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https://github.com/SerenityOS/serenity
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4defa401d3
Aside from a straightforward rebase, this contains an out-of-tree patch from MaskRay which adds the `-Bsymbolic-non-weak-functions` flag to ld.
271 lines
11 KiB
Diff
271 lines
11 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Fangrui Song <maskray@google.com>
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Date: Sat, 22 May 2021 23:10:21 -0700
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Subject: [PATCH] ld: Add -Bsymbolic-non-weak-functions
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This option is a subset of -Bsymbolic-functions: only STB_GLOBAL are
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considered. Vague linkage functions are STB_WEAK. A vague linkage
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function may have different addresses in a -Bsymbolic-functions linked
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shared object and outside the shared object.
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-Bsymbolic-non-weak-functions can keep pointer equality while providing
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most benefits: (a) fewer JUMP_SLOT (symbol lookups) (b) avoid PLT
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entries for default visibility defined functions.
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PR 27871
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include/
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* bfdlink.h (struct bfd_link_info): Add dynamic_weak_functions.
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ld/
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* ldlex.h (enum option_values): Add OPTION_SYMBOLIC_NON_WEAK_FUNCTIONS.
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* lexsup.c (struct ld_options): Add -Bsymbolic-non-weak-functions.
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(enum symbolic_enum): Add symbolic_non_weak_functions.
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(parse_args): Handle -Bsymbolic-non-weak-functions.
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* ld.texi: Document -Bsymbolic-non-weak-functions.
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* NEWS: Mention -Bsymbolic-non-weak-functions.
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* testsuite/ld-elf/shared.exp: Add tests.
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* testsuite/ld-elf/symbolic-non-weak-func.s: New file.
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* testsuite/ld-elf/symbolic-non-weak-func-a.rd: Likewise.
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* testsuite/ld-elf/symbolic-non-weak-func-b.rd: Likewise.
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---
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bfd/elflink.c | 12 +++++-----
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include/bfdlink.h | 3 +++
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ld/NEWS | 2 ++
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ld/ld.texi | 15 ++++++++++---
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ld/ldlex.h | 1 +
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ld/lexsup.c | 17 +++++++++++---
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ld/testsuite/ld-elf/shared.exp | 22 +++++++++++++++++++
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.../ld-elf/symbolic-non-weak-func-a.rd | 4 ++++
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.../ld-elf/symbolic-non-weak-func-b.rd | 4 ++++
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ld/testsuite/ld-elf/symbolic-non-weak-func.s | 18 +++++++++++++++
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10 files changed, 85 insertions(+), 13 deletions(-)
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create mode 100644 ld/testsuite/ld-elf/symbolic-non-weak-func-a.rd
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create mode 100644 ld/testsuite/ld-elf/symbolic-non-weak-func-b.rd
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create mode 100644 ld/testsuite/ld-elf/symbolic-non-weak-func.s
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diff --git a/bfd/elflink.c b/bfd/elflink.c
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index 7217c2f038baf9cf1df122cc5bb82ac99c00a51e..b7f14694f277f91e6a58491548fae52382683ca6 100644
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--- a/bfd/elflink.c
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+++ b/bfd/elflink.c
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@@ -608,14 +608,12 @@ bfd_elf_link_mark_dynamic_symbol (struct bfd_link_info *info,
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if(h->dynamic || bfd_link_relocatable (info))
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return;
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+ int type = sym != NULL ? ELF_ST_TYPE (sym->st_info) : STT_NOTYPE;
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if ((info->dynamic_data
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- && (h->type == STT_OBJECT
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- || h->type == STT_COMMON
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- || (sym != NULL
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- && (ELF_ST_TYPE (sym->st_info) == STT_OBJECT
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- || ELF_ST_TYPE (sym->st_info) == STT_COMMON))))
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- || (d != NULL
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- && h->non_elf
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+ && (type == STT_OBJECT || type == STT_COMMON))
