Re: [PATCH] perf machine: Update kernel map address and re-order properly

[liwei (GF)]

Hi Arnaldo,

Please shoot a glance at this modification, i think this issue is influential.

On 2019/2/28 19:28, Jiri Olsa Wrote:
> On Thu, Feb 28, 2019 at 05:20:03PM +0800, Wei Li wrote:
>> Since commit 1fb87b8e9599 ("perf machine: Don't search for active kernel
>> start in __machine__create_kernel_maps"), the __machine__create_kernel_maps()
>> just create a map what start and end are both zero. Though the address will be
>> updated later, the order of map in the rbtree may be incorrect.
>>
>> The commit ee05d21791db ("perf machine: Set main kernel end address properly")
>> fixed the logic in machine__create_kernel_maps(), but it's still wrong in
>> function machine__process_kernel_mmap_event().
>>
>> To reproduce this issue, we need an environment which the module address
>> is before the kernel text segment. I tested it on an aarch64 machine with
>> kernel 4.19.25:
> 
> so that was the missing piece.. nice
> 
>>
>> [root@localhost hulk]# grep _stext /proc/kallsyms 
>> ffff000008081000 T _stext
>> [root@localhost hulk]# grep _etext /proc/kallsyms 
>> ffff000009780000 R _etext
>> [root@localhost hulk]# tail /proc/modules 
>> hisi_sas_v2_hw 77824 0 - Live 0xffff00000191d000
>> nvme_core 126976 7 nvme, Live 0xffff0000018b6000
>> mdio 20480 1 ixgbe, Live 0xffff0000018ab000
>> hisi_sas_main 106496 1 hisi_sas_v2_hw, Live 0xffff000001861000
>> hns_mdio 20480 2 - Live 0xffff000001822000
>> hnae 28672 3 hns_dsaf,hns_enet_drv, Live 0xffff000001815000
>> dm_mirror 40960 0 - Live 0xffff000001804000
>> dm_region_hash 32768 1 dm_mirror, Live 0xffff0000017f5000
>> dm_log 32768 2 dm_mirror,dm_region_hash, Live 0xffff0000017e7000
>> dm_mod 315392 17 dm_mirror,dm_log, Live 0xffff000001780000
>> [root@localhost hulk]# 
>>
>> Before fix:
>>
>> [root@localhost bin]# perf record sleep 3
>> [ perf record: Woken up 1 times to write data ]
>> [ perf record: Captured and wrote 0.011 MB perf.data (9 samples) ]
>> [root@localhost bin]# perf buildid-list -i perf.data 
>> 4c4e46c971ca935f781e603a09b52a92e8bdfee8 [vdso]
>> [root@localhost bin]# perf buildid-list -i perf.data -H
>> 0000000000000000000000000000000000000000 /proc/kcore
>> [root@localhost bin]# 
>>
>> After fix:
>>
>> [root@localhost tools]# ./perf/perf record sleep 3
>> [ perf record: Woken up 1 times to write data ]
>> [ perf record: Captured and wrote 0.011 MB perf.data (9 samples) ]
>> [root@localhost tools]# ./perf/perf buildid-list -i perf.data 
>> 28a6c690262896dbd1b5e1011ed81623e6db0610 [kernel.kallsyms]
>> 106c14ce6e4acea3453e484dc604d66666f08a2f [vdso]
>> [root@localhost tools]# ./perf/perf buildid-list -i perf.data -H
>> 28a6c690262896dbd1b5e1011ed81623e6db0610 /proc/kcore
>>
>> Signed-off-by: Wei Li <liwei391@xxxxxxxxxx>
> 
> Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> 
> good catch, thanks
> jirka
> 

Thanks,
Wei