* [PATCH v8 1/6] elf: Define DT_RELR related macros and types
2022-04-13 18:25 [PATCH v8 0/6] Support DT_RELR relative relocation format H.J. Lu
@ 2022-04-13 18:25 ` H.J. Lu
2022-04-13 21:43 ` Fangrui Song
2022-04-13 18:25 ` [PATCH v8 2/6] Add GLIBC_ABI_DT_RELR for DT_RELR support H.J. Lu
` (4 subsequent siblings)
5 siblings, 1 reply; 10+ messages in thread
From: H.J. Lu @ 2022-04-13 18:25 UTC (permalink / raw)
To: libc-alpha
---
elf/elf.h | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/elf/elf.h b/elf/elf.h
index 0735f6b579..0195029188 100644
--- a/elf/elf.h
+++ b/elf/elf.h
@@ -443,7 +443,8 @@ typedef struct
#define SHT_PREINIT_ARRAY 16 /* Array of pre-constructors */
#define SHT_GROUP 17 /* Section group */
#define SHT_SYMTAB_SHNDX 18 /* Extended section indices */
-#define SHT_NUM 19 /* Number of defined types. */
+#define SHT_RELR 19 /* RELR relative relocations */
+#define SHT_NUM 20 /* Number of defined types. */
#define SHT_LOOS 0x60000000 /* Start OS-specific. */
#define SHT_GNU_ATTRIBUTES 0x6ffffff5 /* Object attributes. */
#define SHT_GNU_HASH 0x6ffffff6 /* GNU-style hash table. */
@@ -662,6 +663,11 @@ typedef struct
Elf64_Sxword r_addend; /* Addend */
} Elf64_Rela;
+/* RELR relocation table entry */
+
+typedef Elf32_Word Elf32_Relr;
+typedef Elf64_Xword Elf64_Relr;
+
/* How to extract and insert information held in the r_info field. */
#define ELF32_R_SYM(val) ((val) >> 8)
@@ -887,7 +893,10 @@ typedef struct
#define DT_PREINIT_ARRAY 32 /* Array with addresses of preinit fct*/
#define DT_PREINIT_ARRAYSZ 33 /* size in bytes of DT_PREINIT_ARRAY */
#define DT_SYMTAB_SHNDX 34 /* Address of SYMTAB_SHNDX section */
-#define DT_NUM 35 /* Number used */
+#define DT_RELRSZ 35 /* Total size of RELR relative relocations */
+#define DT_RELR 36 /* Address of RELR relative relocations */
+#define DT_RELRENT 37 /* Size of one RELR relative relocaction */
+#define DT_NUM 38 /* Number used */
#define DT_LOOS 0x6000000d /* Start of OS-specific */
#define DT_HIOS 0x6ffff000 /* End of OS-specific */
#define DT_LOPROC 0x70000000 /* Start of processor-specific */
--
2.35.1
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH v8 1/6] elf: Define DT_RELR related macros and types
2022-04-13 18:25 ` [PATCH v8 1/6] elf: Define DT_RELR related macros and types H.J. Lu
@ 2022-04-13 21:43 ` Fangrui Song
0 siblings, 0 replies; 10+ messages in thread
From: Fangrui Song @ 2022-04-13 21:43 UTC (permalink / raw)
To: H.J. Lu; +Cc: libc-alpha, Adhemerval Zanella
On 2022-04-13, H.J. Lu wrote:
>---
> elf/elf.h | 13 +++++++++++--
> 1 file changed, 11 insertions(+), 2 deletions(-)
>
>diff --git a/elf/elf.h b/elf/elf.h
>index 0735f6b579..0195029188 100644
>--- a/elf/elf.h
>+++ b/elf/elf.h
>@@ -443,7 +443,8 @@ typedef struct
> #define SHT_PREINIT_ARRAY 16 /* Array of pre-constructors */
> #define SHT_GROUP 17 /* Section group */
> #define SHT_SYMTAB_SHNDX 18 /* Extended section indices */
>-#define SHT_NUM 19 /* Number of defined types. */
>+#define SHT_RELR 19 /* RELR relative relocations */
>+#define SHT_NUM 20 /* Number of defined types. */
> #define SHT_LOOS 0x60000000 /* Start OS-specific. */
> #define SHT_GNU_ATTRIBUTES 0x6ffffff5 /* Object attributes. */
> #define SHT_GNU_HASH 0x6ffffff6 /* GNU-style hash table. */
>@@ -662,6 +663,11 @@ typedef struct
> Elf64_Sxword r_addend; /* Addend */
> } Elf64_Rela;
>
>+/* RELR relocation table entry */
>+
>+typedef Elf32_Word Elf32_Relr;
>+typedef Elf64_Xword Elf64_Relr;
>+
> /* How to extract and insert information held in the r_info field. */
>
> #define ELF32_R_SYM(val) ((val) >> 8)
>@@ -887,7 +893,10 @@ typedef struct
> #define DT_PREINIT_ARRAY 32 /* Array with addresses of preinit fct*/
> #define DT_PREINIT_ARRAYSZ 33 /* size in bytes of DT_PREINIT_ARRAY */
> #define DT_SYMTAB_SHNDX 34 /* Address of SYMTAB_SHNDX section */
>-#define DT_NUM 35 /* Number used */
>+#define DT_RELRSZ 35 /* Total size of RELR relative relocations */
>+#define DT_RELR 36 /* Address of RELR relative relocations */
>+#define DT_RELRENT 37 /* Size of one RELR relative relocaction */
>+#define DT_NUM 38 /* Number used */
