Learning Porting to Aarch64: Fossil(2)

Learning Porting to Aarch64: fossil

These days I am learning about porting software to Aarch64, and Fossil is the one can not be built in aarch64 architecture environment.

Fossil is a distributed version control like Git and Mercurial. Fossil also supports distributed bug tracking, distributed wiki, and a distributed blog mechanism all in a single integrated package.

I use Foundation model as the virtual aarch64 environment and rpmbuild tools to build the software. OS is fedora 19.

1. Install all the needed tools for rpmbuild,

• "Fedora Packager"
• rpmdevtools
• rpmlint
• yum-utils

2. Download source

    fedpkg clone -a fossil

    cd fossil

    fedpkg srpm

3. check dependencies

    yum-builddep *.rpm (under the fossil directory)

4. preparation for rpmbuild

    rpm -i *.rpm (same directory as above)

5. build it!

    cd ~/rpmbuild/SPECS/
    rpmbuild -ba fossil.spec

Issue: build error because the autosetup's config.guess file can not recognize the aarch 64 machine. 

Then I check the config.guess and find that file's last modified date is 2010-09-24. I go to the internet and find that the lastest version is made on 2014-03-23, I check the script and find that it support aarch 64.
 This the link:
http://git.savannah.gnu.org/gitweb/?p=config.git;a=blob_plain;f=config.guess;hb=HEAD

Then I replace the config.guess file and build again.

Building successfully:

Wrote: /root/rpmbuild/SRPMS/fossil-1.28-1.20140127173344.fc19.src.rpm
Wrote: /root/rpmbuild/RPMS/aarch64/fossil-1.28-1.20140127173344.fc19.aarch64.rpm
Wrote: /root/rpmbuild/RPMS/aarch64/fossil-doc-1.28-1.20140127173344.fc19.aarch64.rpm
Wrote: /root/rpmbuild/RPMS/aarch64/fossil-debuginfo-1.28-1.20140127173344.fc19.aarch64.rpm
Executing(%clean): /bin/sh -e /var/tmp/rpm-tmp.NTvRE9
+ umask 022
+ cd /root/rpmbuild/BUILD
+ cd fossil-src-20140127173344
+ /usr/bin/rm -fr /root/rpmbuild/BUILDROOT/fossil-1.28-1.20140127173344.fc19.aarch64
+ exit 0

Then it is time to take a look at the assembly code in the file to see if I can do something.

only one line:

#define SHA_ROT(op, x, k) \
        ({ unsigned int y; asm(op " %1,%0" : "=r" (y) : "I" (k), "0" (x)); y; })
#define rol(x,k) SHA_ROT("roll", x, k)
#define ror(x,k) SHA_ROT("rorl", x, k)

#else
/* Generic C equivalent */
#define SHA_ROT(x,l,r) ((x) << (l) | (x) >> (r))
#define rol(x,k) SHA_ROT(x,k,32-(k))
#define ror(x,k) SHA_ROT(x,32-(k),k)
#endif


#define blk0le(i) (block[i] = (ror(block[i],8)&0xFF00FF00) \
    |(rol(block[i],8)&0x00FF00FF))
#define blk0be(i) block[i]
#define blk(i) (block[i&15] = rol(block[(i+13)&15]^block[(i+8)&15] \
    ^block[(i+2)&15]^block[i&15],1))

Obviously, it doesn't optimize for aarch64, so in aarch64 it will generate C code "((x) << (l) | (x) >> (r))" for this part.

In aarch64 it only support ror(rotate right), no rol. We can try right a rotate asm code for aarch 64 and try running and compare to the c code part to see which is faster.

Hua