add sigaltstack syscall

libc/arch-sh/syscalls.mk

@@ -41,6 +41,7 @@ syscall_src += arch-sh/syscalls/chroot.S
 syscall_src += arch-sh/syscalls/prctl.S
 syscall_src += arch-sh/syscalls/capget.S
 syscall_src += arch-sh/syscalls/capset.S
+syscall_src += arch-sh/syscalls/sigaltstack.S
 syscall_src += arch-sh/syscalls/acct.S
 syscall_src += arch-sh/syscalls/read.S
 syscall_src += arch-sh/syscalls/write.S

libc/arch-sh/syscalls/sigaltstack.S

@@ -0,0 +1,32 @@
+/* autogenerated by gensyscalls.py */
+#include <sys/linux-syscalls.h>
+
+    .text
+    .type sigaltstack, @function
+    .globl sigaltstack
+    .align 4
+
+sigaltstack:
+
+    /* invoke trap */
+    mov.l   0f, r3  /* trap num */
+    trapa   #(2 + 0x10)
+
+    /* check return value */
+    cmp/pz  r0
+    bt      __NR_sigaltstack_end
+
+    /* keep error number */
+    sts.l   pr, @-r15
+    mov.l   1f, r1
+    jsr     @r1
+    mov     r0, r4
+    lds.l   @r15+, pr
+
+__NR_sigaltstack_end:
+    rts
+    nop
+
+    .align  2
+0:  .long   __NR_sigaltstack
+1:  .long   __set_syscall_errno