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Re: [PATCH 2/4] elf: Extract _dl_sym_post, _dl_sym_find_caller_map from elf/dl-sym.c
On 2/8/20 2:01 PM, Florian Weimer wrote:
> The definitions are moved into a new file, elf/dl-sym-post.h, so that
> this code can be used by the dynamic loader as well.
OK for master. I like the cleanup.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
> ---
> elf/dl-sym-post.h | 106 ++++++++++++++++++++++++++++++++++++++++++++++
> elf/dl-sym.c | 86 ++-----------------------------------
> 2 files changed, 110 insertions(+), 82 deletions(-)
> create mode 100644 elf/dl-sym-post.h
>
> diff --git a/elf/dl-sym-post.h b/elf/dl-sym-post.h
> new file mode 100644
> index 0000000000..4c4f574633
> --- /dev/null
> +++ b/elf/dl-sym-post.h
> @@ -0,0 +1,106 @@
> +/* Post-processing of a symbol produced by dlsym, dlvsym.
> + Copyright (C) 1999-2020 Free Software Foundation, Inc.
> + This file is part of the GNU C Library.
> +
> + The GNU C Library is free software; you can redistribute it and/or
> + modify it under the terms of the GNU Lesser General Public
> + License as published by the Free Software Foundation; either
> + version 2.1 of the License, or (at your option) any later version.
> +
> + The GNU C Library is distributed in the hope that it will be useful,
> + but WITHOUT ANY WARRANTY; without even the implied warranty of
> + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> + Lesser General Public License for more details.
> +
> + You should have received a copy of the GNU Lesser General Public
> + License along with the GNU C Library; if not, see
> + <https://www.gnu.org/licenses/>. */
> +
> +
> +/* Return the link map containing the caller address. */
> +static struct link_map *
> +_dl_sym_find_caller_link_map (ElfW(Addr) caller)
> +{
> + struct link_map *l = _dl_find_dso_for_object (caller);
> + if (l != NULL)
> + return l;
> + else
> + /* If the address is not recognized the call comes from the main
> + program (we hope). */
> + return GL(dl_ns)[LM_ID_BASE]._ns_loaded;
> +}
OK.
> +
> +/* Translates RESULT, *REF, VALUE into a symbol address from the point
> + of view of MATCH. Performs IFUNC resolution and auditing if
> + necessary. If MATCH is NULL, CALLER is used to determine it. */
> +static void *
> +_dl_sym_post (lookup_t result, const ElfW(Sym) *ref, void *value,
> + ElfW(Addr) caller, struct link_map *match)
> +{
> + /* Resolve indirect function address. */
> + if (__glibc_unlikely (ELFW(ST_TYPE) (ref->st_info) == STT_GNU_IFUNC))
> + {
> + DL_FIXUP_VALUE_TYPE fixup
> + = DL_FIXUP_MAKE_VALUE (result, (ElfW(Addr)) value);
> + fixup = elf_ifunc_invoke (DL_FIXUP_VALUE_ADDR (fixup));
> + value = (void *) DL_FIXUP_VALUE_CODE_ADDR (fixup);
> + }
> +
> +#ifdef SHARED
> + /* Auditing checkpoint: we have a new binding. Provide the
> + auditing libraries the possibility to change the value and
> + tell us whether further auditing is wanted. */
> + if (__glibc_unlikely (GLRO(dl_naudit) > 0))
> + {
> + const char *strtab = (const char *) D_PTR (result,
> + l_info[DT_STRTAB]);
> + /* Compute index of the symbol entry in the symbol table of
> + the DSO with the definition. */
> + unsigned int ndx = (ref - (ElfW(Sym) *) D_PTR (result,
> + l_info[DT_SYMTAB]));
> +
> + if (match == NULL)
> + match = _dl_sym_find_caller_link_map (caller);
> +
> + if ((match->l_audit_any_plt | result->l_audit_any_plt) != 0)
> + {
> + unsigned int altvalue = 0;
> + struct audit_ifaces *afct = GLRO(dl_audit);
> + /* Synthesize a symbol record where the st_value field is
> + the result. */
> + ElfW(Sym) sym = *ref;
> + sym.st_value = (ElfW(Addr)) value;
> +
> + for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
> + {
> + struct auditstate *match_audit
> + = link_map_audit_state (match, cnt);
> + struct auditstate *result_audit
> + = link_map_audit_state (result, cnt);
> + if (afct->symbind != NULL
> + && ((match_audit->bindflags & LA_FLG_BINDFROM) != 0
> + || ((result_audit->bindflags & LA_FLG_BINDTO)
> + != 0)))
> + {
> + unsigned int flags = altvalue | LA_SYMB_DLSYM;
> + uintptr_t new_value
> + = afct->symbind (&sym, ndx,
> + &match_audit->cookie,
> + &result_audit->cookie,
> + &flags, strtab + ref->st_name);
> + if (new_value != (uintptr_t) sym.st_value)
> + {
> + altvalue = LA_SYMB_ALTVALUE;
> + sym.st_value = new_value;
> + }
> + }
> +
> + afct = afct->next;
> + }
> +
> + value = (void *) sym.st_value;
> + }
> + }
> +#endif
> + return value;
> +}
OK.
