Messages in this thread | | | From | Namhyung Kim <> | Date | Fri, 18 Sep 2015 00:26:51 +0900 | Subject | Re: [PATCH] tools lib traceevent: Mask higher bits of str addresses for 32-bit traces |
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Hi,
On Thu, Sep 17, 2015 at 11:58 PM, Kapileshwar Singh <kapileshwar.singh@arm.com> wrote: > 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);
What about this? (untested)
addr = *(uint64_t *)(data + field->offset) & ((1ULL << pevent->long_size * 8) - 1);
Do we also need to consider byte endians? Maybe it'd be better adding a helper to dereference pointers then..
Thanks, Namhyung
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