[PATCH 0/1] MIPS SDE-compatible bare metal target

[PATCH 0/1] MIPS SDE-compatible bare metal target

[Kevin Cernekee]

I ran into a couple of semi-obscure issues linking objects generated
from the mips-unknown-elf sample toolchain into a program built with
Sourcery G++ (now Sourcery CodeBench), and I wanted to pitch the idea of
including an SDE-compatible sample config in the release.

I have not performed enough testing to be confident that I know about
all of the changes needed for 100% SDE compatibility, but maybe this
will get the ball rolling and somebody more knowledgeable can help fill
in the gaps...

Problem #1:

mips-unknown-elf uses SGI-compatible symbol ordering:

$ nm -ap _fixunssfsi-sgi.o | nl | tail -n 6
    18  00000000 a /big/ct/sgi/.build/src/gcc-4.4.6/libgcc/../gcc/libgcc2.c
    19           U __gesf2
    20           U __subsf3
    21           U __fixsfsi
    22  00000000 T __fixunssfsi
    23  00000000 r $LC0

In SGI mode, sh_info in the symtab's section header entry points to line
18.

By contrast, a copy of binutils that had been built as an SDE or Linux
toolchain assumes that sh_info points to the first global symbol, and
that all local symbols (such as $LC0) have an index lower than sh_info
(in this case, 20):

$ nm -ap _fixunssfsi.o | nl | tail -n 9
    15  00000000 r $LC0
    16  00000000 r .reginfo
    17  00000000 n .pdr
    18  00000000 n .comment
    19  00000000 n .gnu.attributes
    20           U __gesf2
    21           U __subsf3
    22           U __fixsfsi
    23  00000000 T __fixunssfsi

A non-SGI ld may report the former case as a malformed object file:

mipsel-linux-ld: error: _fixunssfsi-sgi.o contains a reloc (0x0000000000001705) for section .text that references a non-existent global symbol
mipsel-linux-ld: final link failed: Bad value

Fix: use "sde" instead of "unknown" for CT_TARGET_VENDOR.  If the tuple
is mips-sde-elf, binutils will disable the SGI/IRIX quirks.


Problem #2:

In my test runs, CT_CC_GCC_ENABLE_TARGET_OPTSPACE caused libgcc to be
built with the MIPS SDA data model.  i.e. it assumes that $gp always
points to a "small data area" which can access items in the .sdata and
.sbss sections using just a signed 16-bit offset.  Many embedded
programs do use SDA, but some do not and this could cause
incompatibilities.

Fix: disable CT_CC_GCC_ENABLE_TARGET_OPTSPACE

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[PATCH 1/1] samples: add new mipsel-sde-elf sample.

[Kevin Cernekee]

# HG changeset patch
# User Kevin Cernekee <cernekee@gmail.com>
# Date 1316989289 25200
# Node ID f02a0a9c2a054f3ac5791457e157bbfca5bcfd04
# Parent  7df89370f80537d1b36b2fda70e3a1c6bc237a65
samples: add new mipsel-sde-elf sample.

