* [Bug bpf/23860] New: unknown opcode 0x8f in string manipulation code
@ 2018-11-04 18:38 fche at redhat dot com
2018-11-04 21:16 ` [Bug bpf/23860] " mark at klomp dot org
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: fche at redhat dot com @ 2018-11-04 18:38 UTC (permalink / raw)
To: systemtap
https://sourceware.org/bugzilla/show_bug.cgi?id=23860
Bug ID: 23860
Summary: unknown opcode 0x8f in string manipulation code
Product: systemtap
Version: unspecified
Status: NEW
Severity: normal
Priority: P2
Component: bpf
Assignee: systemtap at sourceware dot org
Reporter: fche at redhat dot com
Target Milestone: ---
% stap -p4 --bpf -e 'global e probe kernel.function("vfs_read") { e[execname()]
= 0 }'
% eu-objdump -d stap_FOOBAR.bo
[...]
d0: 57 00 00 00 ff 00 00 00 r0 &= 255
d8: bf 01 00 00 00 00 00 00 r1 = r0
e0: 8f 01 00 00 00 00 00 00 invalid class alu64
e8: 4f 01 00 00 00 00 00 00 r1 |= r0
f0: bf 13 00 00 00 00 00 00 r3 = r1
f8: bf 20 00 00 00 00 00 00 r0 = r2
100: 77 00 00 00 08 00 00 00 r0 >>= 8
108: 57 00 00 00 ff 00 00 00 r0 &= 255
110: bf 01 00 00 00 00 00 00 r1 = r0
118: 8f 01 00 00 00 00 00 00 invalid class alu64
120: 4f 01 00 00 00 00 00 00 r1 |= r0
128: 5f 13 00 00 00 00 00 00 r3 &= r1
130: bf 20 00 00 00 00 00 00 r0 = r2
% stapbpf stap_FOOBAR.bo
(fails with unknown opcode 0x8f)
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* [Bug bpf/23860] unknown opcode 0x8f in string manipulation code
2018-11-04 18:38 [Bug bpf/23860] New: unknown opcode 0x8f in string manipulation code fche at redhat dot com
@ 2018-11-04 21:16 ` mark at klomp dot org
2018-11-05 22:01 ` me at serhei dot io
2018-11-05 22:03 ` me at serhei dot io
2 siblings, 0 replies; 4+ messages in thread
From: mark at klomp dot org @ 2018-11-04 21:16 UTC (permalink / raw)
To: systemtap
https://sourceware.org/bugzilla/show_bug.cgi?id=23860
Mark Wielaard <mark at klomp dot org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |mark at klomp dot org
--- Comment #1 from Mark Wielaard <mark at klomp dot org> ---
If I am decoding this correctly this would be BPF_ALU64 | BPF_NEG | BPF_X.
I am not sure that combination makes sense. I don't believe you can negate a
source operand. You seem to only be able to negate the dest operand (register).
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* [Bug bpf/23860] unknown opcode 0x8f in string manipulation code
2018-11-04 18:38 [Bug bpf/23860] New: unknown opcode 0x8f in string manipulation code fche at redhat dot com
2018-11-04 21:16 ` [Bug bpf/23860] " mark at klomp dot org
@ 2018-11-05 22:01 ` me at serhei dot io
2018-11-05 22:03 ` me at serhei dot io
2 siblings, 0 replies; 4+ messages in thread
From: me at serhei dot io @ 2018-11-05 22:01 UTC (permalink / raw)
To: systemtap
https://sourceware.org/bugzilla/show_bug.cgi?id=23860
Serhei Makarov <me at serhei dot io> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |me at serhei dot io
--- Comment #2 from Serhei Makarov <me at serhei dot io> ---
This was a minor bug in program::mk_unary().
BPF_NEG indeed doesn't fit the pattern for eBPF opcodes: there is no src and
BPF_X is not used even though the disassembly says 'negx'.
Incorrect opcode should be fixed in commit 72ef87bba, but there's another
underlying issue preventing the example from working ('invalid memory access'
according to verifier). Not closing yet.
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* [Bug bpf/23860] unknown opcode 0x8f in string manipulation code
2018-11-04 18:38 [Bug bpf/23860] New: unknown opcode 0x8f in string manipulation code fche at redhat dot com
2018-11-04 21:16 ` [Bug bpf/23860] " mark at klomp dot org
2018-11-05 22:01 ` me at serhei dot io
@ 2018-11-05 22:03 ` me at serhei dot io
2 siblings, 0 replies; 4+ messages in thread
From: me at serhei dot io @ 2018-11-05 22:03 UTC (permalink / raw)
To: systemtap
https://sourceware.org/bugzilla/show_bug.cgi?id=23860
Serhei Makarov <me at serhei dot io> changed:
What |Removed |Added
----------------------------------------------------------------------------
Assignee|systemtap at sourceware dot org |me at serhei dot io
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2018-11-04 18:38 [Bug bpf/23860] New: unknown opcode 0x8f in string manipulation code fche at redhat dot com
2018-11-04 21:16 ` [Bug bpf/23860] " mark at klomp dot org
2018-11-05 22:01 ` me at serhei dot io
2018-11-05 22:03 ` me at serhei dot io
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