* RFC: x86: Fall back to lazy binding for unrelocated IFUNC symbol [BZ #23240] @ 2018-05-26 13:52 H.J. Lu 2018-05-26 21:02 ` Florian Weimer 0 siblings, 1 reply; 14+ messages in thread From: H.J. Lu @ 2018-05-26 13:52 UTC (permalink / raw) To: GNU C Library Since we can't call unrelocated IFUNC function to get the real function addresss, this patch falls back to lazy binding for unrelocated IFUNC symbol. Any comments? H.J. --- [BZ #23240] * elf/Makefile (tests-internal): Add ifuncpreload1 (modules-names): Add ifuncpreloadmod1a and ifuncpreloadmod1b. ($(objpfx)ifuncpreload1): New. ($(objpfx)ifuncpreload1.out): Likewise. (ifuncpreload1-ENV): Likewise. * elf/ifuncpreload1.c: New file. * elf/ifuncpreloadmod1a.c: Likewise. * elf/ifuncpreloadmod1b.c: Likewise. * sysdeps/i386/dl-machine.h (elf_machine_runtime_setup): Always set up GOT. (elf_machine_rel): Fall back to lazy binding for unrelocated IFUNC symbol. * sysdeps/x86_64/dl-machine.h (elf_machine_runtime_setup): Always set up GOT. (elf_machine_rela): Fall back to lazy binding for unrelocated IFUNC symbol. --- elf/Makefile | 10 ++++++-- elf/ifuncpreload1.c | 39 +++++++++++++++++++++++++++++ elf/ifuncpreloadmod1a.c | 23 +++++++++++++++++ elf/ifuncpreloadmod1b.c | 49 +++++++++++++++++++++++++++++++++++++ sysdeps/i386/dl-machine.h | 22 ++++++++++------- sysdeps/x86_64/dl-machine.h | 22 ++++++++++------- 6 files changed, 145 insertions(+), 20 deletions(-) create mode 100644 elf/ifuncpreload1.c create mode 100644 elf/ifuncpreloadmod1a.c create mode 100644 elf/ifuncpreloadmod1b.c diff --git a/elf/Makefile b/elf/Makefile index 2dcd2b88e0..cb203d58b4 100644 --- a/elf/Makefile +++ b/elf/Makefile @@ -328,7 +328,7 @@ tests-internal += \ ifuncmain1staticpic \ ifuncmain2 ifuncmain2pic ifuncmain3 ifuncmain4 \ ifuncmain5 ifuncmain5pic ifuncmain5staticpic \ - ifuncmain7 ifuncmain7pic + ifuncmain7 ifuncmain7pic ifuncpreload1 ifunc-test-modules = ifuncdep1 ifuncdep1pic ifuncdep2 ifuncdep2pic \ ifuncdep5 ifuncdep5pic extra-test-objs += $(ifunc-test-modules:=.o) @@ -339,7 +339,8 @@ ifunc-pie-tests = ifuncmain1pie ifuncmain1vispie ifuncmain1staticpie \ tests-internal += $(ifunc-pie-tests) tests-pie += $(ifunc-pie-tests) endif -modules-names += ifuncmod1 ifuncmod3 ifuncmod5 ifuncmod6 +modules-names += ifuncmod1 ifuncmod3 ifuncmod5 ifuncmod6 \ + ifuncpreloadmod1a ifuncpreloadmod1b endif endif @@ -1454,3 +1455,8 @@ tst-libc_dlvsym-static-ENV = \ $(objpfx)tst-libc_dlvsym-static.out: $(objpfx)tst-libc_dlvsym-dso.so $(objpfx)tst-big-note: $(objpfx)tst-big-note-lib.so + +$(objpfx)ifuncpreload1: $(objpfx)ifuncpreloadmod1a.so +$(objpfx)ifuncpreload1.out: $(objpfx)ifuncpreloadmod1b.so +ifuncpreload1-ENV = \ + LD_PRELOAD=$(objpfx)ifuncpreloadmod1b.so LD_BIND_NOW=1 diff --git a/elf/ifuncpreload1.c b/elf/ifuncpreload1.c new file mode 100644 index 0000000000..172df33ac3 --- /dev/null +++ b/elf/ifuncpreload1.c @@ -0,0 +1,39 @@ +/* Test for relocation over with IFUNC symbols. + Copyright (C) 2018 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 + <http://www.gnu.org/licenses/>. */ + +#include <support/check.h> +#include <support/support.h> +#include <support/test-driver.h> + +extern void bar (char *, const char *, unsigned int); + +static int +do_test (void) +{ + char dst[50]; + const char src[] = + { + "This is a test" + }; + bar (dst, src, sizeof (src)); + if (__builtin_memcmp (dst, src, sizeof (src)) != 0) + __builtin_abort (); + return 0; +} + +#include <support/test-driver.c> diff --git a/elf/ifuncpreloadmod1a.c b/elf/ifuncpreloadmod1a.c new file mode 100644 index 0000000000..be9f8832b8 --- /dev/null +++ b/elf/ifuncpreloadmod1a.c @@ -0,0 +1,23 @@ +/* Shared module to test for relocation over with IFUNC symbols. + Copyright (C) 2018 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 + <http://www.gnu.org/licenses/>. */ + +void +bar (char *dst, const char *src, unsigned int size) +{ + __builtin_memmove (dst, src, size); +} diff --git a/elf/ifuncpreloadmod1b.c b/elf/ifuncpreloadmod1b.c new file mode 100644 index 0000000000..1194ae20e4 --- /dev/null +++ b/elf/ifuncpreloadmod1b.c @@ -0,0 +1,49 @@ +/* Shared module to test for relocation over with IFUNC symbols. + Copyright (C) 2018 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 + <http://www.gnu.org/licenses/>. */ + +#include <stddef.h> + +void * +my_memmove(void *dst_p, const void *src_p, size_t n) +{ + const char *src = src_p; + char *dst = dst_p; + char *ret = dst; + if (src < dst) + { + dst += n; + src += n; + while (n--) + *--dst = *--src; + } + else + while (n--) + *dst++ = *src++; + return ret; +} + +void *memmove (void *, const void *, size_t) + __attribute__ ((ifunc ("resolve_memmove"))); + +typedef void *(*memmove_t) (void *, const void *, size_t); + +static memmove_t +resolve_memmove (void) +{ + return my_memmove; +} diff --git a/sysdeps/i386/dl-machine.h b/sysdeps/i386/dl-machine.h index 1afdcbd9ea..4d0afad074 100644 --- a/sysdeps/i386/dl-machine.h +++ b/sysdeps/i386/dl-machine.h @@ -68,7 +68,9 @@ elf_machine_runtime_setup (struct link_map *l, int lazy, int profile) extern void _dl_runtime_resolve (Elf32_Word) attribute_hidden; extern void _dl_runtime_profile (Elf32_Word) attribute_hidden; - if (l->l_info[DT_JMPREL] && lazy) + /* Always set up GOT since we may have to fall back to lazy binding + even with non-lazy binding is requested. */ + if (l->l_info[DT_JMPREL]) { /* The GOT entries for functions in the PLT have not yet been filled in. Their initial contents will arrange when called to push an @@ -332,16 +334,18 @@ elf_machine_rel (struct link_map *map, const Elf32_Rel *reloc, && sym_map->l_type != lt_executable && !sym_map->l_relocated) { - const char *strtab - = (const char *) D_PTR (map, l_info[DT_STRTAB]); - _dl_error_printf ("\ -%s: Relink `%s' with `%s' for IFUNC symbol `%s'\n", - RTLD_PROGNAME, map->l_name, - sym_map->l_name, - strtab + refsym->st_name); + /* NB: The symbol reference is resolved to IFUNC symbol + from a shared object which hasn't been relocated yet. + Relocate the GOT entry to enable lazy binding. */ + value = map->l_addr + *reloc_addr; + /* Disable RELRO so that the GOT entry can updated by lazy + binding later. */ + if (map->l_info[DT_BIND_NOW] != NULL) + map->l_relro_size = 0; } + else # endif - value = ((Elf32_Addr (*) (void)) value) (); + value = ((Elf32_Addr (*) (void)) value) (); } switch (r_type) diff --git a/sysdeps/x86_64/dl-machine.h b/sysdeps/x86_64/dl-machine.h index 1942ed5061..2aff922f96 100644 --- a/sysdeps/x86_64/dl-machine.h +++ b/sysdeps/x86_64/dl-machine.h @@ -73,7 +73,9 @@ elf_machine_runtime_setup (struct link_map *l, int lazy, int profile) extern void _dl_runtime_profile_avx (ElfW(Word)) attribute_hidden; extern void _dl_runtime_profile_avx512 (ElfW(Word)) attribute_hidden; - if (l->l_info[DT_JMPREL] && lazy) + /* Always set up GOT since we may have to fall back to lazy binding + even with non-lazy binding is requested. */ + if (l->l_info[DT_JMPREL]) { /* The GOT entries for functions in the PLT have not yet been filled in. Their initial contents will arrange when called to push an @@ -318,16 +320,18 @@ elf_machine_rela (struct link_map *map, const ElfW(Rela) *reloc, && sym_map->l_type != lt_executable && !sym_map->l_relocated) { - const char *strtab - = (const char *) D_PTR (map, l_info[DT_STRTAB]); - _dl_error_printf ("\ -%s: Relink `%s' with `%s' for IFUNC symbol `%s'\n", - RTLD_PROGNAME, map->l_name, - sym_map->l_name, - strtab + refsym->st_name); + /* NB: The symbol reference is resolved to IFUNC symbol + from a shared object which hasn't been relocated yet. + Relocate the GOT entry to enable lazy binding. */ + value = map->l_addr + *reloc_addr; + /* Disable RELRO so that the GOT entry can updated by lazy + binding later. */ + if (map->l_info[DT_BIND_NOW] != NULL) + map->l_relro_size = 0; } + else # endif - value = ((ElfW(Addr) (*) (void)) value) (); + value = ((ElfW(Addr) (*) (void)) value) (); } switch (r_type) -- 2.17.0 ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: RFC: x86: Fall back to lazy binding for unrelocated IFUNC symbol [BZ #23240] 2018-05-26 13:52 RFC: x86: Fall back to lazy binding for unrelocated IFUNC symbol [BZ #23240] H.J. Lu @ 2018-05-26 21:02 ` Florian Weimer 2018-05-27 14:36 ` H.J. Lu 0 siblings, 1 reply; 14+ messages in thread From: Florian Weimer @ 2018-05-26 21:02 UTC (permalink / raw) To: H.J. Lu; +Cc: GNU C Library On 05/26/2018 03:52 PM, H.J. Lu wrote: > + /* NB: The symbol reference is resolved to IFUNC symbol > + from a shared object which hasn't been relocated yet. > + Relocate the GOT entry to enable lazy binding. */ > + value = map->l_addr + *reloc_addr; > + /* Disable RELRO so that the GOT entry can updated by lazy > + binding later. */ > + if (map->l_info[DT_BIND_NOW] != NULL) > + map->l_relro_size = 0; People perceive BIND_NOW as a security feature. Silently disabling it in this way, perhaps due to an implementation change in another shared object, looks very wrong to me. Maybe you could share the *concrete* problem you are actually trying to solve? Thanks, Florian ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: RFC: x86: Fall back to lazy binding for unrelocated IFUNC symbol [BZ #23240] 2018-05-26 21:02 ` Florian Weimer @ 2018-05-27 14:36 ` H.J. Lu 2018-05-28 9:27 ` Florian Weimer 0 siblings, 1 reply; 14+ messages in thread From: H.J. Lu @ 2018-05-27 14:36 UTC (permalink / raw) To: Florian Weimer; +Cc: GNU C Library On Sat, May 26, 2018 at 2:02 PM, Florian Weimer <fweimer@redhat.com> wrote: > On 05/26/2018 03:52 PM, H.J. Lu wrote: >> >> + /* NB: The symbol reference is resolved to IFUNC symbol >> + from a shared object which hasn't been relocated yet. >> + Relocate the GOT entry to enable lazy binding. */ >> + value = map->l_addr + *reloc_addr; >> + /* Disable RELRO so that the GOT entry can updated by lazy >> + binding later. */ >> + if (map->l_info[DT_BIND_NOW] != NULL) >> + map->l_relro_size = 0; > > > People perceive