On Thu, Jun 1, 2023 at 4:01 PM HAGIO KAZUHITO(萩尾 一仁) <k-hagio-ab@xxxxxxx> wrote:
>> - if (CRASHDEBUG(1)) {
>> + if (CRASHDEBUG(1) && lm->mod_load_symtable) {
>> for (sp = lm->mod_load_symtable;
>> - sp < lm->mod_load_symend; sp++) {
>> + sp <= lm->mod_load_symend; sp++) {
>>
>
> The real problem might not be here? Some member variables are not properly
> initialized?
sorry, I don't understand this.
There is the read problem here. lm->mod_load_symend is the last
valid syment address.
Ok, Thank you for the explanation, Kazu. But I saw the following code in other patches(06/15,etc):
+ for (sp = lm->mod_load_symtable; sp < lm->mod_load_symend; sp++) {
Are there any differences?
>> +/* Only for 6.4 and later */
>> +struct syment *
>> +next_module_symbol(char *symbol, struct syment *sp_in, ulong val_in)
>> +{
>> + int i, j, k;
>> + struct load_module *lm;
>> + struct syment *sp, *sp_end;
>> +
>> + if (symbol)
>> + goto symbol_search;
>> + if (val_in)
>> + goto value_search;
>> +
>> + /* for sp_in */
>> + for (i = 0; i < st->mods_installed; i++) {
>> + lm = &st->load_modules[i];
>> +
>> + /* quick check: sp_in is not in the module range. */
>> + if (sp_in < lm->symtable[lm->address_order[0]] ||
>> + sp_in > lm->symend[lm->address_order[lm->nr_mems-1]])
>> + continue;
>> +
>> + for (j = 0; j < lm->nr_mems; j++) {
>> + k = lm->address_order[j];
>> + if (sp_in < lm->symtable[k] || sp_in >
>> lm->symend[k])
>> + continue;
>> +
>> + if (sp_in == lm->symend[k])
>> + return next_module_symbol(NULL, NULL,
>> sp_in->value);
>> +
>>
>
> This means it has to be invoked recursively.
It looks to be a recursive call, but actually it's just a composite
of three functions, i.e. symbol, syment and value search, and the
value search does not do a recursive call. So I think it's not a
real recursive call.
Ok, but it looks unusual and hard to understand.
>
> + sp = sp_in + 1;
>> + if (MODULE_PSEUDO_SYMBOL(sp))
>> + return next_module_symbol(NULL, NULL,
>> sp->value);
>> +
>> + return sp;
>> + }
>> + }
>> + return NULL;
>> +
>> +value_search:
>> + sp = sp_end = NULL;
>> + for (i = 0; i < st->mods_installed; i++) {
>> + lm = &st->load_modules[i];
>> +
>> + /* quick check: val_in is higher than the highest in the
>> module. */
>> + if (val_in >
>> lm->symend[lm->address_order[lm->nr_mems-1]]->value)
>> + continue;
>> +
>> + for (j = 0; j < lm->nr_mems; j++) {
>> + k = lm->address_order[j];
>> + if (val_in < lm->symtable[k]->value &&
>> + (sp == NULL || lm->symtable[k]->value <
>> sp->value)) {
>> + sp = lm->symtable[k];
>> + sp_end = lm->symend[k];
>> + break;
>> + }
>> + }
>> + }
>> + for ( ; sp < sp_end; sp++) {
>> + if (MODULE_PSEUDO_SYMBOL(sp))
>> + continue;
>> + if (sp->value > val_in)
>> + return sp;
>> + }
>> + return NULL;
>> +
>> +symbol_search:
>> + /*
>> + * Deal with a few special cases...
>> + *
>> + * hmm, looks like crash now does not use these special cases.
>> + *
>> + if (strstr(symbol, " module)")) {
>> + sprintf(buf, "_MODULE_START_");
>> + strcat(buf, &symbol[1]);
>> + p1 = strstr(buf, " module)");
>> + *p1 = NULLCHAR;
>> + symbol = buf;
>> + }
>> +
>> + if (STREQ(symbol, "_end")) {
>> + if (!st->mods_installed)
>> + return NULL;
>> +
>> + lm = &st->load_modules[0];
>> +
>> + return lm->mod_symtable;
>> + }
>> + */
>>
>
> The symbol_search code block can be moved to the beginning of this
> function, the current code has become very simple, that can avoid the goto
> statement.
Isn't it pointless?
If we do so, we will need something like "goto syment_search" instead.
It's true, I did not see that the next_module_symbol() is called again the label symbol_search.
Thanks
Lianbo
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