> #define DT_LOOS 0x6000000d /* Start of OS-specific */
> #define DT_HIOS 0x6ffff000 /* End of OS-specific */
> #define DT_LOPROC 0x70000000 /* Start of processor-specific */
>--
>2.35.1
>
(inherited from v7)
Reviewed-by: Fangrui Song <maskray@google.com>
^ permalink raw reply [flat|nested] 10+ messages in thread
* [PATCH v8 2/6] Add GLIBC_ABI_DT_RELR for DT_RELR support
2022-04-13 18:25 [PATCH v8 0/6] Support DT_RELR relative relocation format H.J. Lu
2022-04-13 18:25 ` [PATCH v8 1/6] elf: Define DT_RELR related macros and types H.J. Lu
@ 2022-04-13 18:25 ` H.J. Lu
2022-04-13 22:16 ` Fangrui Song
2022-04-13 18:25 ` [PATCH v8 3/6] elf: Support DT_RELR relative relocation format [BZ #27924] H.J. Lu
` (3 subsequent siblings)
5 siblings, 1 reply; 10+ messages in thread
From: H.J. Lu @ 2022-04-13 18:25 UTC (permalink / raw)
To: libc-alpha
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
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH v8 2/6] Add GLIBC_ABI_DT_RELR for DT_RELR support
2022-04-13 18:25 ` [PATCH v8 2/6] Add GLIBC_ABI_DT_RELR for DT_RELR support H.J. Lu
@ 2022-04-13 22:16 ` Fangrui Song
0 siblings, 0 replies; 10+ messages in thread
From: Fangrui Song @ 2022-04-13 22:16 UTC (permalink / raw)
To: H.J. Lu; +Cc: libc-alpha, Adhemerval Zanella
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>
^ permalink raw reply [flat|nested] 10+ messages in thread
* [PATCH v8 3/6] elf: Support DT_RELR relative relocation format [BZ #27924]
2022-04-13 18:25 [PATCH v8 0/6] Support DT_RELR relative relocation format H.J. Lu
2022-04-13 18:25 ` [PATCH v8 1/6] elf: Define DT_RELR related macros and types H.J. Lu
2022-04-13 18:25 ` [PATCH v8 2/6] Add GLIBC_ABI_DT_RELR for DT_RELR support H.J. Lu
@ 2022-04-13 18:25 ` H.J. Lu
2022-04-13 18:25 ` [PATCH v8 4/6] elf: Properly handle zero DT_RELA/DT_REL values H.J. Lu
` (2 subsequent siblings)
5 siblings, 0 replies; 10+ messages in thread
From: H.J. Lu @ 2022-04-13 18:25 UTC (permalink / raw)
To: libc-alpha
From: Fangrui Song <maskray@google.com>
PIE and shared objects usually have many relative relocations. In
2017/2018, SHT_RELR/DT_RELR was proposed on
https://groups.google.com/g/generic-abi/c/bX460iggiKg/m/GxjM0L-PBAAJ
("Proposal for a new section type SHT_RELR") and is a pre-standard. RELR
usually takes 3% or smaller space than R_*_RELATIVE relocations. The
virtual memory size of a mostly statically linked PIE is typically 5~10%
smaller.
---
Notes I will not include in the submitted commit:
Available on https://sourceware.org/git/?p=glibc.git;a=shortlog;h=refs/heads/maskray/relr
"pre-standard": even Solaris folks are happy with the refined generic-abi
proposal. Cary Coutant will apply the change
https://sourceware.org/pipermail/libc-alpha/2021-October/131781.html
This patch is simpler than Chrome OS's glibc patch and makes ELF_DYNAMIC_DO_RELR
available to all ports. I don't think the current glibc implementation
supports ia64 in an ELFCLASS32 container. That said, the style I used is
works with an ELFCLASS32 container for 64-bit machine if ElfW(Addr) is
64-bit.
* Chrome OS folks have carried a local patch since 2018 (latest version:
https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/refs/heads/main/sys-libs/glibc/files/local/glibc-2.32).
I.e. this feature has been battle tested.
* Android bionic supports 2018 and switched to DT_RELR==36 in 2020.
* The Linux kernel has supported CONFIG_RELR since 2019-08
(https://git.kernel.org/linus/5cf896fb6be3effd9aea455b22213e27be8bdb1d).
* A musl patch (by me) exists but is not applied:
https://www.openwall.com/lists/musl/2019/03/06/3
* rtld-elf from FreeBSD 14 will support DT_RELR.
I believe upstream glibc should support DT_RELR to benefit all Linux
distributions. I filed some feature requests to get their attention:
* Gentoo: https://bugs.gentoo.org/818376
* Arch Linux: https://bugs.archlinux.org/task/72433
* Debian https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=996598
* Fedora https://bugzilla.redhat.com/show_bug.cgi?id=2014699
As of linker support (to the best of my knowledge):
* LLD support DT_RELR.
