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

Mathieu Desnoyers
2007-12-05T05:01:29Z

* Andrew Morton (akpm@linux-foundation.org) wrote:
> On Tue, 04 Dec 2007 20:35:32 +0000 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.
>
> Incremental patch:
>
>
>
>
> From: Andrew Morton <akpm@linux-foundation.org>
>
> Fix checkpatch warnings:
>
> ERROR: do not use C99 // comments
> #72: FILE: scripts/kallsyms.c:516:
> + // sort by address first
>
> ERROR: do not use C99 // comments
> #78: FILE: scripts/kallsyms.c:522:
> + // sort by "weakness" type
>
> ERROR: do not use C99 // comments
> #84: FILE: scripts/kallsyms.c:528:
> + // sort by initial order, so that other symbols are left undisturbed
>
> total: 3 errors, 0 warnings, 61 lines checked
>
> Your patch has style problems, please review. If any of these errors
> are false positives report them to the maintainer, see
> CHECKPATCH in MAINTAINERS.
>
> Please run checkpatch prior to sending patches
>
> And a few coding-style things which checkpatch missed.
>
> And fix up constificiation to remove typecasting.
>
> Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
> Cc: Paulo Marques <pmarques@grupopie.com>
> Cc: Sam Ravnborg <sam@ravnborg.org>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

(if it's any useful at this point) The comments were the only problems I
found. I've tested it and it work fine for me in LTTng.

Acked-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>

> ---
>
> scripts/kallsyms.c | 19 +++++++++----------
> 1 file changed, 9 insertions(+), 10 deletions(-)
>
> diff -puN scripts/kallsyms.c~kallsyms-should-prefer-non-weak-symbols-checkpatch-fixes scripts/kallsyms.c
> --- a/scripts/kallsyms.c~kallsyms-should-prefer-non-weak-symbols-checkpatch-fixes
> +++ a/scripts/kallsyms.c
> @@ -31,14 +31,13 @@
>
> #define KSYM_NAME_LEN 128
>
> -
> struct sym_entry {
> unsigned long long addr;
> - unsigned int len, start_pos;
> + unsigned int len;
> + unsigned int start_pos;
> unsigned char *sym;
> };
>
> -
> static struct sym_entry *table;
> static unsigned int table_size, table_cnt;
> static unsigned long long _text, _stext, _etext, _sinittext, _einittext;
> @@ -504,28 +503,28 @@ static void optimize_token_table(void)
> optimize_result();
> }
>
> -
> static int compare_symbols(const void *a, const void *b)
> {
> - struct sym_entry *sa, *sb;
> + const struct sym_entry *sa;
> + const struct sym_entry *sb;
> int wa, wb;
>
> - sa = (struct sym_entry *) a;
> - sb = (struct sym_entry *) b;
> + sa = a;
> + sb = b;
>
> - // sort by address first
> + /* sort by address first */
> if (sa->addr > sb->addr)
> return 1;
> if (sa->addr < sb->addr)
> return -1;
>
> - // sort by "weakness" type
> + /* 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
> + /* sort by initial order, so that other symbols are left undisturbed */
> return sa->start_pos - sb->start_pos;
> }
>
> _
>

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