From 01f0aad7c0fa2d816f9171d21b0168a9c1770a6b Mon Sep 17 00:00:00 2001
From: alexfanqi <alex.fan.q@gmail.com>
Date: Tue, 25 Jan 2022 13:47:06 +1100
Subject: [PATCH] Add riscv64 support for libcontext

modified to match function arguments different from upstream

Author: Andreas Schwab
---
 thirdparty/libcontext/libcontext.cpp | 108 +++++++++++++++++++++++++++
 thirdparty/libcontext/libcontext.h   |   5 ++
 2 files changed, 113 insertions(+)

diff --git a/thirdparty/libcontext/libcontext.cpp b/thirdparty/libcontext/libcontext.cpp
index 44a969d380..a56ff44407 100644
--- a/thirdparty/libcontext/libcontext.cpp
+++ b/thirdparty/libcontext/libcontext.cpp
@@ -1444,6 +1444,114 @@ __asm (
 
 #endif
 
+#if defined(LIBCONTEXT_PLATFORM_linux_riscv64) && defined(LIBCONTEXT_COMPILER_gcc)
+__asm (
+".text\n"
+".align  1\n"
+".global jump_fcontext\n"
+".type   jump_fcontext, %function\n"
+"jump_fcontext:\n"
+"    # prepare stack for GP + FPU\n"
+"    addi  sp, sp, -0xd0\n"
+"    # save fs0 - fs11\n"
+"    fsd  fs0, 0x00(sp)\n"
+"    fsd  fs1, 0x08(sp)\n"
+"    fsd  fs2, 0x10(sp)\n"
+"    fsd  fs3, 0x18(sp)\n"
+"    fsd  fs4, 0x20(sp)\n"
+"    fsd  fs5, 0x28(sp)\n"
+"    fsd  fs6, 0x30(sp)\n"
+"    fsd  fs7, 0x38(sp)\n"
+"    fsd  fs8, 0x40(sp)\n"
+"    fsd  fs9, 0x48(sp)\n"
+"    fsd  fs10, 0x50(sp)\n"
+"    fsd  fs11, 0x58(sp)\n"
+"    # save s0-s11, ra\n"
+"    sd  s0, 0x60(sp)\n"
+"    sd  s1, 0x68(sp)\n"
+"    sd  s2, 0x70(sp)\n"
+"    sd  s3, 0x78(sp)\n"
+"    sd  s4, 0x80(sp)\n"
+"    sd  s5, 0x88(sp)\n"
+"    sd  s6, 0x90(sp)\n"
+"    sd  s7, 0x98(sp)\n"
+"    sd  s8, 0xa0(sp)\n"
+"    sd  s9, 0xa8(sp)\n"
+"    sd  s10, 0xb0(sp)\n"
+"    sd  s11, 0xb8(sp)\n"
+"    sd  ra, 0xc0(sp)\n"
+"    # save RA as PC\n"
+"    sd  ra, 0xc8(sp)\n"
+"    # store SP in the first arg(pointer to fcontext_t)\n"
+"    sd  sp, 0x00(a0)\n"
+"    # restore SP from the second arg(fcontext_t)\n"
+"    mv  sp, a1\n"
+"    # load fs0 - fs11\n"
+"    fld  fs0, 0x00(sp)\n"
+"    fld  fs1, 0x08(sp)\n"
+"    fld  fs2, 0x10(sp)\n"
+"    fld  fs3, 0x18(sp)\n"
+"    fld  fs4, 0x20(sp)\n"
+"    fld  fs5, 0x28(sp)\n"
+"    fld  fs6, 0x30(sp)\n"
+"    fld  fs7, 0x38(sp)\n"
+"    fld  fs8, 0x40(sp)\n"
+"    fld  fs9, 0x48(sp)\n"
+"    fld  fs10, 0x50(sp)\n"
+"    fld  fs11, 0x58(sp)\n"
+"    # load s0-s11,ra\n"
+"    ld  s0, 0x60(sp)\n"
+"    ld  s1, 0x68(sp)\n"
+"    ld  s2, 0x70(sp)\n"
+"    ld  s3, 0x78(sp)\n"
+"    ld  s4, 0x80(sp)\n"
+"    ld  s5, 0x88(sp)\n"
+"    ld  s6, 0x90(sp)\n"
+"    ld  s7, 0x98(sp)\n"
+"    ld  s8, 0xa0(sp)\n"
+"    ld  s9, 0xa8(sp)\n"
+"    ld  s10, 0xb0(sp)\n"
+"    ld  s11, 0xb8(sp)\n"
+"    ld  ra, 0xc0(sp)\n"
+"    # use the third arg as return value\n"
+"    mv a0, a2\n"
+"    # load pc from new context\n"
+"    ld  a4, 0xc8(sp)\n"
+"    # restore stack from GP + FPU\n"
+"    addi  sp, sp, 0xd0\n"
+"    jr a4\n"
+".size   jump_fcontext,.-jump_fcontext\n"
+);
+#endif
+
+#if defined(LIBCONTEXT_PLATFORM_linux_riscv64) && defined(LIBCONTEXT_COMPILER_gcc)
+__asm (
+".text\n"
+".align  1\n"
+".global make_fcontext\n"
+".type   make_fcontext, %function\n"
+"make_fcontext:\n"
+"    # shift address in a0 (allocated stack) to lower 16 byte boundary\n"
+"    andi a0, a0, ~0xF\n"
+"    # reserve space for context-data on context-stack\n"
+"    addi  a0, a0, -0xd0\n"
+"    # third arg of make_fcontext() == address of context-function\n"
+"    # store address as a PC to jump in\n"
+"    sd  a2, 0xc8(a0)\n"
+"    # save address of finish as return-address for context-function\n"
+"    # will be entered after context-function returns (RA register)\n"
+"    lla  a4, finish\n"
+"    sd  a4, 0xc0(a0)\n"
+"    ret # return pointer to context-data (a0)\n"
+"finish:\n"
+"    # exit code is zero\n"
+"    li  a0, 0\n"
+"    # exit application\n"
+"    tail  _exit@plt\n"
+".size   make_fcontext,.-make_fcontext\n"
+);
+#endif
+
 #if defined(LIBCONTEXT_USE_WINFIBER) && (defined(LIBCONTEXT_PLATFORM_msvc_x86_64) || defined(LIBCONTEXT_PLATFORM_msvc_i386))
 
 #include <map>
diff --git a/thirdparty/libcontext/libcontext.h b/thirdparty/libcontext/libcontext.h
index 82141424ab..289e145954 100644
--- a/thirdparty/libcontext/libcontext.h
+++ b/thirdparty/libcontext/libcontext.h
@@ -55,6 +55,11 @@
             #define LIBCONTEXT_PLATFORM_linux_ppc32
             #define LIBCONTEXT_CALL_CONVENTION
         #endif
+    #elif defined(__riscv)
+        #if __riscv_xlen == 64
+            #define LIBCONTEXT_PLATFORM_linux_riscv64
+            #define LIBCONTEXT_CALL_CONVENTION
+        #endif
     #endif
 
     #elif defined(__MINGW32__) || defined(__MINGW64__)