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Message-ID: <20190813083844.GL22009@port70.net>
Date: Tue, 13 Aug 2019 10:38:44 +0200
From: Szabolcs Nagy <nsz@...t70.net>
To: musl@...ts.openwall.com
Subject: Re: [PATCH] make relocation time symbol lookup and dlsym
consistent
* 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.
> + return laddr(def.dso, def.sym->st_value);
> }
>
> int dladdr(const void *addr_arg, Dl_info *info)
> --
> 2.21.0
>
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