BIND_NOW as a security feature. Silently disabling it in > this way, perhaps due to an implementation change in another shared object, > looks very wrong to me. Sounds reasonable/ > Maybe you could share the *concrete* problem you are actually trying to > solve? I am working on the CPU run-time library for C, which is on hjl/cpu-rt/master branch at https://github.com/hjl-tools/glibc The goal is to make the latest x86-64 string/memory functions in glibc available to the distros with older glibcs. libcpu-rt-c.so doesn't requre dynamic relocations and is binary compatible with all x86-64 libc.so. One can use # export LD_PRELOAD=..../libcpu-rt-c.so to use the latest x86-64 string/memory functions. But I got [hjl@gnu-cfl-1 cpu-rt-c]$ LD_PRELOAD=./libcpu-rt-c.so ls / ls: Relink `/lib64/libpthread.so.0' with `./libcpu-rt-c.so' for IFUNC symbol `strlen' ls: Relink `/lib64/libpthread.so.0' with `./libcpu-rt-c.so' for IFUNC symbol `strchr' ls: Relink `/lib64/libpthread.so.0' with `./libcpu-rt-c.so' for IFUNC symbol `memset' ls: Relink `/lib64/libpthread.so.0' with `./libcpu-rt-c.so' for IFUNC symbol `strcmp' ls: Relink `/lib64/libpthread.so.0' with `./libcpu-rt-c.so' for IFUNC symbol `memcpy' ls: Relink `/lib64/libdl.so.2' with `./libcpu-rt-c.so' for IFUNC symbol `strcpy' ls: Relink `/lib64/libpcre2-8.so.0' with `./libcpu-rt-c.so' for IFUNC symbol `strlen' ls: Relink `/lib64/libpcre2-8.so.0' with `./libcpu-rt-c.so' for IFUNC symbol `strchr' ls: Relink `/lib64/libpcre2-8.so.0' with `./libcpu-rt-c.so' for IFUNC symbol `memset' ls: Relink `/lib64/libpcre2-8.so.0' with `./libcpu-rt-c.so' for IFUNC symbol `memchr' ls: Relink `/lib64/libpcre2-8.so.0' with `./libcpu-rt-c.so' for IFUNC symbol `memcmp' ls: Relink `/lib64/libpcre2-8.so.0' with `./libcpu-rt-c.so' for IFUNC symbol `memcpy' ls: Relink `/lib64/libpcre2-8.so.0' with `./libcpu-rt-c.so' for IFUNC symbol `memmove' ls: Relink `/lib64/libcap.so.2' with `./libcpu-rt-c.so' for IFUNC symbol `strlen' ls: Relink `/lib64/libcap.so.2' with `./libcpu-rt-c.so' for IFUNC symbol `memset' ls: Relink `/lib64/libcap.so.2' with `./libcpu-rt-c.so' for IFUNC symbol `memcpy' ls: Relink `/lib64/libselinux.so.1' with `./libcpu-rt-c.so' for IFUNC symbol `strncpy' ls: Relink `/lib64/libselinux.so.1' with `./libcpu-rt-c.so' for IFUNC symbol `strncmp' ls: Relink `/lib64/libselinux.so.1' with `./libcpu-rt-c.so' for IFUNC symbol `strcpy' ls: Relink `/lib64/libselinux.so.1' with `./libcpu-rt-c.so' for IFUNC symbol `strlen' ls: Relink `/lib64/libselinux.so.1' with `./libcpu-rt-c.so' for IFUNC symbol `strchr' ls: Relink `/lib64/libselinux.so.1' with `./libcpu-rt-c.so' for IFUNC symbol `strrchr' ls: Relink `/lib64/libselinux.so.1' with `./libcpu-rt-c.so' for IFUNC symbol `memset' ls: Relink `/lib64/libselinux.so.1' with `./libcpu-rt-c.so' for IFUNC symbol `memcmp' ls: Relink `/lib64/libselinux.so.1' with `./libcpu-rt-c.so' for IFUNC symbol `strcmp' ls: Relink `/lib64/libselinux.so.1' with `./libcpu-rt-c.so' for IFUNC symbol `memcpy' bin dev export lib libx32 media mnt opt root sbin sys usr boot etc home lib64 lost+found misc net proc run srv tmp var [hjl@gnu-cfl-1 cpu-rt-c]$ I'd like to avoid these messages. -- H.J. ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: RFC: x86: Fall back to lazy binding for unrelocated IFUNC symbol [BZ #23240] 2018-05-27 14:36 ` H.J. Lu @ 2018-05-28 9:27 ` Florian Weimer 2018-05-28 13:46 ` Carlos O'Donell 0 siblings, 1 reply; 14+ messages in thread From: Florian Weimer @ 2018-05-28 9:27 UTC (permalink / raw) To: H.J. Lu; +Cc: GNU C Library On 05/27/2018 04:36 PM, H.J. Lu wrote: > I'd like to avoid these messages. We could restrict the warning to LD_DEBUG=bindings. Thanks, Florian ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: RFC: x86: Fall back to lazy binding for unrelocated IFUNC symbol [BZ #23240] 2018-05-28 9:27 ` Florian Weimer @ 2018-05-28 13:46 ` Carlos O'Donell 2018-05-28 19:51 ` H.J. Lu 0 siblings, 1 reply; 14+ messages in thread From: Carlos O'Donell @ 2018-05-28 13:46 UTC (permalink / raw) To: Florian Weimer, H.J. Lu; +Cc: GNU C Library On 05/28/2018 05:27 AM, Florian Weimer wrote: > On 05/27/2018 04:36 PM, H.J. Lu wrote: > >> I'd like to avoid these messages. > > We could restrict the warning to LD_DEBUG=bindings. I agree that this would be a better solution. Disabling BIND_NOW is the wrong thing to do in this case. However, isn't the *real* problem that we lack correct depth-first sorting based on relocation requirements? Could we fix this technically in the future by improving the dynamic loader? Keep in mind if you say "you can't solve circular dependencies" the answer is "We can. We are allowed to break them in any way we want." (which may still leave some applications broken at startup). Cheers, Carlos. ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: RFC: x86: Fall back to lazy binding for unrelocated IFUNC symbol [BZ #23240] 2018-05-28 13:46 ` Carlos O'Donell @ 2018-05-28 19:51 ` H.J. Lu 2018-06-05 19:25 ` Florian Weimer 0 siblings, 1 reply; 14+ messages in thread From: H.J. Lu @ 2018-05-28 19:51 UTC (permalink / raw) To: Carlos O'Donell; +Cc: Florian Weimer, GNU C Library [-- Attachment #1: Type: text/plain, Size: 474 bytes --] On Mon, May 28, 2018 at 6:45 AM, Carlos O'Donell <carlos@redhat.com> wrote: > On 05/28/2018 05:27 AM, Florian Weimer wrote: >> On 05/27/2018 04:36 PM, H.J. Lu wrote: >> >>> I'd like to avoid these messages. >> >> We could restrict the warning to LD_DEBUG=bindings. > > I agree that this would be a better solution. > > Disabling BIND_NOW is the wrong thing to do in this case. > Here is the updated patch. It fails to back lazy binding only if GOT is writable. -- H.J. [-- Attachment #2: 0001-x86-Fall-back-to-lazy-binding-if-possible.patch --] [-- Type: text/x-patch, Size: 14745 bytes --] From 8c7faa86f7c920c530a56100d7e2bbbe9c5b62e9 Mon Sep 17 00:00:00 2001 From: "H.J. Lu" <hjl.tools@gmail.com> Date: Sun, 27 May 2018 07:15:35 -0700 Subject: [PATCH] x86: Fall back to lazy binding if possible Since we can't call unrelocated IFUNC function to get the real function addresss, this patch falls back to lazy binding for unrelocated IFUNC symbol if lazy binding is possible. Also in case of unresolved weak reference in shared object which may be resolved later with lazy binding, this patch sets up lazy binding if lazy binding is possible. Tested on x86-64 and i686 with and without --enable-bind-now. [BZ #23176] [BZ #23240] * elf/Makefile (tests): Add reldep6a. (tests-internal): Add ifuncpreload1 (modules-names): Add ifuncpreloadmod1a and ifuncpreloadmod1b. ($(objpfx)reldep6a): New. ($(objpfx)reldep6a.out): Likewise. (reldep6a-ENV): Likewise. ($(objpfx)ifuncpreload1): Likewise. ($(objpfx)ifuncpreload1.out): Likewise. (ifuncpreload1-ENV): Likewise. * elf/ifuncpreload1.c: New file. * elf/ifuncpreloadmod1a.c: Likewise. * elf/ifuncpreloadmod1b.c: Likewise. * elf/reldep6a.c: Likewise. * sysdeps/i386/dl-machine.h (elf_machine_runtime_setup): Always set up GOT. (elf_machine_rel): Fall back to lazy binding for unrelocated IFUNC symbol and unresolved weak reference if possible. Issue IFUNC warning only for LD_DEBUG=bindings. * sysdeps/x86_64/dl-machine.h (elf_machine_runtime_setup): Always set up GOT. (elf_machine_rela): Fall back to lazy binding for unrelocated IFUNC symbol and unresolved weak reference in shared object if possible. Issue IFUNC warning only for LD_DEBUG=bindings. --- elf/Makefile | 18 ++++++++++--- elf/ifuncpreload1.c | 39 ++++++++++++++++++++++++++++ elf/ifuncpreloadmod1a.c | 23 ++++++++++++++++ elf/ifuncpreloadmod1b.c | 49 ++++++++++++++++++++++++++++++++++ elf/reldep6a.c | 1 + sysdeps/i386/dl-machine.h | 52 +++++++++++++++++++++++++++++++------ sysdeps/x86_64/dl-machine.h | 52 +++++++++++++++++++++++++++++++------ 7 files changed, 214 insertions(+), 20 deletions(-) create mode 100644 elf/ifuncpreload1.c create mode 100644 elf/ifuncpreloadmod1a.c create mode 100644 elf/ifuncpreloadmod1b.c create mode 100644 elf/reldep6a.c diff --git a/elf/Makefile b/elf/Makefile index 2dcd2b88e0..ee03d588eb 100644 --- a/elf/Makefile +++ b/elf/Makefile @@ -170,8 +170,8 @@ tests += restest1 preloadtest loadfail multiload origtest resolvfail \ constload1 order noload filter \ reldep reldep2 reldep3 reldep4 nodelete nodelete2 \ nodlopen nodlopen2 lateglobal initfirst global \ - restest2 next dblload dblunload reldep5 reldep6 reldep7 reldep8 \ - tst-tls4 tst-tls5 \ + restest2 next dblload dblunload reldep5 reldep6 reldep6a \ + reldep7 reldep8 tst-tls4 tst-tls5 \ tst-tls10 tst-tls11 tst-tls12 tst-tls13 tst-tls14 tst-tls15 \ tst-tls16 tst-tls17 tst-tls18 tst-tls19 tst-tls-dlinfo \ tst-align tst-align2 \ @@ -328,7 +328,7 @@ tests-internal += \ ifuncmain1staticpic \ ifuncmain2 ifuncmain2pic ifuncmain3 ifuncmain4 \ ifuncmain5 ifuncmain5pic ifuncmain5staticpic \ - ifuncmain7 ifuncmain7pic + ifuncmain7 ifuncmain7pic ifuncpreload1 ifunc-test-modules = ifuncdep1 ifuncdep1pic ifuncdep2 ifuncdep2pic \ ifuncdep5 ifuncdep5pic extra-test-objs += $(ifunc-test-modules:=.o) @@ -339,7 +339,8 @@ ifunc-pie-tests = ifuncmain1pie ifuncmain1vispie ifuncmain1staticpie \ tests-internal += $(ifunc-pie-tests) tests-pie += $(ifunc-pie-tests) endif -modules-names += ifuncmod1 ifuncmod3 ifuncmod5 ifuncmod6 +modules-names += ifuncmod1 ifuncmod3 ifuncmod5 ifuncmod6 \ + ifuncpreloadmod1a ifuncpreloadmod1b endif endif @@ -885,6 +886,10 @@ $(objpfx)reldep5.out: $(objpfx)reldepmod5.so $(objpfx)reldepmod6.so $(objpfx)reldep6: $(libdl) $(objpfx)reldep6.out: $(objpfx)reldep6mod3.so $(objpfx)reldep6mod4.so +$(objpfx)reldep6a: $(libdl) +$(objpfx)reldep6a.out: $(objpfx)reldep6mod3.so $(objpfx)reldep6mod4.so +reldep6a-ENV = LD_BIND_NOW=1 + $(objpfx)reldep7: $(libdl) $(objpfx)reldep7.out: $(objpfx)reldep7mod1.so $(objpfx)reldep7mod2.so @@ -1454,3 +1459,8 @@ tst-libc_dlvsym-static-ENV = \ $(objpfx)tst-libc_dlvsym-static.out: $(objpfx)tst-libc_dlvsym-dso.so $(objpfx)tst-big-note: $(objpfx)tst-big-note-lib.so + +$(objpfx)ifuncpreload1: $(objpfx)ifuncpreloadmod1a.so +$(objpfx)ifuncpreload1.out: $(objpfx)ifuncpreloadmod1b.so +ifuncpreload1-ENV = \ + LD_PRELOAD=$(objpfx)ifuncpreloadmod1b.so LD_BIND_NOW=1 diff --git a/elf/ifuncpreload1.c b/elf/ifuncpreload1.c new file mode 100644 index 0000000000..172df33ac3 --- /dev/null +++ b/elf/ifuncpreload1.c @@ -0,0 +1,39 @@ +/* Test for relocation over with IFUNC symbols. + Copyright (C) 2018 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 + <http://www.gnu.org/licenses/>. */ + +#include <support/check.h> +#include <support/support.h> +#include <support/test-driver.h> + +extern void bar (char *, const char *, unsigned int); + +static int +do_test (void) +{ + char dst[50]; + const char src[] = + { + "This is a test" + }; + bar (dst, src, sizeof (src)); + if (__builtin_memcmp (dst, src, sizeof (src)) != 0) + __builtin_abort (); + return 0; +} + +#include <support/test-driver.c> diff --git a/elf/ifuncpreloadmod1a.c b/elf/ifuncpreloadmod1a.c new file mode 100644 index 0000000000..be9f8832b8 --- /dev/null +++ b/elf/ifuncpreloadmod1a.c @@ -0,0 +1,23 @@ +/* Shared module to test for relocation over with IFUNC symbols. + Copyright (C) 2018 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 + <http://www.gnu.org/licenses/>. */ + +void +bar (char *dst, const char *src, unsigned int size) +{ + __builtin_memmove (dst, src, size); +} diff --git a/elf/ifuncpreloadmod1b.c b/elf/ifuncpreloadmod1b.c new file mode 100644 index 0000000000..1194ae20e4 --- /dev/null +++ b/elf/ifuncpreloadmod1b.c @@ -0,0 +1,49 @@ +/* Shared module to test for relocation over with IFUNC symbols. + Copyright (C) 2018 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 + <http://www.gnu.org/licenses/>. */ + +#include <stddef.h> + +void * +my_memmove(void *dst_p, const void *src_p, size_t n) +{ + const char *src = src_p; + char *dst = dst_p; + char *ret = dst; + if (src < dst) + { + dst += n; + src += n; + while (n--) + *--dst = *--src; + } + else + while (n--) + *dst++ = *src++; + return ret; +} + +void *memmove (void *, const void *, size_t) + __attribute__ ((ifunc ("resolve_memmove"))); + +typedef void *(*memmove_t) (void *, const void *, size_t); + +static memmove_t +resolve_memmove (void) +{ + return my_memmove; +} diff --git a/elf/reldep6a.c b/elf/reldep6a.c new file mode 100644 index 0000000000..28ed7008fa --- /dev/null +++ b/elf/reldep6a.c @@ -0,0 +1 @@ +#include "reldep6.c" diff --git a/sysdeps/i386/dl-machine.h b/sysdeps/i386/dl-machine.h index 1afdcbd9ea..d5abd6c7dc 100644 --- a/sysdeps/i386/dl-machine.h +++ b/sysdeps/i386/dl-machine.h @@ -68,7 +68,12 @@ elf_machine_runtime_setup (struct link_map *l, int lazy, int profile) extern void _dl_runtime_resolve (Elf32_Word) attribute_hidden; extern void _dl_runtime_profile (Elf32_Word) attribute_hidden; - if (l->l_info[DT_JMPREL] && lazy) + /* Set up GOT if lazy binding is allowed since we may have to fall + back to lazy binding even with non-lazy binding is requested. */ + if (l->l_info[DT_JMPREL] + && (lazy + || l->l_relro_size == 0 + || l->l_info[DT_BIND_NOW] == NULL)) { /* The GOT entries for functions in the PLT have not yet been filled in. Their initial contents will arrange when called to push an @@ -332,16 +337,31 @@ elf_machine_rel (struct link_map *map, const Elf32_Rel *reloc, && sym_map->l_type != lt_executable && !sym_map->l_relocated) { - const char *strtab - = (const char *) D_PTR (map, l_info[DT_STRTAB]); - _dl_error_printf ("\ + /* NB: The symbol reference is resolved to IFUNC symbol + from an unrelocated shared object. Relocate the GOT + entry to enable lazy binding. Issue a warning if lazy + binding isn't possible or GOT will be made read-only + after shared objects have been relocated. */ + if (r_type == R_386_JMP_SLOT + && ((Elf32_Addr *) D_PTR (map, + l_info[DT_PLTGOT]))[2] != 0) + value = map->l_addr + *reloc_addr; + else if (__glibc_unlikely (GLRO(dl_debug_mask) + & (DL_DEBUG_BINDINGS|DL_DEBUG_PRELINK))) + { + const char *strtab + = (const char *) D_PTR (map, l_info[DT_STRTAB]); + _dl_error_printf ("\ %s: Relink `%s' with `%s' for IFUNC symbol `%s'\n", - RTLD_PROGNAME, map->l_name, - sym_map->l_name, - strtab + refsym->st_name); + RTLD_PROGNAME, map->l_name, + sym_map->l_name, + strtab + refsym->st_name); + value = ((Elf32_Addr (*) (void)) value) (); + } } + else # endif - value = ((Elf32_Addr (*) (void)) value) (); + value = ((Elf32_Addr (*) (void)) value) (); } switch (r_type) @@ -353,7 +373,23 @@ elf_machine_rel (struct link_map *map, const Elf32_Rel *reloc, break; # endif case R_386_GLOB_DAT: +# ifdef RTLD_BOOTSTRAP + case R_386_JMP_SLOT: +# endif + *reloc_addr = value; + break; +# ifndef RTLD_BOOTSTRAP case R_386_JMP_SLOT: + /* NB: If a weak symbol reference in shared object isn't + resolved, relocate the GOT entry to enable lazy binding + if possible. */ + if (sym_map == NULL + && map->l_type != lt_executable + && ELF32_ST_BIND (refsym->st_info) == STB_WEAK + && ((Elf32_Addr *) D_PTR (map, + l_info[DT_PLTGOT]))[2] != 0) + value = map->l_addr + *reloc_addr; +# endif *reloc_addr = value; break; diff --git a/sysdeps/x86_64/dl-machine.h b/sysdeps/x86_64/dl-machine.h index 1942ed5061..cf094aa03a 100644 --- a/sysdeps/x86_64/dl-machine.h +++ b/sysdeps/x86_64/dl-machine.h @@ -73,7 +73,12 @@ elf_machine_runtime_setup (struct link_map *l, int lazy, int profile) extern void _dl_runtime_profile_avx (ElfW(Word)) attribute_hidden; extern void _dl_runtime_profile_avx512 (ElfW(Word)) attribute_hidden; - if (l->l_info[DT_JMPREL] && lazy) + /* Set up GOT if lazy binding is allowed since we may have to fall + back to lazy binding even with non-lazy binding is requested. */ + if (l->l_info[DT_JMPREL] + && (lazy + || l->l_relro_size == 0 + || l->l_info[DT_BIND_NOW] == NULL)) { /* The GOT entries for functions in the PLT have not yet been filled in. Their initial contents will arrange when called to push an @@ -318,16 +323,31 @@ elf_machine_rela (struct link_map *map, const ElfW(Rela) *reloc, && sym_map->l_type != lt_executable && !sym_map->l_relocated) { - const char *strtab - = (const char *) D_PTR (map, l_info[DT_STRTAB]); - _dl_error_printf ("\ + /* NB: The symbol reference is resolved to IFUNC symbol + from an unrelocated shared object. Relocate the GOT + entry to enable lazy binding. Issue a warning if lazy + binding isn't possible or GOT will be made read-only + after shared objects have been relocated. */ + if (r_type == R_X86_64_JUMP_SLOT + && ((ElfW(Addr) *) D_PTR (map, + l_info[DT_PLTGOT]))[2] != 0) + value = map->l_addr + *reloc_addr; + else if (__glibc_unlikely (GLRO(dl_debug_mask) + & (DL_DEBUG_BINDINGS|DL_DEBUG_PRELINK))) + { + const char *strtab + = (const char *) D_PTR (map, l_info[DT_STRTAB]); + _dl_error_printf ("\ %s: Relink `%s' with `%s' for IFUNC symbol `%s'\n", - RTLD_PROGNAME, map->l_name, - sym_map->l_name, - strtab + refsym->st_name); + RTLD_PROGNAME, map->l_name, + sym_map->l_name, + strtab + refsym->st_name); + value = ((ElfW(Addr) (*) (void)) value) (); + } } + else # endif - value = ((ElfW(Addr) (*) (void)) value) (); + value = ((ElfW(Addr) (*) (void)) value) (); } switch (r_type) @@ -348,7 +368,23 @@ elf_machine_rela (struct link_map *map, const ElfW(Rela) *reloc, value = sym->st_size; # endif case R_X86_64_GLOB_DAT: +# ifdef RTLD_BOOTSTRAP + case R_X86_64_JUMP_SLOT: +# endif + *reloc_addr = value + reloc->r_addend; + break; +# ifndef RTLD_BOOTSTRAP case R_X86_64_JUMP_SLOT: + /* NB: If a weak symbol reference in shared object isn't + resolved, relocate the GOT entry to enable lazy binding + if possible. */ + if (sym_map == NULL + && map->l_type != lt_executable + && ELFW(ST_BIND) (refsym->st_info) == STB_WEAK + && ((ElfW(Addr) *) D_PTR (map, + l_info[DT_PLTGOT]))[2] != 0) + value = map->l_addr + *reloc_addr; +# endif *reloc_addr = value + reloc->r_addend; break; -- 2.17.0 ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: RFC: x86: Fall back to lazy binding for unrelocated IFUNC symbol [BZ #23240] 2018-05-28 19:51 ` H.J. Lu @ 2018-06-05 19:25 ` Florian Weimer 2018-06-06 14:04 ` Florian Weimer 0 siblings, 1 reply; 14+ messages in thread From: Florian Weimer @ 2018-06-05 19:25 UTC (permalink / raw) To: H.J. Lu, Carlos O'Donell; +Cc: GNU C Library On 05/28/2018 09:51 PM, H.J. Lu wrote: > Here is the updated patch. It fails to back lazy binding only > if GOT is writable. I think this still sets a wrong incentive, as in “you need to have a writable GOT for full forwards compatibility with future library evolutionâ€. I think if we detect an IFUNC-based relocation against a not-yet-fully-relocated object, we need to delay this relocation processing and perform a second pass of all delayed relocations. I have a patch which needs a little bit of work, but looks quite promising (to me at least). Thanks, Florian ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: RFC: x86: Fall back to lazy binding for unrelocated IFUNC symbol [BZ #23240] 2018-06-05 19:25 ` Florian Weimer @ 2018-06-06 14:04 ` Florian Weimer 2018-06-06 14:50 ` H.J. Lu 0 siblings, 1 reply; 14+ messages in thread From: Florian Weimer @ 2018-06-06 14:04 UTC (permalink / raw) To: H.J. Lu, Carlos O'Donell; +Cc: GNU C Library On 06/05/2018 09:24 PM, Florian Weimer wrote: > On 05/28/2018 09:51 PM, H.J. Lu wrote: >> Here is the updated patch. It fails to back lazy binding only >> if GOT is writable. > > I think this still sets a wrong incentive, as in “you need to have a > writable GOT for full forwards compatibility with future library > evolutionâ€. > > I think if we detect an IFUNC-based relocation against a > not-yet-fully-relocated object, we need to delay this relocation > processing and perform a second pass of all delayed relocations. I have > a patch which needs a little bit of work, but looks quite promising (to > me at least). Here are my patches: https://sourceware.org/ml/libc-alpha/2018-06/msg00076.html https://sourceware.org/ml/libc-alpha/2018-06/msg00077.html