| Message ID | 20220413182507.896862-3-hjl.tools@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | Support DT_RELR relative relocation format | expand |
On 2022-04-13, 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. Issue an error if there is a DT_RELR entry >without GLIBC_ABI_DT_RELR dependency nor GLIBC_PRIVATE definition. > >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. >--- > elf/Makefile | 14 ++++++++++++-- > elf/Versions | 5 +++++ > elf/dl-version.c | 38 ++++++++++++++++++++++++++++++++------ > include/link.h | 6 ++++++ > scripts/abilist.awk | 2 ++ > scripts/versions.awk | 7 ++++++- > 6 files changed, 63 insertions(+), 9 deletions(-) > >diff --git a/elf/Makefile b/elf/Makefile >index c96924e9c2..09d3d88336 100644 >--- a/elf/Makefile >+++ b/elf/Makefile >@@ -1105,8 +1105,12 @@ $(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 > >@@ -2725,3 +2729,9 @@ $(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) >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; >diff --git a/elf/dl-version.c b/elf/dl-version.c >index b47bd91727..0537b1c7de 100644 >--- a/elf/dl-version.c >+++ b/elf/dl-version.c >@@ -214,12 +214,20 @@ _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); > >+ if (map->l_abi_version == lav_none >+ /* 0xfd0e42: _dl_elf_hash ("GLIBC_ABI_DT_RELR"). */ >+ && aux->vna_hash == 0xfd0e42 >+ && __glibc_likely (strcmp (string, >+ "GLIBC_ABI_DT_RELR") >+ == 0)) >+ map->l_abi_version = lav_dt_relr_ref; >+ > /* Compare the version index. */ > if ((unsigned int) (aux->vna_other & 0x7fff) > ndx_high) > ndx_high = aux->vna_other & 0x7fff; >@@ -243,16 +251,23 @@ _dl_check_map_versions (struct link_map *map, int verbose, int trace_mode) > } > > /* We also must store the names of the defined versions. Determine >- the maximum index here as well. >- >- XXX We could avoid the loop by just taking the number of definitions >- as an upper bound of new indices. */ >+ the maximum index here as well. */ > if (def != NULL) > { > ElfW(Verdef) *ent; > ent = (ElfW(Verdef) *) (map->l_addr + def->d_un.d_ptr); > while (1) > { >+ /* 0x0963cf85: _dl_elf_hash ("GLIBC_PRIVATE"). */ >+ if (ent->vd_hash == 0x0963cf85) >+ { >+ ElfW(Verdaux) *aux = (ElfW(Verdaux) *) ((char *) ent >+ + ent->vd_aux); >+ if (__glibc_likely (strcmp ("GLIBC_PRIVATE", >+ strtab + aux->vda_name) == 0)) >+ map->l_abi_version = lav_private_def; >+ } >+ > if ((unsigned int) (ent->vd_ndx & 0x7fff) > ndx_high) > ndx_high = ent->vd_ndx & 0x7fff; > >@@ -352,6 +367,17 @@ _dl_check_map_versions (struct link_map *map, int verbose, int trace_mode) > } > } > >+ /* Issue an error if there is a DT_RELR entry without GLIBC_ABI_DT_RELR >+ dependency nor GLIBC_PRIVATE definition. */ >+ if (map->l_info[DT_RELR] != NULL >+ && __glibc_unlikely (map->l_abi_version == lav_none)) >+ { >+ _dl_exception_create >+ (&exception, DSO_FILENAME (map->l_name), >+ N_("DT_RELR without GLIBC_ABI_DT_RELR dependency")); >+ goto call_error; >+ } >+ > return result; > } > >diff --git a/include/link.h b/include/link.h >index 03db14c7b0..8ec5e35cf2 100644 >--- a/include/link.h >+++ b/include/link.h >@@ -177,6 +177,12 @@ struct link_map > lt_library, /* Library needed by main executable. */ > lt_loaded /* Extra run-time loaded shared object. */ > } l_type:2; >+ enum /* ABI dependency of this object. */ >+ { >+ lav_none, /* No ABI dependency. */ >+ lav_dt_relr_ref, /* Need GLIBC_ABI_DT_RELR. */ >+ lav_private_def /* Define GLIBC_PRIVATE. */ >+ } l_abi_version:2; > 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. */ >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) { >-- >2.35.1 I have checked that this (git-pw series apply 8575) works with ld.lld's recent -z pack-relative-relocs: ld.lld 15.0.0 built glibc will run the tests with DT_RELR <3. Reviewed-by: Fangrui Song <maskray@google.com>
diff --git a/elf/Makefile b/elf/Makefile index c96924e9c2..09d3d88336 100644 --- a/elf/Makefile +++ b/elf/Makefile @@ -1105,8 +1105,12 @@ $(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 @@ -2725,3 +2729,9 @@ $(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) 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; diff --git a/elf/dl-version.c b/elf/dl-version.c index b47bd91727..0537b1c7de 100644 --- a/elf/dl-version.c +++ b/elf/dl-version.c @@ -214,12 +214,20 @@ _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); + if (map->l_abi_version == lav_none + /* 0xfd0e42: _dl_elf_hash ("GLIBC_ABI_DT_RELR"). */ + && aux->vna_hash == 0xfd0e42 + && __glibc_likely (strcmp (string, + "GLIBC_ABI_DT_RELR") + == 0)) + map->l_abi_version = lav_dt_relr_ref; + /* Compare the version index. */ if ((unsigned int) (aux->vna_other & 0x7fff) > ndx_high) ndx_high = aux->vna_other & 0x7fff; @@ -243,16 +251,23 @@ _dl_check_map_versions (struct link_map *map, int verbose, int trace_mode) } /* We also must store the names of the defined versions. Determine - the maximum index here as well. - - XXX We could avoid the loop by just taking the number of definitions - as an upper bound of new indices. */ + the maximum index here as well. */ if (def != NULL) { ElfW(Verdef) *ent; ent = (ElfW(Verdef) *) (map->l_addr + def->d_un.d_ptr); while (1) { + /* 0x0963cf85: _dl_elf_hash ("GLIBC_PRIVATE"). */ + if (ent->vd_hash == 0x0963cf85) + { + ElfW(Verdaux) *aux = (ElfW(Verdaux) *) ((char *) ent + + ent->vd_aux); + if (__glibc_likely (strcmp ("GLIBC_PRIVATE", + strtab + aux->vda_name) == 0)) + map->l_abi_version = lav_private_def; + } + if ((unsigned int) (ent->vd_ndx & 0x7fff) > ndx_high) ndx_high = ent->vd_ndx & 0x7fff; @@ -352,6 +367,17 @@ _dl_check_map_versions (struct link_map *map, int verbose, int trace_mode) } } + /* Issue an error if there is a DT_RELR entry without GLIBC_ABI_DT_RELR + dependency nor GLIBC_PRIVATE definition. */ + if (map->l_info[DT_RELR] != NULL + && __glibc_unlikely (map->l_abi_version == lav_none)) + { + _dl_exception_create + (&exception, DSO_FILENAME (map->l_name), + N_("DT_RELR without GLIBC_ABI_DT_RELR dependency")); + goto call_error; + } + return result; } diff --git a/include/link.h b/include/link.h index 03db14c7b0..8ec5e35cf2 100644 --- a/include/link.h +++ b/include/link.h @@ -177,6 +177,12 @@ struct link_map lt_library, /* Library needed by main executable. */ lt_loaded /* Extra run-time loaded shared object. */ } l_type:2; + enum /* ABI dependency of this object. */ + { + lav_none, /* No ABI dependency. */ + lav_dt_relr_ref, /* Need GLIBC_ABI_DT_RELR. */ + lav_private_def /* Define GLIBC_PRIVATE. */ + } l_abi_version:2; 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. */ 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) {