From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) (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 42F9C72 for ; Mon, 18 Oct 2021 13:25:45 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 6588961212; Mon, 18 Oct 2021 13:25:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1634563544; bh=W8d6wLC+qnOY0iDnbVT7BsjQnmwP6Afm/bnrAfCrD8g=; h=From:To:Cc:Subject:Date:From; b=krVkGJS7I1xzvyoiD04XnLt7ZjKO5uXhdFFPU+4iXfASBRZomp2oqGdW9YoIZDB2K mBp4DE0QQz7SGQ26IPEpA5exO9zhw8rcToky5kNMqljIMkcwut7d9TKD15c+UdEnGo HRZf7q9FDUGIEvFeG9Loe4SNGQA24Np2zZhtHKhcEiqzPdWXvOC/gZ2BFAlhuVfkHo uneowA1wt0nTGdfvL97RCV3waOu+rK1cnoqoCMgS3T3+4oQ8FA9ZkKCWICL/0xz9Cb r36Rwccj4ppyXEMELfWCjKgehoml1Js1c0HSHO6w8X6y2WUeIjRsiSmxvkwzNyThBM uj85yUI7N58ZA== From: Arnd Bergmann To: Steven Rostedt , Ingo Molnar Cc: Arnd Bergmann , Nathan Chancellor , Nick Desaulniers , Tom Zanussi , Masami Hiramatsu , Namhyung Kim , Jiapeng Chong , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Qiujun Huang , linux-kernel@vger.kernel.org, llvm@lists.linux.dev Subject: [PATCH] [v2] tracing: use %ps format string to print symbols Date: Mon, 18 Oct 2021 15:25:30 +0200 Message-Id: <20211018132538.2468989-1-arnd@kernel.org> X-Mailer: git-send-email 2.29.2 Precedence: bulk X-Mailing-List: llvm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Arnd Bergmann clang started warning about excessive stack usage in hist_trigger_print_key() kernel/trace/trace_events_hist.c:4723:13: error: stack frame size (1336) exceeds limit (1024) in function 'hist_trigger_print_key' [-Werror,-Wframe-larger-than] The problem is that there are two 512-byte arrays on the stack if hist_trigger_stacktrace_print() gets inlined. I don't think this has changed in the past five years, but something probably changed the inlining decisions made by the compiler, so the problem is now made more obvious. Rather than printing the symbol names into separate buffers, it seems we can simply use the special %ps format string modifier to print the pointers symbolically and get rid of both buffers. Marking hist_trigger_stacktrace_print() would be a simpler way of avoiding the warning, but that would not address the excessive stack usage. Fixes: 69a0200c2e25 ("tracing: Add hist trigger support for stacktraces as keys") Link: https://lore.kernel.org/all/20211015095704.49a99859@gandalf.local.home/ Signed-off-by: Arnd Bergmann --- Changes in v2: - Use %pS instead of %ps to include offset in third string - add (void*) cast to avoid compile-time warnings This is still only compile-tested to ensure that the warning goes away, I have not validated what it does to the formatting. --- kernel/trace/trace_events_hist.c | 15 +++++---------- 1 file changed, 5 insertions(+), 10 deletions(-) diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index a6061a69aa84..d6d4362c273c 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -4706,7 +4706,6 @@ static void hist_trigger_stacktrace_print(struct seq_file *m, unsigned long *stacktrace_entries, unsigned int max_entries) { - char str[KSYM_SYMBOL_LEN]; unsigned int spaces = 8; unsigned int i; @@ -4715,8 +4714,7 @@ static void hist_trigger_stacktrace_print(struct seq_file *m, return; seq_printf(m, "%*c", 1 + spaces, ' '); - sprint_symbol(str, stacktrace_entries[i]); - seq_printf(m, "%s\n", str); + seq_printf(m, "%pS\n", (void*)stacktrace_entries[i]); } } @@ -4726,7 +4724,6 @@ static void hist_trigger_print_key(struct seq_file *m, struct tracing_map_elt *elt) { struct hist_field *key_field; - char str[KSYM_SYMBOL_LEN]; bool multiline = false; const char *field_name; unsigned int i; @@ -4747,14 +4744,12 @@ static void hist_trigger_print_key(struct seq_file *m, seq_printf(m, "%s: %llx", field_name, uval); } else if (key_field->flags & HIST_FIELD_FL_SYM) { uval = *(u64 *)(key + key_field->offset); - sprint_symbol_no_offset(str, uval); - seq_printf(m, "%s: [%llx] %-45s", field_name, - uval, str); + seq_printf(m, "%s: [%llx] %-45ps", field_name, + uval, (void *)uval); } else if (key_field->flags & HIST_FIELD_FL_SYM_OFFSET) { uval = *(u64 *)(key + key_field->offset); - sprint_symbol(str, uval); - seq_printf(m, "%s: [%llx] %-55s", field_name, - uval, str); + seq_printf(m, "%s: [%llx] %-55pS", field_name, + uval, (void *)uval); } else if (key_field->flags & HIST_FIELD_FL_EXECNAME) { struct hist_elt_data *elt_data = elt->private_data; char *comm; -- 2.29.2