Add unshare system call

Adds a C function for the unshare system call supported by Linux since
2.6.16.

Change-Id: I32df4075d875e9f5b5ed716cd7b02cdf82c64526
diff --git a/libc/arch-sh/syscalls.mk b/libc/arch-sh/syscalls.mk
index 6666431..22c7f9f 100644
--- a/libc/arch-sh/syscalls.mk
+++ b/libc/arch-sh/syscalls.mk
@@ -159,6 +159,7 @@
 syscall_src += arch-sh/syscalls/klogctl.S
 syscall_src += arch-sh/syscalls/sysinfo.S
 syscall_src += arch-sh/syscalls/personality.S
+syscall_src += arch-sh/syscalls/unshare.S
 syscall_src += arch-sh/syscalls/futex.S
 syscall_src += arch-sh/syscalls/epoll_create.S
 syscall_src += arch-sh/syscalls/epoll_ctl.S
diff --git a/libc/arch-sh/syscalls/unshare.S b/libc/arch-sh/syscalls/unshare.S
new file mode 100644
index 0000000..59c1e7a
--- /dev/null
+++ b/libc/arch-sh/syscalls/unshare.S
@@ -0,0 +1,32 @@
+/* autogenerated by gensyscalls.py */
+#include <sys/linux-syscalls.h>
+
+    .text
+    .type unshare, @function
+    .globl unshare
+    .align 4
+
+unshare:
+
+    /* invoke trap */
+    mov.l   0f, r3  /* trap num */
+    trapa   #(1 + 0x10)
+
+    /* check return value */
+    cmp/pz  r0
+    bt      __NR_unshare_end
+
+    /* keep error number */
+    sts.l   pr, @-r15
+    mov.l   1f, r1
+    jsr     @r1
+    mov     r0, r4
+    lds.l   @r15+, pr
+
+__NR_unshare_end:
+    rts
+    nop
+
+    .align  2
+0:  .long   __NR_unshare
+1:  .long   __set_syscall_errno