Re: [-mm PATCH] kallsyms should prefer non weak symbols

Mathieu Desnoyers
2007-12-04T21:19:27Z

* Paulo Marques (pmarques@grupopie.com) wrote:
>
> When resolving symbol names from addresses with aliased symbol names,
> kallsyms_lookup always returns the first symbol, even if it is a weak
> symbol.
>
> This patch changes this by sorting the symbols with the weak symbols last
> before feeding them to the kernel. This way the kernel runtime isn't
> changed at all, only the kallsyms build system is changed.
>
> Another side effect is that the symbols get sorted by address, too. So,
> even if future binutils version have some bug in "nm" that makes it fail to
> correctly sort symbols by address, the kernel won't be affected by this.
>
>
> From: Paulo Marques <pmarques@grupopie.com>
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
>

Please wait for me to accept the changes before adding signed-off-by.

See comment below,

> --
> Paulo Marques - www.grupopie.com
>
> "There cannot be a crisis today; my schedule is already full."

> --- ./scripts/kallsyms.c.orig 2007-10-30 18:51:28.000000000 +0000
> +++ ./scripts/kallsyms.c 2007-10-30 19:07:58.000000000 +0000
> @@ -34,7 +34,7 @@
>
> struct sym_entry {
> unsigned long long addr;
> - unsigned int len;
> + unsigned int len, start_pos;
> unsigned char *sym;
> };
>
> @@ -202,8 +202,10 @@ static void read_map(FILE *in)
> exit (1);
> }
> }
> - if (read_symbol(in, &table[table_cnt]) == 0)
> + if (read_symbol(in, &table[table_cnt]) == 0) {
> + table[table_cnt].start_pos = table_cnt;
> table_cnt++;
> + }
> }
> }
>
> @@ -507,6 +509,35 @@ static void optimize_token_table(void)
> }
>
>
> +static int compare_symbols(const void *a, const void *b)
> +{
> + struct sym_entry *sa, *sb;
> + int wa, wb;
> +
> + sa = (struct sym_entry *) a;
> + sb = (struct sym_entry *) b;
> +
> + // sort by address first

Comments should be /* */ , not //.

Please run through scripts/checkpatch.pl before submitting.

> + if (sa->addr > sb->addr)
> + return 1;
> + if (sa->addr < sb->addr)
> + return -1;
> +
> + // sort by "weakness" type
> + wa = (sa->sym[0] == 'w') || (sa->sym[0] == 'W');
> + wb = (sb->sym[0] == 'w') || (sb->sym[0] == 'W');
> + if (wa != wb)
> + return wa - wb;
> +
> + // sort by initial order, so that other symbols are left undisturbed
> + return sa->start_pos - sb->start_pos;
> +}
> +
> +static void sort_symbols(void)
> +{
> + qsort(table, table_cnt, sizeof(struct sym_entry), compare_symbols);
> +}
> +
> int main(int argc, char **argv)
> {
> if (argc >= 2) {
> @@ -527,6 +558,7 @@ int main(int argc, char **argv)
> usage();
>
> read_map(stdin);
> + sort_symbols();
> optimize_token_table();
> write_src();
>
>

--
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68