riscv64: add bionic assembler and string functions.
Pull the portable C string functions from FreeBSD, and do fairly literal
translations of our existing .S files for the bionic-specific stuff.
Test: treehugger
Change-Id: Id42e5b8a51ed73155be020d74edd7011a2103574
diff --git a/libc/arch-riscv64/bionic/__bionic_clone.S b/libc/arch-riscv64/bionic/__bionic_clone.S
new file mode 100644
index 0000000..aeb2da6
--- /dev/null
+++ b/libc/arch-riscv64/bionic/__bionic_clone.S
@@ -0,0 +1,66 @@
+/*
+ * Copyright (C) 2022 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * * Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in
+ * the documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <private/bionic_asm.h>
+
+// pid_t __bionic_clone(int flags, void* child_stack, pid_t* parent_tid, void* tls, pid_t* child_tid, int (*fn)(void*), void* arg);
+
+ENTRY_PRIVATE(__bionic_clone)
+ # Push 'fn' and 'arg' onto the child stack.
+ addi a1, a1, -16
+ sd a5, 0(a1)
+ sd a6, 0(a1)
+
+ # Make the system call.
+ li a7, __NR_clone
+ ecall
+
+ # Are we the child?
+ beqz a0, .L_bc_child
+
+ # Did the clone(2) fail?
+ bltz a0, .L_bc_failure
+ # Nope, we're the parent, and our work here is done.
+ ret
+
+.L_bc_failure:
+ # Set errno if something went wrong.
+ neg a0, a0
+ j __set_errno_internal
+
+.L_bc_child:
+ # We're in the child now. Set the end of the frame record chain.
+ li fp, 0
+ # Setting ra to 0 will make the unwinder stop at __start_thread.
+ li ra, 0
+ # Call __start_thread with the 'fn' and 'arg' we stored on the child stack.
+ ld a0, 0(sp)
+ ld a1, 8(sp)
+ addi sp, sp, 16
+ j __start_thread
+END(__bionic_clone)