> diff --git a/elf/dl-sym.c b/elf/dl-sym.c
> index b43a50e544..361b926ea9 100644
> --- a/elf/dl-sym.c
> +++ b/elf/dl-sym.c
> @@ -28,6 +28,7 @@
> #include <sysdep-cancel.h>
> #include <dl-tls.h>
> #include <dl-irel.h>
> +#include <dl-sym-post.h>
>
>
> #ifdef SHARED
> @@ -80,19 +81,6 @@ call_dl_lookup (void *ptr)
> args->flags, NULL);
> }
>
> -/* Return the link map containing the caller address. */
> -static inline struct link_map *
> -find_caller_link_map (ElfW(Addr) caller)
> -{
> - struct link_map *l = _dl_find_dso_for_object (caller);
> - if (l != NULL)
> - return l;
> - else
> - /* If the address is not recognized the call comes from the main
> - program (we hope). */
> - return GL(dl_ns)[LM_ID_BASE]._ns_loaded;
> -}
> -
> static void *
> do_sym (void *handle, const char *name, void *who,
> struct r_found_version *vers, int flags)
> @@ -106,7 +94,7 @@ do_sym (void *handle, const char *name, void *who,
>
> if (handle == RTLD_DEFAULT)
> {
> - match = find_caller_link_map (caller);
> + match = _dl_sym_find_caller_link_map (caller);
>
> /* Search the global scope. We have the simple case where
> we look up in the scope of an object which was part of
> @@ -140,7 +128,7 @@ do_sym (void *handle, const char *name, void *who,
> }
> else if (handle == RTLD_NEXT)
> {
> - match = find_caller_link_map (caller);
> + match = _dl_sym_find_caller_link_map (caller);
>
> if (__glibc_unlikely (match == GL(dl_ns)[LM_ID_BASE]._ns_loaded))
> {
> @@ -179,73 +167,7 @@ RTLD_NEXT used in code not dynamically loaded"));
> #endif
> value = DL_SYMBOL_ADDRESS (result, ref);
>
> - /* Resolve indirect function address. */
> - if (__glibc_unlikely (ELFW(ST_TYPE) (ref->st_info) == STT_GNU_IFUNC))
> - {
> - DL_FIXUP_VALUE_TYPE fixup
> - = DL_FIXUP_MAKE_VALUE (result, (ElfW(Addr)) value);
> - fixup = elf_ifunc_invoke (DL_FIXUP_VALUE_ADDR (fixup));
> - value = (void *) DL_FIXUP_VALUE_CODE_ADDR (fixup);
> - }
> -
> -#ifdef SHARED
> - /* Auditing checkpoint: we have a new binding. Provide the
> - auditing libraries the possibility to change the value and
> - tell us whether further auditing is wanted. */
> - if (__glibc_unlikely (GLRO(dl_naudit) > 0))
> - {
> - const char *strtab = (const char *) D_PTR (result,
> - l_info[DT_STRTAB]);
> - /* Compute index of the symbol entry in the symbol table of
> - the DSO with the definition. */
> - unsigned int ndx = (ref - (ElfW(Sym) *) D_PTR (result,
> - l_info[DT_SYMTAB]));
> -
> - if (match == NULL)
> - match = find_caller_link_map (caller);
> -
> - if ((match->l_audit_any_plt | result->l_audit_any_plt) != 0)
> - {
> - unsigned int altvalue = 0;
> - struct audit_ifaces *afct = GLRO(dl_audit);
> - /* Synthesize a symbol record where the st_value field is
> - the result. */
> - ElfW(Sym) sym = *ref;
> - sym.st_value = (ElfW(Addr)) value;
> -
> - for (unsigned int cnt = 0; cnt < GLRO(dl_naudit); ++cnt)
> - {
> - struct auditstate *match_audit
> - = link_map_audit_state (match, cnt);
> - struct auditstate *result_audit
> - = link_map_audit_state (result, cnt);
> - if (afct->symbind != NULL
> - && ((match_audit->bindflags & LA_FLG_BINDFROM) != 0
> - || ((result_audit->bindflags & LA_FLG_BINDTO)
> - != 0)))
> - {
> - unsigned int flags = altvalue | LA_SYMB_DLSYM;
> - uintptr_t new_value
> - = afct->symbind (&sym, ndx,
> - &match_audit->cookie,
> - &result_audit->cookie,
> - &flags, strtab + ref->st_name);
> - if (new_value != (uintptr_t) sym.st_value)
> - {
> - altvalue = LA_SYMB_ALTVALUE;
> - sym.st_value = new_value;
> - }
> - }
> -
> - afct = afct->next;
> - }
> -
> - value = (void *) sym.st_value;
> - }
> - }
> -#endif
> -
> - return value;
> + return _dl_sym_post (result, ref, value, caller, match);
> }
>
> return NULL;
>
--
Cheers,
Carlos.