* https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/refs/heads/main/sys-devel/binutils/files/
has a gold patch.
* GNU ld feature request https://sourceware.org/bugzilla/show_bug.cgi?id=27923
Changes from the original patch:
1. Check the linker option, -z pack-relative-relocs, which add a
GLIBC_ABI_DT_RELR symbol version dependency on the shared C library if
it provides a GLIBC_2.XX symbol version.
2. Change make variale to have-dt-relr.
3. Rename tst-relr-no-pie to tst-relr-pie for --disable-default-pie.
4. Use TEST_VERIFY in tst-relr.c.
5. Add the check-tst-relr-pie.out test to check for linker generated
libc.so version dependency on GLIBC_ABI_DT_RELR.
6. Move ELF_DYNAMIC_DO_RELR before ELF_DYNAMIC_DO_REL.
---
configure | 37 ++++++++++++++++++++++++
configure.ac | 5 ++++
elf/Makefile | 25 ++++++++++++++++
elf/dynamic-link.h | 34 ++++++++++++++++++++++
elf/get-dynamic-info.h | 3 ++
elf/tst-relr-pie.c | 1 +
elf/tst-relr.c | 65 ++++++++++++++++++++++++++++++++++++++++++
7 files changed, 170 insertions(+)
create mode 100644 elf/tst-relr-pie.c
create mode 100644 elf/tst-relr.c
diff --git a/configure b/configure
index d2f413d05d..c0c2246597 100755
--- a/configure
+++ b/configure
@@ -6076,6 +6076,43 @@ $as_echo "$libc_linker_feature" >&6; }
config_vars="$config_vars
have-depaudit = $libc_cv_depaudit"
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for linker that supports -z pack-relative-relocs" >&5
+$as_echo_n "checking for linker that supports -z pack-relative-relocs... " >&6; }
+libc_linker_feature=no
+if test x"$gnu_ld" = x"yes"; then
+ cat > conftest.c <<EOF
+int _start (void) { return 42; }
+EOF
+ if { ac_try='${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS $no_ssp
+ -Wl,-z,pack-relative-relocs -nostdlib -nostartfiles
+ -fPIC -shared -o conftest.so conftest.c
+ 1>&5'
+ { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
+ (eval $ac_try) 2>&5
+ ac_status=$?
+ $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+ test $ac_status = 0; }; }
+ then
+ if ${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS $no_ssp -Wl,-z,pack-relative-relocs -nostdlib \
+ -nostartfiles -fPIC -shared -o conftest.so conftest.c 2>&1 \
+ | grep "warning: -z pack-relative-relocs ignored" > /dev/null 2>&1; then
+ true
+ else
+ libc_linker_feature=yes
+ fi
+ fi
+ rm -f conftest*
+fi
+if test $libc_linker_feature = yes; then
+ libc_cv_dt_relr=yes
+else
+ libc_cv_dt_relr=no
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_linker_feature" >&5
+$as_echo "$libc_linker_feature" >&6; }
+config_vars="$config_vars
+have-dt-relr = $libc_cv_dt_relr"
+
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for linker that supports --no-dynamic-linker" >&5
$as_echo_n "checking for linker that supports --no-dynamic-linker... " >&6; }
libc_linker_feature=no
diff --git a/configure.ac b/configure.ac
index b6a747dece..66cad71431 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1336,6 +1336,11 @@ LIBC_LINKER_FEATURE([--depaudit], [-Wl,--depaudit,x],
[libc_cv_depaudit=yes], [libc_cv_depaudit=no])
LIBC_CONFIG_VAR([have-depaudit], [$libc_cv_depaudit])
+LIBC_LINKER_FEATURE([-z pack-relative-relocs],
+ [-Wl,-z,pack-relative-relocs],
+ [libc_cv_dt_relr=yes], [libc_cv_dt_relr=no])
+LIBC_CONFIG_VAR([have-dt-relr], [$libc_cv_dt_relr])
+
LIBC_LINKER_FEATURE([--no-dynamic-linker],
[-Wl,--no-dynamic-linker],
[libc_cv_no_dynamic_linker=yes],
diff --git a/elf/Makefile b/elf/Makefile
index 09d3d88336..979dde046d 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -541,6 +541,25 @@ tests-special += \
# tests-special
endif
