Add musl support to gcc
  
  This patch comes from the musl-cross project at
  https://bitbucket.org/GregorR/musl-cross/src. Compared to the upstream version:
  
   * the config.sub modifications have been removed, because Buildroot
     already overwrites all config.sub with a more recent config.sub
     that has musl support.
  
   * change to ensure that a dummy dynamic linker path
     MUSL_DYNAMIC_LINKER<foo> is defined for all architectures,
     otherwise building gcc for architectures not supported by musl was
     causing build failure. Bug reported upstream at
     https://bitbucket.org/GregorR/musl-gcc-patches/issue/4/musl-gcc-patches-break-the-build-on.
  
   * change the USE_PT_GNU_EH_FRAME logic to keep the existing gcc logic
     and only add the musl one as an addition, not as a replacement. Not
     doing this breaks C++ exception handling with glibc, because
     USE_PT_GNU_EH_FRAME doesn't get defined due to the configure script
     not testing dl_iterate_phdr() on any system except Solaris.
  
  [Gustavo: remove upstream applied gcc/config/sh/sh.c chunk for 4.9.1]
  Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
  ---
  
  Index: b/fixincludes/mkfixinc.sh
  ===================================================================
  --- a/fixincludes/mkfixinc.sh
  +++ b/fixincludes/mkfixinc.sh
  @@ -19,7 +19,8 @@
       powerpc-*-eabi*    | \
       powerpc-*-rtems*   | \
       powerpcle-*-eabisim* | \
  -    powerpcle-*-eabi* )
  +    powerpcle-*-eabi* | \
  +    *-musl* )
   	#  IF there is no include fixing,
   	#  THEN create a no-op fixer and exit
   	(echo "#! /bin/sh" ; echo "exit 0" ) > ${target}
  Index: b/gcc/config.gcc
  ===================================================================
  --- a/gcc/config.gcc
  +++ b/gcc/config.gcc
  @@ -594,7 +594,7 @@
   esac
   
   # Common C libraries.
  -tm_defines="$tm_defines LIBC_GLIBC=1 LIBC_UCLIBC=2 LIBC_BIONIC=3"
  +tm_defines="$tm_defines LIBC_GLIBC=1 LIBC_UCLIBC=2 LIBC_BIONIC=3 LIBC_MUSL=4"
   
   # 32-bit x86 processors supported by --with-arch=.  Each processor
   # MUST be separated by exactly one space.
  @@ -719,6 +719,9 @@
       *-*-*uclibc*)
         tm_defines="$tm_defines DEFAULT_LIBC=LIBC_UCLIBC"
         ;;
  +    *-*-*musl*)
  +      tm_defines="$tm_defines DEFAULT_LIBC=LIBC_MUSL"
  +      ;;
       *)
         tm_defines="$tm_defines DEFAULT_LIBC=LIBC_GLIBC"
         ;;
  @@ -2338,6 +2341,10 @@
   	    powerpc*-*-linux*paired*)
   		tm_file="${tm_file} rs6000/750cl.h" ;;
   	esac
  +        case ${target} in
  +            *-linux*-musl*)
  +                enable_secureplt=yes ;;
  +        esac
   	if test x${enable_secureplt} = xyes; then
   		tm_file="rs6000/secureplt.h ${tm_file}"
   	fi
  Index: b/gcc/config/aarch64/aarch64-linux.h
  ===================================================================
  --- a/gcc/config/aarch64/aarch64-linux.h
  +++ b/gcc/config/aarch64/aarch64-linux.h
  @@ -22,6 +22,8 @@
   #define GCC_AARCH64_LINUX_H
   
   #define GLIBC_DYNAMIC_LINKER "/lib/ld-linux-aarch64%{mbig-endian:_be}.so.1"
  +#undef MUSL_DYNAMIC_LINKER
  +#define MUSL_DYNAMIC_LINKER "/lib/ld-musl-aarch64.so.1"
   
   #define CPP_SPEC "%{pthread:-D_REENTRANT}"
   
  Index: b/gcc/config/arm/linux-eabi.h
  ===================================================================
  --- a/gcc/config/arm/linux-eabi.h
  +++ b/gcc/config/arm/linux-eabi.h
  @@ -77,6 +77,23 @@
       %{mfloat-abi=soft*:" GLIBC_DYNAMIC_LINKER_SOFT_FLOAT "} \
       %{!mfloat-abi=*:" GLIBC_DYNAMIC_LINKER_DEFAULT "}"
   
