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kallsyms: Reduce the memory occupied by kallsyms_seqs_of_names[] 

[ Upstream commit 19bd8981dc ]

kallsyms_seqs_of_names[] records the symbol index sorted by address, the
maximum value in kallsyms_seqs_of_names[] is the number of symbols. And
2^24 = 16777216, which means that three bytes are enough to store the
index. This can help us save (1 * kallsyms_num_syms) bytes of memory.

Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Stable-dep-of: b022f0c7e4 ("tracing/kprobes: Return EADDRNOTAVAIL when func matches several symbols")
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Zhen Lei 2022-11-02 16:49:16 +08:00 committed by Greg Kroah-Hartman
parent 3918cada8f
commit da359f699f
3 changed files with 19 additions and 6 deletions
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18
kernel/kallsyms.c
View File

@ -197,6 +197,16 @@ static int compare_symbol_name(const char *name, char *namebuf)
return strcmp(name, namebuf);
}
static unsigned int get_symbol_seq(int index)
{
unsigned int i, seq = 0;
for (i = 0; i < 3; i++)
seq = (seq << 8) | kallsyms_seqs_of_names[3 * index + i];
return seq;
}
static int kallsyms_lookup_names(const char *name,
unsigned int *start,
unsigned int *end)
@ -211,7 +221,7 @@ static int kallsyms_lookup_names(const char *name,
while (low <= high) {
mid = low + (high - low) / 2;
seq = kallsyms_seqs_of_names[mid];
seq = get_symbol_seq(mid);
off = get_symbol_offset(seq);
kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
ret = compare_symbol_name(name, namebuf);
@ -228,7 +238,7 @@ static int kallsyms_lookup_names(const char *name,
low = mid;
while (low) {
seq = kallsyms_seqs_of_names[low - 1];
seq = get_symbol_seq(low - 1);
off = get_symbol_offset(seq);
kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
if (compare_symbol_name(name, namebuf))
@ -240,7 +250,7 @@ static int kallsyms_lookup_names(const char *name,
if (end) {
high = mid;
while (high < kallsyms_num_syms - 1) {
seq = kallsyms_seqs_of_names[high + 1];
seq = get_symbol_seq(high + 1);
off = get_symbol_offset(seq);
kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
if (compare_symbol_name(name, namebuf))
@ -265,7 +275,7 @@ unsigned long kallsyms_lookup_name(const char *name)
ret = kallsyms_lookup_names(name, &i, NULL);
if (!ret)
return kallsyms_sym_address(kallsyms_seqs_of_names[i]);
return kallsyms_sym_address(get_symbol_seq(i));
return module_kallsyms_lookup_name(name);
}

2
kernel/kallsyms_internal.h
View File

@ -26,6 +26,6 @@ extern const char kallsyms_token_table[] __weak;
extern const u16 kallsyms_token_index[] __weak;
extern const unsigned int kallsyms_markers[] __weak;
extern const unsigned int kallsyms_seqs_of_names[] __weak;
extern const u8 kallsyms_seqs_of_names[] __weak;
#endif // LINUX_KALLSYMS_INTERNAL_H_

5
scripts/kallsyms.c
View File

@ -602,7 +602,10 @@ static void write_src(void)
sort_symbols_by_name();
output_label("kallsyms_seqs_of_names");
for (i = 0; i < table_cnt; i++)
printf("\t.long\t%u\n", table[i]->seq);
printf("\t.byte 0x%02x, 0x%02x, 0x%02x\n",
(unsigned char)(table[i]->seq >> 16),
(unsigned char)(table[i]->seq >> 8),
(unsigned char)(table[i]->seq >> 0));
printf("\n");
output_label("kallsyms_token_table");