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+ || (info->dynamic_weak_functions && type == STT_FUNC
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+ && ELF_ST_BIND (sym->st_info) == STB_WEAK)
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+ || (d != NULL && h->non_elf
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&& (*d->match) (&d->head, NULL, h->root.root.string)))
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{
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h->dynamic = 1;
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diff --git a/include/bfdlink.h b/include/bfdlink.h
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index 840790a298c3f8894494c5266b2de0560ceecfd2..632bf8fdd2ec2c4bf1ee8573884c18b3a2c1bb3f 100644
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--- a/include/bfdlink.h
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+++ b/include/bfdlink.h
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@@ -368,6 +368,9 @@ struct bfd_link_info
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/* TRUE if all data symbols should be dynamic. */
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unsigned int dynamic_data: 1;
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+ /* TRUE if all weak function symbols should be dynamic. */
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+ unsigned int dynamic_weak_functions: 1;
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+
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/* TRUE if section groups should be resolved. */
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unsigned int resolve_section_groups: 1;
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diff --git a/ld/NEWS b/ld/NEWS
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index e1ac20b8a97399136cc04b21e677292dd3bf8c66..5e37f9d0c11f8ef8a4900a9d11ba1df50e26c3d6 100644
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--- a/ld/NEWS
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+++ b/ld/NEWS
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@@ -104,6 +104,8 @@ Changes in 2.37:
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* Add -Bno-symbolic to cancel -Bsymbolic and -Bsymbolic-functions.
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+* Add -Bsymbolic-non-weak-functions as a safe subset of -Bsymbolic-functions.
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+
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Changes in 2.36:
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* Add libdep plugin, for linking dependencies of static libraries that
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diff --git a/ld/ld.texi b/ld/ld.texi
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index aa8b1aa86eb386358bc18662f1f0b2fce4996763..49b7dfe80d81ba59e7bd86dbae8c4dadc25b9c77 100644
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--- a/ld/ld.texi
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+++ b/ld/ld.texi
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@@ -1739,7 +1739,7 @@ libraries.
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@kindex -Bsymbolic
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@item -Bsymbolic
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-When creating a shared library, bind references to global symbols to the
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+When creating a shared library, bind references to non-local symbols to the
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definition within the shared library, if any. Normally, it is possible
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for a program linked against a shared library to override the definition
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within the shared library. This option is only meaningful on ELF
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@@ -1747,11 +1747,20 @@ platforms which support shared libraries.
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@kindex -Bsymbolic-functions
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@item -Bsymbolic-functions
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-When creating a shared library, bind references to global function
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-symbols to the definition within the shared library, if any.
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+When creating a shared library, bind references to non-local function
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+symbols to the definition within the shared library, if any. A vague linkage
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+function definition is weak. It may have different addresses in the linked
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+shared library and outside the shared library.
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This option is only meaningful on ELF platforms which support shared
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libraries.
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+@kindex -Bsymbolic-non-weak-functions
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+@item -Bsymbolic-non-weak-functions
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+When creating a shared library, bind references to @code{STB_GLOBAL} function
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+symbols to the definition within the shared library, if any. Noticeably this
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+option skips C++ vague linkage functions and is thus safe.
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+This option is only meaningful on ELF platforms which support shared libraries.