I hope they address your needs. Thanks, Florian ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: RFC: x86: Fall back to lazy binding for unrelocated IFUNC symbol [BZ #23240] 2018-06-06 14:04 ` Florian Weimer @ 2018-06-06 14:50 ` H.J. Lu 2018-06-06 14:54 ` Florian Weimer 0 siblings, 1 reply; 14+ messages in thread From: H.J. Lu @ 2018-06-06 14:50 UTC (permalink / raw) To: Florian Weimer; +Cc: Carlos O'Donell, GNU C Library On Wed, Jun 6, 2018 at 7:04 AM, Florian Weimer <fweimer@redhat.com> wrote: > On 06/05/2018 09:24 PM, Florian Weimer wrote: >> >> On 05/28/2018 09:51 PM, H.J. Lu wrote: >>> >>> Here is the updated patch. It fails to back lazy binding only >>> if GOT is writable. >> >> >> I think this still sets a wrong incentive, as in “you need to have a >> writable GOT for full forwards compatibility with future library evolution”. >> >> I think if we detect an IFUNC-based relocation against a >> not-yet-fully-relocated object, we need to delay this relocation processing >> and perform a second pass of all delayed relocations. I have a patch which >> needs a little bit of work, but looks quite promising (to me at least). > > > Here are my patches: > > https://sourceware.org/ml/libc-alpha/2018-06/msg00076.html > https://sourceware.org/ml/libc-alpha/2018-06/msg00077.html > > I hope they address your needs. Do you have a git branch I can use? -- H.J. ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: RFC: x86: Fall back to lazy binding for unrelocated IFUNC symbol [BZ #23240] 2018-06-06 14:50 ` H.J. Lu @ 2018-06-06 14:54 ` Florian Weimer 2018-06-06 15:38 ` H.J. Lu 0 siblings, 1 reply; 14+ messages in thread From: Florian Weimer @ 2018-06-06 14:54 UTC (permalink / raw) To: H.J. Lu; +Cc: Carlos O'Donell, GNU C Library On 06/06/2018 04:50 PM, H.J. Lu wrote: > On Wed, Jun 6, 2018 at 7:04 AM, Florian Weimer <fweimer@redhat.com> wrote: >> On 06/05/2018 09:24 PM, Florian Weimer wrote: >>> >>> On 05/28/2018 09:51 PM, H.J. Lu wrote: >>>> >>>> Here is the updated patch. It fails to back lazy binding only >>>> if GOT is writable. >>> >>> >>> I think this still sets a wrong incentive, as in “you need to have a >>> writable GOT for full forwards compatibility with future library evolutionâ€. >>> >>> I think if we detect an IFUNC-based relocation against a >>> not-yet-fully-relocated object, we need to delay this relocation processing >>> and perform a second pass of all delayed relocations. I have a patch which >>> needs a little bit of work, but looks quite promising (to me at least). >> >> >> Here are my patches: >> >> https://sourceware.org/ml/libc-alpha/2018-06/msg00076.html >> https://sourceware.org/ml/libc-alpha/2018-06/msg00077.html >> >> I hope they address your needs. > > Do you have a git branch I can use? I've pushed it to fw/bug21242. Florian ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: RFC: x86: Fall back to lazy binding for unrelocated IFUNC symbol [BZ #23240] 2018-06-06 14:54 ` Florian Weimer @ 2018-06-06 15:38 ` H.J. Lu 2018-06-06 15:53 ` Florian Weimer 0 siblings, 1 reply; 14+ messages in thread From: H.J. Lu @ 2018-06-06 15:38 UTC (permalink / raw) To: Florian Weimer; +Cc: Carlos O'Donell, GNU C Library On Wed, Jun 6, 2018 at 7:54 AM, Florian Weimer <fweimer@redhat.com> wrote: > On 06/06/2018 04:50 PM, H.J. Lu wrote: >> >> On Wed, Jun 6, 2018 at 7:04 AM, Florian Weimer <fweimer@redhat.com> wrote: >>> >>> On 06/05/2018 09:24 PM, Florian Weimer wrote: >>>> >>>> >>>> On 05/28/2018 09:51 PM, H.J. Lu wrote: >>>>> >>>>> >>>>> Here is the updated patch. It fails to back lazy binding only >>>>> if GOT is writable. >>>> >>>> >>>> >>>> I think this still sets a wrong incentive, as in “you need to have a >>>> writable GOT for full forwards compatibility with future library >>>> evolution”. >>>> >>>> I think if we detect an IFUNC-based relocation against a >>>> not-yet-fully-relocated object, we need to delay this relocation >>>> processing >>>> and perform a second pass of all delayed relocations. I have a patch >>>> which >>>> needs a little bit of work, but looks quite promising (to me at least). >>> >>> >>> >>> Here are my patches: >>> >>> https://sourceware.org/ml/libc-alpha/2018-06/msg00076.html >>> https://sourceware.org/ml/libc-alpha/2018-06/msg00077.html >>> >>> I hope they address your needs. >> >> >> Do you have a git branch I can use? > > > I've pushed it to fw/bug21242. > I pushed hjl/pr23240/fw, which is fw/bug21242 + tests for [BZ #23176] and [BZ #23240]. 1. On x86-64: FAIL: elf/reldep6a 2. On i686: FAIL: elf/ifuncpreload1 FAIL: elf/reldep6a So your patches didn't fix: 1,. IFUNC on i686. 2. Weak reference. -- H.J. ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: RFC: x86: Fall back to lazy binding for unrelocated IFUNC symbol [BZ #23240] 2018-06-06 15:38 ` H.J. Lu @ 2018-06-06 15:53 ` Florian Weimer 2018-06-06 16:10 ` H.J. Lu 0 siblings, 1 reply; 14+ messages in thread From: Florian Weimer @ 2018-06-06 15:53 UTC (permalink / raw) To: H.J. Lu; +Cc: Carlos O'Donell, GNU C Library On 06/06/2018 05:38 PM, H.J. Lu wrote: > I pushed hjl/pr23240/fw, which is fw/bug21242 + tests for [BZ #23176] and > [BZ #23240]. > > 1. On x86-64: > > FAIL: elf/reldep6a The crash happens because “weak†is undefined in reldep6mod1.so. The “weak†function is defined in reldep6mod4.so. But reldep6mod1.so is loaded before reldep6mod4.so: 14289: calling init: /home/fweimer/src/gnu/glibc/build/elf/reldep6mod1.so … 14289: opening file=/home/fweimer/src/gnu/glibc/build/elf/reldep6mod4.so [0]; direct_opencount=1 14289: 14289: binding file /home/fweimer/src/gnu/glibc/build/elf/reldep6mod4.so [0] to /home/fweimer/src/gnu/glibc/build/elf/reldep6mod1.so [0]: normal symbol `baz' I think this is simply invalid. I think that if you had a “weak == NULL†check in reldep6mod1.so, it would be false even after loading reldep6mod4.so because the address is not lazily bound. Is this derived from the X server use case, where they load additional DSOs which provide definitions of functions which are lazily bound? That's just not compatible with BIND_NOW, and I don't see a compelling reason why it should be. If it's just about fixing X, then we need to fix X, and not enhance the dynamic linker. > 2. On i686: > > FAIL: elf/ifuncpreload1 > FAIL: elf/reldep6a There's no delayed processing for i686 yet. I wanted to get consensus on the overall approach first. Thanks, Florian ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: RFC: x86: Fall back to lazy binding for unrelocated IFUNC symbol [BZ #23240] 2018-06-06 15:53 ` Florian Weimer @ 2018-06-06 16:10 ` H.J. Lu 2018-06-06 17:31 ` Florian Weimer 0 siblings, 1 reply; 14+ messages in thread From: H.J. Lu @ 2018-06-06 16:10 UTC (permalink / raw) To: Florian Weimer; +Cc: Carlos O'Donell, GNU C Library On Wed, Jun 6, 2018 at 8:53 AM, Florian Weimer <fweimer@redhat.com> wrote: > On 06/06/2018 05:38 PM, H.J. Lu wrote: >> >> I pushed hjl/pr23240/fw, which is fw/bug21242 + tests for [BZ #23176] and >> [BZ #23240]. >> >> 1. On x86-64: >> >> FAIL: elf/reldep6a > > > The crash happens because “weak” is undefined in reldep6mod1.so. > > The “weak” function is defined in reldep6mod4.so. But reldep6mod1.so is > loaded before reldep6mod4.so: > > 14289: calling init: > /home/fweimer/src/gnu/glibc/build/elf/reldep6mod1.so > … > 14289: opening > file=/home/fweimer/src/gnu/glibc/build/elf/reldep6mod4.so [0]; > direct_opencount=1 > 14289: > 14289: binding file > /home/fweimer/src/gnu/glibc/build/elf/reldep6mod4.so [0] to > /home/fweimer/src/gnu/glibc/build/elf/reldep6mod1.so [0]: normal symbol > `baz' > > I think this is simply invalid. I think that if you had a “weak == NULL” > check in reldep6mod1.so, it would be false even after loading reldep6mod4.so > because the address is not lazily bound. > > Is this derived from the X server use case, where they load additional DSOs No idea. It is in elf. > which provide definitions of functions which are lazily bound? That's just > not compatible with BIND_NOW, and I don't see a compelling reason why it > should be. If it's just about fixing X, then we need to fix X, and not > enhance the dynamic linker. > >> 2. On i686: >> >> FAIL: elf/ifuncpreload1 >> FAIL: elf/reldep6a > > > There's no delayed processing for i686 yet. I wanted to get consensus on > the overall approach first. > > Thanks, > Florian -- H.J. ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: RFC: x86: Fall back to lazy binding for unrelocated IFUNC symbol [BZ #23240] 2018-06-06 16:10 ` H.J. Lu @ 2018-06-06 17:31 ` Florian Weimer 0 siblings, 0 replies; 14+ messages in thread From: Florian Weimer @ 2018-06-06 17:31 UTC (permalink / raw) To: H.J. Lu; +Cc: Carlos O'Donell, GNU C Library On 06/06/2018 06:10 PM, H.J. Lu wrote: >> Is this derived from the X server use case, where they load additional DSOs > > No idea. It is in elf. So you have just run the elf testsuite with LD_BIND_NOW=1 and filed a bug because the test failed? I'm not sure if such purely synthetic test cases make sense. If you want to get rid of lazy binding, you should concentrate on actual issues in the GNU system (such as the X issue I mentioned). Thanks, Florian ^ permalink raw reply [flat|nested] 14+ messages in thread
end of thread, other threads:[~2018-06-06 17:31 UTC | newest] Thread overview: 14+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2018-05-26 13:52 RFC: x86: Fall back to lazy binding for unrelocated IFUNC symbol [BZ #23240] H.J. Lu 2018-05-26 21:02 ` Florian Weimer 2018-05-27 14:36 ` H.J. Lu 2018-05-28 9:27 ` Florian Weimer 2018-05-28 13:46 ` Carlos O'Donell 2018-05-28 19:51 ` H.J. Lu 2018-06-05 19:25 ` Florian Weimer 2018-06-06 14:04 ` Florian Weimer 2018-06-06 14:50 ` H.J. Lu 2018-06-06 14:54 ` Florian Weimer 2018-06-06 15:38 ` H.J. Lu 2018-06-06 15:53 ` Florian Weimer 2018-06-06 16:10 ` H.J. Lu 2018-06-06 17:31 ` Florian Weimer
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).