x86 ELF: avoid putting constants in .text section

Some systems (e.g. OpenBSD) can make the text section not readable.

Use .rodata section instead of .text.

Author: xavierleroy

runtime/x86_64/i64_dtou.S

@@ -48,9 +48,9 @@ FUNCTION(__compcert_i64_dtou)
         addq .LC2(%rip), INT_RES
         ret
 
+ENDFUNCTION(__compcert_i64_dtou)
+        
+RODATA
         .p2align 3
 .LC1:   .quad 0x43e0000000000000       // 2^63 in double precision
 .LC2:   .quad 0x8000000000000000       // 2^63 as an integer
-
-ENDFUNCTION(__compcert_i64_dtou)
-        

runtime/x86_64/sysdeps.h

@@ -48,6 +48,8 @@
 #define ENDFUNCTION(f) \
 	.type f, @function; .size f, . - f
 
+#define RODATA .section .rodata
+
 #endif
 
 #if defined(SYS_macos)
@@ -61,6 +63,8 @@ _##f:
 
 #define ENDFUNCTION(f)
 
+#define RODATA .text
+
 #endif
 
 #if defined(SYS_cygwin)
@@ -74,6 +78,8 @@ _##f:
 
 #define ENDFUNCTION(f)
 
+#define RODATA .text
+
 #endif
 
 // Names for argument and result registers