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I'm sponsoring the following case for myself. This case qualifies for
Architectural self-review, but I wish to record the following
information.
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The link-editors -z combreloc flag combines individual relocation sections
(like .rela.data and .rela.bss) into one relocation table .SUNW_reloc.
This concatenation of the standard relocation tables allows ld(1) to sort
all data relocations so that the symbol lookup cost, from ld.so.1(1),
is minimized. The option has existed since Solaris 7 (4044285), and
its use has been enforced for OSnet components via check_rtime.
Linux took the same option, but went one step further and made the
functionality the default behavior for gld as of version 2.13. Gld
produces .rel.dyn sections, whereas ld produces .SUNW_reloc sections -
however, the section names are never referenced, so their names aren't
particularly meaningful. Gld also provides the additional -z nocombreloc
option just in case.
ld(1) should make -z combreloc the default behavior when creating a
final object (ie., an executable or shared object). The -z combreloc
option will still be recognized, but effectively ignored. A new
-z nocombreloc option will be added to disable the relocation section
concatenation.
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The ld(1) man page will be updated to add:
Synopsis ld [-64] [-a | -r] [-b] [-Bdirect | nodirect]
.....
[-z altexec64] [-z combreloc | nocombreloc ] [-z defs | nodefs]
.....
Options
The following options are supported:
.....
-z combreloc | nocombreloc
By default, the link-editor combines multiple relocation
sections when building executables or shared objects.
This section combination differs from relocatable
objects, in which relocation sections are maintained in
a one-to-one relationship with the sections to which the
relocations must be applied. The -z nocombreloc option
disables this merging of relocation sections, and
preserves the one-to-one relationship found in the ori-
ginal relocatable objects.
The link-editor sorts the entries of data relocation
sections by their symbol reference. This sorting reduces
runtime symbol lookup. When multiple relocation sec-
tions are combined, this sorting produces the least pos-
sible relocation overhead when objects are loaded into
memory, and speeds the runtime loading of dynamic
objects.
Historically, the individual relocation sections were
carried over to any executable or shared object, and the
-z combreloc option was required to enable the reloca-
tion section merging previously described. Relocation
section merging is now the default. The -z combreloc
option is still accepted for the benefit of old build
environments, but the option is unnecessary, and has no
effect.
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Release Binding: Patch/Micro
ld -znocombreloc option Committed
--
Rod.
