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Handle copy relocations

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In ELF, if a data symbol is defined in a shared library and used by
the main program, it will be subject to a "copy relocation".  In this
scenario, the main program has a copy of the symbol in question, and a
relocation that tells ld.so to copy the data from the shared library.
Then the symbol in the main program is used to satisfy all references.

This patch changes gdb to handle this scenario.  Data symbols coming
from ELF shared libraries get a special flag that indicates that the
symbol's address may be subject to copy relocation.

I looked briefly into handling copy relocations by looking at the
actual relocations in the main program, but this seemed difficult to
do with BFD.

Note that no caching is done here.  Perhaps this could be changed if
need be; I wanted to avoid possible problems with either objfile
lifetimes and changes, or conflicts with the long-term (vapor-ware)
objfile splitting project.

gdb/ChangeLog
2019-10-02  Tom Tromey  <tromey@adacore.com>

	* symmisc.c (dump_msymbols): Don't use MSYMBOL_VALUE_ADDRESS.
	* ada-lang.c (lesseq_defined_than): Handle
	LOC_STATIC.
	* dwarf2read.c (dwarf2_per_objfile): Add can_copy
	parameter.
	(dwarf2_has_info): Likewise.
	(new_symbol): Set maybe_copied on symbol when
	appropriate.
	* dwarf2read.h (dwarf2_per_objfile): Add can_copy
	parameter.
	<can_copy>: New member.
	* elfread.c (record_minimal_symbol): Set maybe_copied
	on symbol when appropriate.
	(elf_symfile_read): Update call to dwarf2_has_info.
	* minsyms.c (lookup_minimal_symbol_linkage): New
	function.
	* minsyms.h (lookup_minimal_symbol_linkage): Declare.
	* symtab.c (get_symbol_address, get_msymbol_address):
	New functions.
	* symtab.h (get_symbol_address, get_msymbol_address):
	Declare.
	(SYMBOL_VALUE_ADDRESS, MSYMBOL_VALUE_ADDRESS): Handle
	maybe_copied.
	(struct symbol, struct minimal_symbol) <maybe_copied>:
	New member.
This commit is contained in:
Tom Tromey 2019-06-25 12:50:45 -06:00
parent 1dd5885077
commit 4b610737f0
11 changed files with 208 additions and 32 deletions
Download patch file Download diff file Expand all files Collapse all files

9
gdb/ada-lang.c
View file

@ -4724,6 +4724,15 @@ lesseq_defined_than (struct symbol *sym0, struct symbol *sym1)
case LOC_CONST:
return SYMBOL_VALUE (sym0) == SYMBOL_VALUE (sym1)
&& equiv_types (SYMBOL_TYPE (sym0), SYMBOL_TYPE (sym1));
case LOC_STATIC:
{
const char *name0 = SYMBOL_LINKAGE_NAME (sym0);
const char *name1 = SYMBOL_LINKAGE_NAME (sym1);
return (strcmp (name0, name1) == 0
&& SYMBOL_VALUE_ADDRESS (sym0) == SYMBOL_VALUE_ADDRESS (sym1));
}
default:
return 0;
}