endif
+ifeq ($(have-dt-relr),yes)
+tests += \
+ tst-relr \
+# tests
+ifeq ($(have-fpie),yes)
+tests += \
+ tst-relr-pie \
+# tests
+tests-pie += \
+ tst-relr-pie \
+# tests-pie
+tests-special += \
+ $(objpfx)check-tst-relr-pie.out \
+# tests-special
+endif
+CFLAGS-tst-relr-pie.c += $(pie-ccflag)
+LDFLAGS-tst-relr += -Wl,-z,pack-relative-relocs
+LDFLAGS-tst-relr-pie += -Wl,-z,pack-relative-relocs
+endif
endif
ifeq ($(run-built-tests),yes)
@@ -2735,3 +2754,9 @@ $(objpfx)check-abi-version-libc.out: $(common-objpfx)libc.so
| sed -ne '/.gnu.version_d/, /.gnu.version_r/ p' \
| grep GLIBC_ABI_DT_RELR > $@; \
$(evaluate-test)
+
+$(objpfx)check-tst-relr-pie.out: $(objpfx)tst-relr-pie
+ LC_ALL=C $(OBJDUMP) -p $< \
+ | sed -ne '/required from libc.so/,$$ p' \
+ | grep GLIBC_ABI_DT_RELR > $@; \
+ $(evaluate-test)
diff --git a/elf/dynamic-link.h b/elf/dynamic-link.h
index 25dd7ca4f2..7325e0d9fc 100644
--- a/elf/dynamic-link.h
+++ b/elf/dynamic-link.h
@@ -146,12 +146,46 @@ elf_machine_lazy_rel (struct link_map *map, struct r_scope_elem *scope[],
# define ELF_DYNAMIC_DO_RELA(map, scope, lazy, skip_ifunc) /* Nothing to do. */
# endif
+# define ELF_DYNAMIC_DO_RELR(map) \
+ do { \
+ ElfW(Addr) l_addr = (map)->l_addr, *where = 0; \
+ const ElfW(Relr) *r, *end; \
+ if (!(map)->l_info[DT_RELR]) \
+ break; \
+ r = (const ElfW(Relr) *)D_PTR((map), l_info[DT_RELR]); \
+ end = (const ElfW(Relr) *)((const char *)r + \
+ (map)->l_info[DT_RELRSZ]->d_un.d_val); \
+ for (; r < end; r++) \
+ { \
+ ElfW(Relr) entry = *r; \
+ if ((entry & 1) == 0) \
+ { \
+ where = (ElfW(Addr) *)(l_addr + entry); \
+ *where++ += l_addr; \
+ } \
+ else \
+ { \
+ for (long int i = 0; (entry >>= 1) != 0; i++) \
+ if ((entry & 1) != 0) \
+ where[i] += l_addr; \
+ where += CHAR_BIT * sizeof(ElfW(Relr)) - 1; \
+ } \
+ } \
+ } while (0);
+
/* This can't just be an inline function because GCC is too dumb
to inline functions containing inlines themselves. */
+# ifdef RTLD_BOOTSTRAP
+# define DO_RTLD_BOOTSTRAP 1
+# else
+# define DO_RTLD_BOOTSTRAP 0
+# endif
# define ELF_DYNAMIC_RELOCATE(map, scope, lazy, consider_profile, skip_ifunc) \
do { \
int edr_lazy = elf_machine_runtime_setup ((map), (scope), (lazy), \
(consider_profile)); \
+ if (((map) != &GL(dl_rtld_map) || DO_RTLD_BOOTSTRAP)) \
+ ELF_DYNAMIC_DO_RELR (map); \
ELF_DYNAMIC_DO_REL ((map), (scope), edr_lazy, skip_ifunc); \
ELF_DYNAMIC_DO_RELA ((map), (scope), edr_lazy, skip_ifunc); \
} while (0)
diff --git a/elf/get-dynamic-info.h b/elf/get-dynamic-info.h
index 6c2ccd6db4..6c2a3a12b1 100644
--- a/elf/get-dynamic-info.h
+++ b/elf/get-dynamic-info.h
@@ -89,6 +89,7 @@ elf_get_dynamic_info (struct link_map *l, bool bootstrap,
# if ! ELF_MACHINE_NO_REL
ADJUST_DYN_INFO (DT_REL);
# endif
+ ADJUST_DYN_INFO (DT_RELR);
ADJUST_DYN_INFO (DT_JMPREL);
ADJUST_DYN_INFO (VERSYMIDX (DT_VERSYM));
ADJUST_DYN_INFO (ADDRIDX (DT_GNU_HASH));
@@ -113,6 +114,8 @@ elf_get_dynamic_info (struct link_map *l, bool bootstrap,
if (info[DT_REL] != NULL)
assert (info[DT_RELENT]->d_un.d_val == sizeof (ElfW(Rel)));
#endif
+ if (info[DT_RELR] != NULL)
+ assert (info[DT_RELRENT]->d_un.d_val == sizeof (ElfW(Relr)));
if (bootstrap || static_pie_bootstrap)
{
assert (info[DT_RUNPATH] == NULL);
diff --git a/elf/tst-relr-pie.c b/elf/tst-relr-pie.c
new file mode 100644
index 0000000000..7df0cdbfd6
--- /dev/null
+++ b/elf/tst-relr-pie.c
@@ -0,0 +1 @@
+#include "tst-relr.c"
diff --git a/elf/tst-relr.c b/elf/tst-relr.c
new file mode 100644
index 0000000000..c634ce0d21
--- /dev/null
+++ b/elf/tst-relr.c
@@ -0,0 +1,65 @@
+/* Basic tests for DT_RELR.