Signed-off-by: Kevin Cernekee <cernekee@gmail.com>

diff -r 7df89370f805 -r f02a0a9c2a05 samples/mipsel-sde-elf/crosstool.config
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/samples/mipsel-sde-elf/crosstool.config	Sun Sep 25 15:21:29 2011 -0700
@@ -0,0 +1,370 @@
+#
+# Automatically generated make config: don't edit
+# crosstool-NG hg_default@2677_7df89370f805 Configuration
+# Sun Sep 25 14:27:04 2011
+#
+CT_CONFIGURE_has_xzutils=y
+CT_CONFIGURE_has_cvs=y
+CT_CONFIGURE_has_svn=y
+CT_CONFIGURE_static_link_ok=y
+CT_CONFIGURE_has_static_libstdcxx=y
+CT_CONFIGURE_has_expat=y
+CT_CONFIGURE_has_static_expat=y
+CT_MODULES=y
+
+#
+# Paths and misc options
+#
+
+#
+# crosstool-NG behavior
+#
+# CT_OBSOLETE is not set
+# CT_EXPERIMENTAL is not set
+# CT_DEBUG_CT is not set
+
+#
+# Paths
+#
+CT_LOCAL_TARBALLS_DIR="${HOME}/src"
+CT_SAVE_TARBALLS=y
+CT_WORK_DIR="${CT_TOP_DIR}/.build"
+CT_PREFIX_DIR="${HOME}/x-tools/${CT_TARGET}"
+CT_INSTALL_DIR="${CT_PREFIX_DIR}"
+CT_RM_RF_PREFIX_DIR=y
+CT_REMOVE_DOCS=y
+CT_INSTALL_DIR_RO=y
+CT_STRIP_ALL_TOOLCHAIN_EXECUTABLES=y
+
+#
+# Downloading
+#
+# CT_FORBID_DOWNLOAD is not set
+# CT_FORCE_DOWNLOAD is not set
+CT_CONNECT_TIMEOUT=10
+# CT_ONLY_DOWNLOAD is not set
+# CT_USE_MIRROR is not set
+
+#
+# Extracting
+#
+# CT_FORCE_EXTRACT is not set
+CT_OVERIDE_CONFIG_GUESS_SUB=y
+# CT_ONLY_EXTRACT is not set
+CT_PATCH_BUNDLED=y
+# CT_PATCH_LOCAL is not set
+# CT_PATCH_BUNDLED_LOCAL is not set
+# CT_PATCH_LOCAL_BUNDLED is not set
+# CT_PATCH_BUNDLED_FALLBACK_LOCAL is not set
+# CT_PATCH_LOCAL_FALLBACK_BUNDLED is not set
+# CT_PATCH_NONE is not set
+CT_PATCH_ORDER="bundled"
+
+#
+# Build behavior
+#
+CT_PARALLEL_JOBS=1
+CT_LOAD=0
+CT_USE_PIPES=y
+# CT_CONFIG_SHELL_SH is not set
+# CT_CONFIG_SHELL_ASH is not set
+CT_CONFIG_SHELL_BASH=y
+# CT_CONFIG_SHELL_CUSTOM is not set
+CT_CONFIG_SHELL="bash"
+
+#
+# Logging
+#
+# CT_LOG_ERROR is not set
+# CT_LOG_WARN is not set
+# CT_LOG_INFO is not set
+CT_LOG_EXTRA=y
+# CT_LOG_ALL is not set
+# CT_LOG_DEBUG is not set
+CT_LOG_LEVEL_MAX="EXTRA"
+# CT_LOG_SEE_TOOLS_WARN is not set
+CT_LOG_PROGRESS_BAR=y
+CT_LOG_TO_FILE=y
+CT_LOG_FILE_COMPRESS=y
+
+#
+# Target options
+#
+CT_ARCH="mips"
+CT_ARCH_SUPPORTS_BOTH_ENDIAN=y
+CT_ARCH_SUPPORTS_32=y
+CT_ARCH_SUPPORT_ARCH=y
+CT_ARCH_SUPPORT_TUNE=y
+CT_ARCH_DEFAULT_BE=y
+CT_ARCH_DEFAULT_32=y
+CT_ARCH_ARCH=""
+CT_ARCH_TUNE=""
+# CT_ARCH_BE is not set
+CT_ARCH_LE=y
+CT_ARCH_32=y
+CT_ARCH_BITNESS=32
+# CT_ARCH_FLOAT_HW is not set
+CT_ARCH_FLOAT_SW=y
+CT_TARGET_CFLAGS=""
+CT_TARGET_LDFLAGS=""
+# CT_ARCH_alpha is not set
+# CT_ARCH_arm is not set
