lkml.org 
[lkml]   [2018]   [Nov]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: Question: perf dso support for /proc/kallsyms
    On Fri, Nov 02, 2018 at 10:55:16AM +0800, Leo Yan 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.

    Hi Jiri, Arnaldo,

    Could you give some suggestion for this question? Thanks!

    > 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

    \
     
     \ /
      Last update: 2018-11-07 04:34    [W:2.833 / U:0.436 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site