Compiling for RISC-V

[Richard Levitte]

Hi,

when you mentioned cross compiling, that got me a bit more curious, so
I went looking, and noticed that Debian [sid] (which is what I run on
my laptop) has all the cross compiling tools I needed (see
https://wiki.debian.org/RISC-V#Cross_compilation), so I installed
them, and then tried this in my checkout of OpenSSL's master branch:

    ./Configure linux-generic64 no-asm no-threads \
                --cross-compile-prefix=riscv64-linux-gnu-

Running 'make' was a breeze, it went through flawlessly.

I haven't done much further tests, though.

Cheers,
Richard

On Mon, 09 Mar 2020 20:23:09 +0100,
Kristin Barber wrote:
> 
> 
> I did also try configuring for "no-asm", but there still seemed to be architecture-specific issues
> based on which files the errors were coming from.  I should probably also mention that I am
> attempting to cross-compile for RV64 from an x86 machine.
> 
> On Mon, Mar 9, 2020 at 3:12 PM Scott Neugroschl <scott_n at xypro.com> wrote:
> 
>      
>    
>     Is the “no-asm” configuration option still supported?
>    
>      
>    
>     From: openssl-users <openssl-users-bounces at openssl.org> On Behalf Of Kristin Barber
>     Sent: Monday, March 9, 2020 12:03 PM
>     To: Richard Levitte <levitte at openssl.org>
>     Cc: openssl-users at openssl.org
>     Subject: Re: Compiling for RISC-V
>    
>      
>    
>     Hi Richard, thanks for the reply. It was helpful.
>    
>      
>    
>     You are correct, I was able to find a configuration that worked by passing the RISC-V compiler
>     via "make variable" assignment, along with some relevant options.  Things start compiling, but
>     the build fails on what seems to be architecture-specific assembly files which are selected
>     based on which "platform" has been configured.  It did not seem to me that there were RISC-V
>     assembly-specific files as an option here, and based on your reply, I think that is indeed the
>     issue.  Am I understanding this correctly?
>    
>      
>    
>     Thanks,
>    
>      
>    
>     Kristin
>    
>      
>    
>     On Mon, Mar 9, 2020 at 3:03 AM Richard Levitte <levitte at openssl.org> wrote:
>    
>         On Mon, 09 Mar 2020 05:18:17 +0100,
>         Kristin Barber wrote:
>         > I've looked at the INSTALL docs, and it doesn't seem that RISC-V processors are
>         supported
>         > currently as a platform. Is this correct?
>        
>         That is correct.  No one has implemented that support yet.
>        
>         > Is there a branch which enables configuring for a RISC-V machine that hasn't yet made it
>         into a
>         > stable release?  
>        
>         Not that I know of.  Although, this same question has also been raised
>         on github (I forget the issue number).
>        
>         > Any advice on where to look for information or changes to the build process in order to
>         compile
>         > for RISC-V?
>        
>         The first thing to attempt is a generic build with no assembler.
>         There are some really simply config targets that could be a first
>         step, one of:
>        
>             ./Configure cc
>        
>             ./Configure gcc
>        
>         A (pretty big) step up from that, at least if Linux is your target,
>         would be one of these:
>        
>             ./Configure linux-generic32
>        
>             ./Configure linux-generic64
>        
>         Note that in either case, you may have to add C flags and ld flags,
>         which you can do in one of two ways:
>        
>         1)  directly on the configuration command line, like this (Configure
>             makes an educated guess on what flags go where):
>        
>             ./Configure linux-generic64 -m64 -DWHATEVER=value -Wl,-something
>        
>         2)  via "make variable" assignment:
>        
>             ./Configure linux-generic64 \
>                         CPPFLAGS='-DWHATEVER=value' \
>                         CFLAGS='-m64' \
>                         LDFLAGS='-Wl,-something'
>        
>         At some point, you might find a combination that works for you.  We
>         would definitely like to know what you figure out, and it may be that
>         the result makes it into our database of config targets (which, if
>         you're curious, are the files Configurations/*.conf).
>        
>         Now, configuration is the easy bit when it comes to new CPUs,
>         relatively speaking.  I assume that part of your question is whether
>         there is assembler support.  This is the hard part in terms of
>         effort.  We currently have no such thing at all for RISC-V, and I
>         haven't seen any attempts to start such an effort...  PRs would
>         certainly be welcome, but anyone who tries this will have to be
>         prepared for it to take a while to get into the main source.
>        
>         Cheers,
>         Richard
>        
>         --
>         Richard Levitte         levitte at openssl.org
>         OpenSSL Project         http://www.openssl.org/~levitte/
> 
> 
-- 
Richard Levitte         levitte at openssl.org
OpenSSL Project         http://www.openssl.org/~levitte/