From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A407542A14B; Fri, 17 Jul 2026 14:21:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784298094; cv=none; b=jbMFF87CRLPstXJPbypLvs+4CJR8pv22fwfKwD372ScRUyxuUBnTnSVDZFnxQzflhKNerYaumtUWlun+oZDSBzeD7+LEL9H2D91ki8fwh71awK0rZU+yY0L00Zb9H/Bpz9o4c7OMBL8nLOY5LSkMk/iMPL6b/hQFQzORNyml/FI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784298094; c=relaxed/simple; bh=sR2y9qIC1RKJLRmHotwZZfScgtc+4IEyNJ36P0S8fQY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=KxEpV04dvpjuyZAM4JxiQiqjGH7qFuhyC4POgRHovdMsBv4C0mMKn8lHRpS6H1MS7iav5rfwAS8gm58JGbpjYtAljxBa1wUvccKGlGJ5gA+KmeDnCL/rgIMOOilyvMf7XRwrAOVqWlpSHqYqYe+SPxOytNtrWvTa1UYLA3sHsks= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=iLX/JxBh; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="iLX/JxBh" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9F4371F000E9; Fri, 17 Jul 2026 14:21:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784298093; bh=m52Fw9GeEPA0ZBlojXrp/w4D3jkG1Tgk7/BsPis+h84=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=iLX/JxBhSqdn4g16JjHzsZ6tQGUuRS8Jvey1KmxqwabpvdrejjAJ8+o72bnScX3qI fo+2AaSfwB4A8GjwN/DYmScvGeNNzIPKRTwW3BTpr0RyGaoYT0AiqUBoUMTHwd8NM9 kJbUwxk3HkKPlGekgw+7d0HxpbdRS3uPcv+E88w+nylJ2oncLZJv7ONkk0nIbkjHQL vG7w7cfiwxv424Ls5HqMn8IGuII0urUJk1AvKAb7p1nO1OqUTBuHnFfsShduJSluss n4EXWsdJPz8l92cT0jLQa95/ZLhxaXzUH3iQvX2vMT+Dyrq6HEpgtKZnDbKDYc50ud PDdNdDaOrFQoA== From: "Masami Hiramatsu (Google)" To: Steven Rostedt , Peter Zijlstra , Ingo Molnar , x86@kernel.org Cc: Jinchao Wang , Mathieu Desnoyers , Masami Hiramatsu , Thomas Gleixner , Borislav Petkov , Dave Hansen , "H . Peter Anvin" , Alexander Shishkin , Ian Rogers , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-perf-users@vger.kernel.org Subject: [PATCH v9 10/10] tracing/wprobe: Support BTF typecast in fetchargs Date: Fri, 17 Jul 2026 23:21:27 +0900 Message-ID: <178429808731.157981.9671478928789148148.stgit@devnote2> X-Mailer: git-send-email 2.43.0 In-Reply-To: <178429796992.157981.3393977217853767915.stgit@devnote2> References: <178429796992.157981.3393977217853767915.stgit@devnote2> User-Agent: StGit/0.19 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit From: Masami Hiramatsu (Google) Allow BTF typecast syntax (STRUCT)FETCHARG->MEMBER in wprobe event fetchargs. Previously, handle_typecast() rejected any probe context that was not a function entry/return or tracepoint event probe. Wprobe events use (the accessed address) and (the value at that address). By enabling BTF typecast, users can now cast these to a concrete struct type and access its fields directly. For example: echo 'w:watch rw@0:8 dflag=(struct dentry)$addr->d_flags' >> dynamic_events With a set_wprobe trigger pointing the watchpoint at a dentry address, the resulting trace shows d_flags being accessed at that location. Note that and are restricted to kernel-space memory, which is consistent with the existing TPARG_FL_KERNEL flag used when parsing wprobe fetchargs. Assisted-by: Antigravity:gemini-3.5-flash Signed-off-by: Masami Hiramatsu (Google) --- Changes in v9: - Newly added. --- kernel/trace/trace_probe.c | 3 + kernel/trace/trace_probe.h | 5 + .../test.d/trigger/trigger-wprobe-btf-typecast.tc | 80 ++++++++++++++++++++ 3 files changed, 87 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/ftrace/test.d/trigger/trigger-wprobe-btf-typecast.tc diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c index 5d5e9b477b86..8332ff1bb4ff 100644 --- a/kernel/trace/trace_probe.c +++ b/kernel/trace/trace_probe.c @@ -967,7 +967,8 @@ static int handle_typecast(char *arg, struct traceprobe_parse_context *ctx) if (!