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+
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@kindex -Bno-symbolic
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@item -Bno-symbolic
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This option can cancel previously specified @samp{-Bsymbolic} and
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diff --git a/ld/ldlex.h b/ld/ldlex.h
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index 87cac02141d8c8cf090001ec877dd4e458d19c1b..1a571a7ce331487b2d809bbbd562a5ce32d4e6d7 100644
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--- a/ld/ldlex.h
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+++ b/ld/ldlex.h
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@@ -64,6 +64,7 @@ enum option_values
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OPTION_SORT_SECTION,
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OPTION_STATS,
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OPTION_SYMBOLIC,
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+ OPTION_SYMBOLIC_NON_WEAK_FUNCTIONS,
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OPTION_SYMBOLIC_FUNCTIONS,
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OPTION_TASK_LINK,
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OPTION_TBSS,
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diff --git a/ld/lexsup.c b/ld/lexsup.c
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index fe8722313fedf6d72846fc45418831e5c77efab6..128ffadea5e9a8751336bcc86e3243f66a4e7411 100644
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--- a/ld/lexsup.c
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+++ b/ld/lexsup.c
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@@ -315,9 +315,11 @@ static const struct ld_option ld_options[] =
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{ {"Bno-symbolic", no_argument, NULL, OPTION_NO_SYMBOLIC},
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'\0', NULL, N_("Don't bind global references locally"), ONE_DASH },
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{ {"Bsymbolic", no_argument, NULL, OPTION_SYMBOLIC},
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- '\0', NULL, N_("Bind global references locally"), ONE_DASH },
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+ '\0', NULL, N_("Bind default visibility defined symbols locally for -shared"), ONE_DASH },
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+ { {"Bsymbolic-non-weak-functions", no_argument, NULL, OPTION_SYMBOLIC_NON_WEAK_FUNCTIONS},
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+ '\0', NULL, N_("Bind default visibility defined STB_GLOBAL function symbols locally for -shared"), ONE_DASH },
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{ {"Bsymbolic-functions", no_argument, NULL, OPTION_SYMBOLIC_FUNCTIONS},
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- '\0', NULL, N_("Bind global function references locally"), ONE_DASH },
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+ '\0', NULL, N_("Bind default visibility defined function symbols locally for -shared"), ONE_DASH },
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{ {"check-sections", no_argument, NULL, OPTION_CHECK_SECTIONS},
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'\0', NULL, N_("Check section addresses for overlaps (default)"),
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TWO_DASHES },
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@@ -647,8 +649,9 @@ parse_args (unsigned argc, char **argv)
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enum symbolic_enum
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{
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symbolic_unset = 0,
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- symbolic,
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+ symbolic_non_weak_functions,
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symbolic_functions,
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+ symbolic,
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} opt_symbolic = symbolic_unset;
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enum dynamic_list_enum
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{
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@@ -1372,6 +1375,9 @@ parse_args (unsigned argc, char **argv)
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case OPTION_SYMBOLIC:
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opt_symbolic = symbolic;
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break;
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+ case OPTION_SYMBOLIC_NON_WEAK_FUNCTIONS:
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+ opt_symbolic = symbolic_non_weak_functions;
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+ break;
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case OPTION_SYMBOLIC_FUNCTIONS:
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opt_symbolic = symbolic_functions;
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break;
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@@ -1996,6 +2002,11 @@ parse_args (unsigned argc, char **argv)
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link_info.dynamic = true;
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link_info.dynamic_data = true;
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break;
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+ case symbolic_non_weak_functions:
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+ link_info.dynamic = true;
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+ link_info.dynamic_data = true;
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+ link_info.dynamic_weak_functions = true;
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+ break;
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}
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/* -z nosectionheader implies --strip-all. */
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diff --git a/ld/testsuite/ld-elf/shared.exp b/ld/testsuite/ld-elf/shared.exp
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index cf010e5b0e59576a047476ecaa2d9a74c8cc7ed0..d5508912aa286e4a552b9b0270afa815a7d8a960 100644
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--- a/ld/testsuite/ld-elf/shared.exp
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+++ b/ld/testsuite/ld-elf/shared.exp