  +/* For ARM musl currently supports four dynamic linkers:
  +   - ld-musl-arm.so.1 - for the EABI-derived soft-float ABI
  +   - ld-musl-armhf.so.1 - for the EABI-derived hard-float ABI
  +   - ld-musl-armeb.so.1 - for the EABI-derived soft-float ABI, EB
  +   - ld-musl-armebhf.so.1 - for the EABI-derived hard-float ABI, EB
  +   musl does not support the legacy OABI mode.
  +   All the dynamic linkers live in /lib.
  +   We default to soft-float, EL. */
  +#undef  MUSL_DYNAMIC_LINKER
  +#if TARGET_BIG_ENDIAN_DEFAULT
  +#define MUSL_DYNAMIC_LINKER_E "%{mlittle-endian:;:eb}"
  +#else
  +#define MUSL_DYNAMIC_LINKER_E "%{mbig-endian:eb}"
  +#endif
  +#define MUSL_DYNAMIC_LINKER \
  +  "/lib/ld-musl-arm" MUSL_DYNAMIC_LINKER_E "%{mfloat-abi=hard:hf}.so.1"
  +
   /* At this point, bpabi.h will have clobbered LINK_SPEC.  We want to
      use the GNU/Linux version, not the generic BPABI version.  */
   #undef  LINK_SPEC
  Index: b/gcc/config/i386/linux.h
  ===================================================================
  --- a/gcc/config/i386/linux.h
  +++ b/gcc/config/i386/linux.h
  @@ -21,3 +21,5 @@
   
   #define GNU_USER_LINK_EMULATION "elf_i386"
   #define GLIBC_DYNAMIC_LINKER "/lib/ld-linux.so.2"
  +#undef MUSL_DYNAMIC_LINKER
  +#define MUSL_DYNAMIC_LINKER "/lib/ld-musl-i386.so.1"
  Index: b/gcc/config/i386/linux64.h
  ===================================================================
  --- a/gcc/config/i386/linux64.h
  +++ b/gcc/config/i386/linux64.h
  @@ -30,3 +30,10 @@
   #define GLIBC_DYNAMIC_LINKER32 "/lib/ld-linux.so.2"
   #define GLIBC_DYNAMIC_LINKER64 "/lib64/ld-linux-x86-64.so.2"
   #define GLIBC_DYNAMIC_LINKERX32 "/libx32/ld-linux-x32.so.2"
  +
  +#undef MUSL_DYNAMIC_LINKER32
  +#define MUSL_DYNAMIC_LINKER32 "/lib/ld-musl-i386.so.1"
  +#undef MUSL_DYNAMIC_LINKER64
  +#define MUSL_DYNAMIC_LINKER64 "/lib/ld-musl-x86_64.so.1"
  +#undef MUSL_DYNAMIC_LINKERX32
  +#define MUSL_DYNAMIC_LINKERX32 "/lib/ld-musl-x32.so.1"
  Index: b/gcc/config/linux.h
  ===================================================================
  --- a/gcc/config/linux.h
  +++ b/gcc/config/linux.h
  @@ -32,10 +32,12 @@
   #define OPTION_GLIBC  (DEFAULT_LIBC == LIBC_GLIBC)
   #define OPTION_UCLIBC (DEFAULT_LIBC == LIBC_UCLIBC)
   #define OPTION_BIONIC (DEFAULT_LIBC == LIBC_BIONIC)
  +#define OPTION_MUSL   (DEFAULT_LIBC == LIBC_MUSL)
   #else
   #define OPTION_GLIBC  (linux_libc == LIBC_GLIBC)
   #define OPTION_UCLIBC (linux_libc == LIBC_UCLIBC)
   #define OPTION_BIONIC (linux_libc == LIBC_BIONIC)
  +#define OPTION_MUSL   (linux_libc == LIBC_MUSL)
   #endif
   
   #define GNU_USER_TARGET_OS_CPP_BUILTINS()			\
  @@ -53,18 +55,21 @@
      uClibc or Bionic is the default C library and whether
      -muclibc or -mglibc or -mbionic has been passed to change the default.  */
   
  -#define CHOOSE_DYNAMIC_LINKER1(LIBC1, LIBC2, LIBC3, LD1, LD2, LD3)	\
  -  "%{" LIBC2 ":" LD2 ";:%{" LIBC3 ":" LD3 ";:" LD1 "}}"
  +#define CHOOSE_DYNAMIC_LINKER1(LIBC1, LIBC2, LIBC3, LIBC4, LD1, LD2, LD3, LD4)	\
  +  "%{" LIBC2 ":" LD2 ";:%{" LIBC3 ":" LD3 ";:%{" LIBC4 ":" LD4 ";:" LD1 "}}}"
   
