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With "bpftool prog tracelog", bpftool prints messages from the trace
pipe. To do so, it first needs to find the tracefs mount point to open
the pipe. Bpftool looks at a few "default" locations, including
/sys/kernel/debug/tracing and /sys/kernel/tracing.
Some of these locations, namely /tracing and /trace, are not standard.
They are in the list because some users used to hardcode the tracing
directory to short names; but we have no compelling reason to look at
these locations. If we fail to find the tracefs at the default
locations, we have an additional step to find it by parsing /proc/mounts
anyway, so it's safe to remove these entries from the list of default
locations to check.
Additionally, Alexei reports that looking for the tracefs at
/sys/kernel/debug/tracing may automatically mount the file system under
that location, and generate a kernel log message telling that
auto-mounting there is deprecated. To avoid this message, let's swap the
order for checking the potential mount points: try /sys/kernel/tracing
first, which should be the standard location nowadays. The kernel log
message may still appear if the tracefs is not mounted on
/sys/kernel/tracing when we run bpftool.
Reported-by: Alexei Starovoitov <ast@kernel.org>
Closes: https://lore.kernel.org/r/CAADnVQLcMi5YQhZKsU4z3S2uVUAGu_62C33G2Zx_ruG3uXa-Ug@mail.gmail.com/
Signed-off-by: Quentin Monnet <qmo@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/r/20250915134209.36568-1-qmo@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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Fixed some formatting specifiers errors, such as using %d for int and %u
for unsigned int, as well as other byte-length types.
Perform type cast using the type derived from the data type itself, for
example, if it's originally an int, it will be cast to unsigned int if
forced to unsigned.
Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20250311112809.81901-3-jiayuan.chen@linux.dev
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musl does not like including sys/fcntl.h directly:
[...]
1 | #warning redirecting incorrect #include <sys/fcntl.h> to <fcntl.h>
[...]
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Quentin Monnet <quentin@isovalent.com>
Link: https://lore.kernel.org/bpf/20220424051022.2619648-5-asmadeus@codewreck.org
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In order to make life easier for users, bpftool automatically attempts
to mount the BPF virtual file system, if it is not mounted already,
before trying to pin objects in it. Similarly, it attempts to mount
tracefs if necessary before trying to dump the trace pipe to the
console.
While mounting file systems on-the-fly can improve user experience, some
administrators might prefer to avoid that. Let's add an option to block
these mount attempts. Note that it does not prevent automatic mounting
of tracefs by debugfs for the "bpftool prog tracelog" command.
Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
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As a follow-up to commit 30da46b5dc3a ("tools: bpftool: add a command to
dump the trace pipe"), attempt to mount the tracefs virtual file system
if it is not detected on the system before trying to dump content of the
tracing pipe on an invocation of "bpftool prog tracelog".
Usually, tracefs in automatically mounted by debugfs when the user tries
to access it (e.g. "ls /sys/kernel/debug/tracing" mounts the tracefs).
So if we failed to find it, it is probably that debugfs is not here
either. Therefore, we just attempt a single mount, at a location that
does not involve debugfs: /sys/kernel/tracing.
Suggested-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
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BPF programs can use the bpf_trace_printk() helper to print debug
information into the trace pipe. Add a subcommand
"bpftool prog tracelog" to simply dump this pipe to the console.
This is for a good part copied from iproute2, where the feature is
available with "tc exec bpf dbg". Changes include dumping pipe content
to stdout instead of stderr and adding JSON support (content is dumped
as an array of strings, one per line read from the pipe). This version
is dual-licensed, with Daniel's permission.
Cc: Daniel Borkmann <daniel@iogearbox.net>
Suggested-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
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