+ Copyright (C) 2022 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/>. */
+
+#include <link.h>
+#include <stdbool.h>
+#include <array_length.h>
+#include <support/check.h>
+
+static int o, x;
+
+#define ELEMS O O O O O O O O X X X X X X X O O X O O X X X E X E E O X O E
+#define E 0,
+
+#define O &o,
+#define X &x,
+void *arr[] = { ELEMS };
+#undef O
+#undef X
+
+#define O 1,
+#define X 2,
+static char val[] = { ELEMS };
+
+static int
+do_test (void)
+{
+ ElfW(Dyn) *d = _DYNAMIC;
+ if (d)
+ {
+ bool has_relr = false;
+ for (; d->d_tag != DT_NULL; d++)
+ if (d->d_tag == DT_RELR)
+ has_relr = true;
+
+#if defined __PIE__ || defined __pie__ || defined PIE || defined pie
+ TEST_VERIFY (has_relr);
+#else
+ TEST_VERIFY (!has_relr);
+#endif
+ }
+
+ for (int i = 0; i < array_length (arr); i++)
+ TEST_VERIFY ((arr[i] == 0 && val[i] == 0)
+ || (arr[i] == &o && val[i] == 1)
+ || (arr[i] == &x && val[i] == 2));
+
+ return 0;
+}
+
+#include <support/test-driver.c>
--
2.35.1
^ permalink raw reply [flat|nested] 10+ messages in thread* [PATCH v8 4/6] elf: Properly handle zero DT_RELA/DT_REL values
2022-04-13 18:25 [PATCH v8 0/6] Support DT_RELR relative relocation format H.J. Lu
` (2 preceding siblings ...)
2022-04-13 18:25 ` [PATCH v8 3/6] elf: Support DT_RELR relative relocation format [BZ #27924] H.J. Lu
@ 2022-04-13 18:25 ` H.J. Lu
2022-04-13 18:25 ` [PATCH v8 5/6] Add --disable-default-dt-relr H.J. Lu
2022-04-13 18:25 ` [PATCH v8 6/6] NEWS: Mention DT_RELR support H.J. Lu
5 siblings, 0 replies; 10+ messages in thread
From: H.J. Lu @ 2022-04-13 18:25 UTC (permalink / raw)
To: libc-alpha
With DT_RELR, there may be no relocations in DT_RELA/DT_REL and their
entry values are zero. Don't relocate DT_RELA/DT_REL and update the
combined relocation start address if their entry values are zero.
---
elf/dynamic-link.h | 6 +++++-
elf/get-dynamic-info.h | 24 ++++++++++++++++++------
2 files changed, 23 insertions(+), 7 deletions(-)
diff --git a/elf/dynamic-link.h b/elf/dynamic-link.h
index 7325e0d9fc..7dd8f1b1d6 100644
--- a/elf/dynamic-link.h
+++ b/elf/dynamic-link.h
@@ -84,7 +84,9 @@ elf_machine_lazy_rel (struct link_map *map, struct r_scope_elem *scope[],
__typeof (((ElfW(Dyn) *) 0)->d_un.d_val) nrelative; int lazy; } \
ranges[2] = { { 0, 0, 0, 0 }, { 0, 0, 0, 0 } }; \
\
- if ((map)->l_info[DT_##RELOC]) \
+ /* With DT_RELR, DT_RELA/DT_REL can have zero value. */ \
+ if ((map)->l_info[DT_##RELOC] != NULL \
+ && (map)->l_info[DT_##RELOC]->d_un.d_ptr != 0) \
{ \
ranges[0].start = D_PTR ((map), l_info[DT_##RELOC]); \
ranges[0].size = (map)->l_info[DT_##RELOC##SZ]->d_un.d_val; \
@@ -98,6 +100,8 @@ elf_machine_lazy_rel (struct link_map *map, struct r_scope_elem *scope[],
ElfW(Addr) start = D_PTR ((map), l_info[DT_JMPREL]); \
ElfW(Addr) size = (map)->l_info[DT_PLTRELSZ]->d_un.d_val; \
\
+ if (ranges[0].start == 0) \
+ ranges[0].start = start; \
if (ranges[0].start + ranges[0].size == (start + size)) \
ranges[0].size -= size; \
if (!(do_lazy) \
diff --git a/elf/get-dynamic-info.h b/elf/get-dynamic-info.h
index 6c2a3a12b1..0314baf020 100644
--- a/elf/get-dynamic-info.h
+++ b/elf/get-dynamic-info.h
@@ -75,24 +75,36 @@ elf_get_dynamic_info (struct link_map *l, bool bootstrap,
# define ADJUST_DYN_INFO(tag) \
do \
- if (info[tag] != NULL) \
- info[tag]->d_un.d_ptr += l_addr; \
+ { \
+ if (info[tag] != NULL) \
+ info[tag]->d_un.d_ptr += l_addr; \
+ } \
while (0)
ADJUST_DYN_INFO (DT_HASH);
ADJUST_DYN_INFO (DT_PLTGOT);
ADJUST_DYN_INFO (DT_STRTAB);
ADJUST_DYN_INFO (DT_SYMTAB);
+ ADJUST_DYN_INFO (DT_RELR);
+ ADJUST_DYN_INFO (DT_JMPREL);
+ ADJUST_DYN_INFO (VERSYMIDX (DT_VERSYM));
+ ADJUST_DYN_INFO (ADDRIDX (DT_GNU_HASH));
+# undef ADJUST_DYN_INFO
+
+ /* DT_RELA/DT_REL are mandatory. But they may have zero value if
+ there is DT_RELR. Don't relocate them if they are zero. */
+# define ADJUST_DYN_INFO(tag) \
+ do \
+ if (info[tag] != NULL && info[tag]->d_un.d_ptr != 0) \
+ info[tag]->d_un.d_ptr += l_addr; \
+ while (0)
+
# if ! ELF_MACHINE_NO_RELA
ADJUST_DYN_INFO (DT_RELA);
# endif
# if ! ELF_MACHINE_NO_REL
ADJUST_DYN_INFO (DT_REL);
# endif
- ADJUST_DYN_INFO (DT_RELR);
- ADJUST_DYN_INFO (DT_JMPREL);
- ADJUST_DYN_INFO (VERSYMIDX (DT_VERSYM));
- ADJUST_DYN_INFO (ADDRIDX (DT_GNU_HASH));
# undef ADJUST_DYN_INFO
}
if (info[DT_PLTREL] != NULL)
--
2.35.1
^ permalink raw reply [flat|nested] 10+ messages in thread* [PATCH v8 5/6] Add --disable-default-dt-relr
2022-04-13 18:25 [PATCH v8 0/6] Support DT_RELR relative relocation format H.J. Lu
` (3 preceding siblings ...)
