From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
To: "H.J. Lu" <hjl.tools@gmail.com>, libc-alpha@sourceware.org
Subject: Re: [PATCH v10 2/7] Add GLIBC_ABI_DT_RELR for DT_RELR support
Date: Wed, 20 Apr 2022 10:32:45 -0300 [thread overview]
Message-ID: <434a85d7-0842-4387-4773-1bb3a9fb86d4@linaro.org> (raw)
In-Reply-To: <20220414232129.1886210-3-hjl.tools@gmail.com>
On 14/04/2022 20:21, H.J. Lu wrote:
> The EI_ABIVERSION field of the ELF header in executables and shared
> libraries can be bumped to indicate the minimum ABI requirement on the
> dynamic linker. However, EI_ABIVERSION in executables isn't checked by
> the Linux kernel ELF loader nor the existing dynamic linker. Executables
> will crash mysteriously if the dynamic linker doesn't support the ABI
> features required by the EI_ABIVERSION field. The dynamic linker should
> be changed to check EI_ABIVERSION in executables.
>
> Add a glibc version, GLIBC_ABI_DT_RELR, to indicate DT_RELR support so
> that the existing dynamic linkers will issue an error on executables with
> GLIBC_ABI_DT_RELR dependency. When there is a DT_VERNEED entry with
> libc.so on DT_NEEDED, issue an error if there is a DT_RELR entry without
> GLIBC_ABI_DT_RELR dependency.
>
> Support __placeholder_only_for_empty_version_map as the placeholder symbol
> used only for empty version map to generate GLIBC_ABI_DT_RELR without any
> symbols.
LGTM, thanks.
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
> ---
> elf/Makefile | 14 ++++++++++++--
> elf/Versions | 5 +++++
> elf/dl-version.c | 35 +++++++++++++++++++++++++++++++++--
> include/link.h | 2 ++
> scripts/abilist.awk | 2 ++
> scripts/versions.awk | 7 ++++++-
> 6 files changed, 60 insertions(+), 5 deletions(-)
>
> diff --git a/elf/Makefile b/elf/Makefile
> index d30d0ee917..ee8778c3a2 100644
> --- a/elf/Makefile
> +++ b/elf/Makefile
> @@ -1110,8 +1110,12 @@ $(eval $(call include_dsosort_tests,dso-sort-tests-1.def))
> $(eval $(call include_dsosort_tests,dso-sort-tests-2.def))
> endif
>
> -check-abi: $(objpfx)check-abi-ld.out
> -tests-special += $(objpfx)check-abi-ld.out
> +check-abi: $(objpfx)check-abi-ld.out \
> + $(objpfx)check-abi-version-libc.out
> +tests-special += \
> + $(objpfx)check-abi-ld.out \
> + $(objpfx)check-abi-version-libc.out \
> +# tests-special
> update-abi: update-abi-ld
> update-all-abi: update-all-abi-ld
>
> @@ -2733,3 +2737,9 @@ $(objpfx)tst-p_align3: $(objpfx)tst-p_alignmod3.so
> $(objpfx)tst-p_align3.out: tst-p_align3.sh $(objpfx)tst-p_align3
> $(SHELL) $< $(common-objpfx) '$(test-program-prefix)'; \
> $(evaluate-test)
> +
> +$(objpfx)check-abi-version-libc.out: $(common-objpfx)libc.so
> + LC_ALL=C $(READELF) -V -W $< \
> + | sed -ne '/.gnu.version_d/, /.gnu.version_r/ p' \
> + | grep GLIBC_ABI_DT_RELR > $@; \
> + $(evaluate-test)
Ok.
> diff --git a/elf/Versions b/elf/Versions
> index 8bed855d8c..a9ff278de7 100644
> --- a/elf/Versions
> +++ b/elf/Versions
> @@ -23,6 +23,11 @@ libc {
> GLIBC_2.35 {
> _dl_find_object;
> }
> + GLIBC_ABI_DT_RELR {
> + # This symbol is used only for empty version map and will be removed
> + # by scripts/versions.awk.
> + __placeholder_only_for_empty_version_map;
> + }
> GLIBC_PRIVATE {
> # functions used in other libraries
> __libc_early_init;
Ok.
> diff --git a/elf/dl-version.c b/elf/dl-version.c
> index b47bd91727..cda0889209 100644
> --- a/elf/dl-version.c
> +++ b/elf/dl-version.c
> @@ -214,12 +214,19 @@ _dl_check_map_versions (struct link_map *map, int verbose, int trace_mode)
> while (1)
> {
> /* Match the symbol. */
> + const char *string = strtab + aux->vna_name;
> result |= match_symbol (DSO_FILENAME (map->l_name),
> map->l_ns, aux->vna_hash,
> - strtab + aux->vna_name,
> - needed->l_real, verbose,
> + string, needed->l_real, verbose,
> aux->vna_flags & VER_FLG_WEAK);
>
> + /* 0xfd0e42: _dl_elf_hash ("GLIBC_ABI_DT_RELR"). */
> + if (aux->vna_hash == 0xfd0e42
> + && __glibc_likely (strcmp (string,
> + "GLIBC_ABI_DT_RELR")
> + == 0))
> + map->l_dt_relr_ref = 1;
> +
> /* Compare the version index. */
> if ((unsigned int) (aux->vna_other & 0x7fff) > ndx_high)
> ndx_high = aux->vna_other & 0x7fff;
Ok.
