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.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
[Gustavo: Update for gcc 4.8.3]

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/aarch64/aarch64-linux.h
===================================================================
--- a/gcc/config/aarch64/aarch64-linux.h
+++ b/gcc/config/aarch64/aarch64-linux.h
@@ -21,7 +21,12 @@
 #ifndef GCC_AARCH64_LINUX_H
 #define GCC_AARCH64_LINUX_H
 
+/* The AArch64 port currently supports two dynamic linkers:
+   - ld-linux-aarch64.so.1 - GLIBC dynamic linker
+   - ld-musl-aarch64.so.1 - musl libc dynamic linker  */
 #define GLIBC_DYNAMIC_LINKER "/lib/ld-linux-aarch64.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/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/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/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 +87,32 @@
 #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_LINKERX32)
 
 /* Determine whether the entire c99 runtime
    is present in the runtime library.  */
 #undef TARGET_C99_FUNCTIONS
-#define TARGET_C99_FUNCTIONS (OPTION_GLIBC)
+#define TARGET_C99_FUNCTIONS (OPTION_GLIBC || OPTION_MUSL)
 
 /* Whether we have sincos that follows the GNU extension.  */
 #undef TARGET_HAS_SINCOS
@@ -107,3 +121,74 @@
 /* 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
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
@@ -25,7 +25,23 @@
 #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/mips/linux64.h
===================================================================
--- a/gcc/config/mips/linux64.h
+++ b/gcc/config/mips/linux64.h
@@ -29,4 +29,4 @@
 #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
@@ -18,3 +18,11 @@
 <http://www.gnu.org/licenses/>.  */
 
 #define GLIBC_DYNAMIC_LINKER "/lib/ld.so.1"
+
+#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 ".so.1"
Index: b/gcc/config/rs6000/linux64.h
===================================================================
--- a/gcc/config/rs6000/linux64.h
+++ b/gcc/config/rs6000/linux64.h
@@ -374,17 +374,23 @@
 #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/config.gcc
===================================================================
--- a/gcc/config.gcc
+++ b/gcc/config.gcc
@@ -550,7 +550,7 @@
 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"
 
 # Common parts for widely ported systems.
 case ${target} in
@@ -653,6 +653,9 @@
     *-*-*uclibc*)
       tm_defines="$tm_defines DEFAULT_LIBC=LIBC_UCLIBC"
       ;;
+    *-*-*musl*)
+      tm_defines="$tm_defines DEFAULT_LIBC=LIBC_MUSL"
+      ;;
     *)
       tm_defines="$tm_defines DEFAULT_LIBC=LIBC_GLIBC"
       ;;
@@ -2135,6 +2138,10 @@
 	    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/configure
===================================================================
--- a/gcc/configure
+++ b/gcc/configure
@@ -26936,6 +26940,9 @@
       gcc_cv_target_dl_iterate_phdr=no
     fi
     ;;
+  *-linux-musl*)
+    gcc_cv_target_dl_iterate_phdr=yes
+    ;;
 esac
 
 if test x$gcc_cv_target_dl_iterate_phdr = xyes; then
Index: b/gcc/configure.ac
===================================================================
--- a/gcc/configure.ac
+++ b/gcc/configure.ac
@@ -4848,6 +4852,9 @@
       gcc_cv_target_dl_iterate_phdr=no
     fi
     ;;
+  *-linux-musl*)
+    gcc_cv_target_dl_iterate_phdr=yes
+    ;;
 esac
 GCC_TARGET_TEMPLATE([TARGET_DL_ITERATE_PHDR])
 if test x$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
@@ -75,6 +75,13 @@
 # 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)
 
 #include <link.h>
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
@@ -264,6 +264,13 @@
     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
@@ -272,6 +279,9 @@
       os_include_dir="os/gnu-linux"
     fi
     ;;
+
+    esac
+    ;;
   hpux*)
     os_include_dir="os/hpux"
     ;;