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Message-ID: <20071030234550.GA27171@Krystal>
Date: Tue, 30 Oct 2007 19:45:50 -0400
From: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To: Paulo Marques <pmarques@...popie.com>
Cc: Rusty Russell <rusty@...tcorp.com.au>,
linux-kernel@...r.kernel.org,
"systemtap@...rceware.org" <systemtap@...rceware.org>
Subject: Re: kallsyms __print_symbol prints first weak symbol encountered
* Paulo Marques (pmarques@...popie.com) wrote:
> Mathieu Desnoyers wrote:
> >Hi,
>
> Hi,
>
> >[...]
> >kallsyms returns the first symbol encountered, even though it is weak,
> >when it should in fact return sys_ni_syscall.
> >
> >Is it a concern for anyone else out there ? Would it make sense to fix
> >it ?
>
> I don't know if it is a concern, but if we're going to fix it, we should
> probably do it in "scripts/kallsyms" by providing a list that is already
> sorted according to "address, weakness".
>
> This way the run-time kernel keeps the current behavior, without any
> overhead. Something along the lines of the attached patch (just compile
> tested).
>
> However, this is an area where we've had problems in the past with some
> architectures giving different results between passes, and then any
> change to the symbol order might make the problem worse and make the
> build process fail with a "Inconsistent kallsyms data" error message.
>
> So, if someone wants to use this, it should go through -mm for a while,
> first.
>
Runtime test is ok. It fixes the problem. Thanks!
Mathieu
> --
> Paulo Marques - www.grupopie.com
>
> "All I ask is a chance to prove that money can't make me happy."
> --- ./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
> + 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
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