From: "H.J. Lu" <hjl.tools@gmail.com>
To: Binutils <binutils@sourceware.org>,
Nick Clifton <nickc@redhat.com>, Alan Modra <amodra@gmail.com>
Subject: PING: [PATCH v3] elf: Always honor the first definition in shared object and archive
Date: Thu, 28 Mar 2024 06:30:43 -0700 [thread overview]
Message-ID: <CAMe9rOoujzXdDr0EMW5Ze5D-SN6vXaTRmfk4HGxDLXKgcEK-uA@mail.gmail.com> (raw)
In-Reply-To: <20240315194350.2697266-1-hjl.tools@gmail.com>
On Fri, Mar 15, 2024 at 12:43 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> GCC doesn't put builtin function symbol references, which are defined in
> the shared C library, in the IR symbol table. When linker rescans shared
> objects and archives for newly added symbol references generated from the
> IR inputs, it skips definitions of the builtin functions in shared
> objects and archives.
>
> Add first_hash to elf_link_hash_table to track unreferenced definitions
> defined first in shared objects and archives. Always use them to resolve
> any references.
>
> bfd/
>
> PR ld/31482
> PR ld/31489
> * elf-bfd.h (elf_link_hash_table): Add first_hash.
> * elflink.c (elf_link_add_object_symbols): Initialize first_hash
> for an IR input. Always use the first definition in shared
> object. Add the first unreferenced dynamic definition to
> first_hash.
> (_bfd_elf_archive_symbol_lookup): Add the first unreferenced
> definition to first_hash..
> (elf_link_add_archive_symbols): Use the symbol definition in
> archive if symbol is defined first in this archive.
> (_bfd_elf_link_hash_table_free): Also free first_hash.
>
> ld/
>
> PR ld/31482
> PR ld/31489
> * testsuite/ld-plugin/lto.exp: Add PR ld/31482 and PR ld/31489
> tests.
> * testsuite/ld-elf/pr31482a-no-lto.c: New file.
> * testsuite/ld-elf/pr31482b-no-lto.c: Likewise.
> * testsuite/ld-elf/pr31482c-no-lto.c: Likewise.
> * testsuite/ld-elf/pr31482d-no-lto.c: Likewise.
> * testsuite/ld-plugin/pass1.out: Likewise.
> * testsuite/ld-plugin/pr31482a.c: Likewise.
> * testsuite/ld-plugin/pr31482b.c: Likewise.
> * testsuite/ld-plugin/pr31482c.c: Likewise.
> ---
> bfd/elf-bfd.h | 4 +
> bfd/elflink.c | 171 ++++++++++++++++++++------
> ld/testsuite/ld-elf/pr31482a-no-lto.c | 8 ++
> ld/testsuite/ld-elf/pr31482b-no-lto.c | 10 ++
> ld/testsuite/ld-elf/pr31482c-no-lto.c | 15 +++
> ld/testsuite/ld-elf/pr31482d-no-lto.c | 9 ++
> ld/testsuite/ld-elf/shared.exp | 36 ++++++
> ld/testsuite/ld-plugin/lto.exp | 32 +++++
> ld/testsuite/ld-plugin/pass1.out | 1 +
> ld/testsuite/ld-plugin/pr31482a.c | 8 ++
> ld/testsuite/ld-plugin/pr31482b.c | 9 ++
> ld/testsuite/ld-plugin/pr31482c.c | 9 ++
> 12 files changed, 275 insertions(+), 37 deletions(-)
> create mode 100644 ld/testsuite/ld-elf/pr31482a-no-lto.c
> create mode 100644 ld/testsuite/ld-elf/pr31482b-no-lto.c
> create mode 100644 ld/testsuite/ld-elf/pr31482c-no-lto.c
> create mode 100644 ld/testsuite/ld-elf/pr31482d-no-lto.c
> create mode 100644 ld/testsuite/ld-plugin/pass1.out
> create mode 100644 ld/testsuite/ld-plugin/pr31482a.c
> create mode 100644 ld/testsuite/ld-plugin/pr31482b.c
> create mode 100644 ld/testsuite/ld-plugin/pr31482c.c
>
> diff --git a/bfd/elf-bfd.h b/bfd/elf-bfd.h
> index c5d325435b6..034afa65593 100644
> --- a/bfd/elf-bfd.h
> +++ b/bfd/elf-bfd.h
> @@ -737,6 +737,10 @@ struct elf_link_hash_table
> /* Small local sym cache. */
> struct sym_cache sym_cache;
>
> + /* Hash table of symbols which are first defined in archives or shared
> + objects when there are any IR inputs. */
> + struct bfd_link_hash_table *first_hash;
> +
> /* Short-cuts to get to dynamic linker sections. */
> asection *sgot;
> asection *sgotplt;
