Majority of stack frames show '[unknown]' for stackcount.py on Android

[jchowdha]

On a hikey960 device with the following:

1. Kernel - android linux hikey kernel - 4.9.88, default config + configs for bpf
2. Userspace - aosp-master branch

./stackcount.py submit_bio -v

ffffff800851b748 [unknown] ffffff80082b2a10 [unknown] ffffff8008365554 [unknown] ffffff8008366718 [unknown] ffffff800836c390 [unknown] ffffff80080f05d0 [unknown] ffffff80080836f0 [unknown] jbd2/sdd13-8 [2143] 1

ffffff800851b748 [unknown] ffffff80082b24c4 [unknown] ffffff80082b2934 [unknown] ffffff80082b57c8 [unknown] ffffff80081fd488 [unknown] ffffff80081fdddc [unknown] ffffff80081fe0bc [unknown] ffffff80082b575c [unknown] ffffff80082007a0 [unknown] ffffff80082a6f90 [unknown] ffffff80082a7960 [unknown] ffffff80082a7c74 [unknown] ffffff80082a7f9c [unknown] ffffff80082a8180 [unknown] ffffff80082a8a90 [unknown] ffffff80080e93d8 [unknown] ffffff80080e9724 [unknown] ffffff80080f05d0 [unknown] ffffff80080836f0 [unknown] kworker/u16:0 [5436] 1 Seems like there might be an issue with the stack address -> symbol translation.

[jcanseco]

Hi, I can't seem to reproduce this.

# ./stackcount.py submit_bio -v
Tracing 1 functions for "submit_bio"... Hit Ctrl-C to end.

  ffffff8008511ca0 submit_bio
  ffffff80082b045c __block_write_full_page
  ffffff80082b08cc block_write_full_page
  ffffff80082b3760 blkdev_writepage
  ffffff80081fb87c __writepage
  ffffff80081fc1d0 write_cache_pages
  ffffff80081fc4b0 generic_writepages
  ffffff80082b36f4 blkdev_writepages
  ffffff80081feb94 do_writepages
  ffffff80082a4f34 __writeback_single_inode
  ffffff80082a5904 writeback_sb_inodes
  ffffff80082a5c18 __writeback_inodes_wb
  ffffff80082a5f40 wb_writeback
  ffffff80082a6124 wb_check_old_data_flush
  ffffff80082a6a34 wb_workfn
  ffffff80080e5f6c process_one_work
  ffffff80080e62b8 worker_thread
  ffffff80080ed158 kthread
  ffffff8008083680 ret_from_fork
    kworker/u16:4 [5411]
    1

  ffffff8008511ca0 submit_bio
  ffffff80082b09a8 submit_bh
  ffffff8008363228 journal_submit_commit_record
  ffffff80083643ec jbd2_journal_commit_transaction
  ffffff800836a064 kjournald2
  ffffff80080ed158 kthread
  ffffff8008083680 ret_from_fork
    jbd2/sdd13-8 [2081]
    1

  ffffff8008511ca0 submit_bio
  ffffff80082b09a8 submit_bh
  ffffff8008363cd8 jbd2_journal_commit_transaction
  ffffff800836a064 kjournald2
  ffffff80080ed158 kthread
  ffffff8008083680 ret_from_fork
    jbd2/sdd13-8 [2081]
    2

Detaching...

Questions:

1. Is your BCC tree up-to-date with remote? (namely the bcc-bpfd branch)
2. Is /proc/sys/kernel/kptr_restrict set to 0 in your HiKey?