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

[Jiri Olsa]

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