   #if DEFAULT_LIBC == LIBC_GLIBC
  -#define CHOOSE_DYNAMIC_LINKER(G, U, B) \
  -  CHOOSE_DYNAMIC_LINKER1 ("mglibc", "muclibc", "mbionic", G, U, B)
  +#define CHOOSE_DYNAMIC_LINKER(G, U, B, M) \
  +  CHOOSE_DYNAMIC_LINKER1 ("mglibc", "muclibc", "mbionic", "mmusl", G, U, B, M)
   #elif DEFAULT_LIBC == LIBC_UCLIBC
  -#define CHOOSE_DYNAMIC_LINKER(G, U, B) \
  -  CHOOSE_DYNAMIC_LINKER1 ("muclibc", "mglibc", "mbionic", U, G, B)
  +#define CHOOSE_DYNAMIC_LINKER(G, U, B, M) \
  +  CHOOSE_DYNAMIC_LINKER1 ("muclibc", "mglibc", "mbionic", "mmusl", U, G, B, M)
   #elif DEFAULT_LIBC == LIBC_BIONIC
  -#define CHOOSE_DYNAMIC_LINKER(G, U, B) \
  -  CHOOSE_DYNAMIC_LINKER1 ("mbionic", "mglibc", "muclibc", B, G, U)
  +#define CHOOSE_DYNAMIC_LINKER(G, U, B, M) \
  +  CHOOSE_DYNAMIC_LINKER1 ("mbionic", "mglibc", "muclibc", "mmusl", B, G, U, M)
  +#elif DEFAULT_LIBC == LIBC_MUSL
  +#define CHOOSE_DYNAMIC_LINKER(G, U, B, M) \
  +  CHOOSE_DYNAMIC_LINKER1 ("mmusl", "mglibc", "muclibc", "mbionic", M, G, U, B)
   #else
   #error "Unsupported DEFAULT_LIBC"
   #endif /* DEFAULT_LIBC */
  @@ -82,23 +87,103 @@
   #define BIONIC_DYNAMIC_LINKER64 "/system/bin/linker64"
   #define BIONIC_DYNAMIC_LINKERX32 "/system/bin/linkerx32"
   
  +/* Musl dynamic linker paths must be defined on a per-architecture
  +   basis, for each architecture supported by Musl. However, in order
  +   to let other architectures continue to build with other C
  +   libraries, we provide a dummy definition of the following defines. */
  +#define MUSL_DYNAMIC_LINKER "invalid"
  +#define MUSL_DYNAMIC_LINKER32 "invalid"
  +#define MUSL_DYNAMIC_LINKER64 "invalid"
  +#define MUSL_DYNAMIC_LINKERX32 "invalid"
  +
   #define GNU_USER_DYNAMIC_LINKER						\
     CHOOSE_DYNAMIC_LINKER (GLIBC_DYNAMIC_LINKER, UCLIBC_DYNAMIC_LINKER,	\
  -			 BIONIC_DYNAMIC_LINKER)
  +			 BIONIC_DYNAMIC_LINKER, MUSL_DYNAMIC_LINKER)
   #define GNU_USER_DYNAMIC_LINKER32					\
     CHOOSE_DYNAMIC_LINKER (GLIBC_DYNAMIC_LINKER32, UCLIBC_DYNAMIC_LINKER32, \
  -			 BIONIC_DYNAMIC_LINKER32)
  +			 BIONIC_DYNAMIC_LINKER32, MUSL_DYNAMIC_LINKER32)
   #define GNU_USER_DYNAMIC_LINKER64					\
     CHOOSE_DYNAMIC_LINKER (GLIBC_DYNAMIC_LINKER64, UCLIBC_DYNAMIC_LINKER64, \
  -			 BIONIC_DYNAMIC_LINKER64)
  +			 BIONIC_DYNAMIC_LINKER64, MUSL_DYNAMIC_LINKER64)
   #define GNU_USER_DYNAMIC_LINKERX32					\
     CHOOSE_DYNAMIC_LINKER (GLIBC_DYNAMIC_LINKERX32, UCLIBC_DYNAMIC_LINKERX32, \
  -			 BIONIC_DYNAMIC_LINKERX32)
  +			 BIONIC_DYNAMIC_LINKERX32, MUSL_DYNAMIC_LINKER32)
   
   /* Whether we have Bionic libc runtime */
   #undef TARGET_HAS_BIONIC
   #define TARGET_HAS_BIONIC (OPTION_BIONIC)
   