(tparg_is_event_probe(ctx->flags) || tparg_is_function_entry(ctx->flags) || - tparg_is_function_return(ctx->flags))) { + tparg_is_function_return(ctx->flags) || + tparg_is_wprobe(ctx->flags))) { trace_probe_log_err(ctx->offset, NOSUP_BTFARG); return -EOPNOTSUPP; } diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h index 7380502a85af..0a83b3fb6128 100644 --- a/kernel/trace/trace_probe.h +++ b/kernel/trace/trace_probe.h @@ -439,6 +439,11 @@ static inline bool tparg_is_event_probe(unsigned int flags) return !!(flags & TPARG_FL_TEVENT); } +static inline bool tparg_is_wprobe(unsigned int flags) +{ + return !!(flags & TPARG_FL_WPROBE); +} + /* Each typecast consumes nested level. So the max number of typecast is 8. */ #define TRACEPROBE_MAX_NESTED_LEVEL 8 diff --git a/tools/testing/selftests/ftrace/test.d/trigger/trigger-wprobe-btf-typecast.tc b/tools/testing/selftests/ftrace/test.d/trigger/trigger-wprobe-btf-typecast.tc new file mode 100644 index 000000000000..8962c91d8428 --- /dev/null +++ b/tools/testing/selftests/ftrace/test.d/trigger/trigger-wprobe-btf-typecast.tc @@ -0,0 +1,80 @@ +#!/bin/sh +# SPDX-License-Identifier: GPL-2.0 +# description: event trigger - test wprobe trigger with BTF typecast fetchargs +# requires: dynamic_events "w[:[/][]] [r|w|rw]@[:]":README events/sched/sched_process_fork/trigger "[(structname[,field])][->field[->field|.field...]]":README + +echo 0 >> tracing_on + +rm -f $TMPDIR/hoge + +# we will skip this test if fprobe is not supported. +if ! grep -Fq "f[:[/][]] [%return] []" README; then + echo "UNRESOLVED: fprobe is not supported" + exit_unresolved +fi + +# we will skip this test if the target function does not exist. +if ! grep -wq "do_truncate" /proc/kallsyms; then + echo "UNRESOLVED: do_truncate not found" + exit_unresolved +fi +if ! grep -wq "dentry_kill" /proc/kallsyms; then + echo "UNRESOLVED: dentry_kill not found" + exit_unresolved +fi + +:;: "Add a wprobe event with BTF typecast fetchargs" ;: +# $addr is the address being accessed (= dentry pointer when watching dentry) +# (dentry)$addr->d_flags reads d_flags from the dentry struct via BTF typecast +# Note: BTF typecast uses (STRUCT) without the 'struct' keyword, matching +# the fetcharg syntax used in fprobe/tprobe events. +echo 'w:watch rw@0:8 address=$addr dflag=(dentry)$addr->d_flags' >> dynamic_events + +:;: "Check the wprobe event is registered with dflag field" ;: +grep -q "dflag" dynamic_events + +:;: "Add events for triggering wprobe" ;: +echo 'f:truncate do_truncate dentry=$arg2' >> dynamic_events +echo 'f:dentry_kill dentry_kill dentry=$arg1' >> dynamic_events + +:;: "Add wprobe triggers" ;: +echo 'set_wprobe:watch:dentry' >> events/fprobes/truncate/trigger +echo 'clear_wprobe:watch:dentry' >> events/fprobes/dentry_kill/trigger +cat events/fprobes/truncate/trigger | grep ^set_wprobe +cat events/fprobes/dentry_kill/trigger | grep ^clear_wprobe + +:;: "Ensure wprobe is still disabled" ;: +cat events/wprobes/watch/enable | grep 0 + +:;: "Enable events for triggers" ;: +echo 1 >> events/fprobes/truncate/enable +echo 1 >> events/fprobes/dentry_kill/enable + +:;: "Start test workload" ;: +echo 1 >> tracing_on + +echo aaa > $TMPDIR/hoge +sleep 1 +echo bbb > $TMPDIR/hoge +sleep 1 +echo ccc > $TMPDIR/hoge +sleep 1 +rm $TMPDIR/hoge + +:;: "Drop dentry caches (for dentry_kill)" ;: +sync && echo 2 >> /proc/sys/vm/drop_caches + +:;: "Check trace results include BTF typecast field dflag" ;: +cat trace > /tmp/test-trace-typecast.log +cat trace | grep "watch.*dflag=" + +:;: "Ensure wprobe becomes disabled again" ;: +cat events/wprobes/watch/enable | grep 0 + +:;: "Remove wprobe triggers" ;: +echo '!set_wprobe:watch:dentry' >> events/fprobes/truncate/trigger +echo '!clear_wprobe:watch' >> events/fprobes/dentry_kill/trigger +! grep ^set_wprobe events/fprobes/truncate/trigger +! grep ^clear_wprobe events/fprobes/dentry_kill/trigger + +exit 0