> diff --git a/bfd/elflink.c b/bfd/elflink.c
> index 5a6cb07b2ce..797ba8231f0 100644
> --- a/bfd/elflink.c
> +++ b/bfd/elflink.c
> @@ -4265,7 +4265,22 @@ elf_link_add_object_symbols (bfd *abfd, struct bfd_link_info *info)
> }
>
> if ((abfd->flags & DYNAMIC) == 0)
> - dynamic = false;
> + {
> + dynamic = false;
> + if ((abfd->flags & BFD_PLUGIN) != 0
> + && is_elf_hash_table (&htab->root)
> + && htab->first_hash == NULL)
> + {
> + /* Initialize first_hash for an IR input. */
> + htab->first_hash = (struct bfd_link_hash_table *)
> + xmalloc (sizeof (struct bfd_link_hash_table));
> + if (!bfd_hash_table_init (&htab->first_hash->table,
> + _bfd_link_hash_newfunc,
> + sizeof (struct bfd_link_hash_entry)))
> + info->callbacks->einfo
> + (_("%F%P: first_hash failed to initialize: %E\n"));
> + }
> + }
> else
> {
> dynamic = true;
> @@ -5118,16 +5133,31 @@ elf_link_add_object_symbols (bfd *abfd, struct bfd_link_info *info)
> if (skip)
> continue;
>
> - /* Override a definition only if the new symbol matches the
> - existing one. */
> - if (override && matched)
> - definition = false;
> -
> h = *sym_hash;
> while (h->root.type == bfd_link_hash_indirect
> || h->root.type == bfd_link_hash_warning)
> h = (struct elf_link_hash_entry *) h->root.u.i.link;
>
> + /* Override a definition only if the new symbol matches the
> + existing one. */
> + if (override && matched)
> + {
> + definition = false;
> + if (htab->first_hash != NULL
> + && (elf_dyn_lib_class (abfd) & DYN_AS_NEEDED) != 0
> + && h->root.non_ir_ref_regular)
> + {
> + /* When reloading --as-needed shared objects for new
> + symbols added from IR inputs, if this shared object
> + has the first definition, use it. */
> + struct bfd_link_hash_entry *e
> + = bfd_link_hash_lookup (htab->first_hash, name,
> + false, false, true);
> + if (e != NULL && e->u.undef.abfd == abfd)
> + definition = true;
> + }
> + }
> +
> if (h->versioned != unversioned
> && elf_tdata (abfd)->verdef != NULL
> && vernum > 1
> @@ -5477,8 +5507,9 @@ elf_link_add_object_symbols (bfd *abfd, struct bfd_link_info *info)
> if (!add_needed
> && matched
> && definition
> - && h->root.type != bfd_link_hash_indirect
> - && ((dynsym
> + && h->root.type != bfd_link_hash_indirect)
> + {
> + if ((dynsym
> && h->ref_regular_nonweak)
> || (old_bfd != NULL
> && (old_bfd->flags & BFD_PLUGIN) != 0
> @@ -5487,37 +5518,60 @@ elf_link_add_object_symbols (bfd *abfd, struct bfd_link_info *info)
> || (h->ref_dynamic_nonweak
> && (elf_dyn_lib_class (abfd) & DYN_AS_NEEDED) != 0
> && !on_needed_list (elf_dt_name (abfd),
> - htab->needed, NULL))))
> - {
> - const char *soname = elf_dt_name (abfd);
> + htab->needed, NULL)))
> + {
> + const char *soname = elf_dt_name (abfd);
> +
> + info->callbacks->minfo ("%!", soname, old_bfd,
> + h->root.root.string);
> +
> + /* A symbol from a library loaded via DT_NEEDED of some
> + other library is referenced by a regular object.
> + Add a DT_NEEDED entry for it. Issue an error if
> + --no-add-needed is used and the reference was not
> + a weak one. */
> + if (old_bfd != NULL
> + && (elf_dyn_lib_class (abfd) & DYN_NO_NEEDED) != 0)
> + {
> + _bfd_error_handler
> + /* xgettext:c-format */
> + (_("%pB: undefined reference to symbol '%s'"),
> + old_bfd, name);
> + bfd_set_error (bfd_error_missing_dso);
> + goto error_free_vers;
> + }
>
> - info->callbacks->minfo ("%!", soname, old_bfd,
> - h->root.root.string);
> + elf_dyn_lib_class (abfd) = (enum dynamic_lib_link_class)
> + (elf_dyn_lib_class (abfd) & ~DYN_AS_NEEDED);
>
> - /* A symbol from a library loaded via DT_NEEDED of some
> - other library is referenced by a regular object.