+# CT_ARCH_avr32 is not set
+# CT_ARCH_blackfin is not set
+CT_ARCH_mips=y
+# CT_ARCH_powerpc is not set
+# CT_ARCH_sh is not set
+# CT_ARCH_sparc is not set
+# CT_ARCH_x86 is not set
+CT_ARCH_alpha_AVAILABLE=y
+CT_ARCH_arm_AVAILABLE=y
+CT_ARCH_avr32_AVAILABLE=y
+CT_ARCH_blackfin_AVAILABLE=y
+CT_ARCH_m68k_AVAILABLE=y
+CT_ARCH_mips_AVAILABLE=y
+CT_ARCH_powerpc_AVAILABLE=y
+CT_ARCH_s390_AVAILABLE=y
+CT_ARCH_sh_AVAILABLE=y
+CT_ARCH_sparc_AVAILABLE=y
+CT_ARCH_x86_AVAILABLE=y
+
+#
+# Generic target options
+#
+CT_ARCH_USE_MMU=y
+
+#
+# Target optimisations
+#
+
+#
+# mips other options
+#
+CT_ARCH_mips_o32=y
+CT_ARCH_mips_ABI="32"
+
+#
+# Toolchain options
+#
+
+#
+# General toolchain options
+#
+CT_FORCE_SYSROOT=y
+CT_USE_SYSROOT=y
+CT_SYSROOT_NAME="sysroot"
+CT_SYSROOT_DIR_PREFIX=""
+CT_STATIC_TOOLCHAIN_POSSIBLE=y
+CT_TOOLCHAIN_PKGVERSION=""
+CT_TOOLCHAIN_BUGURL=""
+
+#
+# Tuple completion and aliasing
+#
+CT_TARGET_VENDOR="sde"
+CT_TARGET_ALIAS_SED_EXPR=""
+CT_TARGET_ALIAS=""
+
+#
+# Toolchain type
+#
+CT_CROSS=y
+CT_TOOLCHAIN_TYPE="cross"
+
+#
+# Build system
+#
+CT_BUILD=""
+CT_BUILD_PREFIX=""
+CT_BUILD_SUFFIX=""
+
+#
+# Operating System
+#
+CT_BARE_METAL=y
+CT_KERNEL="bare-metal"
+CT_KERNEL_bare_metal=y
+# CT_KERNEL_linux is not set
+CT_KERNEL_bare_metal_AVAILABLE=y
+CT_KERNEL_linux_AVAILABLE=y
+CT_KERNEL_mingw32_AVAILABLE=y
+
+#
+# Common kernel options
+#
+
+#
+# Binary utilities
+#
+CT_ARCH_BINFMT_ELF=y
+
+#
+# GNU binutils
+#
+CT_BINUTILS_V_2_21_1a=y
+# CT_BINUTILS_V_2_20_1a is not set
+# CT_BINUTILS_V_2_19_1a is not set
+# CT_BINUTILS_V_2_18a is not set
+CT_BINUTILS_VERSION="2.21.1a"
+CT_BINUTILS_2_21_or_later=y
+CT_BINUTILS_2_20_or_later=y
+CT_BINUTILS_2_19_or_later=y
+CT_BINUTILS_2_18_or_later=y
+CT_BINUTILS_HAS_GOLD=y
+CT_BINUTILS_HAS_PLUGINS=y
+CT_BINUTILS_HAS_PKGVERSION_BUGURL=y
+CT_BINUTILS_LINKER_LD=y
+CT_BINUTILS_LINKERS_LIST="ld"
+CT_BINUTILS_LINKER_DEFAULT="bfd"
+# CT_BINUTILS_PLUGINS is not set
+CT_BINUTILS_EXTRA_CONFIG_ARRAY=""
+
+#
+# C compiler
+#
+CT_CC="gcc"
+CT_CC_VERSION="4.4.6"
+CT_CC_gcc=y
+CT_CC_V_4_4_6=y
+# CT_CC_V_4_4_5 is not set
+# CT_CC_V_4_4_4 is not set
+# CT_CC_V_4_4_3 is not set
+# CT_CC_V_4_4_2 is not set
+# CT_CC_V_4_4_1 is not set
+# CT_CC_V_4_4_0 is not set
+# CT_CC_V_4_3_6 is not set
+# CT_CC_V_4_3_5 is not set
+# CT_CC_V_4_3_4 is not set
+# CT_CC_V_4_3_3 is not set
+# CT_CC_V_4_3_2 is not set
+# CT_CC_V_4_3_1 is not set
+# CT_CC_V_4_2_4 is not set
+# CT_CC_V_4_2_2 is not set
+CT_CC_GCC_4_2_or_later=y
+CT_CC_GCC_4_3_or_later=y
+CT_CC_GCC_4_4=y
+CT_CC_GCC_4_4_or_later=y
