lkml.org 
[lkml]   [2019]   [Jun]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH v2 3/4] perf augmented_raw_syscalls: Support arm64 raw syscalls
Em Tue, Jun 11, 2019 at 12:18:31PM +0800, Leo Yan escreveu:
> On Mon, Jun 10, 2019 at 03:47:54PM -0300, Arnaldo Carvalho de Melo wrote:
>
> [...]
>
> > > > 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
> >
> > Humm, I think that we can just make the code that parses the
> > tools/perf/trace/strace/groups/string file to ignore syscalls it can't
> > find in the syscall_tbl, i.e. trace those if they exist in the arch.
>
> Agree.
>
> > > > 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 ...
> >
> > So, we need to investigate why is that these are missing, good thing we
> > have this 'strings' group :-)
> >
> > > > You could refer the generated syscalltbl_arm64 in:
> > > > http://paste.ubuntu.com/p/8Bj7Jkm2mP/
> > >
> > > After digging into this issue on Arm64, below is summary info:
> > >
> > > - arm64 uses the header include/uapi/linux/unistd.h to define system
> > > call numbers, in this header some system calls are not defined (I
> > > think the reason is these system calls are obsolete at the end) so the
> > > corresponding strings are missed in the array syscalltbl_native,
> > > for arm64 the array is defined in the file:
> > > tools/perf/arch/arm64/include/generated/asm/syscalls.c.
> >
> > Yeah, I looked at the 'access' case and indeed it is not present in
> > include/uapi/asm-generic/unistd.h, which is the place
> > include/uapi/linux/unistd.h ends up.
> >
> > Ok please take a look at the patch at the end of this message, should be ok?
> >
> > I tested it by changing the strace/gorups/string file to have a few
> > unknown syscalls, running it with -v we see:
> >
> > [root@quaco perf]# perf trace -v -e string ls
> > Skipping unknown syscalls: access99, acct99, add_key99
> > <SNIP other verbose messages>
> > normal operation not considering those unknown syscalls.
>
> I did testing with the patch, but it failed after I added eBPF event
> with below command, I even saw segmentation fault; please see below
> inline comments.
>
> perf --debug verbose=10 trace -e string -e \
> /mnt/linux-kernel/linux-cs-dev/tools/perf/examples/bpf/augmented_raw_syscalls.c
>
> [...]
>
> > commit e0b34a78c4ed0a6422f5b2dafa0c8936e537ee41
> > Author: Arnaldo Carvalho de Melo <acme@redhat.com>
> > Date: Mon Jun 10 15:37:45 2019 -0300
> >
> > perf trace: Skip unknown syscalls when expanding strace like syscall groups
> >
> > We have $INSTALL_DIR/share/perf-core/strace/groups/string files with
> > syscalls that should be selected when 'string' is used, meaning, in this
> > case, syscalls that receive as one of its arguments a string, like a
> > pathname.
> >
> > But those were first selected and tested on x86_64, and end up failing
> > in architectures where some of those syscalls are not available, like
> > the 'access' syscall on arm64, which makes using 'perf trace -e string'
> > in such archs to fail.
> >
> > Since this the routine doing the validation is used only when reading
> > such files, do not fail when some syscall is not found in the
> > syscalltbl, instead just use pr_debug() to register that in case people
> > are suspicious of problems.
> >
> > Now using 'perf trace -e string' should work on arm64, selecting only
> > the syscalls that have a string and are available on that architecture.
> >
> > Reported-by: Leo Yan <leo.yan@linaro.org>
> > Cc: Adrian Hunter <adrian.hunter@intel.com>
> > Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
> > Cc: Alexei Starovoitov <ast@kernel.org>
