[lldb-dev] [PATCH] Dealing with CPU subtypes (architecture variants)
Greg Clayton
gclayton at apple.com
Tue Aug 26 11:23:00 PDT 2014
The patch looks fine and yes it is ok to have Kalimba specific stuff in the ObjectFileELF as it is specific to ELF and you are only checking it if the machine type is set to Kalimba.
So the changes look good, go ahead and check it in, we can fix the Xcode project breakage, but your patch below doesn't seem to have any since it doesn't require an extra file.
> On Aug 26, 2014, at 5:56 AM, Matthew Gardiner <mg11 at csr.com> wrote:
>
> Hi folks,
>
> The kalimba architecture has a number of variants. The ones of interest to me being 3, 4 and 5. I have added some additional entries to the g_elf_arch_entries to describe these variants. However, up until now, no subtypes (architecture variants), for ELF objectfiles exist in lldb. So I've found it necessary to modify the invocation of ArchSpec.SetArchitecture from ObjectFileELF to deal with this.
>
> Now the kalimba variant specification can be deduced by parsing the e_flags field from the ELF header. So I've written a specific routine which extracts the variant spec from the e_flags. What I'm not too happy about, and would appreciate lldb-dev's opinion on, is if it is ok for the extraction routine (kalimbaVariantFromElfFlags) to remain in ObjectFileELF.cpp? If not, where should the routine go? Furthermore how do I get any new files into the xcode project file, given that I have no xcode system - shall I just change the make and cmake build and rely on an Apple person to fix any xcode build breakage?
>
> Below is a diff of what I have done recognize kalimba variants, basically:
>
> 1. add new entries to ArchSpec::enum Core, and g_elf_arch_entries
> 2. supply routine to extract the kalimba variant from the e_flags
> 3. if e_machine == EM_CSR_KALIMBA, extract the kalimba variant and pass it to SetArchitecture as the cpu sub type.
>
> --- a/include/lldb/Core/ArchSpec.h 2014-08-18
> +++ b/include/lldb/Core/ArchSpec.h 2014-08-18
> @@ -103,6 +103,9 @@
> eCore_uknownMach64,
>
> eCore_kalimba,
> + eCore_kalimba3,
> + eCore_kalimba4,
> + eCore_kalimba5,
>
> kNumCores,
>
> --- a/source/Core/ArchSpec.cpp 2014-08-05
> +++ b/source/Core/ArchSpec.cpp 2014-08-05
> @@ -115,7 +115,10 @@
> { eByteOrderLittle, 4, 4, 4 , llvm::Triple::UnknownArch , ArchSpec::eCore_uknownMach32 , "unknown-mach-32" },
> { eByteOrderLittle, 8, 4, 4 , llvm::Triple::UnknownArch , ArchSpec::eCore_uknownMach64 , "unknown-mach-64" },
>
> - { eByteOrderLittle, 4, 1, 1 , llvm::Triple::kalimba , ArchSpec::eCore_kalimba , "kalimba" }
> + { eByteOrderLittle, 4, 1, 1 , llvm::Triple::kalimba , ArchSpec::eCore_kalimba , "kalimba" },
> + { eByteOrderLittle, 4, 1, 1 , llvm::Triple::kalimba , ArchSpec::eCore_kalimba3 , "kalimba3" },
> + { eByteOrderLittle, 4, 1, 1 , llvm::Triple::kalimba , ArchSpec::eCore_kalimba4 , "kalimba4" },
> + { eByteOrderLittle, 4, 1, 1 , llvm::Triple::kalimba , ArchSpec::eCore_kalimba5 , "kalimba5" }
> };
>
> // Ensure that we have an entry in the g_core_definitions for each core. If you comment out an entry above,
> @@ -257,7 +260,10 @@