+CT_CC_GCC_HAS_GRAPHITE=y
+CT_CC_GCC_HAS_PKGVERSION_BUGURL=y
+CT_CC_GCC_USE_GMP_MPFR=y
+CT_CC_GCC_USE_PPL_CLOOG=y
+CT_CC_SUPPORT_CXX=y
+CT_CC_SUPPORT_FORTRAN=y
+CT_CC_SUPPORT_JAVA=y
+CT_CC_SUPPORT_ADA=y
+CT_CC_SUPPORT_OBJC=y
+CT_CC_SUPPORT_OBJCXX=y
+
+#
+# Additional supported languages:
+#
+# CT_CC_LANG_CXX is not set
+
+#
+# gcc other options
+#
+CT_CC_ENABLE_CXX_FLAGS=""
+CT_CC_CORE_EXTRA_CONFIG_ARRAY=""
+CT_CC_STATIC_LIBSTDCXX=y
+
+#
+# Optimisation features
+#
+CT_CC_GCC_USE_GRAPHITE=y
+
+#
+# Settings for libraries running on target
+#
+# CT_CC_GCC_ENABLE_TARGET_OPTSPACE is not set
+# CT_CC_GCC_LIBMUDFLAP is not set
+# CT_CC_GCC_LIBGOMP is not set
+# CT_CC_GCC_LIBSSP is not set
+
+#
+# Misc. obscure options.
+#
+# CT_CC_GCC_DISABLE_PCH is not set
+CT_CC_GCC_LDBL_128=m
+CT_CC_GCC_HAS_ARCH_OPTIONS=y
+
+#
+# archictecture-specific options
+#
+CT_CC_GCC_mips_llsc=m
+CT_CC_GCC_mips_synci=m
+# CT_CC_GCC_mips_plt is not set
+
+#
+# C-library
+#
+CT_LIBC="none"
+# CT_LIBC_newlib is not set
+CT_LIBC_none=y
+CT_LIBC_eglibc_AVAILABLE=y
+CT_LIBC_glibc_AVAILABLE=y
+CT_LIBC_mingw_AVAILABLE=y
+CT_LIBC_newlib_AVAILABLE=y
+CT_LIBC_none_AVAILABLE=y
+CT_LIBC_uClibc_AVAILABLE=y
+CT_THREADS="none"
+
+#
+# Debug facilities
+#
+# CT_DEBUG_dmalloc is not set
+# CT_DEBUG_duma is not set
+CT_DEBUG_gdb=y
+CT_GDB_CROSS=y
+# CT_GDB_CROSS_STATIC is not set
+
+#
+# In bare-metal, you'll need to   
+#
+
+#
+# provide your own gdbserver stub.
+#
+
+#
+# gdb version
+#
+CT_GDB_V_6_8a=y
+CT_GDB_VERSION="6.8a"
+# CT_DEBUG_ltrace is not set
+# CT_DEBUG_strace is not set
+
+#
+# Companion libraries
+#
+CT_COMPLIBS_NEEDED=y
+CT_GMP_NEEDED=y
+CT_MPFR_NEEDED=y
+CT_PPL_NEEDED=y
+CT_CLOOG_NEEDED=y
+CT_COMPLIBS=y
+CT_GMP=y
+CT_MPFR=y
+CT_PPL=y
+CT_CLOOG=y
+CT_GMP_V_4_3_2=y
+# CT_GMP_V_4_3_1 is not set
+# CT_GMP_V_4_3_0 is not set
+CT_GMP_VERSION="4.3.2"
+# CT_MPFR_V_3_0_0 is not set
+CT_MPFR_V_2_4_2=y
+# CT_MPFR_V_2_4_1 is not set
+# CT_MPFR_V_2_4_0 is not set
+CT_MPFR_VERSION="2.4.2"
+CT_PPL_V_0_10_2=y
+CT_PPL_VERSION="0.10.2"
+CT_CLOOG_V_0_15_10=y
+# CT_CLOOG_V_0_15_9 is not set
+# CT_CLOOG_V_0_15_8 is not set
+# CT_CLOOG_V_0_15_7 is not set
+# CT_CLOOG_V_0_15_6 is not set
+CT_CLOOG_VERSION="0.15.10"
+
+#
+# Companion libraries common options
+#
+# CT_COMPLIBS_CHECK is not set
diff -r 7df89370f805 -r f02a0a9c2a05 samples/mipsel-sde-elf/reported.by
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/samples/mipsel-sde-elf/reported.by	Sun Sep 25 15:21:29 2011 -0700
@@ -0,0 +1,3 @@
+reporter_name="Kevin Cernekee"
+reporter_url=""
+reporter_comment="MIPS SDE-compatible toolchain"