> - Add a DT_NEEDED entry for it. Issue an error if
> - --no-add-needed is used and the reference was not
> - a weak one. */
> - if (old_bfd != NULL
> - && (elf_dyn_lib_class (abfd) & DYN_NO_NEEDED) != 0)
> - {
> - _bfd_error_handler
> - /* xgettext:c-format */
> - (_("%pB: undefined reference to symbol '%s'"),
> - old_bfd, name);
> - bfd_set_error (bfd_error_missing_dso);
> - goto error_free_vers;
> + /* Create dynamic sections for backends that require
> + that be done before setup_gnu_properties. */
> + if (!_bfd_elf_link_create_dynamic_sections (abfd, info))
> + return false;
> + add_needed = true;
> }
> + else if (dynamic
> + && htab->first_hash != NULL
> + && h->root.u.def.section->owner == abfd)
> + {
> + /* Add this symbol to first hash if this shared
> + object has the first definition. */
> + struct bfd_link_hash_entry *e
> + = bfd_link_hash_lookup (htab->first_hash, name, true,
> + false, true);
> + if (e == NULL)
> + info->callbacks->einfo
> + (_("%F%P: %pB: failed to add %s to first hash\n"),
> + abfd, name);
>
> - elf_dyn_lib_class (abfd) = (enum dynamic_lib_link_class)
> - (elf_dyn_lib_class (abfd) & ~DYN_AS_NEEDED);
> -
> - /* Create dynamic sections for backends that require
> - that be done before setup_gnu_properties. */
> - if (!_bfd_elf_link_create_dynamic_sections (abfd, info))
> - return false;
> - add_needed = true;
> + if (e->type == bfd_link_hash_new)
> + {
> + /* Change the type to bfd_link_hash_defined and
> + store ABFD in u.undef->abfd. */
> + e->type = bfd_link_hash_defined;
> + e->u.undef.abfd = abfd;
> + }
> + }
> }
> }
> }
> @@ -5963,7 +6017,30 @@ _bfd_elf_archive_symbol_lookup (bfd *abfd,
>
> p = strchr (name, ELF_VER_CHR);
> if (p == NULL || p[1] != ELF_VER_CHR)
> - return h;
> + {
> + struct elf_link_hash_table *htab = elf_hash_table (info);
> + if (htab->first_hash != NULL)
> + {
> + /* Add this symbol to first hash if this archive has the
> + first definition. */
> + struct bfd_link_hash_entry *e
> + = bfd_link_hash_lookup (htab->first_hash, name, true,
> + false, true);
> + if (e == NULL)
> + info->callbacks->einfo
> + (_("%F%P: %pB: failed to add %s to first hash\n"),
> + abfd, name);
> +
> + if (e->type == bfd_link_hash_new)
> + {
> + /* Change the type to bfd_link_hash_defined and store
> + ABFD in u.undef->abfd. */
> + e->type = bfd_link_hash_defined;
> + e->u.undef.abfd = abfd;
> + }
> + }
> + return h;
> + }
>
> /* First check with only one `@'. */
> len = strlen (name);
> @@ -6102,7 +6179,22 @@ elf_link_add_archive_symbols (bfd *abfd, struct bfd_link_info *info)
> if (h->type != bfd_link_hash_undefweak)
> /* Symbol must be defined. Don't check it again. */
> included[i] = true;
> - continue;
> +
> + /* Ignore the archive if the symbol isn't defined in a
> + shared object. */
> + if (!((struct elf_link_hash_entry *) h)->def_dynamic)
> + continue;
> + /* Ignore the dynamic definition if symbol is first
> + defined in this archive. */
> + struct elf_link_hash_table *htab = elf_hash_table (info);
> + if (htab->first_hash == NULL)
> + continue;
> + struct bfd_link_hash_entry *e
> + = bfd_link_hash_lookup (htab->first_hash,
> + symdef->name, false, false,
> + true);