  +/* musl avoids problematic includes by rearranging the include directories.
  + * Unfortunately, this is mostly duplicated from cppdefault.c */
  +#if DEFAULT_LIBC == LIBC_MUSL
  +#define INCLUDE_DEFAULTS_MUSL_GPP			\
  +    { GPLUSPLUS_INCLUDE_DIR, "G++", 1, 1,		\
  +      GPLUSPLUS_INCLUDE_DIR_ADD_SYSROOT, 0 },		\
  +    { GPLUSPLUS_TOOL_INCLUDE_DIR, "G++", 1, 1,		\
  +      GPLUSPLUS_INCLUDE_DIR_ADD_SYSROOT, 1 },		\
  +    { GPLUSPLUS_BACKWARD_INCLUDE_DIR, "G++", 1, 1,	\
  +      GPLUSPLUS_INCLUDE_DIR_ADD_SYSROOT, 0 },
  +
  +#ifdef LOCAL_INCLUDE_DIR
  +#define INCLUDE_DEFAULTS_MUSL_LOCAL			\
  +    { LOCAL_INCLUDE_DIR, 0, 0, 1, 1, 2 },		\
  +    { LOCAL_INCLUDE_DIR, 0, 0, 1, 1, 0 },
  +#else
  +#define INCLUDE_DEFAULTS_MUSL_LOCAL
  +#endif
  +
  +#ifdef PREFIX_INCLUDE_DIR
  +#define INCLUDE_DEFAULTS_MUSL_PREFIX			\
  +    { PREFIX_INCLUDE_DIR, 0, 0, 1, 0, 0},
  +#else
  +#define INCLUDE_DEFAULTS_MUSL_PREFIX
  +#endif
  +
  +#ifdef CROSS_INCLUDE_DIR
  +#define INCLUDE_DEFAULTS_MUSL_CROSS			\
  +    { CROSS_INCLUDE_DIR, "GCC", 0, 0, 0, 0},
  +#else
  +#define INCLUDE_DEFAULTS_MUSL_CROSS
  +#endif
  +
  +#ifdef TOOL_INCLUDE_DIR
  +#define INCLUDE_DEFAULTS_MUSL_TOOL			\
  +    { TOOL_INCLUDE_DIR, "BINUTILS", 0, 1, 0, 0},
  +#else
  +#define INCLUDE_DEFAULTS_MUSL_TOOL
  +#endif
  +
  +#ifdef NATIVE_SYSTEM_HEADER_DIR
  +#define INCLUDE_DEFAULTS_MUSL_NATIVE			\
  +    { NATIVE_SYSTEM_HEADER_DIR, 0, 0, 0, 1, 2 },	\
  +    { NATIVE_SYSTEM_HEADER_DIR, 0, 0, 0, 1, 0 },
  +#else
  +#define INCLUDE_DEFAULTS_MUSL_NATIVE
  +#endif
  +
  +#if defined (CROSS_DIRECTORY_STRUCTURE) && !defined (TARGET_SYSTEM_ROOT)
  +# undef INCLUDE_DEFAULTS_MUSL_LOCAL
  +# define INCLUDE_DEFAULTS_MUSL_LOCAL
  +# undef INCLUDE_DEFAULTS_MUSL_NATIVE
  +# define INCLUDE_DEFAULTS_MUSL_NATIVE
  +#else
  +# undef INCLUDE_DEFAULTS_MUSL_CROSS
  +# define INCLUDE_DEFAULTS_MUSL_CROSS
  +#endif
  +
  +#undef INCLUDE_DEFAULTS
  +#define INCLUDE_DEFAULTS				\
  +  {							\
  +    INCLUDE_DEFAULTS_MUSL_GPP				\
  +    INCLUDE_DEFAULTS_MUSL_PREFIX			\
  +    INCLUDE_DEFAULTS_MUSL_CROSS				\
  +    INCLUDE_DEFAULTS_MUSL_TOOL				\
  +    INCLUDE_DEFAULTS_MUSL_NATIVE			\
  +    { GCC_INCLUDE_DIR, "GCC", 0, 1, 0, 0 },		\
  +    { 0, 0, 0, 0, 0, 0 }				\
  +  }
  +#endif
  +
   #if (DEFAULT_LIBC == LIBC_UCLIBC) && defined (SINGLE_LIBC) /* uClinux */
   /* This is a *uclinux* target.  We don't define below macros to normal linux
      versions, because doing so would require *uclinux* targets to include
  Index: b/gcc/config/linux.opt
  ===================================================================
  --- a/gcc/config/linux.opt
  +++ b/gcc/config/linux.opt
  @@ -30,3 +30,7 @@
   muclibc
   Target Report RejectNegative Var(linux_libc,LIBC_UCLIBC) Negative(mbionic)
   Use uClibc C library
  +
  +mmusl
  +Target Report RejectNegative Var(linux_libc,LIBC_MUSL) Negative(mglibc)
  +Use musl C library
  Index: b/gcc/config/microblaze/linux.h
  ===================================================================
  --- a/gcc/config/microblaze/linux.h
  +++ b/gcc/config/microblaze/linux.h
  @@ -28,7 +28,23 @@
   #undef TLS_NEEDS_GOT
   #define TLS_NEEDS_GOT 1
   
