linux-kernel - [tip:perf/urgent] kallsyms: Simplify update_iter

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Date:   Sat, 18 Aug 2018 04:59:21 -0700
From:   tip-bot for Adrian Hunter <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     luto@...nel.org, jolsa@...hat.com, peterz@...radead.org,
        rostedt@...dmis.org, mingo@...nel.org,
        linux-kernel@...r.kernel.org, dave.hansen@...ux.intel.com,
        tglx@...utronix.de, alexander.shishkin@...ux.intel.com,
        joro@...tes.org, ak@...ux.intel.com, hpa@...or.com,
        acme@...hat.com, adrian.hunter@...el.com
Subject: [tip:perf/urgent] kallsyms: Simplify update_iter_mod()

Commit-ID:  b96679422007c3fa04625be14977904c27c722eb
Gitweb:     https://git.kernel.org/tip/b96679422007c3fa04625be14977904c27c722eb
Author:     Adrian Hunter <adrian.hunter@...el.com>
AuthorDate: Wed, 6 Jun 2018 15:54:09 +0300
Committer:  Arnaldo Carvalho de Melo <acme@...hat.com>
CommitDate: Tue, 14 Aug 2018 19:10:23 -0300

kallsyms: Simplify update_iter_mod()

The logic in update_iter_mod() is overcomplicated and gets worse every
time another get_ksymbol_* function is added.

In preparation for adding another get_ksymbol_* function, simplify logic
in update_iter_mod().

Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
Tested-by: (ftrace changes only) Steven Rostedt (VMware) <rostedt@...dmis.org>
Acked-by: Andi Kleen <ak@...ux.intel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Joerg Roedel <joro@...tes.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: x86@...nel.org
Link: http://lkml.kernel.org/r/1528289651-4113-2-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 kernel/kallsyms.c | 25 +++++++++++--------------
 1 file changed, 11 insertions(+), 14 deletions(-)

diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index a23e21ada81b..aa31aa07f2ef 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -506,27 +506,24 @@ static void reset_iter(struct kallsym_iter *iter, loff_t new_pos)
 	}
 }
 
+/*
+ * The end position (last + 1) of each additional kallsyms section is recorded
+ * in iter->pos_..._end as each section is added, and so can be used to
+ * determine which get_ksymbol_...() function to call next.
+ */
 static int update_iter_mod(struct kallsym_iter *iter, loff_t pos)
 {
 	iter->pos = pos;
 
-	if (iter->pos_ftrace_mod_end > 0 &&
-	    iter->pos_ftrace_mod_end < iter->pos)
-		return get_ksymbol_bpf(iter);
-
-	if (iter->pos_mod_end > 0 &&
-	    iter->pos_mod_end < iter->pos) {
-		if (!get_ksymbol_ftrace_mod(iter))
-			return get_ksymbol_bpf(iter);
+	if ((!iter->pos_mod_end || iter->pos_mod_end > pos) &&
+	    get_ksymbol_mod(iter))
 		return 1;
-	}
 
-	if (!get_ksymbol_mod(iter)) {
-		if (!get_ksymbol_ftrace_mod(iter))
-			return get_ksymbol_bpf(iter);
-	}
+	if ((!iter->pos_ftrace_mod_end || iter->pos_ftrace_mod_end > pos) &&
+	    get_ksymbol_ftrace_mod(iter))
+		return 1;
 
-	return 1;
+	return get_ksymbol_bpf(iter);
 }
 
 /* Returns false if pos at or past end of file. */