152 lines
4.1 KiB
Diff
152 lines
4.1 KiB
Diff
From 2fab8fbc0c4f1c4cbe889de4cead5f7457a19f77 Mon Sep 17 00:00:00 2001
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From: Tao Liu <ltao@redhat.com>
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Date: Sat, 16 Oct 2021 13:21:11 +0800
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Subject: [PATCH 1/9] symbols: Implement install and remove operations for
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mod_symname_hash
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Currently the sequence for symbol_search to search a symbol is: 1) kernel
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symname hash table, 2) iterate all kernel symbols, 3) iterate all kernel
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modules and their symbols. In the worst case, if a non-exist symbol been
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searched, all 3 stages will be went through. The time consuming status for
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each stage is like:
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stage 1 stage 2 stage 3
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0.007000(ms) 0.593000(ms) 2.421000(ms)
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stage 3 takes too much time when comparing to stage 1. This patch series
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introduces a symname hash table for kernel modules, to improve the
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performance of symbol searching.
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Functions symbol_search() and symbol_exists() are fundamental and widely
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used by other crash functions, thus the benefit of performance improvement
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can get accumulated. For example, "ps -m" and "irq" commands, which call
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the functions many times, will become faster with the patch series.
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This patch indroduces mod_symname_hash, and its install/remove operations.
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Since symbol_search() has to return the lowest address symbol and
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symbol_search_next() returns the next lowest symbol, thus the installation
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should be sorted ascendingly.
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In mod_symname_hash_install_range() scenario, spn are already arranged
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ascendingly, so for mod_symname_hash_install():
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Install spn previous to sp:
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If sp is the start of bucket, or
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1) spn->value is smaller than sp->value.
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Install spn next to sp:
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1) sp->name_hash_next is NULL, or
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2) sp->name_hash_next->value is larger than spn->value
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spn->value is the kernel address of the symbol and will not change.
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So we use it mainly to determine the sequence. When spn->value equals
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sp->value, they must be symbols within a kernel module.
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Signed-off-by: Tao Liu <ltao@redhat.com>
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---
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defs.h | 1 +
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symbols.c | 73 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
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2 files changed, 74 insertions(+)
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diff --git a/defs.h b/defs.h
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index cbd45e52f9da..bbdca799f72d 100644
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--- a/defs.h
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+++ b/defs.h
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@@ -2755,6 +2755,7 @@ struct symbol_table_data {
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double val_hash_searches;
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double val_hash_iterations;
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struct syment *symname_hash[SYMNAME_HASH];
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+ struct syment *mod_symname_hash[SYMNAME_HASH];
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struct symbol_namespace kernel_namespace;
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struct syment *ext_module_symtable;
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struct syment *ext_module_symend;
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diff --git a/symbols.c b/symbols.c
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index 69dccdb09d5f..ad12d1c22225 100644
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--- a/symbols.c
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+++ b/symbols.c
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@@ -1157,6 +1157,79 @@ symname_hash_install(struct syment *spn)
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}
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}
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+/*
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+ * Install a single kernel module symbol into the mod_symname_hash.
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+ */
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+static void
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+mod_symname_hash_install(struct syment *spn)
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+{
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+ struct syment *sp;
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+ int index;
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+
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+ if (!spn)
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+ return;
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+
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+ index = SYMNAME_HASH_INDEX(spn->name);
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+
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+ sp = st->mod_symname_hash[index];
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+
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+ if (!sp || (spn->value < sp->value)) {
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+ st->mod_symname_hash[index] = spn;
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+ spn->name_hash_next = sp;
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+ return;
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+ }
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+ for (; sp; sp = sp->name_hash_next) {
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+ if (!sp->name_hash_next ||
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+ spn->value < sp->name_hash_next->value) {
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+ spn->name_hash_next = sp->name_hash_next;
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+ sp->name_hash_next = spn;
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+ return;
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+ }
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+ }
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+}
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+
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+static void
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+mod_symname_hash_remove(struct syment *spn)
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+{
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+ struct syment *sp;
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+ int index;
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+
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+ if (!spn)
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+ return;
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+
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+ index = SYMNAME_HASH_INDEX(spn->name);
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+
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+ if (st->mod_symname_hash[index] == spn) {
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+ st->mod_symname_hash[index] = spn->name_hash_next;
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+ return;
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+ }
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+
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+ for (sp = st->mod_symname_hash[index]; sp; sp = sp->name_hash_next) {
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+ if (sp->name_hash_next == spn) {
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+ sp->name_hash_next = spn->name_hash_next;
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+ return;
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+ }
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+ }
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+}
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+
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+static void
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+mod_symtable_hash_install_range(struct syment *from, struct syment *to)
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+{
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+ struct syment *sp;
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+
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+ for (sp = from; sp <= to; sp++)
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+ mod_symname_hash_install(sp);
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+}
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+
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+static void
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+mod_symtable_hash_remove_range(struct syment *from, struct syment *to)
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+{
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+ struct syment *sp;
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+
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+ for (sp = from; sp <= to; sp++)
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+ mod_symname_hash_remove(sp);
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+}
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+
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/*
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* Static kernel symbol value search
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*/
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--
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2.30.2
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