> @@ -352,6 +359,30 @@ _dl_check_map_versions (struct link_map *map, int verbose, int trace_mode)
> }
> }
>
> + /* When there is a DT_VERNEED entry with libc.so on DT_NEEDED, issue
> + an error if there is a DT_RELR entry without GLIBC_ABI_DT_RELR
> + dependency. */
> + if (dyn != NULL
> + && map->l_info[DT_NEEDED] != NULL
> + && map->l_info[DT_RELR] != NULL
> + && __glibc_unlikely (!map->l_dt_relr_ref))
> + {
> + const char *strtab = (const void *) D_PTR (map, l_info[DT_STRTAB]);
> + const ElfW(Dyn) *d;
> + for (d = map->l_ld; d->d_tag != DT_NULL; ++d)
> + if (d->d_tag == DT_NEEDED)
> + {
> + const char *name = strtab + d->d_un.d_val;
> + if (strncmp (name, "libc.so.", 8) == 0)
> + {
> + _dl_exception_create
> + (&exception, DSO_FILENAME (map->l_name),
> + N_("DT_RELR without GLIBC_ABI_DT_RELR dependency"));
> + goto call_error;
> + }
> + }
> + }
> +
> return result;
> }
>
Ok.
> diff --git a/include/link.h b/include/link.h
> index 03db14c7b0..0ac82d7c77 100644
> --- a/include/link.h
> +++ b/include/link.h
> @@ -177,6 +177,8 @@ struct link_map
> lt_library, /* Library needed by main executable. */
> lt_loaded /* Extra run-time loaded shared object. */
> } l_type:2;
> + unsigned int l_dt_relr_ref:1; /* Nonzero if GLIBC_ABI_DT_RELR is
> + referenced. */
> unsigned int l_relocated:1; /* Nonzero if object's relocations done. */
> unsigned int l_init_called:1; /* Nonzero if DT_INIT function called. */
> unsigned int l_global:1; /* Nonzero if object in _dl_global_scope. */
Ok.
> diff --git a/scripts/abilist.awk b/scripts/abilist.awk
> index 24a34ccbed..6cc7af6ac8 100644
> --- a/scripts/abilist.awk
> +++ b/scripts/abilist.awk
> @@ -55,6 +55,8 @@ $2 == "g" || $2 == "w" && (NF == 7 || NF == 8) {
> # caused STV_HIDDEN symbols to appear in .dynsym, though that is useless.
> if (NF > 7 && $7 == ".hidden") next;
>
> + if (version ~ /^GLIBC_ABI_/ && !include_abi_version) next;
> +
> if (version == "GLIBC_PRIVATE" && !include_private) next;
>
> desc = "";
> diff --git a/scripts/versions.awk b/scripts/versions.awk
> index 357ad1355e..d70b07bd1a 100644
> --- a/scripts/versions.awk
> +++ b/scripts/versions.awk
> @@ -185,8 +185,13 @@ END {
> closeversion(oldver, veryoldver);
> veryoldver = oldver;
> }
> - printf("%s {\n global:\n", $2) > outfile;
> oldver = $2;
> + # Skip the placeholder symbol used only for empty version map.
> + if ($3 == "__placeholder_only_for_empty_version_map;") {
> + printf("%s {\n", $2) > outfile;
> + continue;
> + }
> + printf("%s {\n global:\n", $2) > outfile;
> }
> printf(" ") > outfile;
> for (n = 3; n <= NF; ++n) {
Ok.
next prev parent reply other threads:[~2022-04-20 13:32 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-14 23:21 [PATCH v10 0/7] Support DT_RELR relative relocation format H.J. Lu
2022-04-14 23:21 ` [PATCH v10 1/7] elf: Define DT_RELR related macros and types H.J. Lu
2022-04-20 12:45 ` Adhemerval Zanella
2022-04-14 23:21 ` [PATCH v10 2/7] Add GLIBC_ABI_DT_RELR for DT_RELR support H.J. Lu
2022-04-20 13:32 ` Adhemerval Zanella [this message]
2022-04-14 23:21 ` [PATCH v10 3/7] elf: Support DT_RELR relative relocation format [BZ #27924] H.J. Lu
2022-04-20 13:44 ` Adhemerval Zanella
2022-04-22 18:47 ` H.J. Lu
2022-04-14 23:21 ` [PATCH v10 4/7] elf: Properly handle zero DT_RELA/DT_REL values H.J. Lu
2022-04-20 17:10 ` Adhemerval Zanella
2022-04-14 23:21 ` [PATCH v10 5/7] elf: Add more DT_RELR tests H.J. Lu
2022-04-20 17:24 ` Adhemerval Zanella
2022-04-20 17:41 ` Adhemerval Zanella
2022-04-22 18:44 ` H.J. Lu
2022-04-14 23:21 ` [PATCH v10 6/7] Add --disable-default-dt-relr H.J. Lu
2022-04-20 17:49 ` Adhemerval Zanella
2022-04-22 18:41 ` H.J. Lu
2022-04-14 23:21 ` [PATCH v10 7/7] NEWS: Mention DT_RELR support H.J. Lu
2022-04-20 17:49 ` Adhemerval Zanella
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