  -#define DYNAMIC_LINKER "/lib/ld.so.1"
  +#if TARGET_BIG_ENDIAN_DEFAULT == 0 /* LE */
  +#define MUSL_DYNAMIC_LINKER_E "%{EB:;:el}"
  +#else
  +#define MUSL_DYNAMIC_LINKER_E "%{EL:el}"
  +#endif
  +
  +#undef MUSL_DYNAMIC_LINKER
  +#define MUSL_DYNAMIC_LINKER "/lib/ld-musl-microblaze" MUSL_DYNAMIC_LINKER_E ".so.1"
  +#define GLIBC_DYNAMIC_LINKER "/lib/ld.so.1"
  +
  +#if DEFAULT_LIBC == LIBC_MUSL
  +#define DYNAMIC_LINKER MUSL_DYNAMIC_LINKER
  +#else
  +#define DYNAMIC_LINKER GLIBC_DYNAMIC_LINKER
  +#endif
  +
  +
   #undef  SUBTARGET_EXTRA_SPECS
   #define SUBTARGET_EXTRA_SPECS \
     { "dynamic_linker", DYNAMIC_LINKER }
  Index: b/gcc/config/rs6000/linux64.h
  ===================================================================
  --- a/gcc/config/rs6000/linux64.h
  +++ b/gcc/config/rs6000/linux64.h
  @@ -371,17 +371,23 @@
   #endif
   #define UCLIBC_DYNAMIC_LINKER32 "/lib/ld-uClibc.so.0"
   #define UCLIBC_DYNAMIC_LINKER64 "/lib/ld64-uClibc.so.0"
  +#undef MUSL_DYNAMIC_LINKER32
  +#define MUSL_DYNAMIC_LINKER32 "/lib/ld-musl-powerpc.so.1"
  +#undef MUSL_DYNAMIC_LINKER64
  +#define MUSL_DYNAMIC_LINKER64 "/lib/ld-musl-powerpc64.so.1"
   #if DEFAULT_LIBC == LIBC_UCLIBC
  -#define CHOOSE_DYNAMIC_LINKER(G, U) "%{mglibc:" G ";:" U "}"
  +#define CHOOSE_DYNAMIC_LINKER(G, U, M) "%{mglibc:" G ";:%{mmusl:" M ";:" U "}}"
   #elif DEFAULT_LIBC == LIBC_GLIBC
  -#define CHOOSE_DYNAMIC_LINKER(G, U) "%{muclibc:" U ";:" G "}"
  +#define CHOOSE_DYNAMIC_LINKER(G, U, M) "%{muclibc:" U ";:%{mmusl:" M ";:" G "}}"
  +#elif DEFAULT_LIBC == LIBC_MUSL
  +#define CHOOSE_DYNAMIC_LINKER(G, U, M) "%{mglibc:" G ";:%{muclibc:" U ";:" M "}}"
   #else
   #error "Unsupported DEFAULT_LIBC"
   #endif
   #define GNU_USER_DYNAMIC_LINKER32 \
  -  CHOOSE_DYNAMIC_LINKER (GLIBC_DYNAMIC_LINKER32, UCLIBC_DYNAMIC_LINKER32)
  +  CHOOSE_DYNAMIC_LINKER (GLIBC_DYNAMIC_LINKER32, UCLIBC_DYNAMIC_LINKER32, MUSL_DYNAMIC_LINKER32)
   #define GNU_USER_DYNAMIC_LINKER64 \
  -  CHOOSE_DYNAMIC_LINKER (GLIBC_DYNAMIC_LINKER64, UCLIBC_DYNAMIC_LINKER64)
  +  CHOOSE_DYNAMIC_LINKER (GLIBC_DYNAMIC_LINKER64, UCLIBC_DYNAMIC_LINKER64, MUSL_DYNAMIC_LINKER64)
   
