Retsnoop injection probes and other improvements #70
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This might be less surprising for tracing mode. Doing `-T -Sn` is non-obvious, while `-T -x any` is probably more intuitive. Unfortunately, due to how argp library handles ARG_OPTIONAL arguments, we can't mark -x as having optional value and allow to specify just `-x` to mean any error, because it has bad interaction with subsequent arguments. E.g., '-x -v' is not really two separate options, but rather passing '-v' as a value to '-x' argument. argp expectx '-x=blah', which is also not super obvious and not what users came to expect with -x argument. Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Older kernels might not verify retsnoop with -A (function args) feature enabled. Make sure that compiler won't re-load validated len by using barrier_var() and sticking to full-sized u64. Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
argp is really buggy about help output, but do what we can to mitigate this a littel bit. Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
This makes it easier to distinguish it in bpftool output. Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
I don't even remember what that was supposed to be used for. Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
We'll use this for detecting if rawtp-based injected probes are supported. Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Add ability to specify point-like injection probes, which allow to get more visibility into what the kernel is doing, in addition to function entry/exit data that retsnoop collects already. Four types of injection probes are supported: - kprobes (including with non-zero offset into the function); - kretprobe; - raw tracepoints; - classic tracepoints. Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
We are going to add generic injected probes capture next. Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Also generalize some naming, fix commit, etc. Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Add capture of pt_regs for kprobe/kretprobe injection probes. Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Wire up preparing and formatting injected probe context arguments. BPF sie doesn't really follow it yet, but existing kprobe capture code is memory-layout compatible already, so we can test end-to-end. Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Use consistent and obvious rec_xxx naming convention. Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Make it possible to reuse not just for function arguments capture. Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
This will now be tested with kprobe probes. Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Augment context args capture with raw tracepoint support. Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Some PIDs are larger than 1 mln, so bump the heuristics to emit integers as decimal up to about 4 millions. Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
We don't really need to re-read ksyms 3 times. One is more than enough. Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Teach retsnoop to find, parse, and capture classic tracepoint arguments. See extensive comment for how we go about this, because tracepoint name isn't enough, we also need tracepoint "class". Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
We accidentally used function count instead of injected probe cnt. Fix it. Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Complete a set of injected probe functionality with extending README.md with documentation on how to use this feature, with some examples. Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
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