2022-04-13 18:25 ` [PATCH v8 4/6] elf: Properly handle zero DT_RELA/DT_REL values H.J. Lu
@ 2022-04-13 18:25 ` H.J. Lu
2022-04-13 18:25 ` [PATCH v8 6/6] NEWS: Mention DT_RELR support H.J. Lu
5 siblings, 0 replies; 10+ messages in thread
From: H.J. Lu @ 2022-04-13 18:25 UTC (permalink / raw)
To: libc-alpha
Enable DT_RELR in glibc shared libraries and position independent
executables (PIE) automatically if linker supports -z pack-relative-relocs.
Also add a new configuration option, --disable-default-dt-relr, to
avoid DT_RELR usage in glibc shared libraries and PIEs.
---
INSTALL | 6 ++++++
Makeconfig | 19 +++++++++++++++++++
Makerules | 2 ++
configure | 18 ++++++++++++++++++
configure.ac | 13 +++++++++++++
elf/Makefile | 4 +++-
manual/install.texi | 5 +++++
7 files changed, 66 insertions(+), 1 deletion(-)
diff --git a/INSTALL b/INSTALL
index 63c022d6b9..4a6506f11f 100644
--- a/INSTALL
+++ b/INSTALL
@@ -133,6 +133,12 @@ if 'CFLAGS' is specified it must enable optimization. For example:
used with the GCC option, -static-pie, which is available with GCC
8 or above, to create static PIE.
+'--disable-default-dt-relr'
+ Don't enable DT_RELR in glibc shared libraries and position
+ independent executables (PIE). By default, DT_RELR is enabled in
+ glibc shared libraries and position independent executables on
+ targets that support it.
+
'--enable-cet'
'--enable-cet=permissive'
Enable Intel Control-flow Enforcement Technology (CET) support.
diff --git a/Makeconfig b/Makeconfig
index 0aa5fb0099..b75f28f837 100644
--- a/Makeconfig
+++ b/Makeconfig
@@ -358,6 +358,23 @@ else
real-static-start-installed-name = $(static-start-installed-name)
endif
+# Linker option to enable and disable DT-RELR.
+ifeq ($(have-dt-relr),yes)
+dt-relr-ldflag = -Wl,-z,pack-relative-relocs
+no-dt-relr-ldflag = -Wl,-z,nopack-relative-relocs
+else
+dt-relr-ldflag =
+no-dt-relr-ldflag =
+endif
+
+# Default linker option for DT-RELR.
+ifeq (yes,$(build-dt-relr-default))
+default-rt-relr-ldflag = $(dt-relr-ldflag)
+else
+default-rt-relr-ldflag = $(no-dt-relr-ldflag)
+endif
+LDFLAGS-rtld += $(default-rt-relr-ldflag)
+
relro-LDFLAGS = -Wl,-z,relro
LDFLAGS.so += $(relro-LDFLAGS)
LDFLAGS-rtld += $(relro-LDFLAGS)
@@ -413,6 +430,7 @@ link-extra-libs-tests = $(libsupport)
