Trivally backported the upstream commit
b685411208e0aaa79190d54faf945763514706b8
(different directory, some files not present, etc.)
We only really use x86* from those, probably, so I didn't bother much.
diff --git a/gcc/config/alpha/linux-unwind.h b/gcc/config/alpha/linux-unwind.h
index bdbba4a..e84812e 100644
--- a/gcc/config/alpha/linux-unwind.h
+++ b/gcc/config/alpha/linux-unwind.h
@@ -51,7 +51,7 @@ alpha_fallback_frame_state (struct _Unwind_Context *context,
     {
       struct rt_sigframe {
 	siginfo_t info;
-	struct ucontext uc;
+	ucontext_t uc;
       } *rt_ = context->cfa;
       sc = &rt_->uc.uc_mcontext;
     }
diff --git a/gcc/config/bfin/linux-unwind.h b/gcc/config/bfin/linux-unwind.h
index 77b7c23..8bf5e82 100644
--- a/gcc/config/bfin/linux-unwind.h
+++ b/gcc/config/bfin/linux-unwind.h
@@ -52,7 +52,7 @@ bfin_fallback_frame_state (struct _Unwind_Context *context,
 	void *puc;
 	char retcode[8];
 	siginfo_t info;
-	struct ucontext uc;
+	ucontext_t uc;
       } *rt_ = context->cfa;
 
       /* The void * cast is necessary to avoid an aliasing warning.
diff --git a/gcc/config/i386/linux-unwind.h b/gcc/config/i386/linux-unwind.h
index 540a0a2..29efbe3 100644
--- a/gcc/config/i386/linux-unwind.h
+++ b/gcc/config/i386/linux-unwind.h
@@ -58,7 +58,7 @@ x86_64_fallback_frame_state (struct _Unwind_Context *context,
   if (*(unsigned char *)(pc+0) == 0x48
       && *(unsigned long long *)(pc+1) == RT_SIGRETURN_SYSCALL)
     {
-      struct ucontext *uc_ = context->cfa;
+      ucontext_t *uc_ = context->cfa;
       /* The void * cast is necessary to avoid an aliasing warning.
          The aliasing warning is correct, but should not be a problem
          because it does not alias anything.  */
@@ -138,7 +138,7 @@ x86_fallback_frame_state (struct _Unwind_Context *context,
 	siginfo_t *pinfo;
 	void *puc;
 	siginfo_t info;
-	struct ucontext uc;
+	ucontext_t uc;
       } *rt_ = context->cfa;
       /* The void * cast is necessary to avoid an aliasing warning.
          The aliasing warning is correct, but should not be a problem
diff --git a/gcc/config/m68k/linux-unwind.h b/gcc/config/m68k/linux-unwind.h
index 75b7cf7..f964e24 100644
--- a/gcc/config/m68k/linux-unwind.h
+++ b/gcc/config/m68k/linux-unwind.h
@@ -33,7 +33,7 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 /* <sys/ucontext.h> is unfortunately broken right now.  */
 struct uw_ucontext {
 	unsigned long	  uc_flags;
-	struct ucontext  *uc_link;
+	ucontext_t	 *uc_link;
 	stack_t		  uc_stack;
 	mcontext_t	  uc_mcontext;
 	unsigned long	  uc_filler[80];
diff --git a/gcc/config/pa/linux-unwind.h b/gcc/config/pa/linux-unwind.h
index 9a2657f..e47493d 100644
--- a/gcc/config/pa/linux-unwind.h
+++ b/gcc/config/pa/linux-unwind.h
@@ -80,7 +80,7 @@ pa32_fallback_frame_state (struct _Unwind_Context *context,
   struct sigcontext *sc;
   struct rt_sigframe {
     siginfo_t info;
-    struct ucontext uc;
+    ucontext_t uc;
   } *frame;
 
   /* rt_sigreturn trampoline:
diff --git a/gcc/config/sh/linux-unwind.h b/gcc/config/sh/linux-unwind.h
index e389cac..0bf43ba 100644
--- a/gcc/config/sh/linux-unwind.h
+++ b/gcc/config/sh/linux-unwind.h
@@ -180,7 +180,7 @@ sh_fallback_frame_state (struct _Unwind_Context *context,
     {
       struct rt_sigframe {
 	siginfo_t info;
-	struct ucontext uc;
+	ucontext_t uc;
       } *rt_ = context->cfa;
       /* The void * cast is necessary to avoid an aliasing warning.
          The aliasing warning is correct, but should not be a problem
diff --git a/gcc/config/xtensa/linux-unwind.h b/gcc/config/xtensa/linux-unwind.h
index 9872492..586a9d4 100644
--- a/gcc/config/xtensa/linux-unwind.h
+++ b/gcc/config/xtensa/linux-unwind.h
@@ -67,7 +67,7 @@ xtensa_fallback_frame_state (struct _Unwind_Context *context,
 
   struct rt_sigframe {
     siginfo_t info;
-    struct ucontext uc;
+    ucontext_t uc;
   } *rt_;
 
   /* movi a2, __NR_rt_sigreturn; syscall */
-- 
2.9.3