riscv64: build the linker.

The only meaningful change from alibaba's version is jr instead of jalr.

Also fix the comment that's in all the begin.S files while we're here.

Signed-off-by: Mao Han <han_mao@linux.alibaba.com>
Signed-off-by: Xia Lifang <lifang_xia@linux.alibaba.com>
Signed-off-by: Chen Guoyin <chenguoyin.cgy@linux.alibaba.com>
Signed-off-by: Wang Chen <wangchen20@iscas.ac.cn>
Signed-off-by: Lu Xufan <luxufan@iscas.ac.cn>
Test: ran mksh
Change-Id: I2645c78bd700b8a55bde363600d7f8b87de641a1
diff --git a/linker/Android.bp b/linker/Android.bp
index 57420a9..83077c6 100644
--- a/linker/Android.bp
+++ b/linker/Android.bp
@@ -52,6 +52,9 @@
         arm64: {
             srcs: ["arch/arm64/linker_wrapper_begin.S"],
         },
+        riscv64: {
+            srcs: ["arch/riscv64/linker_wrapper_begin.S"],
+        },
         x86_64: {
             srcs: ["arch/x86_64/linker_wrapper_begin.S"],
         },
@@ -208,6 +211,13 @@
 }
 
 filegroup {
+    name: "linker_sources_riscv64",
+    srcs: [
+        "arch/riscv64/begin.S",
+    ],
+}
+
+filegroup {
     name: "linker_sources_x86",
     srcs: [
         "arch/x86/begin.S",
@@ -224,10 +234,11 @@
 cc_defaults {
     name: "linker_version_script_overlay",
     arch: {
-        arm:    { version_script: "linker.arm.map"      },
-        arm64:  { version_script: "linker.generic.map"  },
-        x86:    { version_script: "linker.generic.map"  },
-        x86_64: { version_script: "linker.generic.map"  },
+        arm:     { version_script: "linker.arm.map"      },
+        arm64:   { version_script: "linker.generic.map"  },
+        riscv64: { version_script: "linker.generic.map"  },
+        x86:     { version_script: "linker.generic.map"  },
+        x86_64:  { version_script: "linker.generic.map"  },
     },
 }
 
@@ -259,6 +270,15 @@
                 keep_symbols: true,
             },
         },
+        riscv64: {
+            srcs: [":linker_sources_riscv64"],
+
+            // Leave the symbols in the shared library so that stack unwinders can produce
+            // meaningful name resolution.
+            strip: {
+                keep_symbols: true,
+            },
+        },
         x86: {
             srcs: [":linker_sources_x86"],
 
@@ -426,6 +446,7 @@
         "-Wl,--exclude-libs=libgcc_stripped.a",
         "-Wl,--exclude-libs=libclang_rt.builtins-arm-android.a",
         "-Wl,--exclude-libs=libclang_rt.builtins-aarch64-android.a",
+        "-Wl,--exclude-libs=libclang_rt.builtins-riscv64-android.a",
         "-Wl,--exclude-libs=libclang_rt.builtins-i686-android.a",
         "-Wl,--exclude-libs=libclang_rt.builtins-x86_64-android.a",
     ],
diff --git a/linker/NOTICE b/linker/NOTICE
index 8f70d87..d61a193 100644
--- a/linker/NOTICE
+++ b/linker/NOTICE
@@ -334,3 +334,31 @@
 
 -------------------------------------------------------------------
 
+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.
+
+-------------------------------------------------------------------
+
diff --git a/linker/arch/arm/begin.S b/linker/arch/arm/begin.S
index 80d9fe1..3b673f0 100644
--- a/linker/arch/arm/begin.S
+++ b/linker/arch/arm/begin.S
@@ -35,6 +35,6 @@
   mov r0, sp
   bl __linker_init
 
-  /* linker init returns the _entry address in the main image */
+  // __linker_init returns the address of the entry point in the main image.
   bx r0
 END(_start)
diff --git a/linker/arch/arm64/begin.S b/linker/arch/arm64/begin.S
index a947475..14999cd 100644
--- a/linker/arch/arm64/begin.S
+++ b/linker/arch/arm64/begin.S
@@ -35,6 +35,6 @@
   mov x0, sp
   bl __linker_init
 
-  /* linker init returns the _entry address in the main image */
+  // __linker_init returns the address of the entry point in the main image.
   br x0
 END(_start)
diff --git a/linker/arch/riscv64/begin.S b/linker/arch/riscv64/begin.S
new file mode 100644
index 0000000..f7509c6
--- /dev/null
+++ b/linker/arch/riscv64/begin.S
@@ -0,0 +1,40 @@
+/*
+ * 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>
+
+ENTRY(_start)
+  // Force unwinds to end in this function.
+  .cfi_undefined ra
+
+  mv a0, sp
+  jal __linker_init
+
+  // __linker_init returns the address of the entry point in the main image.
+  jr a0
+END(_start)
diff --git a/linker/arch/x86/begin.S b/linker/arch/x86/begin.S
index 3812646..81e2740 100644
--- a/linker/arch/x86/begin.S
+++ b/linker/arch/x86/begin.S
@@ -38,6 +38,6 @@
   call __linker_init      // %esp is aligned to 16 before the call.
   addl $16, %esp
 
-  /* linker init returns (%eax) the _entry address in the main image */
+  // __linker_init returns the address of the entry point in the main image.
   jmp *%eax
 END(_start)
diff --git a/linker/arch/x86_64/begin.S b/linker/arch/x86_64/begin.S
index 4722301..baba0db 100644
--- a/linker/arch/x86_64/begin.S
+++ b/linker/arch/x86_64/begin.S
@@ -35,6 +35,6 @@
   mov %rsp, %rdi
   call __linker_init
 
-  /* linker init returns (%rax) the _entry address in the main image */
+  // __linker_init returns the address of the entry point in the main image.
   jmp *%rax
 END(_start)