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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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