Re: [PATCH bpf-next v3 9/9] tools/bpf: add a test for bpf_get_stack with tracepoint prog

[Yonghong Song <yhs@fb.com>]

On 4/22/18 5:27 PM, Alexei Starovoitov wrote:
> On Fri, Apr 20, 2018 at 03:18:42PM -0700, Yonghong Song wrote:
>> The test_stacktrace_map and test_stacktrace_build_id are
>> enhanced to call bpf_get_stack in the helper to get the
>> stack trace as well.  The stack traces from bpf_get_stack
>> and bpf_get_stackid are compared to ensure that for the
>> same stack as represented as the same hash, their ip addresses
>> or build id's must be the same.
>>
>> Signed-off-by: Yonghong Song <yhs@fb.com>
>> ---
>>   tools/testing/selftests/bpf/test_progs.c           | 63 +++++++++++++++++++---
>>   .../selftests/bpf/test_stacktrace_build_id.c       | 20 ++++++-
>>   tools/testing/selftests/bpf/test_stacktrace_map.c  | 20 +++++--
>>   3 files changed, 92 insertions(+), 11 deletions(-)
>>
>> diff --git a/tools/testing/selftests/bpf/test_progs.c b/tools/testing/selftests/bpf/test_progs.c
>> index dad4c3f..06b922a 100644
>> --- a/tools/testing/selftests/bpf/test_progs.c
>> +++ b/tools/testing/selftests/bpf/test_progs.c
>> @@ -897,11 +897,40 @@ static int compare_map_keys(int map1_fd, int map2_fd)
>>   	return 0;
>>   }
>>   
>> +static int compare_stack_ips(int smap_fd, int amap_fd, int stack_trace_len)
>> +{
>> +	__u32 key, next_key, *cur_key_p, *next_key_p;
>> +	char val_buf1[stack_trace_len], val_buf2[stack_trace_len];
> 
> the kernel is trying to get rid of VLAs.
> test_progs.c already uses them, but if possible let's not
> add more uses of them.

okay, try to get rid of these two VLAs.

> Other than that looks great.