ARM64: Allow building with unwinding disabled.

(cherry-picked from commit 5677985)

Prior to this patch, the LuaJIT build with the
`-DLUAJIT_NO_UNWIND=1` option enabled failed on ARM64 because of
linker relocation error related to dwarf-specific code:
| /usr/bin/ld: lj_vm_dyn.o: relocation R_AARCH64_PREL32 against
| symbol `lj_err_unwind_dwarf' which may bind externally can not
| be used when making a shared object; recompile with -fPIC
| lj_vm_dyn.o:(.eh_frame+0x12): dangerous relocation: unsupported
| relocation

This patch disables emission of the `.eh_frame` section for
builds without unwinding to solve the issue.

The `LUAJIT_NO_UNWIND` build option is added to CMakeLists.txt.
This patch adds this build flavor to our exotic builds workflow.

Maxim Kokryashkin:
* added the description for the problem

Part of tarantool/tarantool#9145

Reviewed-by: Sergey Kaplun <[email protected]>
Reviewed-by: Sergey Bronnikov <[email protected]>
Signed-off-by: Igor Munkin <[email protected]>
(cherry picked from commit 022e3c7)

Author: Mike Pall

.github/workflows/exotic-builds-testing.yml

@@ -34,7 +34,7 @@ jobs:
         BUILDTYPE: [Debug, Release]
         ARCH: [ARM64, x86_64]
         GC64: [ON, OFF]
-        FLAVOR: [checkhook, dualnum, gdbjit, nojit]
+        FLAVOR: [checkhook, dualnum, gdbjit, nojit, nounwind]
         include:
           - BUILDTYPE: Debug
             CMAKEFLAGS: -DCMAKE_BUILD_TYPE=Debug -DLUA_USE_ASSERT=ON -DLUA_USE_APICHECK=ON
@@ -48,6 +48,8 @@ jobs:
             FLAVORFLAGS: -DLUAJIT_DISABLE_JIT=ON
           - FLAVOR: gdbjit
             FLAVORFLAGS: -DLUAJIT_USE_GDBJIT=ON
+          - FLAVOR: nounwind
+            FLAVORFLAGS: -DLUAJIT_NO_UNWIND=ON
         exclude:
           - ARCH: ARM64
             GC64: OFF

CMakeLists.txt

@@ -202,6 +202,11 @@ if(LUAJIT_DISABLE_UNWIND_JIT)
   AppendFlags(TARGET_C_FLAGS -DLUAJIT_DISABLE_UNWIND_JIT)
 endif()
 
+option(LUAJIT_NO_UNWIND "Disable external unwinding.")
+if(LUAJIT_NO_UNWIND)
+  AppendFlags(TARGET_C_FLAGS -DLUAJIT_NO_UNWIND)
+endif()
+
 # Disable memory profiler.
 option(LUAJIT_DISABLE_MEMPROF "LuaJIT memory profiler support" OFF)
 if(LUAJIT_DISABLE_MEMPROF)

src/vm_arm64.dasc

@@ -3915,6 +3915,7 @@ static void emit_asm_debug(BuildCtx *ctx)
 	"\t.align 3\n"
 	".LEFDE1:\n\n", (int)ctx->codesz - fcofs);
 #endif
+#if !LJ_NO_UNWIND
     fprintf(ctx->fp, "\t.section .eh_frame,\"a\",%%progbits\n");
     fprintf(ctx->fp,
 	".Lframe1:\n"
@@ -3982,6 +3983,7 @@ static void emit_asm_debug(BuildCtx *ctx)
 	"\t.byte 0x94\n\t.uleb128 4\n"		/* offset x20 */
 	"\t.align 3\n"
 	".LEFDE3:\n\n", (int)ctx->codesz - fcofs);
+#endif
 #endif
     break;
 #if !LJ_NO_UNWIND