Re: [PATCH 31/32] tools lib traceevent: Support function __get_dynamic_array_len

[Alexei Starovoitov]

On 8/28/15 12:06 AM, Wang Nan wrote:
> From: He Kuang<hekuang@xxxxxxxxxx>
>
> Support helper function __get_dynamic_array_len() in libtraceevent,
> this function is used accompany with __print_array() or __print_hex(),
> but currently it is not an available function in the function list of
> process_function().
>
> The total allocated length of the dynamic array is embedded in the top
> half of __data_loc_##item field. This patch adds new arg type
> PRINT_DYNAMIC_ARRAY_LEN to return the length to eval_num_arg(),
>
> Signed-off-by: He Kuang<hekuang@xxxxxxxxxx>
> Acked-by: Namhyung Kim<namhyung@xxxxxxxxxx>

Tested-by: Alexei Starovoitov <ast@xxxxxxxxxxxx>

this patch fixes the perf crash:
  Warning: [bpf:bpf_output_data] function __get_dynamic_array_len not 
defined
  Warning: Error: expected type 5 but read 0
*** glibc detected *** perf_4.2.0: double free or corruption (fasttop): 
0x00000000032caf20 ***
======= Backtrace: =========
/lib/x86_64-linux-gnu/libc.so.6(+0x7ec96)[0x7f0d5d2d3c96]

it's not strictly necessary until patch 32 lands, but I think it's
a good fix regardless.
Steven, could you take it into your tree?

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