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SubjectRe: [PATCH v9 perf,bpf 04/15] perf, bpf: synthesize bpf events with bpf_program__get_prog_info_linear()
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> On Mar 13, 2019, at 2:08 PM, Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com> wrote:
>
> Em Wed, Mar 13, 2019 at 06:00:30PM -0300, Arnaldo Carvalho de Melo escreveu:
>> Em Mon, Mar 11, 2019 at 10:30:40PM -0700, Song Liu escreveu:
>>> -
>>> /* Synthesize PERF_RECORD_KSYMBOL */
>>> for (i = 0; i < sub_prog_cnt; i++) {
>>> + u8 (*prog_tags)[BPF_TAG_SIZE] = (void *)(info->prog_tags);
>>
>> Need this:
>>
>> - u8 (*prog_tags)[BPF_TAG_SIZE] = (void *)(info->prog_tags);
>> + u8 (*prog_tags)[BPF_TAG_SIZE] = (u8 *)(info->prog_tags);
>>
>>
>> To overcome this on debian:experimental-x-mips, i.e. Debian Experimental
>> cross building to MIPS 32-bit:
>>
>> util/bpf-event.c: In function 'perf_event__synthesize_one_bpf_prog':
>> util/bpf-event.c:143:35: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
>> u8 (*prog_tags)[BPF_TAG_SIZE] = (void *)(info->prog_tags);
>> ^
>> util/bpf-event.c:144:22: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
>> __u32 *prog_lens = (__u32 *)(info->jited_func_lens);
>> ^
>> util/bpf-event.c:145:23: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
>> __u64 *prog_addrs = (__u64 *)(info->jited_ksyms);
>> ^
>> util/bpf-event.c:146:22: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
>> void *func_infos = (void *)(info->func_info);
>> ^
>> CC /tmp/build/perf/util/pmu.o
>> CC /tmp/build/perf/util/pmu-flex.o
>> cc1: all warnings being treated as errors
>
> Argh, hit the send button too fast, that is not the only case and then
> my change just changed the error:
>
> util/bpf-event.c: In function 'perf_event__synthesize_one_bpf_prog':
> util/bpf-event.c:143:35: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
> u8 (*prog_tags)[BPF_TAG_SIZE] = (u8 *)(info->prog_tags);
> ^
> util/bpf-event.c:143:35: error: initialization of 'u8 (*)[8]' {aka 'unsigned char (*)[8]'} from incompatible pointer type 'u8 *' {aka 'unsigned char *'} [-Werror=incompatible-pointer-types]
> util/bpf-event.c:144:22: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
> __u32 *prog_lens = (__u32 *)(info->jited_func_lens);
> ^
> util/bpf-event.c:145:23: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
> __u64 *prog_addrs = (__u64 *)(info->jited_ksyms);
> ^
> util/bpf-event.c:146:22: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
> void *func_infos = (void *)(info->func_info);
> ^
> CC /tmp/build/perf/util/pmu.o
> CC /tmp/build/perf/util/pmu-flex.o
> cc1: all warnings being treated as errors
> mv: cannot stat '/tmp/build/perf/util/.bpf-event.o.tmp': No such file or directory
>

We can fix it with the following:

- u8 (*prog_tags)[BPF_TAG_SIZE] = (void *)(info->prog_tags);
- __u32 *prog_lens = (__u32 *)(info->jited_func_lens);
- __u64 *prog_addrs = (__u64 *)(info->jited_ksyms);
- void *func_infos = (void *)(info->func_info);
+ u8 (*prog_tags)[BPF_TAG_SIZE] = (void *)(intptr_t)(info->prog_tags);
+ __u32 *prog_lens = (__u32 *)(intptr_t)(info->jited_func_lens);
+ __u64 *prog_addrs = (__u64 *)(intptr_t)(info->jited_ksyms);
+ void *func_infos = (void *)(intptr_t)(info->func_info);

Thanks,
Song

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