Re: [PATCH v2 3/4] perf augmented_raw_syscalls: Support arm64 raw syscalls

[Leo Yan]

Hi Arnaldo,

On Thu, Jun 06, 2019 at 11:44:12AM -0300, Arnaldo Carvalho de Melo wrote:
> Em Thu, Jun 06, 2019 at 10:12:31PM +0800, Leo Yan escreveu:
> > Hi Arnaldo,
> > 
> > On Thu, Jun 06, 2019 at 10:38:38AM -0300, Arnaldo Carvalho de Melo wrote:
> > > Em Thu, Jun 06, 2019 at 05:48:44PM +0800, Leo Yan escreveu:
> > > > This patch adds support for arm64 raw syscall numbers so that we can use
> > > > it on arm64 platform.
> > > > 
> > > > After applied this patch, we need to specify macro -D__aarch64__ or
> > > > -D__x86_64__ in compilation option so Clang can use the corresponding
> > > > syscall numbers for arm64 or x86_64 respectively, other architectures
> > > > will report failure when compilation.
> > > 
> > > So, please check what I have in my perf/core branch, I've completely
> > > removed arch specific stuff from augmented_raw_syscalls.c.
> > > 
> > > What is done now is use a map to specify what to copy, that same map
> > > that is used to state which syscalls should be traced.
> > > 
> > > It uses that tools/perf/arch/arm64/entry/syscalls/mksyscalltbl to figure
> > > out the mapping of syscall names to ids, just like is done for x86_64
> > > and other arches, falling back to audit-libs when that syscalltbl thing
> > > is not present.
> > 
> > Actually I have noticed mksyscalltbl has been enabled for arm64, and
> > had to say your approach is much better :)
> > 
> > Thanks for the info and I will try your patch at my side.
> 
> That is excellent news! I'm eager to hear from you if this perf+BPF
> integration experiment works for arm64.

I tested with the lastest perf/core branch which contains the patch:
'perf augmented_raw_syscalls: Tell which args are filenames and how
many bytes to copy' and got the error as below:

# perf trace -e string -e /mnt/linux-kernel/linux-cs-dev/tools/perf/examples/bpf/augmented_raw_syscalls.c
Error:  Invalid syscall access, chmod, chown, creat, futimesat, lchown, link, lstat, mkdir, mknod, newfstatat, open, readlink, rename,
rmdir, stat, statfs, symlink, truncate, unlink
Hint:   try 'perf list syscalls:sys_enter_*'
Hint:   and: 'man syscalls'

So seems mksyscalltbl has not included completely for syscalls, I
use below command to generate syscalltbl_arm64[] array and it don't
include related entries for access, chmod, chown, etc ...

You could refer the generated syscalltbl_arm64 in:
http://paste.ubuntu.com/p/8Bj7Jkm2mP/

> I'm now trying to get past the verifier when checking if more than one
> syscall arg is a filename, i.e. things like the rename* family, that
> take two filenames.
> 
> An exercise in loop unrolling, providing the right hints to the
> verifier, making sure clang don't trash those via explicit barriers, and
> a lot of patience, limitless fun! ;-)

Cool!  Please feel free let me know if need me to do testing for this.

Thanks,
Leo Yan