   #undef  DEFAULT_ASM_ENDIAN
   #if (TARGET_DEFAULT & MASK_LITTLE_ENDIAN)
  Index: b/gcc/config/rs6000/secureplt.h
  ===================================================================
  --- a/gcc/config/rs6000/secureplt.h
  +++ b/gcc/config/rs6000/secureplt.h
  @@ -18,3 +18,4 @@
   <http://www.gnu.org/licenses/>.  */
   
   #define CC1_SECURE_PLT_DEFAULT_SPEC "-msecure-plt"
  +#define LINK_SECURE_PLT_DEFAULT_SPEC "--secure-plt"
  Index: b/gcc/config/rs6000/sysv4.h
  ===================================================================
  --- a/gcc/config/rs6000/sysv4.h
  +++ b/gcc/config/rs6000/sysv4.h
  @@ -537,6 +537,9 @@
   #ifndef CC1_SECURE_PLT_DEFAULT_SPEC
   #define CC1_SECURE_PLT_DEFAULT_SPEC ""
   #endif
  +#ifndef LINK_SECURE_PLT_DEFAULT_SPEC
  +#define LINK_SECURE_PLT_DEFAULT_SPEC ""
  +#endif
   
   /* Pass -G xxx to the compiler.  */
   #define	CC1_SPEC "%{G*} %(cc1_cpu)" \
  @@ -585,7 +588,8 @@
   
   /* Override the default target of the linker.  */
   #define	LINK_TARGET_SPEC \
  -  ENDIAN_SELECT("", " --oformat elf32-powerpcle", "")
  +  ENDIAN_SELECT("", " --oformat elf32-powerpcle", "") \
  +  "%{!mbss-plt: %{!msecure-plt: %(link_secure_plt_default)}}"
   
   /* Any specific OS flags.  */
   #define LINK_OS_SPEC "\
  @@ -763,15 +767,18 @@
   
   #define GLIBC_DYNAMIC_LINKER "/lib/ld.so.1"
   #define UCLIBC_DYNAMIC_LINKER "/lib/ld-uClibc.so.0"
  +#define MUSL_DYNAMIC_LINKER "/lib/ld-musl-powerpc.so.1"
   #if DEFAULT_LIBC == LIBC_UCLIBC
  -#define CHOOSE_DYNAMIC_LINKER(G, U) "%{mglibc:" G ";:" U "}"
  +#define CHOOSE_DYNAMIC_LINKER(G, U, M) "%{mglibc:" G ";:%{mmusl:" M ";:" U "}}"
  +#elif DEFAULT_LIBC == LIBC_MUSL
  +#define CHOOSE_DYNAMIC_LINKER(G, U, M) "%{mglibc:" G ";:%{muclibc:" U ";:" M "}}"
   #elif !defined (DEFAULT_LIBC) || DEFAULT_LIBC == LIBC_GLIBC
  -#define CHOOSE_DYNAMIC_LINKER(G, U) "%{muclibc:" U ";:" G "}"
  +#define CHOOSE_DYNAMIC_LINKER(G, U, M) "%{muclibc:" U ";:%{mmusl:" M ";:" G "}}"
   #else
   #error "Unsupported DEFAULT_LIBC"
   #endif
   #define GNU_USER_DYNAMIC_LINKER \
  -  CHOOSE_DYNAMIC_LINKER (GLIBC_DYNAMIC_LINKER, UCLIBC_DYNAMIC_LINKER)
  +  CHOOSE_DYNAMIC_LINKER (GLIBC_DYNAMIC_LINKER, UCLIBC_DYNAMIC_LINKER, MUSL_DYNAMIC_LINKER)
   
   #define LINK_OS_LINUX_SPEC "-m elf32ppclinux %{!shared: %{!static: \
     %{rdynamic:-export-dynamic} \
  @@ -894,6 +901,7 @@
     { "link_os_openbsd",		LINK_OS_OPENBSD_SPEC },			\
     { "link_os_default",		LINK_OS_DEFAULT_SPEC },			\
     { "cc1_secure_plt_default",	CC1_SECURE_PLT_DEFAULT_SPEC },		\
  +  { "link_secure_plt_default",	LINK_SECURE_PLT_DEFAULT_SPEC },		\
     { "cpp_os_ads",		CPP_OS_ADS_SPEC },			\
     { "cpp_os_yellowknife",	CPP_OS_YELLOWKNIFE_SPEC },		\
     { "cpp_os_mvme",		CPP_OS_MVME_SPEC },			\
  Index: b/gcc/config/sh/linux.h
  ===================================================================
  --- a/gcc/config/sh/linux.h
  +++ b/gcc/config/sh/linux.h
  @@ -43,7 +43,15 @@
   
