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Date: Tue, 13 Aug 2019 10:24:24 -0400
From: Rich Felker <dalias@...c.org>
To: musl@...ts.openwall.com
Subject: Re: [PATCH] make relocation time symbol lookup and dlsym
consistent
On Tue, Aug 13, 2019 at 10:38:44AM +0200, Szabolcs Nagy wrote:
> * Szabolcs Nagy <nsz@...t70.net> [2019-08-11 01:18:11 +0200]:
> > static void *do_dlsym(struct dso *p, const char *s, void *ra)
> > {
> > - size_t i;
> > - uint32_t h = 0, gh = 0, *ght;
> > - Sym *sym;
> > - if (p == head || p == RTLD_DEFAULT || p == RTLD_NEXT) {
> > - if (p == RTLD_DEFAULT) {
> > - p = head;
> > - } else if (p == RTLD_NEXT) {
> > - p = addr2dso((size_t)ra);
> > - if (!p) p=head;
> > - p = p->next;
> > - }
> > - struct symdef def = find_sym(p, s, 0);
> > - if (!def.sym) goto failed;
> > - if ((def.sym->st_info&0xf) == STT_TLS)
> > - return __tls_get_addr((tls_mod_off_t []){def.dso->tls_id, def.sym->st_value-DTP_OFFSET});
> > - if (DL_FDPIC && (def.sym->st_info&0xf) == STT_FUNC)
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > - return def.dso->funcdescs + (def.sym - def.dso->syms);
> > - return laddr(def.dso, def.sym->st_value);
> > - }
> > - if (__dl_invalid_handle(p))
> > + int use_deps = 0;
> > + if (p == head || p == RTLD_DEFAULT) {
> > + p = head;
> > + } else if (p == RTLD_NEXT) {
> > + p = addr2dso((size_t)ra);
> > + if (!p) p=head;
> > + p = p->next;
> > + } else if (__dl_invalid_handle(p)) {
> > return 0;
> > - if ((ght = p->ghashtab)) {
> > - gh = gnu_hash(s);
> > - sym = gnu_lookup(gh, ght, p, s);
> > - } else {
> > - h = sysv_hash(s);
> > - sym = sysv_lookup(s, h, p);
> > - }
> > - if (sym && (sym->st_info&0xf) == STT_TLS)
> > - return __tls_get_addr((tls_mod_off_t []){p->tls_id, sym->st_value-DTP_OFFSET});
> > - if (DL_FDPIC && sym && sym->st_shndx && (sym->st_info&0xf) == STT_FUNC)
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > - return p->funcdescs + (sym - p->syms);
> > - if (sym && sym->st_value && (1<<(sym->st_info&0xf) & OK_TYPES))
> > - return laddr(p, sym->st_value);
> > - for (i=0; p->deps[i]; i++) {
> > - if ((ght = p->deps[i]->ghashtab)) {
> > - if (!gh) gh = gnu_hash(s);
> > - sym = gnu_lookup(gh, ght, p->deps[i], s);
> > - } else {
> > - if (!h) h = sysv_hash(s);
> > - sym = sysv_lookup(s, h, p->deps[i]);
> > - }
> > - if (sym && (sym->st_info&0xf) == STT_TLS)
> > - return __tls_get_addr((tls_mod_off_t []){p->deps[i]->tls_id, sym->st_value-DTP_OFFSET});
> > - if (DL_FDPIC && sym && sym->st_shndx && (sym->st_info&0xf) == STT_FUNC)
> > - return p->deps[i]->funcdescs + (sym - p->deps[i]->syms);
> > - if (sym && sym->st_value && (1<<(sym->st_info&0xf) & OK_TYPES))
> > - return laddr(p->deps[i], sym->st_value);
> > - }
> > -failed:
> > - error("Symbol not found: %s", s);
> > - return 0;
> > + } else
> > + use_deps = 1;
> > + struct symdef def = find_sym2(p, s, 0, use_deps);
> > + if (!def.sym) {
> > + error("Symbol not found: %s", s);
> > + return 0;
> > + }
> > + if ((def.sym->st_info&0xf) == STT_TLS)
> > + return __tls_get_addr((tls_mod_off_t []){def.dso->tls_id, def.sym->st_value-DTP_OFFSET});
> > + if (DL_FDPIC && (def.sym->st_info&0xf) == STT_FUNC)
> > + return def.dso->funcdescs + (def.sym - def.dso->syms);
>
> there is another behaviour change i did not notice before:
>
> st_shndx is no longer checked in DL_FDPIC case here, i assumed
> find_sym did that, but there is no fdpic specific logic there.
>
> the old code was inconsistent in the RTLD_DEFAULT vs shared lib
> dlsym case.
>
> i dont know if this is relevant for fdpic, i didnt test that case.
Thanks for catching. I'll take a look at this.
Rich
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