# Command for linking PIE programs with the C library.
ifndef +link-pie
+link-pie-before-inputs = $(if $($(@F)-no-pie),$(no-pie-ldflag),-pie) \
+ $(if $($(@F)-no-dt-relr),$(no-dt-relr-ldflag),$(default-rt-relr-ldflag)) \
-Wl,-O1 -nostdlib -nostartfiles \
$(sysdep-LDFLAGS) $(LDFLAGS) $(LDFLAGS-$(@F)) \
$(relro-LDFLAGS) $(hashstyle-LDFLAGS) \
@@ -445,6 +463,7 @@ endif
ifndef +link-static
+link-static-before-inputs = -nostdlib -nostartfiles -static \
$(if $($(@F)-no-pie),$(no-pie-ldflag),$(static-pie-ldflag)) \
+ $(if $($(@F)-no-dt-relr),$(no-dt-relr-ldflag),$(default-rt-relr-ldflag)) \
$(sysdep-LDFLAGS) $(LDFLAGS) $(LDFLAGS-$(@F)) \
$(firstword $(CRT-$(@F)) $(csu-objpfx)$(real-static-start-installed-name)) \
$(+preinit) $(+prectorT)
diff --git a/Makerules b/Makerules
index 428464f092..7c1da551bf 100644
--- a/Makerules
+++ b/Makerules
@@ -536,6 +536,7 @@ lib%.so: lib%_pic.a $(+preinit) $(+postinit) $(link-libc-deps)
define build-shlib-helper
$(LINK.o) -shared -static-libgcc -Wl,-O1 $(sysdep-LDFLAGS) \
$(if $($(@F)-no-z-defs)$(no-z-defs),,-Wl,-z,defs) $(rtld-LDFLAGS) \
+ $(if $($(@F)-no-dt-relr),$(no-dt-relr-ldflag),$(default-rt-relr-ldflag)) \
$(extra-B-$(@F:lib%.so=%).so) -B$(csu-objpfx) \
$(extra-B-$(@F:lib%.so=%).so) $(load-map-file) \
-Wl,-soname=lib$(libprefix)$(@F:lib%.so=%).so$($(@F)-version) \
@@ -595,6 +596,7 @@ endef
define build-module-helper
$(LINK.o) -shared -static-libgcc $(sysdep-LDFLAGS) $(rtld-LDFLAGS) \
$(if $($(@F)-no-z-defs)$(no-z-defs),,-Wl,-z,defs) \
+ $(if $($(@F)-no-dt-relr),$(no-dt-relr-ldflag),$(default-rt-relr-ldflag)) \
-B$(csu-objpfx) $(load-map-file) \
$(LDFLAGS.so) $(LDFLAGS-$(@F:%.so=%).so) \
$(link-test-modules-rpath-link) \
diff --git a/configure b/configure
index c0c2246597..d230c2c673 100755
--- a/configure
+++ b/configure
@@ -767,6 +767,7 @@ enable_sanity_checks
enable_shared
enable_profile
enable_default_pie
+enable_default_dt_relr
enable_timezone_tools
enable_hardcoded_path_in_tests
enable_hidden_plt
@@ -1424,6 +1425,7 @@ Optional Features:
--enable-profile build profiled library [default=no]
--disable-default-pie Do not build glibc programs and the testsuite as PIE
[default=no]
+ --disable-dt-relr Do not enable DT_RELR in glibc[default=no]
--disable-timezone-tools
do not install timezone tools [default=install]
--enable-hardcoded-path-in-tests
@@ -3440,6 +3442,13 @@ else
default_pie=yes
fi
+# Check whether --enable-default-dt-relr was given.
+if test "${enable_default_dt_relr+set}" = set; then :
+ enableval=$enable_default_dt_relr; default_dt_relr=$enableval
+else
+ default_dt_relr=yes
+fi
+
# Check whether --enable-timezone-tools was given.
if test "${enable_timezone_tools+set}" = set; then :
enableval=$enable_timezone_tools; enable_timezone_tools=$enableval
@@ -7092,6 +7101,15 @@ fi
config_vars="$config_vars
enable-static-pie = $libc_cv_static_pie"
+# Disable build-dt-relr-default if linker does not support it or if glibc
+# is configured with --disable-default-dt-relr.
+build_dt_relr_default=$default_dt_relr
+if test "x$build_dt_relr_default" != xno; then
+ build_dt_relr_default=$libc_cv_dt_relr
+fi
+config_vars="$config_vars
+build-dt-relr-default = $build_dt_relr_default"
+
# Set the `multidir' variable by grabbing the variable from the compiler.
# We do it once and save the result in a generated makefile.
libc_cv_multidir=`${CC-cc} $CFLAGS $CPPFLAGS -print-multi-directory`
diff --git a/configure.ac b/configure.ac
index 66cad71431..1aa152b901 100644
--- a/configure.ac
+++ b/configure.ac
@@ -197,6 +197,11 @@ AC_ARG_ENABLE([default-pie],
[Do not build glibc programs and the testsuite as PIE @<:@default=no@:>@]),
[default_pie=$enableval],
[default_pie=yes])
+AC_ARG_ENABLE([default-dt-relr],
+ AS_HELP_STRING([--disable-dt-relr],
+ [Do not enable DT_RELR in glibc@<:@default=no@:>@]),
+ [default_dt_relr=$enableval],
+ [default_dt_relr=yes])
AC_ARG_ENABLE([timezone-tools],
AS_HELP_STRING([--disable-timezone-tools],
[do not install timezone tools @<:@default=install@:>@]),
@@ -1878,6 +1883,14 @@ if test "$libc_cv_static_pie" = "yes"; then
fi
LIBC_CONFIG_VAR([enable-static-pie], [$libc_cv_static_pie])
+# Disable build-dt-relr-default if linker does not support it or if glibc
+# is configured with --disable-default-dt-relr.