> { ArchSpec::eCore_x86_64_x86_64 , llvm::ELF::EM_X86_64 , LLDB_INVALID_CPUTYPE, 0xFFFFFFFFu, 0xFFFFFFFFu }, // AMD64
> { ArchSpec::eCore_mips64 , llvm::ELF::EM_MIPS , LLDB_INVALID_CPUTYPE, 0xFFFFFFFFu, 0xFFFFFFFFu }, // MIPS
> { ArchSpec::eCore_hexagon_generic , llvm::ELF::EM_HEXAGON, LLDB_INVALID_CPUTYPE, 0xFFFFFFFFu, 0xFFFFFFFFu }, // HEXAGON
> - { ArchSpec::eCore_kalimba , llvm::ELF::EM_CSR_KALIMBA, LLDB_INVALID_CPUTYPE, 0xFFFFFFFFu, 0xFFFFFFFFu } // KALIMBA
> + { ArchSpec::eCore_kalimba , llvm::ELF::EM_CSR_KALIMBA, LLDB_INVALID_CPUTYPE, 0xFFFFFFFFu, 0xFFFFFFFFu }, // KALIMBA
> + { ArchSpec::eCore_kalimba3 , llvm::ELF::EM_CSR_KALIMBA, 3, 0xFFFFFFFFu, 0xFFFFFFFFu }, // KALIMBA
> + { ArchSpec::eCore_kalimba4 , llvm::ELF::EM_CSR_KALIMBA, 4, 0xFFFFFFFFu, 0xFFFFFFFFu }, // KALIMBA
> + { ArchSpec::eCore_kalimba5 , llvm::ELF::EM_CSR_KALIMBA, 5, 0xFFFFFFFFu, 0xFFFFFFFFu } // KALIMBA
>
> };
>
> --- a/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp 2014-07-22
> +++ b/source/Plugins/ObjectFile/ELF/ObjectFileELF.cpp 2014-07-22
> @@ -257,6 +257,27 @@
> return true;
> }
>
> +static uint32_t
> +kalimbaVariantFromElfFlags(const elf::elf_word e_flags)
> +{
> + const uint32_t dsp_rev = e_flags & 0xFF;
> + uint32_t kal_arch_variant = LLDB_INVALID_CPUTYPE;
> + switch(dsp_rev)
> + {
> + // TODO(mg11) Support more variants
> + case 10:
> + kal_arch_variant = 3;
> + break;
> + case 14:
> + kal_arch_variant = 4;
> + break;
> + default:
> + break;
> + }
> + return kal_arch_variant;
> +}
> +
> +
> // Arbitrary constant used as UUID prefix for core files.
> const uint32_t
> ObjectFileELF::g_core_uuid_magic(0xE210C);
> @@ -544,9 +565,15 @@
> {
> ModuleSpec spec;
> spec.GetFileSpec() = file;
> +
> + const uint32_t sub_type =
> + llvm::ELF::EM_CSR_KALIMBA == header.e_machine ?
> + kalimbaVariantFromElfFlags(header.e_flags) :
> + LLDB_INVALID_CPUTYPE;
> spec.GetArchitecture().SetArchitecture(eArchTypeELF,
> header.e_machine,
> - LLDB_INVALID_CPUTYPE);
> + sub_type);
> +
> if (spec.GetArchitecture().IsValid())
> {
> llvm::Triple::OSType ostype;
> @@ -1269,7 +1296,12 @@
> // We'll refine this with note data as we parse the notes.
> if (arch_spec.GetTriple ().getOS () == llvm::Triple::OSType::UnknownOS)
> {
> - arch_spec.SetArchitecture (eArchTypeELF, header.e_machine, LLDB_INVALID_CPUTYPE);
> + const uint32_t sub_type =
> + llvm::ELF::EM_CSR_KALIMBA == header.e_machine ?
> + kalimbaVariantFromElfFlags(header.e_flags) :
> + LLDB_INVALID_CPUTYPE;
> + arch_spec.SetArchitecture (eArchTypeELF, header.e_machine, sub_type);
> +
> switch (arch_spec.GetAddressByteSize())
> {
> case 4:
>
> I'd appreciate people's opinion on this diff, before I commit anything. (The reason I need to know the variant type, is because some kalimba variants have a different notion of "byte-size" i.e. minimum addressable unit. For example for kalimba3 the minimum addressable unit from the data bus is 24-bits, whereas for kalimba4 it is the more conventional 8-bits. I'd like to reserve the problems/challenges this presents for me, regarding my kalimba lldb port, to a future email).
>
> thanks
> Matt
>
>
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