openssl: Unable to run asm code on OpenBSD

perlasm files should keep constants/data in ‘.section .rodata’:

Running openssl tests on OpenBSD is futile unless build is configured with ./Configure no-asm which disables optimized routines written in assembly. I’ll demonstrate the issue on simple example. This is a main.c

#include <stdio.h>

extern int get_fee();
extern int get_foo();

int
main(int argc, const char *argv[0])
{
        printf("%x\n", get_fee());
        printf("%x\n", get_foo());

        return (0);
}

The code above is linked with .o file which is produced from .s below:

.global  get_foo
.type   get_foo,@function
get_foo:
        mov .foo(%rip), %rax
        ret

.global  get_fee
.type   get_fee,@function
get_fee:
        mov .fee(%rip), %rax
        ret

.foo:
        .long 0x00f00f00

.section .rodata

.fee:
        .byte 0x00,0xfe,0xef,0xee

The module above defines functions get_foo() and get_fee(). both functions return int which is a constant foo (fee) in module test.s Code can be built using Makefile as follows:

test: main.o test.o
        $(CC) -o test main.o test.o

main.o: main.c
        $(CC) -g -O0 -c -o main.o main.c

test.o: test.s
        $(CC) -c  test.s 

clean:
        rm -f test.o main.o

Building it and running it as-is on linux (Ubuntu) yields following output:

sashan@ubuntu:~/rodata$ make && ./test
cc -g -O0 -c -o main.o main.c
cc -c  test.s 
cc -o test main.o test.o
eeeffe00
f00f00

doing the same on OpenBSD box gives me a .core file.

lifty$ make && ./test
cc -g -O0 -c -o main.o main.c
cc -c  test.s 
cc -o test main.o test.o
eeeffe00
Segmentation fault (core dumped) 

Poking at core file we see we die as soon as we load constant foo to eax output register

lifty$ egdb test test.core  
...
Core was generated by `test'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0  0x00000b9e9d689a20 in get_foo ()
(gdb) disassemble get_foo
Dump of assembler code for function get_foo:
=> 0x00000b9e9d689a20 <+0>:     mov    0x9(%rip),%rax        # 0xb9e9d689a30 <.foo>
   0x00000b9e9d689a27 <+7>:     retq   
End of assembler dump.
(gdb) quit

Apart from returning different constants the functions get_foo() and get_fee() are identical

(gdb) disassemble get_fee
Dump of assembler code for function get_fee:
   0x00000b9e9d689a28 <+0>:     mov    -0x1523(%rip),%rax        # 0xb9e9d68850c
   0x00000b9e9d689a2f <+7>:     retq   
End of assembler dump.

What makes difference here is where fee and foo constants/data are placed. The constant fee is found in .rodata segment, while constant foo is placed to .text segment along the code. OpenBSD does not like variables/constants (a.k.a. data) to be placed into .text segment where code lives.

The CPU I was using to convey my test was amd ryzen.