>On 4/24/23 20:58, Xueming Feng wrote:
>>> On 4/24/23 02:09, Xueming Feng wrote:
>>>> When using `bpftool map dump` in plain format, it is usually
>>>> more convenient to show the inner map id instead of raw value.
>>>> Changing this behavior would help with quick debugging with
>>>> `bpftool`, without disrupting scripted behavior. Since user
>>>> could dump the inner map with id, and need to convert value.
>>>>
>>>> Signed-off-by: Xueming Feng <kuro@xxxxxxxx>
>>>> ---
>>>> Changes in v2:
>>>> - Fix commit message grammar.
>>>> - Change `print_uint` to only print to stdout, make `arg` const, and rename
>>>> `n` to `arg_size`.
>>>> - Make `print_uint` able to take any size of argument up to `unsigned long`,
>>>> and print it as unsigned decimal.
>>>>
>>>> Thanks for the review and suggestions! I have changed my patch accordingly.
>>>> There is a possibility that `arg_size` is larger than `unsigned long`,
>>>> but previous review suggested that it should be up to the caller function to
>>>> set `arg_size` correctly. So I didn't add check for that, should I?
>>>>
>>>> tools/bpf/bpftool/main.c | 15 +++++++++++++++
>>>> tools/bpf/bpftool/main.h | 1 +
>>>> tools/bpf/bpftool/map.c | 9 +++++++--
>>>> 3 files changed, 23 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/tools/bpf/bpftool/main.c b/tools/bpf/bpftool/main.c
>>>> index 08d0ac543c67..810c0dc10ecb 100644
>>>> --- a/tools/bpf/bpftool/main.c
>>>> +++ b/tools/bpf/bpftool/main.c
>>>> @@ -251,6 +251,21 @@ int detect_common_prefix(const char *arg, ...)
>>>> return 0;
>>>> }
>>>>
>>>> +void print_uint(const void *arg, unsigned int arg_size)
>>>> +{
>>>> + const unsigned char *data = arg;
>>>> + unsigned long val = 0ul;
>>>> +
>>>> + #if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
>>>> + memcpy(&val, data, arg_size);
>>>> + #else
>>>> + memcpy((unsigned char *)&val + sizeof(val) - arg_size,
>>>> + data, arg_size);
>>>> + #endif
>>
>> On Mon, 24 Apr 2023 09:44:18 -0700, Kui-Feng Lee wrote:
>>> Is it possible that arg_size is bigger than sizeof(val)?
>>
>> Yes it is possible, I had the thought of adding a check. But as I mentioned
>> before the diff section, previous review
>> https://lore.kernel.org/bpf/20230421101154.23690-1-kuro@xxxxxxxx/ suggested that
>> I should leave it to the caller function to behave. If I were to add a check,
>> what action do you recommend if the check fails? Print a '-1', do nothing,
>> or just use the first sizeof(val) bytes?
On Mon, 24 Apr 2023 22:19:52 -0700, Kui-Feng Lee wrote:
> In the previous patch, it may have integer overflow, but it is never
> buffer underrun. This version uses memcpy and may cause buffer underrun
> if arg_size is bigger than sizeof(val). I would say that at least
> prevent buffer underrun from happening.
Thanks for the advice! This function is pending remove in the next version of
this patch. But I will remember this for future patches.
>>> +
>>> + fprintf(stdout, "%lu", val);
>>> +}
>>> +
>>> void fprint_hex(FILE *f, void *arg, unsigned int n, const char *sep)
>>> {
>>> unsigned char *data = arg;
>>> diff --git a/tools/bpf/bpftool/main.h b/tools/bpf/bpftool/main.h
>>> index 0ef373cef4c7..0de671423431 100644
>>> --- a/tools/bpf/bpftool/main.h
>>> +++ b/tools/bpf/bpftool/main.h
>>> @@ -90,6 +90,7 @@ void __printf(1, 2) p_info(const char *fmt, ...);
>>>
>>> bool is_prefix(const char *pfx, const char *str);
>>> int detect_common_prefix(const char *arg, ...);
>>> +void print_uint(const void *arg, unsigned int arg_size);
>>> void fprint_hex(FILE *f, void *arg, unsigned int n, const char *sep);
>>> void usage(void) __noreturn;
>>>
>>> diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
>>> index aaeb8939e137..f5be4c0564cf 100644
>>> --- a/tools/bpf/bpftool/map.c
>>> +++ b/tools/bpf/bpftool/map.c
>>> @@ -259,8 +259,13 @@ static void print_entry_plain(struct bpf_map_info *info, unsigned char *key,
>>> }
>>>
>>> if (info->value_size) {
>>> - printf("value:%c", break_names ? '\n' : ' ');
>>> - fprint_hex(stdout, value, info->value_size, " ");
>>> + if (map_is_map_of_maps(info->type)) {
>>> + printf("id:%c", break_names ? '\n' : ' ');
>>> + print_uint(value, info->value_size);
>>> + } else {
>>> + printf("value:%c", break_names ? '\n' : ' ');
>>> + fprint_hex(stdout, value, info->value_size, " ");
>>> + }
>>> }
>>>
>>> printf("\n");
