Index: share/mk/bsd.cpu.mk
===================================================================
--- share/mk/bsd.cpu.mk
+++ share/mk/bsd.cpu.mk
@@ -273,9 +273,34 @@
 . endif
 .endif
 
-.if ${MACHINE_CPUARCH} == "mips"
-CFLAGS += -G0
-.endif
+# All the special-case hacks for robust external toolchain support
+. if ${MACHINE_CPUARCH} == "mips"
+# always add -G0
+_ABI_CFLAGS += -G0
+# Get endian right in case the default isn't correct
+.  if ${MACHINE_ARCH:M*el} != ""
+_ABI_CFLAGS += -EL
+.  else
+_ABI_CFLAGS += -EB
+.  endif
+# Get ABI right in case the default is wrong
+.  if ${MACHINE_ARCH} == "mips" || ${MACHINE_ARCH} == "mipsel"
+_ABI_CFLAGS += -mabi=32
+.  elif ${MACHINE_ARCH} == "mipsn32"
+_ABI_CFLAGS += -mabi=n32
+.  else
+_ABI_CFLAGS += -mabi=64
+.  endif
+# Get the default ISA correct. Kinda trick to pull off, hope this hueristic
+# works out: specify it when no CPUTYPE is specified
+.  if !defined(CPUTYPE) || empty(CPUTYPE)
+.   if ${MACHINE_ARCH:Mmips64*} || ${MACHINE_ARCH} == "mipsn32"
+_ABI_CFLAGS += -march=mips64
+.   else
+_ABI_CFLAGS += -march=mips3
+.   endif
+.  endif
+. endif
 
 ########## arm
 .if ${MACHINE_CPUARCH} == "arm"
@@ -290,10 +315,16 @@
 . if ${MACHINE_ARCH:Marmv6*} == ""
 MACHINE_CPU += softfp
 . endif
+# Get endian right for external toolchains
+.if ${MACHINE_ARCH} == "armeb"
+_ABI_CFLAGS += -mbig-endian
+.else
+_ABI_CFLAGS += -mlittle-endian
+.endif
 .if ${MACHINE_ARCH} == "armv6"
 # Needs to be CFLAGS not _CPUCFLAGS because it's needed for the ABI
 # not a nice optimization.
-CFLAGS += -mfloat-abi=softfp
+_ABI_CFLAGS += -mfloat-abi=softfp
 .endif
 .endif
 
@@ -302,6 +333,8 @@
 .if !defined(NO_CPU_CFLAGS)
 CFLAGS += ${_CPUCFLAGS}
 .endif
+CFLAGS += ${_ABI_CFLAGS}
+ACFLAGS+= ${_ABI_CFLAGS}
 
 #
 # Prohibit the compiler from emitting SIMD instructions.
Index: sys/conf/kern.pre.mk
===================================================================
--- sys/conf/kern.pre.mk
+++ sys/conf/kern.pre.mk
@@ -60,6 +60,7 @@
 .if !defined(NO_CPU_COPTFLAGS)
 COPTFLAGS+= ${_CPUCFLAGS}
 .endif
+COPTFLAGS+= ${_ABI_CFLAGS}
 NOSTDINC= -nostdinc
 
 INCLUDES= ${NOSTDINC} ${INCLMAGIC} -I. -I$S