Messages in this thread | | | Date | Thu, 17 Sep 2015 15:58:26 +0100 | From | Kapileshwar Singh <> | Subject | Re: [PATCH] tools lib traceevent: Mask higher bits of str addresses for 32-bit traces |
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Hi Steve,
Thanks for looking into this!
On 17/09/15 14:11, Steven Rostedt wrote: > On Thu, 17 Sep 2015 12:14:36 +0100 > Kapileshwar Singh <kapileshwar.singh@arm.com> wrote: > >> When a trace recorded on a 32-bit device is processed with a 64-bit >> binary, the higher 32-bits of the address need to be masked. >> >> The lack of this results in the output of the 64-bit pointer >> value to the trace as the 32-bit address lookup fails in find_printk. >> >> Before: >> burn-1778 [003] 548.600305: bputs: 0xc0046db2s: 2cec5c058d98c >> >> After: >> burn-1778 [003] 548.600305: bputs: 0xc0046db2s: RT throttling activated >> >> The problem occurs in PRINT_FEILD when the field is recognized as a pointer >> to a string (of the type const char *) > > Actually, there's two bugs here. You only fixed one of them. > >> >> Cc: Steven Rostedt <rostedt@goodmis.org> >> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> >> Cc: Namhyung Kim <namhyung@kernel.org> >> Cc: Javi Merino <javi.merino@arm.com> >> Cc: David Ahern <dsahern@gmail.com> >> Cc: Jiri Olsa <jolsa@kernel.org> >> Reported-by: Juri-Lelli <juri.lelli@arm.com> >> Signed-off-by: Kapileshwar Singh <kapileshwar.singh@arm.com> >> --- >> tools/lib/traceevent/event-parse.c | 11 +++++++++++ >> 1 file changed, 11 insertions(+) >> >> diff --git a/tools/lib/traceevent/event-parse.c b/tools/lib/traceevent/event-parse.c >> index 4d885934b919..39163ea4a048 100644 >> --- a/tools/lib/traceevent/event-parse.c >> +++ b/tools/lib/traceevent/event-parse.c >> @@ -3829,6 +3829,17 @@ static void print_str_arg(struct trace_seq *s, void *data, int size, >> if (!(field->flags & FIELD_IS_ARRAY) && >> field->size == pevent->long_size) { >> addr = *(unsigned long *)(data + field->offset); > > addr is of type unsigned long. That means if we read a 64 bit record on > a 32 bit machine (which is supported), this will be truncated. > > Perhaps we need to make addr into a unsigned long long, and then add: > > addr = (pevent->long_size == 8) ? > *(unsigned long long *)(data + field->offset) : > (unsigned long long )*(unsigned int *)(data + field->offset);
I agree, we need to handle both cases:
* Traces recorded using 32-bit addresses processed on a 64-bit machine * Traces recorded using 64-bit addresses processed on a 32-bit machine
The change you suggested fixes both these cases.
Will send a v2 of the patch with the changes.
Regards, KP
> > > > -- Steve > > >> + >> + /* In case the long_size is 4. The higher 32bits >> + * need to be masked for a successful lookup in >> + * in the printk table. As the pointers are 32-bit >> + * long. This could happen if a trace recorded on >> + * 32-bit platform is processed using a 64-bit >> + * binary >> + */ >> + if (pevent->long_size == 4) >> + addr = addr & 0xffffffff; >> + >> /* Check if it matches a print format */ >> printk = find_printk(pevent, addr); >> if (printk) >
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