linux-stable.git/Documentation/trace, branch v6.18.41

tracing/eprobes: Allow use of BTF names to dereference pointers

2026-07-24T14:16:42+00:00

[ Upstream commit 69efd863a78584b9416ed6be0e1e7349124b4a00 ]

Add syntax to the parsing of eprobes to be able to typecast a trace event
field that is a pointer to a structure.

Currently, a dereference must be a number, where the user has to figure
out manually the offset of a member of a structure that they want to
dereference.

But for event probes that records a field that happens to be a pointer to
a structure, it cannot dereference these values with BTF naming, but
must use numerical offsets.

For example, to find out what device a sk_buff is pointing to in the
net_dev_xmit trace event, one must first use gdb to find the offsets of the
members of the structures:

 (gdb) p &((struct sk_buff *)0)->dev
 $1 = (struct net_device **) 0x10
 (gdb) p &((struct net_device *)0)->name
 $2 = (char (*)[16]) 0x118

And then use the raw numbers to dereference:

  # echo 'e:xmit net.net_dev_xmit +0x118(+0x10($skbaddr)):string' >> dynamic_events

If BTF is in the kernel, then instead, the skbaddr can be typecast to
sk_buff and use the normal dereference logic.

  # echo 'e:xmit net.net_dev_xmit (sk_buff)skbaddr->dev->name:string' >> dynamic_events
  # echo 1 > events/eprobes/xmit/enable
  # cat trace
[..]
    sshd-session-1022    [000] b..2.   860.249343: xmit: (net.net_dev_xmit) arg1="enp7s0"
    sshd-session-1022    [000] b..2.   860.250061: xmit: (net.net_dev_xmit) arg1="enp7s0"
    sshd-session-1022    [000] b..2.   860.250142: xmit: (net.net_dev_xmit) arg1="enp7s0"
    sshd-session-1022    [000] b..2.   860.263553: xmit: (net.net_dev_xmit) arg1="enp7s0"
    sshd-session-1022    [000] b..2.   860.283820: xmit: (net.net_dev_xmit) arg1="enp7s0"
    sshd-session-1022    [000] b..2.   860.302716: xmit: (net.net_dev_xmit) arg1="enp7s0"
    sshd-session-1022    [000] b..2.   860.322905: xmit: (net.net_dev_xmit) arg1="enp7s0"
    sshd-session-1022    [000] b..2.   860.342828: xmit: (net.net_dev_xmit) arg1="enp7s0"
    sshd-session-1022    [000] b..2.   860.362268: xmit: (net.net_dev_xmit) arg1="enp7s0"
    sshd-session-1022    [000] b..2.   860.382335: xmit: (net.net_dev_xmit) arg1="enp7s0"
    sshd-session-1022    [000] b..2.   860.400856: xmit: (net.net_dev_xmit) arg1="enp7s0"
    sshd-session-1022    [000] b..2.   860.419893: xmit: (net.net_dev_xmit) arg1="enp7s0"

The syntax is simply: (STRUCT)(FIELD)->MEMBER[->MEMBER..]

Also add comments around the #else and #endif of #ifdef CONFIG_PROBE_EVENTS_BTF_ARGS
to know what they are for.

Link: https://lore.kernel.org/all/20260601130746.2139d926@gandalf.local.home/

Signed-off-by: Steven Rostedt (Google) 
Signed-off-by: Masami Hiramatsu (Google) 
Stable-dep-of: 251a8fe1b9ae ("tracing/probes: Remove WARN_ON_ONCE from parse_btf_arg")
Signed-off-by: Sasha Levin

Documentation/rv: Replace stale website link

2026-07-24T14:15:45+00:00

[ Upstream commit 49cbd359e4a7501e9d6694c072031d9ae6b2d1a5 ]

The sched monitor page was linking to Daniel's website which is now
down. The main purpose of the link was to point to a source for the
models from the original author and that can be found also in his
published paper.

Replace the link with a reference to Daniel's "A thread synchronization
model for the PREEMPT_RT Linux kernel" which can be found online and
includes the models definitions as well as the work behind them (not the
original patches but since they're based on a 5.0 kernel and are mostly
included upstream, there's little value in keeping them in the docs).

Fixes: 03abeaa63c08 ("Documentation/rv: Add docs for the sched monitors")
Signed-off-by: Gabriele Monaco 
Acked-by: Matteo Martelli 
Tested-by: Matteo Martelli 
Tested-by: Randy Dunlap 
Acked-by: Randy Dunlap 
Signed-off-by: Jonathan Corbet 
Message-ID: <20260427131709.170505-2-gmonaco@redhat.com>
Signed-off-by: Sasha Levin

Documentation: tracing: Add PCI tracepoint documentation

2026-02-26T22:59:16+00:00

[ Upstream commit 8236fc613d44e59f6736d6c3e9efffaf26ab7f00 ]

The PCI tracing system provides tracepoints to monitor critical hardware
events that can impact system performance and reliability. Add
documentation about it.