> + if (e == NULL || e->u.undef.abfd != abfd)
> + continue;
> }
>
> /* We need to include this archive member. */
> @@ -8185,6 +8277,11 @@ _bfd_elf_link_hash_table_free (bfd *obfd)
> _bfd_elf_strtab_free (htab->dynstr);
> _bfd_merge_sections_free (htab->merge_info);
> _bfd_generic_link_hash_table_free (obfd);
> + if (htab->first_hash != NULL)
> + {
> + bfd_hash_table_free (&htab->first_hash->table);
> + free (htab->first_hash);
> + }
> }
>
> /* This is a hook for the ELF emulation code in the generic linker to
> diff --git a/ld/testsuite/ld-elf/pr31482a-no-lto.c b/ld/testsuite/ld-elf/pr31482a-no-lto.c
> new file mode 100644
> index 00000000000..abc23be0714
> --- /dev/null
> +++ b/ld/testsuite/ld-elf/pr31482a-no-lto.c
> @@ -0,0 +1,8 @@
> +extern void foo (void);
> +
> +int
> +main()
> +{
> + foo ();
> + return 0;
> +}
> diff --git a/ld/testsuite/ld-elf/pr31482b-no-lto.c b/ld/testsuite/ld-elf/pr31482b-no-lto.c
> new file mode 100644
> index 00000000000..f88254d4ee1
> --- /dev/null
> +++ b/ld/testsuite/ld-elf/pr31482b-no-lto.c
> @@ -0,0 +1,10 @@
> +void
> +func (void)
> +{
> +}
> +
> +void
> +bar (void)
> +{
> + func ();
> +}
> diff --git a/ld/testsuite/ld-elf/pr31482c-no-lto.c b/ld/testsuite/ld-elf/pr31482c-no-lto.c
> new file mode 100644
> index 00000000000..bf326dd399d
> --- /dev/null
> +++ b/ld/testsuite/ld-elf/pr31482c-no-lto.c
> @@ -0,0 +1,15 @@
> +#include <stdlib.h>
> +#include <stdio.h>
> +
> +void
> +abort (void)
> +{
> + printf ("PASS\n");
> + exit (0);
> +}
> +
> +void
> +foo (void)
> +{
> + abort ();
> +}
> diff --git a/ld/testsuite/ld-elf/pr31482d-no-lto.c b/ld/testsuite/ld-elf/pr31482d-no-lto.c
> new file mode 100644
> index 00000000000..7cdaff09c72
> --- /dev/null
> +++ b/ld/testsuite/ld-elf/pr31482d-no-lto.c
> @@ -0,0 +1,9 @@
> +void
> +func (void)
> +{
> +}
> +
> +void
> +foo (void)
> +{
> +}
> diff --git a/ld/testsuite/ld-elf/shared.exp b/ld/testsuite/ld-elf/shared.exp
> index 277dc7bf2de..9e89077af89 100644
> --- a/ld/testsuite/ld-elf/shared.exp
> +++ b/ld/testsuite/ld-elf/shared.exp
> @@ -912,6 +912,30 @@ run_cc_link_tests [list \
> {{readelf {--dyn-syms --wide} pr28348.rd}} \
> "pr28348" \
> ] \
> + [list \
> + "Build pr31482b-no-lto.so" \
> + "-shared" \
> + "-fPIC" \
> + {pr31482b-no-lto.c} \
> + {} \
> + "pr31482b-no-lto.so" \
> + ] \
> + [list \
> + "Build pr31482c-no-lto.a" \
> + "" \
> + "" \
> + {pr31482c-no-lto.c} \
> + {} \
> + "pr31482c-no-lto.a" \
> + ] \
> + [list \
> + "Build pr31482d-no-lto.a" \
> + "" \
> + "" \
> + {pr31482d-no-lto.c} \
> + {} \
> + "pr31482d-no-lto.a" \
> + ] \
> ]
>
> # pr19073.s uses .set, which has a different meaning on alpha.
> @@ -1165,6 +1189,18 @@ set run_tests [list \
> "" "" \
> {pr26590c.c pr26590d.c} "pr26590" "pass.out" "" "c" "" \
> "-Wl,--as-needed tmpdir/libpr26590a.so tmpdir/libpr26590b.so" ] \
> + [list "Run pr31482 (no-lto)" \
> + "-Wl,--no-as-needed" \
> + "" \
> + {pr31482a-no-lto.c} \
> + "pr31482-no-lto" \
> + "pass.out" \
> + "" \
> + "c" \
> + "" \
> + "tmpdir/pr31482b-no-lto.so tmpdir/pr31482c-no-lto.a \
> + tmpdir/pr31482d-no-lto.a" \
> + ] \
> ]
>
> # NetBSD ELF systems do not currently support the .*_array sections.
