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Subject[tip:perf/urgent] kallsyms: Simplify update_iter_mod()
Commit-ID:  b96679422007c3fa04625be14977904c27c722eb
Gitweb: https://git.kernel.org/tip/b96679422007c3fa04625be14977904c27c722eb
Author: Adrian Hunter <adrian.hunter@intel.com>
AuthorDate: Wed, 6 Jun 2018 15:54:09 +0300
Committer: Arnaldo Carvalho de Melo <acme@redhat.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@intel.com>
Tested-by: (ftrace changes only) Steven Rostedt (VMware) <rostedt@goodmis.org>
Acked-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: x86@kernel.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@redhat.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. */
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