Signed-off-by: Shuai Xue 
[bhelgaas: squash fixes:
https://lore.kernel.org/r/20260108013956.14351-2-bagasdotme@gmail.com
https://lore.kernel.org/r/20260108013956.14351-3-bagasdotme@gmail.com]
Signed-off-by: Bjorn Helgaas 
Reviewed-by: Ilpo Järvinen 
Link: https://patch.msgid.link/20251210132907.58799-4-xueshuai@linux.alibaba.com
Signed-off-by: Sasha Levin

Documentation: trace: histogram: Convert ftrace docs cross-reference

2025-09-18T17:49:26+00:00

In brief "Extended error information" section, details on error
condition is referred to ftrace docs, which is written in :file:
directive instead of a proper cross-reference. Convert it.

Reviewed-by: Tom Zanussi 
Signed-off-by: Bagas Sanjaya 
Acked-by: Steven Rostedt (Google) 
Signed-off-by: Jonathan Corbet 
Message-ID: <20250916054202.582074-7-bagasdotme@gmail.com>

Documentation: trace: histogram-design: Wrap introductory note in note:: directive

2025-09-18T17:49:26+00:00

Use Sphinx note:: directive for the introductory note at the beginning
of docs, instead of aligned-text paragraph that renders as definition
list.

Reviewed-by: Tom Zanussi 
Reviewed-by: Masami Hiramatsu (Google) 
Signed-off-by: Bagas Sanjaya 
Acked-by: Steven Rostedt (Google) 
Signed-off-by: Jonathan Corbet 
Message-ID: <20250916054202.582074-6-bagasdotme@gmail.com>

Documentation: trace: historgram-design: Separate sched_waking histogram section heading and the following diagram

2025-09-18T17:49:26+00:00

Section heading for sched_waking histogram is shown as normal paragraph
instead due to codeblock marker for the following diagram being in the
same line as the section underline. Separate them.

Fixes: daceabf1b494 ("tracing/doc: Fix ascii-art in histogram-design.rst")
Reviewed-by: Tom Zanussi 
Reviewed-by: Masami Hiramatsu (Google) 
Signed-off-by: Bagas Sanjaya 
Acked-by: Steven Rostedt (Google) 
Signed-off-by: Jonathan Corbet 
Message-ID: <20250916054202.582074-5-bagasdotme@gmail.com>

Documentation: trace: histogram-design: Trim trailing vertices in diagram explanation text

2025-09-18T17:49:26+00:00

Diagram explanation text is supposed to be interleaved commentary
between diagram parts that are spread out, but it outputs ugly in
htmldocs due to trailing vertices as if both the explanation and the
diagram are in the same literal code block.

Trim trailing vertices.

Reviewed-by: Tom Zanussi 
Reviewed-by: Masami Hiramatsu (Google) 
Signed-off-by: Bagas Sanjaya 
Acked-by: Steven Rostedt (Google) 
Signed-off-by: Jonathan Corbet 
Message-ID: <20250916054202.582074-4-bagasdotme@gmail.com>

Documentation: trace: histogram: Fix histogram trigger subsection number order

2025-09-18T17:49:26+00:00

Section numbering in subsections of "Histogram Trigger Command" sections
is inconsistent in order. In particular, "'hist' trigger examples" is
erroneously numbered as 6.2, which is a leftover from  b8df4a3634e08a
("tracing: Move hist trigger Documentation to histogram.txt").

Fix the order.

Reviewed-by: Tom Zanussi 
Reviewed-by: Masami Hiramatsu (Google) 
Signed-off-by: Bagas Sanjaya 
Acked-by: Steven Rostedt (Google) 
Signed-off-by: Jonathan Corbet 
Message-ID: <20250916054202.582074-3-bagasdotme@gmail.com>

tracing: fix grammar error in debugging.rst

2025-09-03T21:31:48+00:00

Signed-off-by: Ryan Chung 
Acked-by: Steven Rostedt (Google) 
Signed-off-by: Jonathan Corbet 
Link: https://lore.kernel.org/r/20250831101736.11519-3-seokwoo.chung130@gmail.com

tracing: rephrase for clearer documentation

2025-09-03T21:31:30+00:00

Signed-off-by: Ryan Chung 
Acked-by: Steven Rostedt (Google) 
Signed-off-by: Jonathan Corbet 
Link: https://lore.kernel.org/r/20250831101736.11519-2-seokwoo.chung130@gmail.com