Messages in this thread | | | From | Mike Leach <> | Date | Fri, 2 Nov 2018 13:08:40 +0000 | Subject | Re: Question: perf dso support for /proc/kallsyms |
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Hi Leo,
My understanding is that when we decode CoreSight trace - be it on the system that generated it, or off target device on a separate host system, we are using the dso files in .debug/ as these represent the memory layout at the time trace was recorded.
If I look into a recent session copied up to my linux box from DB410, is see ~/.debug/\[kernel.kallsyms\]/ee80c1f3a434469f6174e1cf4bb5583d83a013dc/kallsyms - which seems to me to be the relevant symbol file to use rather than the live one generated by /proc/kallsyms. I don't really want to use the local /proc/kallsyms on my x86 linux box when decoding an ARM trace captured elsewhere.
So perhaps the problem to be solved is not how to use /proc/kallsyms if no vmlinux is supplied to the script, but ensure that the [kernel.kallsyms] is used?
Regards
Mike On Fri, 2 Nov 2018 at 02:55, <leo.yan@linaro.org> wrote: > > Hi all, > > Now I found that if use the command 'perf script' for Arm CoreSight trace > data, it fails to parse kernel symbols if we don't specify kernel vmlinux > file. So when we don't specify kernel symbol files then perf tool will > roll back to use /proc/kallsyms for kernel symbols parsing, as result it will > run into below flow: > > thread__find_addr_map(thread, cpumode, MAP__FUNCTION, address, &al); > map__load(al.map); > dso__data_read_offset(al.map->dso, machine, offset, buffer, size); > `-> data_read_offset() > > I can observe the function data_read_offset() returns failure, this is caused > by checking the offset sanity "if (offset > dso->data.file_size)" (I pasted > the whole function code at below in case you want to get more context for it), > but if perf use "/proc/kallsyms" to load kernel symbols, the variable > 'dso->data.file_size' will be set to zero thus the sanity checking always > thinks the offset is out of the file size bound. > > Now I still don't understand how the dso/map support "/proc/kallsyms" and > have no idea to fix this issue, though I spent some time to look into it. > > Could you give some suggestion for this? Or even better if you have fixing > for this, I am glad to test at my side. > > static ssize_t data_read_offset(struct dso *dso, struct machine *machine, > u64 offset, u8 *data, ssize_t size) > { > if (data_file_size(dso, machine)) > return -1; > > /* Check the offset sanity. */ > if (offset > dso->data.file_size) > return -1; > > if (offset + size < offset) > return -1; > > return cached_read(dso, machine, offset, data, size); > } > > Thanks, > Leo Yan > _______________________________________________ > CoreSight mailing list > CoreSight@lists.linaro.org > https://lists.linaro.org/mailman/listinfo/coresight
-- Mike Leach Principal Engineer, ARM Ltd. Manchester Design Centre. UK
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