kbuild: rust: keep Rust objects out of Clang LTO with inline helpersgrafted

Under `CONFIG_LTO_CLANG` + `CONFIG_RUST_INLINE_HELPERS`, one may hit
`objtool` errors such as:

    vmlinux.o: error: objtool: _R..._3Gsp4boot+0xd6a:
    can't find jump dest instruction at .text._R..._3Gsp4boot+0x1dfd

The reason is that in such builds, the Clang invocation that compiles
the combined Rust plus helpers bitcode emits LLVM bitcode (again) --
the final code generation happens in the linker's LTO step, which the
`-mllvm` trap options passed to Clang do not reach.

This, in turn, means that unreachable traps are missing, and the
impossible paths do not merely fallthrough to the next symbol, but past
the end of their own section, since LTO builds place each function in
its own section.

Thus filter `CC_FLAGS_LTO` out of the Clang invocation, so that it always
emits machine code directly, with the traps in place.

Assisted-by: LLM
Cc: Gary Guo <gary@garyguo.net>
Cc: Boqun Feng <boqun@kernel.org>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Matthew Maurer <mmaurer@google.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust")
Acked-by: Gary Guo <gary@garyguo.net>
Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

1 files changed, 82 insertions, 0 deletions

diff --git a/tools/perf/Documentation/perf-data.txt b/tools/perf/Documentation/perf-data.txt
new file mode 100644
index 000000000..20f178d61
--- /dev/null
+++ b/tools/perf/Documentation/perf-data.txt
@@ -0,0 +1,82 @@
+perf-data(1)
+============
+
+NAME
+----
+perf-data - Data file related processing
+
+SYNOPSIS
+--------
+[verse]
+'perf data' [<common options>] <command> [<options>]",
+
+DESCRIPTION
+-----------
+Data file related processing.
+
+COMMANDS
+--------
+convert::
+	Converts perf data file into another format.
+	It's possible to set data-convert debug variable to get debug messages from conversion,
+	like:
+	  perf --debug data-convert data convert ...
+
+OPTIONS for 'convert'
+---------------------
+--to-ctf::
+	Triggers the CTF conversion, specify the path of CTF data directory.
+
+--to-json::
+	Triggers JSON conversion. Specify the JSON filename to output.
+
+--tod::
+	Convert time to wall clock time.
+
+-i::
+	Specify input perf data file path.
+
+-f::
+--force::
+	Don't complain, do it.
+
+--time::
+	Only convert samples within given time window: <start>,<stop>. Times
+	have the format seconds.nanoseconds. If start is not given (i.e. time
+	string is ',x.y') then analysis starts at the beginning of the file. If
+	stop time is not given (i.e. time string is 'x.y,') then analysis goes
+	to end of file. Multiple ranges can be separated by spaces, which
+	requires the argument to be quoted e.g. --time "1234.567,1234.789 1235,"
+
+	Also support time percent with multiple time ranges. Time string is
+	'a%/n,b%/m,...' or 'a%-b%,c%-%d,...'.
+
+	For example:
+	Select the second 10% time slice:
+
+	  perf data convert --to-json out.json --time 10%/2
+
+	Select from 0% to 10% time slice:
+
+	  perf data convert --to-json out.json --time 0%-10%
+
+	Select the first and second 10% time slices:
+
+	  perf data convert --to-json out.json --time 10%/1,10%/2
+
+	Select from 0% to 10% and 30% to 40% slices:
+
+	  perf data convert --to-json out.json --time 0%-10%,30%-40%
+
+-v::
+--verbose::
+        Be more verbose (show counter open errors, etc).
+
+--all::
+	Convert all events, including non-sample events (comm, fork, ...), to output.
+	Default is off, only convert samples.
+
+SEE ALSO
+--------
+linkperf:perf[1]
+[1] Common Trace Format - http://www.efficios.com/ctf