   #define TARGET_ASM_FILE_END file_end_indicate_exec_stack
   
  +#if TARGET_BIG_ENDIAN_DEFAULT /* BE */
  +#define MUSL_DYNAMIC_LINKER_E "eb"
  +#else
  +#define MUSL_DYNAMIC_LINKER_E
  +#endif
  +
   #define GLIBC_DYNAMIC_LINKER "/lib/ld-linux.so.2"
  +#undef MUSL_DYNAMIC_LINKER
  +#define MUSL_DYNAMIC_LINKER "/lib/ld-musl-sh" MUSL_DYNAMIC_LINKER_E ".so.1"
   
   #undef SUBTARGET_LINK_EMUL_SUFFIX
   #define SUBTARGET_LINK_EMUL_SUFFIX "_linux"
  Index: b/gcc/configure
  ===================================================================
  --- a/gcc/configure
  +++ b/gcc/configure
  @@ -27601,6 +27601,9 @@
         gcc_cv_target_dl_iterate_phdr=no
       fi
       ;;
  +  *-linux-musl*)
  +    gcc_cv_target_dl_iterate_phdr=yes
  +    ;;
   esac
   
   if test x$gcc_cv_target_dl_iterate_phdr = xyes; then
  Index: b/gcc/configure.ac
  ===================================================================
  --- a/gcc/configure.ac
  +++ b/gcc/configure.ac
  @@ -5173,6 +5173,9 @@
         gcc_cv_target_dl_iterate_phdr=no
       fi
       ;;
  +  *-linux-musl*)
  +    gcc_cv_target_dl_iterate_phdr=yes
  +    ;;
   esac
   GCC_TARGET_TEMPLATE([TARGET_DL_ITERATE_PHDR])
   if test x$gcc_cv_target_dl_iterate_phdr = xyes; then
  Index: b/gcc/ginclude/stddef.h
  ===================================================================
  --- a/gcc/ginclude/stddef.h
  +++ b/gcc/ginclude/stddef.h
  @@ -181,6 +181,7 @@
   #ifndef _GCC_SIZE_T
   #ifndef _SIZET_
   #ifndef __size_t
  +#ifndef __DEFINED_size_t /* musl */
   #define __size_t__	/* BeOS */
   #define __SIZE_T__	/* Cray Unicos/Mk */
   #define _SIZE_T
  @@ -197,6 +198,7 @@
   #define ___int_size_t_h
   #define _GCC_SIZE_T
   #define _SIZET_
  +#define __DEFINED_size_t /* musl */
   #if (defined (__FreeBSD__) && (__FreeBSD__ >= 5)) \
     || defined(__FreeBSD_kernel__)
   /* __size_t is a typedef on FreeBSD 5, must not trash it. */
  @@ -214,6 +216,7 @@
   typedef long ssize_t;
   #endif /* __BEOS__ */
   #endif /* !(defined (__GNUG__) && defined (size_t)) */
  +#endif /* __DEFINED_size_t */
   #endif /* __size_t */
   #endif /* _SIZET_ */
   #endif /* _GCC_SIZE_T */
  Index: b/libgcc/unwind-dw2-fde-dip.c
  ===================================================================
  --- a/libgcc/unwind-dw2-fde-dip.c
  +++ b/libgcc/unwind-dw2-fde-dip.c
  @@ -73,6 +73,13 @@
       && defined(TARGET_DL_ITERATE_PHDR) \
       && defined(__sun__) && defined(__svr4__)
   # define USE_PT_GNU_EH_FRAME
  + #endif
  +
  +/* For musl libc, TARGET_DL_ITERATE_PHDR gets defined by the configure
  +   script. */
  +#if !defined(inhibit_libc) && defined(HAVE_LD_EH_FRAME_HDR)	\
  +  && defined(TARGET_DL_ITERATE_PHDR)
  +# define USE_PT_GNU_EH_FRAME
   #endif
   
   #if defined(USE_PT_GNU_EH_FRAME)
  Index: b/libgomp/config/posix/time.c
  ===================================================================
  --- a/libgomp/config/posix/time.c
  +++ b/libgomp/config/posix/time.c
  @@ -28,6 +28,8 @@
      The following implementation uses the most simple POSIX routines.
      If present, POSIX 4 clocks should be used instead.  */
   
