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SubjectRe: [PATCH v4 01/19] [BUGFIX] tracing: probeevent: Fix to support minus offset from symbol
On Fri, 2 Mar 2018 13:49:51 +0900
Namhyung Kim <namhyung@kernel.org> wrote:

> Hi Masami,
>
> On Wed, Feb 28, 2018 at 12:19:53PM +0900, Masami Hiramatsu wrote:
> > In Documentation/trace/kprobetrace.txt, it says
> >
> > @SYM[+|-offs] : Fetch memory at SYM +|- offs (SYM should be a data symbol)
> >
> > However, the parser doesn't parse minus offset correctly, since
> > commit 2fba0c8867af ("tracing/kprobes: Fix probe offset to be
> > unsigned") drops minus ("-") offset support for kprobe probe
> > address usage.
> >
> > This fixes the traceprobe_split_symbol_offset() to parse minus
> > offset again with checking the offset range, and add a minus
> > offset check in kprobe probe address usage.
>
> It now parses a minus offset but doesn't allow it, right?

No, split_symbol_offset() is used for 2 cases
- kprobe-event probe point
- kporbe-event symbol-based argument

Former one doesn't accept a minus offset, but latter accepts it.

(Frankly to say, I guess no one care about supporting minus offset :P)

Thanks,

> Then I still think it's better to fix the documentation.
>
>
> >
> > Fixes: 2fba0c8867af ("tracing/kprobes: Fix probe offset to be unsigned")
> > Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
> > ---
> > Changes in v3:
> > - Use kstrtol instead of kstrtoul. (Thanks Namhyung!)
> > Changes in v4:
> > - Fix to decode sign. (Thanks Namhyung!)
> > - Fix to check UINT_MAX for kprobe offset.
> > ---
> > kernel/trace/trace_kprobe.c | 4 ++--
> > kernel/trace/trace_probe.c | 8 +++-----
> > kernel/trace/trace_probe.h | 2 +-
> > 3 files changed, 6 insertions(+), 8 deletions(-)
> >
> > diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
> > index 5ce9b8cf7be3..1cd3fb4d70f8 100644
> > --- a/kernel/trace/trace_kprobe.c
> > +++ b/kernel/trace/trace_kprobe.c
> > @@ -667,7 +667,7 @@ static int create_trace_kprobe(int argc, char **argv)
> > char *symbol = NULL, *event = NULL, *group = NULL;
> > int maxactive = 0;
> > char *arg;
> > - unsigned long offset = 0;
> > + long offset = 0;
> > void *addr = NULL;
> > char buf[MAX_EVENT_NAME_LEN];
> >
> > @@ -755,7 +755,7 @@ static int create_trace_kprobe(int argc, char **argv)
> > symbol = argv[1];
> > /* TODO: support .init module functions */
> > ret = traceprobe_split_symbol_offset(symbol, &offset);
> > - if (ret) {
> > + if (ret || offset < 0 || offset > UINT_MAX) {
> > pr_info("Failed to parse either an address or a symbol.\n");
> > return ret;
>
> Wouldn't it be confusing if it returns 0 for an invalid input?
>
> Thanks,
> Namhyung
>
>
> > }
> > diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
> > index d59357308677..daf54bda4dc8 100644
> > --- a/kernel/trace/trace_probe.c
> > +++ b/kernel/trace/trace_probe.c
> > @@ -320,7 +320,7 @@ static fetch_func_t get_fetch_size_function(const struct fetch_type *type,
> > }
> >
> > /* Split symbol and offset. */
> > -int traceprobe_split_symbol_offset(char *symbol, unsigned long *offset)
> > +int traceprobe_split_symbol_offset(char *symbol, long *offset)
> > {
> > char *tmp;
> > int ret;
> > @@ -328,13 +328,11 @@ int traceprobe_split_symbol_offset(char *symbol, unsigned long *offset)
> > if (!offset)
> > return -EINVAL;
> >
> > - tmp = strchr(symbol, '+');
> > + tmp = strpbrk(symbol, "+-");
> > if (tmp) {
> > - /* skip sign because kstrtoul doesn't accept '+' */
> > - ret = kstrtoul(tmp + 1, 0, offset);
> > + ret = kstrtol(tmp, 0, offset);
> > if (ret)
> > return ret;
> > -
> > *tmp = '\0';
> > } else
> > *offset = 0;
> > diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h
> > index 0745f895f780..75daff22ccea 100644
> > --- a/kernel/trace/trace_probe.h
> > +++ b/kernel/trace/trace_probe.h
> > @@ -365,7 +365,7 @@ extern int traceprobe_conflict_field_name(const char *name,
> > extern void traceprobe_update_arg(struct probe_arg *arg);
> > extern void traceprobe_free_probe_arg(struct probe_arg *arg);
> >
> > -extern int traceprobe_split_symbol_offset(char *symbol, unsigned long *offset);
> > +extern int traceprobe_split_symbol_offset(char *symbol, long *offset);
> >
> > /* Sum up total data length for dynamic arraies (strings) */
> > static nokprobe_inline int
> >


--
Masami Hiramatsu <mhiramat@kernel.org>

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