Re: [RFC] ARM binutils feature churn causing kernel problems

Richard Earnshaw
2004-10-05T12:57:55Z

On Tue, 2004-10-05 at 12:53, Russell King wrote:
> On Tue, Oct 05, 2004 at 11:10:46AM +0000, Richard Earnshaw wrote:
> > Rusty Russell <rusty <at> rustcorp.com.au> writes:
> > > Russell, I thought about not including any symbol which is not of form
> > > "[A-Za-z0-9_]+" in kallsyms, for all archs: you are not the only one
> > > with weird-ass symbols. Is it that you want these mapping symbols in
> > > /proc/kallsyms but ignored in backtraces, or you don't need them in
> > > kallsyms altogether?
> > >
> > > Thanks,
> > > Rusty.
> >
> >
> > Mapping symbols will always be encoded with STB_LOCAL and STT_NOTYPE.
> > I would have thought it unlikely that the kernel would ever want to
> > report against any symbol with those attributes and they could all
> > be dropped on that basis.
>
> (Richard - your mailer appears to have dropped people from the CC: list...)
>

Not by me, I don't subscribe to the list in question and was pointed to
gmane.linux.kernel newsgroup by Phillipe. I simply followed up to that
message.

> How about this patch? Is there a better way to parse the 'nm' output
> to achieve the same as your suggestion above?
>
> diff -up -x BitKeeper -x ChangeSet -x SCCS -x _xlk -x *.orig -x *.rej orig/kernel/module.c linux/kernel/module.c
> --- orig/kernel/module.c Wed Sep 22 16:07:38 2004
> +++ linux/kernel/module.c Tue Oct 5 12:46:01 2004
> @@ -1923,6 +1923,10 @@ static const char *get_ksymbol(struct mo
> if (mod->symtab[i].st_shndx == SHN_UNDEF)
> continue;
>
> + if (ELF_ST_BIND(mod->symtab[i].st_info) == STB_LOCAL
> + && ELF_ST_TYPE(mod->symtab[i].st_info) == STT_NOTYPE)
> + continue;
> +
> /* We ignore unnamed symbols: they're uninformative
> * and inserted at a whim. */
> if (mod->symtab[i].st_value <= addr
> diff -up -x BitKeeper -x ChangeSet -x SCCS -x _xlk -x *.orig -x *.rej orig/scripts/kallsyms.c linux/scripts/kallsyms.c
> --- orig/scripts/kallsyms.c Sun Jul 11 22:56:39 2004
> +++ linux/scripts/kallsyms.c Tue Oct 5 12:51:26 2004
> @@ -32,6 +32,17 @@ usage(void)
> exit(1);
> }
>
> +/*
> + * This ignores the intensely annoying "mapping symbols" found
> + * in ARM ELF files: $a, $t and $d.
> + */
> +static inline int
> +is_arm_mapping_symbol(const char *str)
> +{
> + return str[0] == '$' && strchr("atd", str[1]) &&
> + (str[2] == '\0' || str[2] == '.');
> +}
> +
> static int
> read_symbol(FILE *in, struct sym_entry *s)
> {
> @@ -56,7 +67,8 @@ read_symbol(FILE *in, struct sym_entry *
> _sinittext = s->addr;
> else if (strcmp(str, "_einittext") == 0)
> _einittext = s->addr;
> - else if (toupper(s->type) == 'A' || toupper(s->type) == 'U')
> + else if (toupper(s->type) == 'A' || toupper(s->type) == 'U' ||
> + is_arm_mapping_symbol(str))
> return -1;
>
> s->sym = strdup(str);

Why don't you pass s to is_arm_mapping_symbol and have it do the same
thing as you've done in get_ksymbol?

R.
--
Richard Earnshaw Email: Richard.Earnshaw@arm.com
ARM Ltd Phone: +44 1223 400569 (Direct + VoiceMail)
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