  +#define _POSIX_C_SOURCE 199309L /* for clocks */
  +
   #include "libgomp.h"
   #include <unistd.h>
   #if TIME_WITH_SYS_TIME
  Index: b/libitm/config/arm/hwcap.cc
  ===================================================================
  --- a/libitm/config/arm/hwcap.cc
  +++ b/libitm/config/arm/hwcap.cc
  @@ -40,7 +40,11 @@
   
   #ifdef __linux__
   #include <unistd.h>
  +#ifdef __GLIBC__
   #include <sys/fcntl.h>
  +#else
  +#include <fcntl.h>
  +#endif
   #include <elf.h>
   
   static void __attribute__((constructor))
  Index: b/libitm/config/linux/x86/tls.h
  ===================================================================
  --- a/libitm/config/linux/x86/tls.h
  +++ b/libitm/config/linux/x86/tls.h
  @@ -25,16 +25,19 @@
   #ifndef LIBITM_X86_TLS_H
   #define LIBITM_X86_TLS_H 1
   
  -#if defined(__GLIBC_PREREQ) && __GLIBC_PREREQ(2, 10)
  +#if defined(__GLIBC_PREREQ)
  +#if __GLIBC_PREREQ(2, 10)
   /* Use slots in the TCB head rather than __thread lookups.
      GLIBC has reserved words 10 through 13 for TM.  */
   #define HAVE_ARCH_GTM_THREAD 1
   #define HAVE_ARCH_GTM_THREAD_DISP 1
   #endif
  +#endif
   
   #include "config/generic/tls.h"
   
  -#if defined(__GLIBC_PREREQ) && __GLIBC_PREREQ(2, 10)
  +#if defined(__GLIBC_PREREQ)
  +#if __GLIBC_PREREQ(2, 10)
   namespace GTM HIDDEN {
   
   #ifdef __x86_64__
  @@ -101,5 +104,6 @@
   
   } // namespace GTM
   #endif /* >= GLIBC 2.10 */
  +#endif
   
   #endif // LIBITM_X86_TLS_H
  Index: b/libstdc++-v3/configure.host
  ===================================================================
  --- a/libstdc++-v3/configure.host
  +++ b/libstdc++-v3/configure.host
  @@ -266,6 +266,13 @@
       os_include_dir="os/bsd/freebsd"
       ;;
     gnu* | linux* | kfreebsd*-gnu | knetbsd*-gnu)
  +    # check for musl by target
  +    case "${host_os}" in
  +      *-musl*)
  +        os_include_dir="os/generic"
  +        ;;
  +      *)
  +
       if [ "$uclibc" = "yes" ]; then
         os_include_dir="os/uclibc"
       elif [ "$bionic" = "yes" ]; then
  @@ -274,6 +281,9 @@
         os_include_dir="os/gnu-linux"
       fi
       ;;
  +
  +    esac
  +    ;;
     hpux*)
       os_include_dir="os/hpux"
       ;;
  Index: b/gcc/config/mips/linux64.h
  ===================================================================
  --- a/gcc/config/mips/linux64.h
  +++ b/gcc/config/mips/linux64.h
  @@ -41,4 +41,4 @@
   #define BIONIC_DYNAMIC_LINKERN32 "/system/bin/linker32"
   #define GNU_USER_DYNAMIC_LINKERN32 \
     CHOOSE_DYNAMIC_LINKER (GLIBC_DYNAMIC_LINKERN32, UCLIBC_DYNAMIC_LINKERN32, \
  -			 BIONIC_DYNAMIC_LINKERN32)
  +			 BIONIC_DYNAMIC_LINKERN32, MUSL_DYNAMIC_LINKER)
  Index: b/gcc/config/mips/linux.h
  ===================================================================
  --- a/gcc/config/mips/linux.h
  +++ b/gcc/config/mips/linux.h
  @@ -23,3 +23,11 @@
   #undef UCLIBC_DYNAMIC_LINKER
   #define UCLIBC_DYNAMIC_LINKER \
     "%{mnan=2008:/lib/ld-uClibc-mipsn8.so.0;:/lib/ld-uClibc.so.0}"
  +
  +#if TARGET_ENDIAN_DEFAULT == 0 /* LE */
  +#define MUSL_DYNAMIC_LINKER_E "%{EB:;:el}"
  +#else
  +#define MUSL_DYNAMIC_LINKER_E "%{EL:el}"
  +#endif
  +#undef MUSL_DYNAMIC_LINKER
  +#define MUSL_DYNAMIC_LINKER "/lib/ld-musl-mips" MUSL_DYNAMIC_LINKER_E "%{msoft-float:-sf}.so.1"