This is the mail archive of the systemtap@sourceware.org mailing list for the systemtap project.
Index Nav: | [Date Index] [Subject Index] [Author Index] [Thread Index] | |
---|---|---|
Message Nav: | [Date Prev] [Date Next] | [Thread Prev] [Thread Next] |
Other format: | [Raw text] |
On 12/10/2015 04:12 PM, David Long wrote: > On 12/10/2015 03:24 PM, William Cohen wrote: >> The fslatency-nd and fsslower-nd tests need further investigation: >> >> PASS: ./systemtap.examples/lwtools/fslatency-nd build >> meta taglines 'test_installcheck: stap fslatency-nd.stp 1 1' tag 'test_installcheck' value 'stap fslatency-nd.stp 1 1' >> attempting command stap fslatency-nd.stp 1 1 >> OUT ERROR: read fault [man error::fault] at 0x0000000000000034 (addr) near operator '@cast' at fslatency-nd.stp:66:15 >> Tracing FS sync reads and writes... Output every 1 secs. >> WARNING: Number of errors: 1, skipped probes: 1 >> WARNING: /root/systemtap_write/install/bin/staprun exited with status: 1 >> Pass 5: run failed. [man error::pass5] >> child process exited abnormally >> RC 1 >> FAIL: ./systemtap.examples/lwtools/fslatency-nd run >> >> PASS: ./systemtap.examples/lwtools/fsslower-nd build >> meta taglines 'test_installcheck: stap fsslower-nd.stp -c "sleep 1"' tag 'test_installcheck' value 'stap fsslower-nd.stp -c "sleep 1"' >> attempting command stap fsslower-nd.stp -c "sleep 1" >> OUT ERROR: read fault [man error::fault] at 0x0000000000000034 (addr) near operator '@cast' at fsslower-nd.stp:68:15 >> Tracing FS sync reads and writes slower than 10 ms... Hit Ctrl-C to end. >> TIME PID COMM FUNC SIZE LAT(ms) >> WARNING: Number of errors: 1, skipped probes: 1 >> WARNING: /root/systemtap_write/install/bin/staprun exited with status: 1 >> Pass 5: run failed. [man error::pass5] >> child process exited abnormally >> RC 1 >> FAIL: ./systemtap.examples/lwtools/fsslower-nd run > > Cool. Wish I could make sense of systemtap error messages. > > At Will Deacon's suggested I tested probing the instruction in __copy_to_user that can cause a captured kernel exception when an application passes in a bad buffer address. Unfortunately the result was a hang. So copy_to/from user is going to have to be blacklisted for now, unless there turns out to be a simple fix. I'm worried there might be other places in the kernel where an otherwise probeable instruction might be expected to generate an exception. > > -dl > > > Hi Dave and Pratyush, I did some more experimentation with the fslatency-nd and fsslow-nd tests to see what is going on. The problem seems to be related to the return probes. I have a small reproducer attached which runs fine on x86_64 machine. However on aarch64 it has the bogus read because some of the argument registers have changed value # ../install/bin/stap ./aarch64_retkprobe_issue2.stp ERROR: read fault [man error::fault] at 0x0000000000000034 (addr) near operator '@cast' at ./aarch64_retkprobe_issue2.stp:13:7 pc : [<fffffe000021e37c>] lr : [<fffffe000021eb64>] pstate: 80000145 sp : fffffe00bad7be30 x29: fffffe00bad7be30 x28: fffffe00bad78000 x27: fffffe0000912000 x26: 000000000000003f x25: 000000000000011d x24: 0000000000000015 x23: 0000000080000000 x22: 000003fff82b9760 x21: fffffe00bad7bec8 x20: 0000000000002004 x19: fffffe01b716e100 x18: 000003fff82b8160 x17: 000003ff849bf0a0 x16: fffffe000021f4a0 x15: 0000000000000004 x14: 000003fff82bb910 x13: 0000000000000001 x12: 000003ff7d75f200 x11: 00000000003d0f00 x10: 000003ff849b7af4 x9 : 0000000000000028 x8 : 0000000000000020 x7 : fffffe00bc5c3600 x6 : 0000000000000000 x5 : 0000000000000000 x4 : 0000000000000000 x3 : fffffe00bad7bec8 x2 : 0000000000002004 x1 : 000003fff82b9760 x0 : fffffe01b716e100 pc : [<fffffe000021e37c>] lr : [<fffffe000009fbe0>] pstate: 60000145 sp : fffffe00bad7be30 x29: fffffe00bad7be30 x28: fffffe00bad78000 x27: fffffe0000912000 x26: 000000000000003f x25: 000000000000011d x24: 0000000000000015 x23: 0000000080000000 x22: 000003fff82b9760 x21: fffffe00bad7bec8 x20: 0000000000002004 x19: fffffe01b716e100 x18: 000003fff82b8160 x17: 000003ff849bf0a0 x16: fffffe000021f4a0 x15: 0000000000000004 x14: 000003fff82bb910 x13: 0000000000000001 x12: 000003ff7d75f200 x11: 00000000003d0f00 x10: 000003ff849b7af4 x9 : 0000000000000028 x8 : 0000000000000020 x7 : fffffe00bc5c3600 x6 : 000003fff82b976c x5 : 000003fff82b976c x4 : 0000000000000000 x3 : 0000000000000000 x2 : 0000000000000000 x1 : 0000000000000000 x0 : 000000000000000c WARNING: Number of errors: 1, skipped probes: 1 WARNING: /root/systemtap_write/install/bin/staprun exited with status: 1 Pass 5: run failed. [man error::pass5] Comment the return probe with a '#' at the beginning of the line with "kprobe.function("__vfs_read").return," and the script runs fine. The systemtap pointer_arg() doesn't take into account that the register might be used as a scratch register and the value changed after entry into the function. This is an issue with the systemtap scripts. I have patched the systemtap scripts to addresss this issue.. -Will
Attachment:
aarch64_retkprobe_issue2.stp
Description: Text document
Index Nav: | [Date Index] [Subject Index] [Author Index] [Thread Index] | |
---|---|---|
Message Nav: | [Date Prev] [Date Next] | [Thread Prev] [Thread Next] |