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SubjectRe: [PATCH] perf machine: Fix load kernel symbol with '-k' option
Hi Leo,

On 27 February 2018 at 00:17, Leo Yan <leo.yan@linaro.org> wrote:
> On Hikey arm64 octa A53 platform, when use command './perf report -v
> -k vmlinux --stdio' it outputs below error info, and it skips to load
> kernel symbol and doesn't print symbol for event:
> Failed to open [kernel.kallsyms]_text, continuing without symbols.
>
> The regression is introduced by commit ("8c7f1bb37b29 perf machine: Move
> kernel mmap name into struct machine"), which changes the logic for
> machine mmap_name by removing function machine__mmap_name() and always
> use 'machine->mmap_name'. Comparing difference between
> machine__mmap_name() and 'machine->mmap_name', the later one includes
> the string for specified kernel vmlinux string with option '-k' in
> command, but the old function machine__mmap_name() ignores vmlinux
> path string. As result, event's mmap file name doesn't match with
> machine mmap file name anymore and it skips to load kernel symbol from
> vmlinux file.
>
> To resolve this issue, this patch adds extra checking for
> 'machine->mmap_name', when its start char is not '[' then we can know
> it includes vmlinux path string specified for option '-k'. For this
> case it sets 'is_kernel_mmap = true' and run into flow to load kernel
> symbol from vmlinux.
>
> This patch has been verified with two commands: './perf report -v
> -k vmlinux --stdio' and './perf script -v -F cpu,event,ip,sym,symoff
> -k vmlinux'.
>
> Signed-off-by: Leo Yan <leo.yan@linaro.org>
> ---
> tools/perf/util/machine.c | 15 ++++++++++++---
> 1 file changed, 12 insertions(+), 3 deletions(-)
>
> diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c
> index 12b7427..ffd709d 100644
> --- a/tools/perf/util/machine.c
> +++ b/tools/perf/util/machine.c
> @@ -1299,9 +1299,18 @@ static int machine__process_kernel_mmap_event(struct machine *machine,
> else
> kernel_type = DSO_TYPE_GUEST_KERNEL;
>
> - is_kernel_mmap = memcmp(event->mmap.filename,
> - machine->mmap_name,
> - strlen(machine->mmap_name) - 1) == 0;
> + /*
> + * If machine mmap_name doesn't start with char '[', it includes
> + * the specified kernel vmlinux name with option '-k'. So set
> + * is_kernel_mmap as true to create machine symbol map.
> + */
> + if (machine->mmap_name[0] != '[')

I have tested your patch and it indeed solves the problem but I
suggest to replace the above with:

if (symbol_conf.vmlinux_name)

That is consistent with the test in function machine__set_mmap_name()
and doesn't rely on a user specified input to operate properly.

Thanks,
Mathieu

> + is_kernel_mmap = true;
> + else
> + is_kernel_mmap = memcmp(event->mmap.filename,
> + machine->mmap_name,
> + strlen(machine->mmap_name) - 1) == 0;
> +
> if (event->mmap.filename[0] == '/' ||
> (!is_kernel_mmap && event->mmap.filename[0] == '[')) {
> map = machine__findnew_module_map(machine, event->mmap.start,
> --
> 2.7.4
>

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