* [Bug bpf/24758] New: stapbpf-next: more robust and generous userspace interpreter
@ 2019-07-02 15:38 me at serhei dot io
2020-06-19 15:03 ` [Bug bpf/24758] " me at serhei dot io
0 siblings, 1 reply; 2+ messages in thread
From: me at serhei dot io @ 2019-07-02 15:38 UTC (permalink / raw)
To: systemtap
https://sourceware.org/bugzilla/show_bug.cgi?id=24758
Bug ID: 24758
Summary: stapbpf-next: more robust and generous userspace
interpreter
Product: systemtap
Version: unspecified
Status: NEW
Severity: normal
Priority: P2
Component: bpf
Assignee: systemtap at sourceware dot org
Reporter: me at serhei dot io
Target Milestone: ---
The BPF interpreter (in stapbpf/bpfinterp.cxx) is still a cobbled-together
thing with some holes and probable bugs lurking. It needs a pass over the code
to be brought up to standard bytecode-interpreter 'best practice'. No need for
fancy performance tricks, but:
- It could be more robust (runtime errors handled properly, memory management
with fewer pitfalls).
- It could be more generous (some of the kernel bpf restrictions are still
duplicated in userspace where there's no need for them -- pr24528 allows us to
generate different code for userspace probes).
- It could maybe use fewer hacky C++ interfaces.
- It could maybe do with refactoring to include some code from the lkm runtime
where functionality is being duplicated. (We already use lkm code in-userspace
for the dyninst backend, so reusing it here is not totally shocking.)
The only thing that's needed for certain is 'more robust' so I am filing just
one PR for now to track this work.
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* [Bug bpf/24758] stapbpf-next: more robust and generous userspace interpreter
2019-07-02 15:38 [Bug bpf/24758] New: stapbpf-next: more robust and generous userspace interpreter me at serhei dot io
@ 2020-06-19 15:03 ` me at serhei dot io
0 siblings, 0 replies; 2+ messages in thread
From: me at serhei dot io @ 2020-06-19 15:03 UTC (permalink / raw)
To: systemtap
https://sourceware.org/bugzilla/show_bug.cgi?id=24758
--- Comment #1 from Serhei Makarov <me at serhei dot io> ---
Took an initial step in this direction by bumping stack size (commit
9a2cd427a6a4) to 64k (iirc first suggested for xbpf by Jose Marchesi; if GCC
can compile to this, so can we).
fche suggesting using realloc() to resize the stack dynamically if this
solution turns out to be insufficient.
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