184 lines
6.2 KiB
Diff
184 lines
6.2 KiB
Diff
From f2922a47c8e0f858649d5867df3eff9186bac583 Mon Sep 17 00:00:00 2001
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From: Octavian Purdila <octavian dot purdila at intel dot com>
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Date: Mon, 26 Oct 2015 15:57:33 +0200
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Subject: [PATCH 1/3] Fix linker error when using NT weak externals
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Lets take the following example:
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a.c:
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void foo(void);
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int main()
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{
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foo();
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return 0;
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}
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b.c:
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#include <stdio.h>
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void __attribute__((weak)) foo(void)
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{
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printf("%s weak\n", __func__);
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}
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Compiling this with mingw will trigger the following linker error:
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$ i686-w64-mingw32-gcc -o a.exe a.c b.c
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/tmp/ccZ6Yw7O.o:a.c:(.text+0xc): undefined reference to `foo'
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collect2: error: ld returned 1 exit status
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Depending on the order in which a.c and b.c are linked the following
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is happening in _bfd_generic_link_add_one_symbol:
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1. If we link in a.c b.c order then foo will be added in as an
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undefined symbol from a.c. Then it will be added as a weak undefined*
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symbol from b.c (section undefined, flags BSF_WEAK) and the action
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taken will be no action, i.e. keep the symbol undefined.
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2. If we link in b.c a.c order then foo will first be added as an
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undefined weak symbol from b.c. Then it will be added as undefined
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from a.c and the action taken will be to make the symbol undefined.
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To fix this issue, this patch checks for an weak external symbol when
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doing relocations even if the symbol is undefined. In order to do so,
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we also have to also populate the symbol_class and aux members when
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adding a weak external symbol over an undefined or weak defined
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symbol.
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*In PE COFF case defined weak symbols are implemented as weak
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externals which requires them to be seen as undefined (weak) symbols.
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bfd/
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2015-10-26 Octavian Purdila <octavian.purdila@intel.com>
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* cofflink.c: Move weak external relocation code to a new function
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(_bfd_coff_relocate_weak_externals)
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* cofflink.c (_bfd_coff_generic_relocate_section): Check if we
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need to relocate a weak external even if the symbol is undefined
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* cofflink.c (coff_link_add_symbols): Fill in the class and aux
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when adding a weak external over an undefined or weakly defined
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symbol
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---
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bfd/ChangeLog | 10 +++++++++
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bfd/cofflink.c | 66 ++++++++++++++++++++++++++++++++--------------------------
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2 files changed, 46 insertions(+), 30 deletions(-)
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diff --git a/bfd/ChangeLog b/bfd/ChangeLog
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index 96152768ab..b5b5df1b13 100644
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--- a/bfd/ChangeLog
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+++ b/bfd/ChangeLog
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@@ -1,3 +1,13 @@
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+2015-10-26 octavian purdila <octavian.purdila@intel.com>
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+
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+ * cofflink.c: Move weak external relocation code to a new function
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+ (_bfd_coff_relocate_weak_externals)
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+ * cofflink.c (_bfd_coff_generic_relocate_section): Check if we
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+ need to relocate a weak external even if the symbol is undefined
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+ * cofflink.c (coff_link_add_symbols): Fill in the class and aux
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+ when adding a weak external over an undefined or weakly defined
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+ symbol
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+
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2015-07-21 Tristan Gingold <gingold@adacore.com>
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* version.m4: Bump version to 2.25.1
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diff --git a/bfd/cofflink.c b/bfd/cofflink.c
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index ef9e3623fe..caed7e4aa9 100644
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--- a/bfd/cofflink.c
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+++ b/bfd/cofflink.c
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@@ -426,7 +426,7 @@ coff_link_add_symbols (bfd *abfd,
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if (((*sym_hash)->symbol_class == C_NULL
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&& (*sym_hash)->type == T_NULL)
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|| sym.n_scnum != 0
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- || (sym.n_value != 0
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+ || ((sym.n_value != 0 || IS_WEAK_EXTERNAL(abfd, sym))
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&& (*sym_hash)->root.type != bfd_link_hash_defined
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&& (*sym_hash)->root.type != bfd_link_hash_defweak))
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{
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@@ -2890,6 +2890,37 @@ _bfd_coff_reloc_link_order (bfd *output_bfd,
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return TRUE;
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}
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+/* See _Microsoft Portable Executable and Common Object File Format
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+ Specification_, section 5.5.3. Note that weak symbols without aux records
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+ are a GNU extension.
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+
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+ FIXME: All weak externals are treated as having characteristic
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+ IMAGE_WEAK_EXTERN_SEARCH_NOLIBRARY (1). These behave as per SVR4 ABI: A
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+ library member will resolve a weak external only if a normal external causes
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+ the library member to be linked. See also linker.c:
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+ generic_link_check_archive_element. */
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+
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+static void _bfd_coff_relocate_weak_externals(struct coff_link_hash_entry *h,
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+ bfd_vma *val)
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+{
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+ long aux_index = h->aux->x_sym.x_tagndx.l;
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+ struct coff_tdata *cdata = h->auxbfd->tdata.coff_obj_data;
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+ struct coff_link_hash_entry *h2 = cdata->sym_hashes[aux_index];
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+ asection *sec;
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+
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+ if (!h2 || h2->root.type == bfd_link_hash_undefined)
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+ {
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+ *val = 0;
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+ }
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+ else
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+ {
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+ sec = h2->root.u.def.section;
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+ *val = h2->root.u.def.value + sec->output_section->vma +
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+ sec->output_offset;
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+ }
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+}
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+
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+
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/* A basic reloc handling routine which may be used by processors with
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simple relocs. */
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@@ -3007,39 +3038,14 @@ _bfd_coff_generic_relocate_section (bfd *output_bfd,
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else if (h->root.type == bfd_link_hash_undefweak)
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{
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if (h->symbol_class == C_NT_WEAK && h->numaux == 1)
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- {
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- /* See _Microsoft Portable Executable and Common Object
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- File Format Specification_, section 5.5.3.
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- Note that weak symbols without aux records are a GNU
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- extension.
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- FIXME: All weak externals are treated as having
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- characteristic IMAGE_WEAK_EXTERN_SEARCH_NOLIBRARY (1).
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- These behave as per SVR4 ABI: A library member
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- will resolve a weak external only if a normal
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- external causes the library member to be linked.
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- See also linker.c: generic_link_check_archive_element. */
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- asection *sec;
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- struct coff_link_hash_entry *h2 =
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- h->auxbfd->tdata.coff_obj_data->sym_hashes[
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- h->aux->x_sym.x_tagndx.l];
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-
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- if (!h2 || h2->root.type == bfd_link_hash_undefined)
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- {
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- sec = bfd_abs_section_ptr;
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- val = 0;
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- }
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- else
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- {
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- sec = h2->root.u.def.section;
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- val = h2->root.u.def.value
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- + sec->output_section->vma + sec->output_offset;
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- }
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- }
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+ _bfd_coff_relocate_weak_externals(h, &val);
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else
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/* This is a GNU extension. */
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val = 0;
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}
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-
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+ else if (h->root.type == bfd_link_hash_undefined &&
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+ h->symbol_class == C_NT_WEAK && h->numaux == 1)
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+ _bfd_coff_relocate_weak_externals(h, &val);
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else if (! info->relocatable)
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{
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if (! ((*info->callbacks->undefined_symbol)
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--
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2.11.0
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