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Re: [PATCH 0/1] MIPS SDE-compatible bare metal target

[Yann E. MORIN]

On Monday 26 September 2011 00:49:15 Kevin Cernekee wrote:
> I ran into a couple of semi-obscure issues linking objects generated
> from the mips-unknown-elf sample toolchain into a program built with
> Sourcery G++ (now Sourcery CodeBench), and I wanted to pitch the idea of
> including an SDE-compatible sample config in the release.
> 
> I have not performed enough testing to be confident that I know about
> all of the changes needed for 100% SDE compatibility, but maybe this
> will get the ball rolling and somebody more knowledgeable can help fill
> in the gaps...
> 
> Problem #1:
> 
> mips-unknown-elf uses SGI-compatible symbol ordering:
[--SNIP--]
> In SGI mode, sh_info in the symtab's section header entry points to line
> 18.
> 
> By contrast, a copy of binutils that had been built as an SDE or Linux
> toolchain assumes that sh_info points to the first global symbol, and
> that all local symbols (such as $LC0) have an index lower than sh_info
> (in this case, 20):
[--SNIP--]
> A non-SGI ld may report the former case as a malformed object file:
> 
> mipsel-linux-ld: error: _fixunssfsi-sgi.o contains a reloc
> (0x0000000000001705) for section .text that references a non-existent
> global symbol
> mipsel-linux-ld: final link failed: Bad value
> 
> Fix: use "sde" instead of "unknown" for CT_TARGET_VENDOR.  If the tuple
> is mips-sde-elf, binutils will disable the SGI/IRIX quirks.

Oh, so we have a case where the vendor part of the tuple *is* actually
meaningful. Sigh...

> Problem #2:
> 
> In my test runs, CT_CC_GCC_ENABLE_TARGET_OPTSPACE caused libgcc to be
> built with the MIPS SDA data model.  i.e. it assumes that $gp always
> points to a "small data area" which can access items in the .sdata and
> .sbss sections using just a signed 16-bit offset.  Many embedded
> programs do use SDA, but some do not and this could cause
> incompatibilities.
> 
> Fix: disable CT_CC_GCC_ENABLE_TARGET_OPTSPACE

OK.

Thank you for documenting all of this. :-)

Regards,
Yann E. MORIN.

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Re: [PATCH 1/1] samples: add new mipsel-sde-elf sample.

[Yann E. MORIN]

Kevin, All,

On Monday 26 September 2011 00:49:16 Kevin Cernekee wrote:
> # HG changeset patch
> # User Kevin Cernekee <cernekee@gmail.com>
> # Date 1316989289 25200
> # Node ID f02a0a9c2a054f3ac5791457e157bbfca5bcfd04
> # Parent  7df89370f80537d1b36b2fda70e3a1c6bc237a65
> samples: add new mipsel-sde-elf sample.
> 
> Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
[--SNIP--]
> diff -r 7df89370f805 -r f02a0a9c2a05 samples/mipsel-sde-elf/reported.by
> --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
> +++ b/samples/mipsel-sde-elf/reported.by	Sun Sep 25 15:21:29 2011 -0700
> @@ -0,0 +1,3 @@
> +reporter_name="Kevin Cernekee"
> +reporter_url=""

I'll add a pointer to this thread in the url above.

> +reporter_comment="MIPS SDE-compatible toolchain"

I'll push it in a moment. Thank you!

Regards,
Yann E. MORIN.

-- 
.-----------------.--------------------.------------------.--------------------.
|  Yann E. MORIN  | Real-Time Embedded | /"\ ASCII RIBBON | Erics' conspiracy: |
| +33 662 376 056 | Software  Designer | \ / CAMPAIGN     |  ___               |
| +33 223 225 172 `------------.-------:  X  AGAINST      |  \e/  There is no  |
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Re: [PATCH 1/1] samples: add new mipsel-sde-elf sample.

[Yann E. MORIN]

Kevin, All,

On Monday 26 September 2011 00:49:16 Kevin Cernekee wrote:
> # HG changeset patch
> # User Kevin Cernekee <cernekee@gmail.com>
> # Date 1316989289 25200
> # Node ID f02a0a9c2a054f3ac5791457e157bbfca5bcfd04
> # Parent  7df89370f80537d1b36b2fda70e3a1c6bc237a65
> samples: add new mipsel-sde-elf sample.

Pushed as #ced78fd59221. Thank you!

Regards,
Yann E. MORIN.

-- 
.-----------------.--------------------.------------------.--------------------.
|  Yann E. MORIN  | Real-Time Embedded | /"\ ASCII RIBBON | Erics' conspiracy: |
| +33 662 376 056 | Software  Designer | \ / CAMPAIGN     |  ___               |
| +33 223 225 172 `------------.-------:  X  AGAINST      |  \e/  There is no  |
| http://ymorin.is-a-geek.org/ | _/*\_ | / \ HTML MAIL    |   v   conspiracy.  |
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