> diff --git a/ld/testsuite/ld-plugin/lto.exp b/ld/testsuite/ld-plugin/lto.exp
> index cf1691fec6d..9e53e2d3cec 100644
> --- a/ld/testsuite/ld-plugin/lto.exp
> +++ b/ld/testsuite/ld-plugin/lto.exp
> @@ -539,6 +539,22 @@ set lto_link_elf_tests [list \
> "" \
> "pr30281.so" \
> ] \
> + [list \
> + "Build pr31482b.a" \
> + "" \
> + "" \
> + {pr31482b.c} \
> + "" \
> + "pr31482b.a" \
> + ] \
> + [list \
> + "Build pr31482c.so" \
> + "-shared" \
> + "-fPIC" \
> + {pr31482c.c} \
> + "" \
> + "pr31482c.so" \
> + ] \
> ]
>
> # PR 14918 checks that libgcc is not spuriously included in a shared link of
> @@ -722,6 +738,22 @@ set lto_run_elf_shared_tests [list \
> {-Wl,--as-needed,-R,tmpdir} {} \
> {lto-19c.c} {lto-19.exe} {pass.out} {-flto -O2} {c} {} \
> {tmpdir/liblto-19.so tmpdir/liblto-19.a}] \
> + [list {pr31482a} \
> + {-Wl,--no-as-needed,-R,tmpdir} {} \
> + {pr31482a.c} {pr31482a.exe} {pass.out} {-flto} {c} {} \
> + {tmpdir/pr31482b.a tmpdir/pr31482c.so}] \
> + [list {pr31482b} \
> + {-Wl,--no-as-needed,-R,tmpdir} {} \
> + {pr31482a.c} {pr31482b.exe} {pass1.out} {-flto} {c} {} \
> + {tmpdir/pr31482c.so tmpdir/pr31482b.a}] \
> + [list {pr31489a} \
> + {-Wl,--as-needed,-R,tmpdir} {} \
> + {pr31482a.c} {pr31489a.exe} {pass.out} {-flto} {c} {} \
> + {tmpdir/pr31482b.a tmpdir/pr31482c.so}] \
> + [list {pr31489b} \
> + {-Wl,--as-needed,-R,tmpdir} {} \
> + {pr31482a.c} {pr31489b.exe} {pass1.out} {-flto} {c} {} \
> + {tmpdir/pr31482c.so tmpdir/pr31482b.a}] \
> ]
>
> # LTO run-time tests for ELF
> diff --git a/ld/testsuite/ld-plugin/pass1.out b/ld/testsuite/ld-plugin/pass1.out
> new file mode 100644
> index 00000000000..8e5c818f1a6
> --- /dev/null
> +++ b/ld/testsuite/ld-plugin/pass1.out
> @@ -0,0 +1 @@
> +PASS1
> diff --git a/ld/testsuite/ld-plugin/pr31482a.c b/ld/testsuite/ld-plugin/pr31482a.c
> new file mode 100644
> index 00000000000..0693e471123
> --- /dev/null
> +++ b/ld/testsuite/ld-plugin/pr31482a.c
> @@ -0,0 +1,8 @@
> +#include <stdlib.h>
> +
> +int
> +main()
> +{
> + abort ();
> + return 0;
> +}
> diff --git a/ld/testsuite/ld-plugin/pr31482b.c b/ld/testsuite/ld-plugin/pr31482b.c
> new file mode 100644
> index 00000000000..3c241735c16
> --- /dev/null
> +++ b/ld/testsuite/ld-plugin/pr31482b.c
> @@ -0,0 +1,9 @@
> +#include <stdlib.h>
> +#include <stdio.h>
> +
> +void
> +abort (void)
> +{
> + printf ("PASS\n");
> + exit (0);
> +}
> diff --git a/ld/testsuite/ld-plugin/pr31482c.c b/ld/testsuite/ld-plugin/pr31482c.c
> new file mode 100644
> index 00000000000..5c3b5099b52
> --- /dev/null
> +++ b/ld/testsuite/ld-plugin/pr31482c.c
> @@ -0,0 +1,9 @@
> +#include <stdlib.h>
> +#include <stdio.h>
> +
> +void
> +abort (void)
> +{
> + printf ("PASS1\n");
> + exit (0);
> +}
> --
> 2.44.0
>
PING.
--
H.J.
next prev parent reply other threads:[~2024-03-28 13:31 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-15 19:43 H.J. Lu
2024-03-28 13:30 ` H.J. Lu [this message]
2024-04-04 13:29 ` PING^2: " H.J. Lu
2024-04-05 10:15 ` Nick Clifton
2024-04-05 12:00 ` H.J. Lu
2024-04-05 22:16 ` Alan Modra
2024-04-05 23:37 ` H.J. Lu
2024-04-05 23:45 ` Alan Modra
2024-04-05 23:48 ` H.J. Lu
2024-04-04 23:54 ` Alan Modra
2024-04-05 1:50 ` H.J. Lu
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