Add support for probes on variables with DW_OP_call_frame_cfa
as the dwarf operation in the debug info.

Some compilers (specifically Golang compiler) output
DW_OP_call_frame_cfa instead of DW_OP_fbreg for variables
on the stack. If DW_OP_call_frame_cfa is the only expression
than it is the same as DW_OP_fbreg with an offset of zero.
In the case of the Golang compiler, DW_OP_call_frame_cfa may
be followed by DW_OP_consts, with a number and than DW_OP_plus.
This trio is the same as DW_OP_fbreg with the number from
DW_OP_consts as the offset.

With this change, probing on functions in Golang with variables works.

Signed-off-by: Daniel Shaulov <[email protected]>

Up untill now, static compilation of perf was still trying to dynamically
load the backends for libebl. Starting with version 0.178 of elfutils,
libebl no longer needs to dynamicall load backends. This means that
perf compiled statically with elfutils>=0.178 is trully static.

In elfutils 0.178, libebl is also no longer a standalone library,
it is included as part of libdw, so there is no longer a need for -lebl.
Also - some of the backends required -lpthread, and since they are now
included in the static build, we also need to add -lpthread.

This change does not support older versions of elfutils.

Signed-off-by: Daniel Shaulov <[email protected]>

When a binary has debug symbols, but they are incomplete,
some files compiled with debug info and some didn't, perf-probe will
look for the debuginfo, and when it fails to find it will refuse to add the probe.
If the debug info is removed entirely perf-probe gracefully degrades to using symbols.
This commit adds the fallback to symbols for cases where dwarf exists but fails

The issue was found with a nodejs binary which ships with debug info only
for the '.c' files but no for '.cc' (c++) files, and trying to probe a c++ function.

Signed-off-by: Daniel Shaulov <[email protected]>

When trying to cast a probe variable to string, the type is checked
to be "(unsigned) char *". In Golang debug info, the strings are
ultimately "uint8 *", so the cast fails.

This commit adds the type to the list of types that can be casted
to string, and also prints the type when it is found to not match
one the types, for easier debugging of future issues.

Signed-off-by: Daniel Shaulov <[email protected]>

Add a Dockerfile that can be used to build a static perf
The image is based on ubunut:16.04 to have a libc that supports older
kernel versions.

To build a static perf using the Dockerfile you can run the following (at the repo root):
docker build -t buildbox - < tools/perf/Dockerfile
docker run -v $PWD:/linux -w /linux/tools/perf buildbox sh -c "make clean all LDFLAGS=-static"

Signed-off-by: Daniel Shaulov <[email protected]>

Force "perf inject" to write the cmdline it has read from the input file,
instead of writing its own cmdline. "perf inject" cmdline is hardly useful,
"perf record"s is what we care about.

Do note it's not exactly complete - I did not change write_cmdline() so
that one still writes readlink("/proc/self/exe") of "perf inject" as the
argv[0], and we drop the argv[0] we've read from the file. Unless you use
different "perf" binaries for "record" and "inject", this doesn't matter.

Signed-off-by: Yonatan Goldschmidt <[email protected]>

Process names are much clearer as the first line in a flamegraph
If we ever want to upstream this, it needs to be a separate option

…ork event (#2)

This reverts commit 5ad1beb.

Linux 6.0

The use case is, I'd like to switch upon signal but still protect with a timeout.