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)
diff --git a/libc/arch-riscv64/bionic/__set_tls.c b/libc/arch-riscv64/bionic/__set_tls.c
new file mode 100644
index 0000000..57383ab
--- /dev/null
+++ b/libc/arch-riscv64/bionic/__set_tls.c
@@ -0,0 +1,33 @@
+/*
+ * 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 <sys/cdefs.h>
+
+__LIBC_HIDDEN__ void __set_tls(void* tls) {
+  asm("mv tp, %0" : : "r"(tls));
+}
diff --git a/libc/arch-riscv64/bionic/_exit_with_stack_teardown.S b/libc/arch-riscv64/bionic/_exit_with_stack_teardown.S
new file mode 100644
index 0000000..f7bf58b
--- /dev/null
+++ b/libc/arch-riscv64/bionic/_exit_with_stack_teardown.S
@@ -0,0 +1,41 @@
+/*
+ * 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>
+
+// void _exit_with_stack_teardown(void* stackBase, size_t stackSize)
+ENTRY_PRIVATE(_exit_with_stack_teardown)
+  li a7, __NR_munmap
+  ecall
+  // If munmap failed, we ignore the failure and exit anyway.
+
+  li a0, 0
+  li a7, __NR_exit
+  ecall
+  // The exit syscall does not return.
+END(_exit_with_stack_teardown)
diff --git a/libc/arch-riscv64/bionic/syscall.S b/libc/arch-riscv64/bionic/syscall.S
new file mode 100644
index 0000000..7b9d3ca
--- /dev/null
+++ b/libc/arch-riscv64/bionic/syscall.S
@@ -0,0 +1,53 @@
+/*
+ * Copyright (C) 2020 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>
+
+ENTRY(syscall)
+  // Move the syscall number up.
+  mv a7, a0
+
+  // Shuffle the arguments down.
+  mv a0, a1
+  mv a1, a2
+  mv a2, a3
+  mv a3, a4
+  mv a4, a5
+  mv a5, a6
+
+  ecall
+
+  // Did it fail?
+  li a7, -MAX_ERRNO
+  bgtu a0, a7, 1f
+
+  ret
+1:
+  neg a0, a0
+  j __set_errno_internal
+END(syscall)
diff --git a/libc/arch-riscv64/bionic/vfork.S b/libc/arch-riscv64/bionic/vfork.S
new file mode 100644
index 0000000..0eff9e9
--- /dev/null
+++ b/libc/arch-riscv64/bionic/vfork.S
@@ -0,0 +1,66 @@
+/*
+ * Copyright (C) 2020 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 <platform/bionic/tls_defines.h>
+#include <private/bionic_asm.h>
+#include <asm/signal.h>
+#include <linux/sched.h>
+
+ENTRY(vfork)
+  // t0 = __get_tls()[TLS_SLOT_THREAD_ID]
+  mv      t0, tp
+  ld      t0, TLS_SLOT_THREAD_ID * 8(t0)
+
+  // Set cached_pid_ to 0, vforked_ to 1, and stash the previous value.
+  li      t1, 0x80000000
+  lw      t2, 20(t0)
+  sw      t1, 20(t0)
+
+  li      a0, (CLONE_VM | CLONE_VFORK | SIGCHLD)
+  li      a1, 0 //uses a duplicate of the parent's stack
+  li      a2, 0
+  li      a3, 0
+  li      a4, 0
+
+  li      a7, __NR_clone
+  ecall
+
+  // if (rc == 0) we're the child, and finished...
+  beqz    a0, .L_success
+
+  // else if (rc != 0): reset cached_pid_ and vforked_...
+  sw      t2, 20(t0)
+  // ...and work out whether we succeeded or failed.
+  bltz    a0, .L_failure
+.L_success:
+  ret
+
+.L_failure:
+  neg     a0, a0
+  j       __set_errno_internal
+END(vfork)