+build_dt_relr_default=$default_dt_relr
+if test "x$build_dt_relr_default" != xno; then
+ build_dt_relr_default=$libc_cv_dt_relr
+fi
+LIBC_CONFIG_VAR([build-dt-relr-default], [$build_dt_relr_default])
+
# Set the `multidir' variable by grabbing the variable from the compiler.
# We do it once and save the result in a generated makefile.
libc_cv_multidir=`${CC-cc} $CFLAGS $CPPFLAGS -print-multi-directory`
diff --git a/elf/Makefile b/elf/Makefile
index 979dde046d..ac6a73ec5e 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -1580,6 +1580,7 @@ $(objpfx)nodlopen2.out: $(objpfx)nodlopenmod2.so
$(objpfx)filtmod1.so: $(objpfx)filtmod1.os $(objpfx)filtmod2.so
$(LINK.o) -shared -o $@ -B$(csu-objpfx) $(LDFLAGS.so) \
+ $(default-rt-relr-ldflag) \
-L$(subst :, -L,$(rpath-link)) \
-Wl,-rpath-link=$(rpath-link) \
$< -Wl,-F,$(objpfx)filtmod2.so
@@ -2379,7 +2380,7 @@ $(objpfx)tst-big-note: $(objpfx)tst-big-note-lib.so
# artificial, large note in tst-big-note-lib.o and invalidate the
# test.
$(objpfx)tst-big-note-lib.so: $(objpfx)tst-big-note-lib.o
- $(LINK.o) -shared -o $@ $(LDFLAGS.so) $<
+ $(LINK.o) -shared -o $@ $(LDFLAGS.so) $(default-rt-relr-ldflag) $<
$(objpfx)tst-unwind-ctor: $(objpfx)tst-unwind-ctor-lib.so
@@ -2685,6 +2686,7 @@ $(objpfx)tst-ro-dynamic: $(objpfx)tst-ro-dynamic-mod.so
$(objpfx)tst-ro-dynamic-mod.so: $(objpfx)tst-ro-dynamic-mod.os \
tst-ro-dynamic-mod.map
$(LINK.o) -nostdlib -nostartfiles -shared -o $@ \
+ $(default-rt-relr-ldflag) \
-Wl,--script=tst-ro-dynamic-mod.map \
$(objpfx)tst-ro-dynamic-mod.os
diff --git a/manual/install.texi b/manual/install.texi
index 29c52f2927..04ea996561 100644
--- a/manual/install.texi
+++ b/manual/install.texi
@@ -161,6 +161,11 @@ and architecture support it, static executables are built as static PIE and the
resulting glibc can be used with the GCC option, -static-pie, which is
available with GCC 8 or above, to create static PIE.
+@item --disable-default-dt-relr
+Don't enable DT_RELR in glibc shared libraries and position independent
+executables (PIE). By default, DT_RELR is enabled in glibc shared
+libraries and position independent executables on targets that support it.
+
@item --enable-cet
@itemx --enable-cet=permissive
Enable Intel Control-flow Enforcement Technology (CET) support. When
--
2.35.1
^ permalink raw reply [flat|nested] 10+ messages in thread* [PATCH v8 6/6] NEWS: Mention DT_RELR support
2022-04-13 18:25 [PATCH v8 0/6] Support DT_RELR relative relocation format H.J. Lu
` (4 preceding siblings ...)
2022-04-13 18:25 ` [PATCH v8 5/6] Add --disable-default-dt-relr H.J. Lu
@ 2022-04-13 18:25 ` H.J. Lu
2022-04-13 21:43 ` Fangrui Song
5 siblings, 1 reply; 10+ messages in thread
From: H.J. Lu @ 2022-04-13 18:25 UTC (permalink / raw)
To: libc-alpha
---
NEWS | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/NEWS b/NEWS
index 4b6d9de2b5..ef8ac4acd2 100644
--- a/NEWS
+++ b/NEWS
@@ -9,7 +9,12 @@ Version 2.36
Major new features:
- [Add new features here]
+* Support for DT_RELR relative relocation format has been added to
+ glibc. This is a new ELF dynamic tag that improves the size of
+ relative relocations in shared object files and position independent
+ executables (PIE). DT_RELR generation requires linker support for
+ -z pack-relative-relocs option, which is supported for some targets
+ in recent binutils versions. Lazy binding doesn't apply to DT_RELR.
Deprecated and removed features, and other changes affecting compatibility:
--
2.35.1
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH v8 6/6] NEWS: Mention DT_RELR support
2022-04-13 18:25 ` [PATCH v8 6/6] NEWS: Mention DT_RELR support H.J. Lu
@ 2022-04-13 21:43 ` Fangrui Song
0 siblings, 0 replies; 10+ messages in thread
From: Fangrui Song @ 2022-04-13 21:43 UTC (permalink / raw)
To: H.J. Lu; +Cc: libc-alpha, Adhemerval Zanella
On 2022-04-13, H.J. Lu wrote:
>---
> NEWS | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
>diff --git a/NEWS b/NEWS
>index 4b6d9de2b5..ef8ac4acd2 100644
>--- a/NEWS
>+++ b/NEWS
>@@ -9,7 +9,12 @@ Version 2.36
>
> Major new features:
>
>- [Add new features here]
>+* Support for DT_RELR relative relocation format has been added to
>+ glibc. This is a new ELF dynamic tag that improves the size of
>+ relative relocations in shared object files and position independent
>+ executables (PIE). DT_RELR generation requires linker support for
>+ -z pack-relative-relocs option, which is supported for some targets
>+ in recent binutils versions. Lazy binding doesn't apply to DT_RELR.
>
> Deprecated and removed features, and other changes affecting compatibility:
>
>--
>2.35.1
>
(inherited from v4 and v7)
Reviewed-by: Fangrui Song <maskray@google.com>
^ permalink raw reply [flat|nested] 10+ messages in thread