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@@ -459,6 +459,28 @@ run_ld_link_tests [list \
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"symbolic-func.so"] \
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]
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+if {[istarget "aarch64*-*-*"] || [istarget "powerpc*-*-*"] ||
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+ [istarget "i?86-*-*"] || [istarget "x86_64-*-*"]} {
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+ run_ld_link_tests [list \
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+ [list "-Bsymbolic-non-weak-functions -Bsymbolic" \
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+ "-shared -Bsymbolic-non-weak-functions -Bsymbolic" "" "$AFLAGS_PIC" \
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+ {symbolic-non-weak-func.s} {{readelf {-r --wide} symbolic-non-weak-func-a.rd}} \
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+ "symbolic-non-weak-func-a.so"] \
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+ ]
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+ run_ld_link_tests [list \
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+ [list "-Bsymbolic-non-weak-functions" \
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+ "-shared -Bsymbolic-non-weak-functions" "" "$AFLAGS_PIC" \
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+ {symbolic-non-weak-func.s} {{readelf {-r --wide} symbolic-non-weak-func-b.rd}} \
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+ "symbolic-non-weak-func-b.so"] \
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+ ]
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+ run_ld_link_tests [list \
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+ [list "-Bsymbolic-functions -Bsymbolic-non-weak-functions" \
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+ "-shared -Bsymbolic-functions -Bsymbolic-non-weak-functions" "" "$AFLAGS_PIC" \
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+ {symbolic-non-weak-func.s} {{readelf {-r --wide} symbolic-non-weak-func-b.rd}} \
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+ "symbolic-non-weak-func-b.so"] \
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+ ]
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+}
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+
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run_ld_link_tests [list \
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[list "Build pr20995.so" \
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"-shared" "" "$AFLAGS_PIC" \
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diff --git a/ld/testsuite/ld-elf/symbolic-non-weak-func-a.rd b/ld/testsuite/ld-elf/symbolic-non-weak-func-a.rd
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new file mode 100644
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index 0000000000000000000000000000000000000000..ef591840f5c338a55f6d44fc372568569011c430
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--- /dev/null
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+++ b/ld/testsuite/ld-elf/symbolic-non-weak-func-a.rd
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@@ -0,0 +1,4 @@
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+#...
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+[0-9a-f]+ +[0-9a-f]+ +R_.*_RELATIVE .*
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+[0-9a-f]+ +[0-9a-f]+ +R_.*_RELATIVE .*
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+[0-9a-f]+ +[0-9a-f]+ +R_.*_RELATIVE .*
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diff --git a/ld/testsuite/ld-elf/symbolic-non-weak-func-b.rd b/ld/testsuite/ld-elf/symbolic-non-weak-func-b.rd
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new file mode 100644
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index 0000000000000000000000000000000000000000..34228b0627b226cfdc76e3cedff6f515b7c27872
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--- /dev/null
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+++ b/ld/testsuite/ld-elf/symbolic-non-weak-func-b.rd
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@@ -0,0 +1,4 @@
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+#...
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+[0-9a-f]+ +[0-9a-f]+ +R_.*_RELATIVE .*
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+[0-9a-f]+ +[0-9a-f]+ +R_.*_RELATIVE .*
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+[0-9a-f]+ +[0-9a-f]+ +R_.* weak_fun.*
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diff --git a/ld/testsuite/ld-elf/symbolic-non-weak-func.s b/ld/testsuite/ld-elf/symbolic-non-weak-func.s
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new file mode 100644
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index 0000000000000000000000000000000000000000..e259f12bfc126bf2ef9bf16aba64667ca4e2bfd5
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--- /dev/null
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+++ b/ld/testsuite/ld-elf/symbolic-non-weak-func.s
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@@ -0,0 +1,18 @@
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+ .text
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+ .global global_fun
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+ .type global_fun, %function
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+global_fun:
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+ .space 4
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+ .weak weak_fun
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+ .type weak_fun, %function
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+weak_fun:
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+ .space 4
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+
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+ .section .data,"aw",%progbits
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+ .p2align 3
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+ .dc.a global_data
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+ .dc.a global_fun
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+ .dc.a weak_fun
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+
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+ .global global_data
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+global_data:
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