> > Cc: Daniel Borkmann <daniel@iogearbox.net>
> > Cc: Jiri Olsa <jolsa@redhat.com>
> > Cc: Martin KaFai Lau <kafai@fb.com>
> > Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
> > Cc: Mike Leach <mike.leach@linaro.org>
> > Cc: Namhyung Kim <namhyung@kernel.org>
> > Cc: Song Liu <songliubraving@fb.com>
> > Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
> > Cc: Yonghong Song <yhs@fb.com>
> > Link: https://lkml.kernel.org/n/tip-oa4c2x8p3587jme0g89fyg18@git.kernel.org
> > Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
> >
> > diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
> > index 1a2a605cf068..eb70a4b71755 100644
> > --- a/tools/perf/builtin-trace.c
> > +++ b/tools/perf/builtin-trace.c
> > @@ -1529,6 +1529,7 @@ static int trace__read_syscall_info(struct trace *trace, int id)
> > static int trace__validate_ev_qualifier(struct trace *trace)
> > {
> > int err = 0, i;
> > + bool printed_invalid_prefix = false;
> > size_t nr_allocated;
> > struct str_node *pos;
> >
> > @@ -1555,14 +1556,15 @@ static int trace__validate_ev_qualifier(struct trace *trace)
> > if (id >= 0)
> > goto matches;
> >
> > - if (err == 0) {
> > - fputs("Error:\tInvalid syscall ", trace->output);
> > - err = -EINVAL;
> > + if (!printed_invalid_prefix) {
> > + pr_debug("Skipping unknown syscalls: ");
> > + printed_invalid_prefix = true;
> > } else {
> > - fputs(", ", trace->output);
> > + pr_debug(", ");
> > }
> >
> > - fputs(sc, trace->output);
> > + pr_debug("%s", sc);
> > + continue;
>
> Here adds 'continue' so that we want to let ev_qualifier_ids.entries
> to only store valid system call ids. But this is not sufficient,
> because we have initialized ev_qualifier_ids.nr at the beginning of
> the function:
>
> trace->ev_qualifier_ids.nr = strlist__nr_entries(trace->ev_qualifier);
> This sentence will set ids number to the string table's length; but
> actually some strings are not really supported; this leads to some
> items in trace->ev_qualifier_ids.entries[] will be not initialized
> properly.
>
> If we want to get neat entries and entry number, I suggest at the
> beginning of the function we use variable 'nr_allocated' to store
> string table length and use it to allocate entries:
>
> nr_allocated = strlist__nr_entries(trace->ev_qualifier);
> trace->ev_qualifier_ids.entries = malloc(nr_allocated *
> sizeof(trace->ev_qualifier_ids.entries[0]));
>
> If we find any matched string, then increment the nr field under
> 'matches' tag:
>
> matches:
> trace->ev_qualifier_ids.nr++;
> trace->ev_qualifier_ids.entries[i++] = id;
>
> This can ensure the entries[0..nr-1] has valid id and we can use
> ev_qualifier_ids.nr to maintain the valid system call numbers.

yeah, you're right, I'll address these issues in a followup patch,
tomorrow.

- Arnaldo

>
> > }
> > matches:
> > trace->ev_qualifier_ids.entries[i++] = id;
> > @@ -1591,15 +1593,14 @@ static int trace__validate_ev_qualifier(struct trace *trace)
> > }
> > }
> >
> > - if (err < 0) {
> > - fputs("\nHint:\ttry 'perf list syscalls:sys_enter_*'"
> > - "\nHint:\tand: 'man syscalls'\n", trace->output);
> > -out_free:
> > - zfree(&trace->ev_qualifier_ids.entries);
> > - trace->ev_qualifier_ids.nr = 0;
> > - }
> > out:
> > + if (printed_invalid_prefix)
> > + pr_debug("\n");
> > return err;
> > +out_free:
> > + zfree(&trace->ev_qualifier_ids.entries);
> > + trace->ev_qualifier_ids.nr = 0;
> > + goto out;
>
> Nitpick: directly return err and 'goto out' is not necessary.
>
> Thanks,
> Leo Yan
>
> > }
> >
> > /*

--

- Arnaldo

\
 
 \ /
  Last update: 2019-06-12 04:50    [W:0.123 / U:3.132 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site