sizeof(ELFLinuxPrStatus), byteorder, this);
-    break;
-  case ArchSpec::eCore_s390x_generic:
-  case ArchSpec::eCore_x86_32_i386:
-  case ArchSpec::eCore_x86_32_i486: {
-    // Parsing from a 32 bit ELF core file, and populating/reusing the structure
-    // properly, because the struct is for the 64 bit version
-    offset_t offset = 0;
-    si_signo = data.GetU32(&offset);
-    si_code = data.GetU32(&offset);
-    si_errno = data.GetU32(&offset);
 
-    break;
-  }
-  default:
-    error.SetErrorStringWithFormat("ELFLinuxSigInfo::%s Unknown architecture",
-                                   __FUNCTION__);
-    break;
-  }
-
   return error;
 }